OK I just got done searching through 10 pages of people saying to resolder the tach. I only ran across a few people that this actually worked for... What if it didn't work, any thoughts on what to do next?

I was talking to a buddy this past week and he said that he put in 3 other whole clusters and it still didn't fix his tach problem. He and I have the same issues. Our problem started after our new engines were dropped in by the way. I've checked every connection I could find and they are all connected and making good contact.

My tach only works every once and a while. When it does work it bounces everywhere most of the time. Only rarely will it stay steady and act right.

I'm going to take my cluter apart and resolder it soon but what if this doesn't fix my problem? What if I replace my whole cluster and still have the same problem? Any thoughts? I just want my tach to work, is that too much to ask for???

 

If the problem arose when you put the engine in, it might be a problem with the ignition harness or the wiring to the coils. The tach gets a signal back from them, if the signal or wiring is flaky, you could have tach problems.

Dale

 

^^

Agreed.

Erratic tach readings are usually a sign of ignition problems (tach and wiring to the tach is working correctly, but the ignition problems give bad signals) or the wiring from the ignition to the tach is intermittent, or picking up electrical noise from the high-tension wires, etc.

Did you use non-resistor HT wires, or install a higher capacity ignition system?

 

I'll recheck all that, thanks for the idea. I put a new wiring harness in to help get rid of problems like this...

 

I had the proverbial "bouncing" tach problem a few months back. The needle would bounce all over the place one minute and then just lay dead the next. After resoldering all the connections and replacing a bad resistor, it works like a champ. I don't know if doing that will fix yours but it worked for me.

 

I'm using the same ignition set-up as before. Taylor plug wires and a HKS twin power with the stock coils. All that was added was the engine and a new set of turbos. That and the new wiring harness.

 

I resoldered my tach and changed the capacitors and it worked fine !

 

Alright I found this somewhere about 6 months ago. I don't know who wrote it because this is what I was really looking for when I was flipping through those 10 pages of threads... Are these capacitors easy to replace??? And does this below pretty much sum up the process??? Thanks!

"Well, I can detail the entire process now.... to get to the dash, take of the steering wheel column cover (two screws, then gently squeeze/pull apart) then several screws to loosen the gauge cluster part of the dash (see RX7 manual at iluvmyrx7.com for diagrams). Three very tight push clips hold this part of the dash around the top. I used a screwdriver to pry apart the two sections of the dash to an extent and pulled and wiggled to get it off, it was quite difficult. Be very careful to watch the rest of the dash when you're pulling, as I pulled too hard and have a some misaligned pieces now (rampant cursing.....). There are about six to eight wiring harnesses to unclip, I had someone in the passenger seat reach over while someone outside the car looking in the windshield guided them, because the wires are very short and don't allow much visual inspection. Unclip all those by squeezing the tabs) and twist to loosen the light for the cigarrette lighter and it will pop out. Then remove that section of dashboard from the car. Several screws hold the cluster into the dash, remove these and press in the clips from one side to the other to separate the two halves. This can be difficult, as the clips want to pop back in as soon as you go on to the next one. You can use pennies inserted between the halves to keep them apart, and more than two hands helps as well. Then unscrew the tachometer from the plastic base. Apparently the solder joints that were cracked on my tach (as described in other posts) are the round ones on the very back of the tach... they are hard to find the first time, and are between the white plastic electric part of the tach and the face...look between these two pieces to find them. Mine were indeed cracked, exactly as described elsewhere. You must remove the needle to get the face off. Be careful with this, it is easy to break. The flourescent part of the needle is what is attached to the motor, not the black. I held the needle portion with thumb and forefinger on both sides of the black and used leverage against the gauge face to pull it off... seemingly no other method/amount of tugging worked (you must be firm, but pull it straight up!). It is tight.

With the needle off you can separate the face from the motor and get to the joints. I resoldered all of them, even though only a couple were cracked (use a magnifying glass to see better).

Now, with all that said, beware that this DID NOT fix my tach problem, even though my solder joints were definately cracked. I am going to take everything apart again this weekend and try again. The posts underneath the joints could also be cracked apparently, and I will inspect those as well. My problem has also seemingly been ignition wire related, so it may be a combination of things. Oh, and I didn't get the needle recalibrated correctly either with the method I used.... so if anyone has a sure-fire method fill me in. I have confidence this is at least part of my problem, if anyone has any questions PM me I'd be glad to at least offer more of what was involved."

 

Oh yeah, I checked all my connections that I could think of and still no luck. I guess I'll try the resoldering now. I hope that does the trick...

 

AgentSpeed -

Yeah those instructions are pretty good, but FDjunkie hooked me up with some sweet instructions with pictures included (especially helpful for aligning the needle properly). I bought the capacitors online at mouser.com (Radio Shack didn't have jack!) and ended up bringing the circuit board to a local TV repair shop and had a professional do it... I don't trust myself with a soldering iron and a magnifying glass! He resoldered all the connections along with replacing both capacitors, he said it was a breeze (He only charged me $20, I think it was well worth it). You should PM FDjunkie and see if he still has those instructions, I'd give them to you but I don't have access to my home computer right now. I might be able to get them for you in the next day or so...best of luck

 

I would like a copy of those as well. Thanks.

 

xcelir8-

No prob, I'll let you know when I find them, should be today sometime. I'll PM you.
And anyone else who wants them just PM me, thanks.

 

If the tach gradually builds, suspect a capacitor problem. You can check the diagnostic terminal for a square wave tach signal. This will help you understand if there is a signal to start with. Also, look in the shop manual for the tach terminal on the ECU. You can check it there. Then, you can check the tach signal behind the dash for a square wave.

If the needle moves at all, the windings are good and the circuit just needs repaired. If the tach is totally dead, you might also conisder the Speedo because that is where the signal comes through..

A normal tach has a point about midway that will allow need to swing either to full or to zero.

Twist the needle against the full scale stop before trying to pop it off. Note the mark before twisting to recalibrate on assembly.

The face turns 90 degrees before it will come off..... You need to dismantle it this way to get to the electronics.

 

Sorry for bringing up the old thread.. but did you get this fixed??

I'm confused about the soldeing thing? Where do you solder?? ON the tach?? I've tried 3 cluster on a friends car and all did the same. And I know at least 2 of them are good clusters.

Anyone know which wires are from the ecu to tach?? I lost my shop manual.

 

I haven't messed with it yet. Drew told me that he checked the ground next to the coils and it made his work. My coils were relocated so I need to pull the UIM and check the ground. It could be my ground wire since the bracket has been moved. I hope so at least. I've just been lazy...

 

I still have my write-up for the DIY tach repair. In fact I've updated it a couple of times over the last two years since I orignally repaired my own tach; which is still working great. PM me with your e-mail address for a copy.

 

yep, FDjunkie e-mailed it to me and I executed the tach repair and no more bouncy tach. Be careful realigning the needle for the tach other wise it will be incorrect. I had an electronic repair shop do the soldering and cap replacement for me, $20.00. Or you can do it yourself.