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Troubleshooting the FD Speedometer-Odometer-Tachometer Circuit Board

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Troubleshooting the FD Speedometer-Odometer-Tachometer Circuit Board

Old 03-18-18, 10:42 PM
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Originally Posted by Riccardo View Post
Hope I am in the right thread
Originally odometer was not working => replaced all diodes / capacitors and now works YET Speedo at idle has decided to show some MPH !!! (ie. car is not moving yet Speedo is showing speed) - once car moves Speedo works fine until car stops again. Then sometimes after a few miles everything works fine.
Any ideas more than welcome !
Hi Ricaardo,

You are in the right thread to discuss problems with the speedo board. Could you please answer these questions:

1. What diodes did you replace? These diodes are usually tough. Unless they were physically damaged?
2. What did you replace the original diodes with? List part numbers where appropriate.
3. What capacitors did you replace?
4. What did you as a resource to replace these components - a repair thread?
5. Did you replace these components yourself? Are you confident to solder electrical components?
6. What tools and equipment did you use to replace the components? Please state the wattage of soldering iron used.
7. Do you have any photos of the speedo board? Please post photos here.

Cheers,
George
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Old 03-19-18, 01:15 AM
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George ,
I don't have any cluster issue.
But I just want to thank you for the amazing job you do at helping the community

It's really nice to read the dedication you have at helping others fixing their cluster , A+++

Maurice
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Old 03-19-18, 02:14 AM
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Hey Gen2n3,

The glock pad is very handy, as are many of the other toys I have.

The previous owner installed SPA dual digital gauges and he tore quite a bit of the housing up. There is still good contact because everything works with the exception of the tacho problems. Here are the pictures you requested. I also cleaned up the tacho board. I didn't remove the odo but took pictures around it if thats okay.









-groovin
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Old 03-19-18, 09:40 AM
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Originally Posted by 7krayziboi View Post
George ,
I don't have any cluster issue.
But I just want to thank you for the amazing job you do at helping the community

It's really nice to read the dedication you have at helping others fixing their cluster , A+++

Maurice
Maurice,

Good to hear that your cluster is working normally. Thank you for the compliments!

Cheers,
George
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Old 03-19-18, 10:26 AM
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Groovin,

Did you always have problems with the tach? What about the previous owner? Did the tach board have any work done to it?

Based upon the photos of the speedo board, it looks good. However, its detail is not very good. Please remove the speedo and inspect each capacitor for any swelling. The tops of the capacitors should be flat. When they begin to fail the tops will typically bow up as a physical indicator. You do not need to separate the speedo face from the board at this time.

The capacitor C1 on the tach board is not the correct one. It has the correct capacitance value but the voltage rating is incorrect. Based upon the evidence on your tach board, replace capacitors C1 & C5 then test the tach for proper operation. Please refer to my FD Tach Component thread for the correct values of components and part numbers.


C1 has incorrect values, 1uF @ 63V or 6.3V. It is hard to tell from this angle and the magnification level from the original photo.

Take a closer look at all the solder joints to the IC chip. Specifically, the one in the red circle. Is the joint broken? Are all the other solder joints filled in? Use a magnifying lens if needed.


Inspect IC1 solder joints for any cracks. The red circle has a suspect joint.



Cheers,
George
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Old 03-19-18, 03:46 PM
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Originally Posted by Gen2n3 View Post
Groovin,

Did you always have problems with the tach? What about the previous owner? Did the tach board have any work done to it?

Based upon the photos of the speedo board, it looks good. However, its detail is not very good. Please remove the speedo and inspect each capacitor for any swelling. The tops of the capacitors should be flat. When they begin to fail the tops will typically bow up as a physical indicator. You do not need to separate the speedo face from the board at this time.

The capacitor C1 on the tach board is not the correct one. It has the correct capacitance value but the voltage rating is incorrect. Based upon the evidence on your tach board, replace capacitors C1 & C5 then test the tach for proper operation. Please refer to my FD Tach Component thread for the correct values of components and part numbers.


C1 has incorrect values, 1uF @ 63V or 6.3V. It is hard to tell from this angle and the magnification level from the original photo.

Take a closer look at all the solder joints to the IC chip. Specifically, the one in the red circle. Is the joint broken? Are all the other solder joints filled in? Use a magnifying lens if needed.


Inspect IC1 solder joints for any cracks. The red circle has a suspect joint.



Cheers,
George
I bought the car site unseen by a private dealer who was only able to provide me with what ever information he had. Since I received the vehicle I've been trying to figure out everything that has been done to it, performing basic maintenance, repair work, cleaning up previous work, all while discovering more surprises. Some good some bad. So I can't say if the previous owner had tach problems but as you noted earlier the two common caps are outliers from the norm so it may be safe to assume they had tach issues. I suspect c1 and c5 may be the culprits as well. I ordered the new caps using the reference numbers from your tach components thread a few days ago. As soon as they arrive from digikey I'll replace them. I recall you mentioning c1 is polarized? Does the cap indicate which side is what? I can see the circuit board says negative opposite of the c1 label.

Here is a closer picture of that soldered area. Looks like a small divot but still filled in and has good contact but I am open to your recommendations.

The odometer seems to be in good shape from what I can tell (again untrained eyes). Btw, do you know what led bulbs I can use to replace these since I already have them out? Wide spread leds that have diodes on the face and its sides.

Here are more pictures.





Thanks again Gen2n3,
-groovin
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Old 03-19-18, 05:13 PM
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Groovin,

You are more than welcome for the help. And please, call me George.

Thank you for explaining your circumstances with the car's history. Do the good surprises outweigh the bad surprises? I meant to ask, how are your soldering skills and what tools would you use (if you tackle the repair on your own)? Good on you for ordering both C1 & C5. The replacement caps should arrive quickly from Digikey. Who ever replaced those caps did a good job, too bad the values were off. BTW, do not play with the variable resistor, VR1 unless your rev counter is off. If you use a PFC then you should be able to adjust the needle to reflect the actual RPMs.

To answer your question: yes, C1 is a polarized cap. The cap will have a white stripe to denote the negative leg. It would also be shorter than the positive leg. All you need to do is align the negative leg to the negative hole on the tach board. As you mentioned, the tach board has a negative marking for C1's negative leg.

Thanks for the additional photos. I'll provide commentary on them in the captions.


IC1 solder joints. These look ok but if your tach still jumps around after the capacitor replacement then consider removing and replacing the old solder with new. Other joints on IC1 may need similar treatment.


Speedo board. Clean off the dried flux along these solder joints. Additionally, how do the 4 joints look in the center? Those provide signal & power to the speedometer face (needle). Otherwise, the speedo board looks pretty healthy!


Side view of speedo board. This capacitor is the same cap that you should have on the tach board's C5.

Lastly, I may be a minority voice but I recommend that you do NOT change the bulbs to LEDs. Use the recommended incandescent bulbs for the dash. Generally, LEDs consume less voltage (power) so a ballast resistor is used to mimic the original power consumption in the circuit. In modern cars, the lighting systems are designed around LEDs. IMHO, a brighter dash at night is more of a distraction than an aid to the driver. The dash should be bright enough for the driver to identify switches & read gauges. It should not provide a background glow that may alter one's night vision. But that is a topic for another time.

Does this new info help? Please keep me posted on your progress!

Cheers,
George
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Old 03-19-18, 05:53 PM
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Originally Posted by Gen2n3 View Post
Hi Ricaardo,

You are in the right thread to discuss problems with the speedo board. Could you please answer these questions:

1. What diodes did you replace? These diodes are usually tough. Unless they were physically damaged?
2. What did you replace the original diodes with? List part numbers where appropriate.
3. What capacitors did you replace?
4. What did you as a resource to replace these components - a repair thread?
5. Did you replace these components yourself? Are you confident to solder electrical components?
6. What tools and equipment did you use to replace the components? Please state the wattage of soldering iron used.
7. Do you have any photos of the speedo board? Please post photos here.

Cheers,
George
Many thanks George
I did not doo the fix myself and here is what I could find

1. What diodes did you replace? These diodes are usually tough. Unless they were physically damaged?
TR5, TR7 and TR8 (initially used 2 diodes to replace transistors then when they eventually arrived replaced with the transistors)
2. What did you replace the original diodes with? List part numbers where appropriate.
3. What capacitors did you replace?
All the capacitors (two were blown BTW)


4. What did you as a resource to replace these components - a repair thread?
Yes =>
just got done figuring out how to fix an FD odometer - RX7Club.com - Mazda RX7 Forum

5. Did you replace these components yourself? Are you confident to solder electrical components?
My electrician did it 2x

6. What tools and equipment did you use to replace the components? Please state the wattage of soldering iron used.
I am afraid here first time round may have been quite hot...


7. Do you have any photos of the speedo board? Please post photos here.
Unfortunately not as it is on the car : (

Help very much appreciated and apologies cannot be more specific
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Old 03-19-18, 08:32 PM
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Riccardo,

Thanks for answering my questions.

What part number did you use to replace transistor TR5? I recently discovered new information about it. Did you use this thread to order replacements? FD Speedo Components Pg2

I recommend that you remove the instrument cluster and inspect the speedo board for any other problems. You may have a cold solder joint causing the erroneous measurement on the speedometer. Please take photos and post. It is difficult to make an assessment of your board without them.

Cheers,
George
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Old 03-19-18, 08:37 PM
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Originally Posted by Gen2n3 View Post
Groovin,

You are more than welcome for the help. And please, call me George.

Thank you for explaining your circumstances with the car's history. Do the good surprises outweigh the bad surprises? I meant to ask, how are your soldering skills and what tools would you use (if you tackle the repair on your own)? Good on you for ordering both C1 & C5. The replacement caps should arrive quickly from Digikey. Who ever replaced those caps did a good job, too bad the values were off. BTW, do not play with the variable resistor, VR1 unless your rev counter is off. If you use a PFC then you should be able to adjust the needle to reflect the actual RPMs.

To answer your question: yes, C1 is a polarized cap. The cap will have a white stripe to denote the negative leg. It would also be shorter than the positive leg. All you need to do is align the negative leg to the negative hole on the tach board. As you mentioned, the tach board has a negative marking for C1's negative leg.

Thanks for the additional photos. I'll provide commentary on them in the captions.


IC1 solder joints. These look ok but if your tach still jumps around after the capacitor replacement then consider removing and replacing the old solder with new. Other joints on IC1 may need similar treatment.


Speedo board. Clean off the dried flux along these solder joints. Additionally, how do the 4 joints look in the center? Those provide signal & power to the speedometer face (needle). Otherwise, the speedo board looks pretty healthy!


Side view of speedo board. This capacitor is the same cap that you should have on the tach board's C5.

Lastly, I may be a minority voice but I recommend that you do NOT change the bulbs to LEDs. Use the recommended incandescent bulbs for the dash. Generally, LEDs consume less voltage (power) so a ballast resistor is used to mimic the original power consumption in the circuit. In modern cars, the lighting systems are designed around LEDs. IMHO, a brighter dash at night is more of a distraction than an aid to the driver. The dash should be bright enough for the driver to identify switches & read gauges. It should not provide a background glow that may alter one's night vision. But that is a topic for another time.

Does this new info help? Please keep me posted on your progress!

Cheers,
George
Hey George,

I've worked on a circuit board or two and know they are very sensitive to heat so using fine soldering pins and working quickly is best. I have a solder vacuum pump but no desoldering wick, a wired and wireless solder gun, flux but don't think I have anymore flux cored wire. The wire I have is fairly thick too. I'm accustomed to soldering wires but recently began to do more depining and crimping new terminals with spliced in wires to avoid cutting wires and avoid soldering. I don't mind buying supplies or tools. I love to stack up on both. Even If I'll only use a tool once in my life I just need to have it because I love having every tool on hand. This life long endeavor I will never get tired of.

I'd like to say I've discovered more good surprises than bad. Its not that the previous owner did anything bad, its just I like to do things a certain way that emphasizes on reliability, organization, cleanliness, and having the ability to reverse any work that was performed to OEM standards if possible. This of course is only when I'm not lazy. I do take my share of shortcuts sometimes.

I was hoping for a plug in play replacement for the LEDs given the advancements in tech but if that is not yet available then I'll just leave them as is. Might just swap to brighter and long life incandescent then.

Heres an example of what I mean.

Previous owner used a vampire splice clip to tap the cigarette light for 12v ign power for the aftermarket SPA gauges. Whats disconcerting is the fact that they left the spliced wire end exposed making it vulnerable to being grounded.



This is what I did. Pulled out the pin and crimped a new terminal with fresh set of clean wire to work with. Ideally I would run a new set of wire from the battery to an independent fuse block under the dash with a relay that is activated from an ign source (ie cigarette light). That way I have have a new 12v fuse block with multiple power sources for added accessories like gauges and such. but that can always be done at a later time.



Here is a picture of the 4 solder points you requested. They look good. I cleaned them up further after the pictures were taken.





-groovin
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Old 03-19-18, 09:24 PM
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Groovin,

Your speedo board really is clean! I believe the problem truly rests in the tach. I have a general soldering thread that covers tools & equipment that is typically suited for soldering electronic components.

BTW, the wire splice you took a photo of has an insulation break in the blue/black wire. Did you seal the joint and that insulation cut with heat shrink? You could also get away with using liquid electric tape for small breaks.

Good to hear that you find more good surprises than bad.

Cheers,
George
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Old 03-19-18, 10:27 PM
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Originally Posted by Gen2n3 View Post
Groovin,

Your speedo board really is clean! I believe the problem truly rests in the tach. I have a general soldering thread that covers tools & equipment that is typically suited for soldering electronic components.

BTW, the wire splice you took a photo of has an insulation break in the blue/black wire. Did you seal the joint and that insulation cut with heat shrink? You could also get away with using liquid electric tape for small breaks.

Good to hear that you find more good surprises than bad.

Cheers,
George
I'm about to purchase some quadhands to replace my old pair of extrahands, desoldering wick, and a bunch of other toys. I'll review your thread when I'm ready to work on the tacho when the caps arrive.

The speedo works great, odo works great, and the rest of the cluster works great. Outside of the aftermarket gauges the only problem with the cluster is the reset stick for the odo is missing so I can't depress the button when the cluster face is on. On the other hand the aftermarket gauges required some ingenuity on my behalf. Its not as clean as speedhut replacements but I can't deny the convenience of having 2 additional gauge readings. Boost/oil temp, and oil pressure/water temp vs OEM. The previous owner removed the casing of the gauges and hot glued it on the clusters face. The wires are straight shots to the sensors so removal of the cluster require removal of the hot glued gauges. At this point I don't have many options for mounting it so I had to repeat that hot glue gun installation however I cut all the wires, crimped new terminals and placed weather pack connectors on everything so I can remove them along with the other gauges as a whole.

I also beleive the tach issues derive from the caps as we discussed earlier. Keeping finger crossed of course.

The break was definitely addressed. Electrical tape and heat shrinked.

-groovin
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Old 03-20-18, 05:48 PM
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Originally Posted by Gen2n3 View Post
Riccardo,

Thanks for answering my questions.

What part number did you use to replace transistor TR5? I recently discovered new information about it. Did you use this thread to order replacements? FD Speedo Components Pg2

I recommend that you remove the instrument cluster and inspect the speedo board for any other problems. You may have a cold solder joint causing the erroneous measurement on the speedometer. Please take photos and post. It is difficult to make an assessment of your board without them.

Cheers,
George
Ok thank you George
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Old 03-21-18, 07:19 PM
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Initial attempt unsuccessful. Could my soldering be the culprit? I did have some trouble removing the previous caps and ended up delaminating 2 of the metal o-rings the solder adheres to but still got good penetration through and through. Also the caps particularly the .015 appears much different than my expectation. Here are pictures of the work I did and a video of the tach being uncooperative. Just to confirm, only the black connector needs to be connected in order for the tach to operate?

video link below

https://drive.google.com/file/d/12FK0YHcoKFxCCaP8KuGcdMCs5NFBCnz8/view?usp=drivesdk












-groovin

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Old 03-21-18, 08:51 PM
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Groovin,

I have bad news...the board has damaged eyelets. Damaged eyelets are VERY difficult to repair. This is typically caused during component removal. Did you have to pry out the old components? The solder on the 0.015uF cap is excessive. The bond may be physically good however, the damaged eyelet(s) make poor electrical bonds. That could still cause the problem to persist. I recommend connecting all 4 connectors to the instrument cluster, the 2 for the headlight & cruise control are not needed for this check. Is the flat connector from the cluster connected to the speedo board?


Red circles indicate damaged eyelets on the board. They are often difficult to repair!

I don't know what to tell you about the difference in the 0.015uF cap. I do know that the original spec was discontinued and the one listed on my thread is supposed to be a suitable replacement.

I was unable to follow the link you provided. It requires special access.

Cheers,
George
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Old 03-21-18, 09:22 PM
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Originally Posted by Gen2n3 View Post
Groovin,

I have bad news...the board has damaged eyelets. Damaged eyelets are VERY difficult to repair. This is typically caused during component removal. Did you have to pry out the old components? The solder on the 0.015uF cap is excessive. The bond may be physically good however, the damaged eyelet(s) make poor electrical bonds. That could still cause the problem to persist. I recommend connecting all 4 connectors to the instrument cluster, the 2 for the headlight & cruise control are not needed for this check. Is the flat connector from the cluster connected to the speedo board?


Red circles indicate damaged eyelets on the board. They are often difficult to repair!

I don't know what to tell you about the difference in the 0.015uF cap. I do know that the original spec was discontinued and the one listed on my thread is supposed to be a suitable replacement.

I was unable to follow the link you provided. It requires special access.

Cheers,
George
The labeling on the caps and the package was correct and figured the design simply changed. I only connected the black connector and nothing else for the test. I will go ahead and connect everything and retest the tacho. How would I go about verifying contact on the circuit. Can I use a multimeter and check for continuity or anything of that sort? How difficult is an eyelet repair?

Try this link for the video:
https://drive.google.com/open?id=12F...GcdMCs5NFBCnz8

Thanks for chiming in quickly, George.
-groovin

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Old 03-21-18, 11:35 PM
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Groovin,

You could check the trace of each leg from the component side of each leg to another solder joint on the trace side of the board. Follow the trace to a different point. Use the resistance setting, do not use continuity. If the reading fluctuates then consider the joint bad. An eyelet repair requires special skills and experience that would exceed the novice or DIY-er. I would recommend that you seek a professional solder tech to repair a damaged eyelet. Feel free to google "pcb eyelet repair" and see for yourself.

Use this as a guide to take resistance measurements:


Follow the letter sequence.

Place the positive (red) lead on the component side and the negative (black) lead on the trace side. You are only verifying the connection from each leg, through the eyelet (or barrel), to an adjoining solder joint. You should measure a short, or anything close to 0 Ohms.

Sequence:
Component side "A" to Trace Side "B"
Component side "C" to Trace Side "D"
Component side "E" to Trace Side "F"
Component side "G" to Trace Side "H???"*

* - You may have to find the trace for "H???", it may be on the component side. If that is the case, then reverse the connection: Trace Side "G" to the alternate "H" location.

Please post your findings. I hope this helps!

Cheers,
George
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Old 03-22-18, 01:21 AM
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Originally Posted by Gen2n3 View Post
Groovin,

You could check the trace of each leg from the component side of each leg to another solder joint on the trace side of the board. Follow the trace to a different point. Use the resistance setting, do not use continuity. If the reading fluctuates then consider the joint bad. An eyelet repair requires special skills and experience that would exceed the novice or DIY-er. I would recommend that you seek a professional solder tech to repair a damaged eyelet. Feel free to google "pcb eyelet repair" and see for yourself.

Use this as a guide to take resistance measurements:


Follow the letter sequence.

Place the positive (red) lead on the component side and the negative (black) lead on the trace side. You are only verifying the connection from each leg, through the eyelet (or barrel), to an adjoining solder joint. You should measure a short, or anything close to 0 Ohms.

Sequence:
Component side "A" to Trace Side "B"
Component side "C" to Trace Side "D"
Component side "E" to Trace Side "F"
Component side "G" to Trace Side "H???"*

* - You may have to find the trace for "H???", it may be on the component side. If that is the case, then reverse the connection: Trace Side "G" to the alternate "H" location.

Please post your findings. I hope this helps!

Cheers,
George
Hello George,

Here are the numbers. I didn't get a chance to recheck the tach with all the connectors on but I'll do so when I get a chance. Assuming component side is where the tach motor sits and trace side is the RPM face/needle side.

Sequence:
Component side "A" to Trace Side "B" - Resistance 0.1-0.4
Component side "C" to Trace Side "D" Resistance 0.1-0.3
Component side "E" to Trace Side "F" Resistance 0.2-0.4
Component side "G" to Trace Side "H???"* Resistance 0.1-0.4 component side on IC1 pin just next to "1" on IC1 appears to be the trace. (red lead on component side G to black lead on trace side "1")

Resistance seems consistent and low. The readings are very sensitive to movement, I assume, because the contact point is minimal but these are the constants that populate when firm and consistent contact is applied when I'm able to manage.

Picture of component side for trace between G and 1. Is this the correct trace location for G? 2nd pin which is between VR1 and IC1 labels.


If I do need to, I might be willing to tackle the task of repairing the eyelets. Of course it means I would need more tools and supplies. (aka toys).
eyelet repair video I watched.

-groovin

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Old 03-22-18, 11:04 PM
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Groovin,

Thank you for posting the results and pic. Nicely done! Those resistance values indicate a good connection. If the tach still bounces, you may want to de-solder then remove IC1. Clean up the rest of the eyelets of IC1 then reinstall it with fresh solder. IC1 has a notch on one side of the chip. That is an index mark; Pin 1 is always to the left of the index notch.

And please, do NOT force this chip out or damage the eyelets! Too much heat or excessive force will easily damage an eyelet. The pins of IC1 can easily bend/break. BTW, this chip cannot be purchased new! It must be scavenged.

Cheers,
George
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Old 03-22-18, 11:07 PM
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So initial attempt was successful after all. Tach is smooth as butter. Before I did the trace I noticed the 3 bolts holding the tach in place were loose and came off easily. Immediate suspect on why the tach did not want to cooperate. Assuming the trace through the eyelets and to the pathways were good I figured it had to have been a bad connection. Also taking your input into consideration I plugged in all 4 main connectors for the second test. Started the car up and instantly the tach does what it was engineered to do, read rpms.

George you've been great help. I appreciate all your guidance and glad to have you as a member of the community. I'll get a video of the working tach when I get a chance. Thanks again!

-groovin
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Old 03-22-18, 11:12 PM
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Groovin,

Thank you very much for the compliments! I'm glad to help. Feel free hit that "thank" button on any relevant post throughout this process. I look forward to seeing your video confirming the tach works!

Cheers,
George
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Old 03-23-18, 01:44 PM
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Originally Posted by Gen2n3 View Post
Groovin,

Thank you very much for the compliments! I'm glad to help. Feel free hit that "thank" button on any relevant post throughout this process. I look forward to seeing your video confirming the tach works!

Cheers,
George
Here is a video with a cold engine. I didn't drive it around just rev'd it a bit. Appears to be consistent with the engine sound.

https://drive.google.com/open?id=1mv...YJIYlzGHqnAJwK

-groovin
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Old 03-23-18, 01:48 PM
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Groovin,

Thanks for sharing the video link. Sounds & looks good! Do you have a way to compare the Tach with either an external tach or PowerFC?

Again, I'm glad to see the repair worked!

Cheers,
George
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Old 03-23-18, 02:52 PM
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Originally Posted by Gen2n3 View Post
Groovin,

Thanks for sharing the video link. Sounds & looks good! Do you have a way to compare the Tach with either an external tach or PowerFC?

Again, I'm glad to see the repair worked!

Cheers,
George
Car has an adaptronic select series 6 ecu. Just need to get the program and figure out which connection method it uses to the laptop.

-groovin
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Old 03-23-18, 10:38 PM
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So I got a chance to thoroughly test it it and discovered it is finicky at 3k rpm. When the RPM climbs or drops pass the 3k mark it goes crazy but immediately returns to normal afterwards. Holding throttle at 3k RPM and the tach spikes up and down until the RPM drops below or goes above 3k. The rest of the RPM bandwidth is fine. Any ideas? On a side note, I was able to confirmed tach is calibrated with adaptronic ecu.

Sorry to bug you again, George.
-groovin
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