extremely simple FD tach/ odometer repair - Page 2 - RX7Club.com - Mazda RX7 Forum

Go Back  RX7Club.com - Mazda RX7 Forum > Tech and Performance > Interior / Exterior / Audio
Reload this Page > extremely simple FD tach/ odometer repair
Interior / Exterior / Audio Talk about interior and exterior mods including audio.
Sponsored by: CARiD

extremely simple FD tach/ odometer repair

Reply

 
 
Old 06-29-16, 02:50 PM
  #26
Junior Member
iTrader: (13)
 
jakewah's Avatar
 
Join Date: Feb 2016
Location: Tulsa, Ok
Posts: 35
Thanked 3 Times in 3 Posts
Not a solution but just a note:

The speedometer and tachometer are somehow connected. I mentioned that because of my jumper wire, I must have the lights on for the tach to work. They also must be on for the speedometer and odometer to work.
jakewah is offline  
Reply With Quote
Old 11-17-16, 05:45 AM
  #27
Full Member
 
psyposa's Avatar
 
Join Date: Nov 2016
Location: Germany
Posts: 53
Thanks: 0
Thanked 0 Times in 0 Posts
I have the same issue right now.
My Tachometer stops working.
Any news which wire has to be jumpered for the tach signal?
I will go this way before soldering something.
psyposa is offline  
Reply With Quote
Old 11-17-16, 10:20 AM
  #28
Time or Money, Pick one
iTrader: (31)
 
silverTRD's Avatar
 
Join Date: Oct 2005
Location: Torrance, ca.
Posts: 2,605
Thanks: 0
Thanked 2 Times in 2 Posts
Its pin 2b on the ecu pinout diagram.
silverTRD is offline  
Reply With Quote
Old 11-17-16, 12:04 PM
  #29
Full Member
 
psyposa's Avatar
 
Join Date: Nov 2016
Location: Germany
Posts: 53
Thanks: 0
Thanked 0 Times in 0 Posts
Thank. It was really funny today.
Changed the stock ecu through the Apexi and viola, the tach lives
psyposa is offline  
Reply With Quote
Old 11-17-16, 02:00 PM
  #30
Junior Member
iTrader: (13)
 
jakewah's Avatar
 
Join Date: Feb 2016
Location: Tulsa, Ok
Posts: 35
Thanked 3 Times in 3 Posts
Caution note: When jumping the wires did not work I attempted switching the wires to make sure I didn't have it wrong. Something I did killed the speedometer too. Whoops!
jakewah is offline  
Reply With Quote
Old 11-23-16, 06:54 PM
  #31
Full Member
iTrader: (2)
 
redheddude222's Avatar
 
Join Date: Dec 2008
Location: Evansville, IN
Posts: 235
Thanks: 0
Thanked 0 Times in 0 Posts
Everything in my cluster works except for the odometer, so I tried this fix today. The yellow/blue wire didn't have voltage when the key was on, but the black/yellow wire next to it did. So I used that black/yellow wire as my voltage source, and I tapped the ground into the cigarette lighter ground.

No change. Everything still works except for my odometer. I've already tried soldering in new capacitors behind the speedo. The odometer's back light lights up now, but I still just have faint 8s all the way across both lines.
redheddude222 is offline  
Reply With Quote
Old 01-08-17, 03:19 AM
  #32
Can Post Only in New Member Section
 
Join Date: Dec 2016
Location: Long Beach, CA
Posts: 2
Thanks: 0
Thanked 0 Times in 0 Posts
So, have been carefully checking the published wiring diagrams and come to the following conclusions:


1) Ground that goes to the tachometer is pin 1E on the 8-pin connector at the back of the instrument panel. This is a Black wire with Blue stripe. This wire also goes through the X-18 20-pin Blue connector on the dash structure behind the instrument panel.


2) +12V power for the tachometer should come from Pin 2D on the 10-pin connector at the back of the instrument panel. This is a Black wire with Yellow stripe. This wire also goes through the X-18 20-pin Blue connector on the dash structure behind the instrument panel.


3) Signal for the tachometer should come from pin 3F on one of the 12-pin connectors at the back of the instrument panel. This is a Yellow wire with Blue stripe. Be careful because there is also a Blue wire with Yellow stripe on the other 12-pin connector, so make sure you get the colors right. The correct wire goes through a number of connectors back to pin 2B on the ECU. It also goes to the pin labeled IG- on the test connector in the engine bay.


Hopefully, that clears up the confusion about which wires should be connected to what and gives people options for jumpering to get the instruments working again.
NPrincen is offline  
Reply With Quote
Old 01-17-17, 03:35 PM
  #33
Junior Member
 
Join Date: Aug 2016
Location: Ontario, Canada
Posts: 7
Thanks: 0
Thanked 0 Times in 0 Posts
Going to try repairing my OEM cluster myself after reading this. Thanks for posting this up
JDMREFD3S is offline  
Reply With Quote
Old 01-17-17, 04:35 PM
  #34
Rotary Enthusiast
 
Join Date: Aug 2008
Location: Portsmouth UK
Posts: 1,013
Thanks: 0
Thanked 0 Times in 0 Posts
anyone had any oil pressure gauge issues that were the gauge and not the sender? I fixed my tach and now my oil gauge has died. I tried a second sender and it still doesn't work so I am pretty sure it is the gauge!?
Leeroy_25 is offline  
Reply With Quote
Old 07-12-17, 06:50 PM
  #35
Rotor Head Extreme
iTrader: (8)
 
t-von's Avatar
 
Join Date: Apr 2002
Location: Midland Texas
Posts: 6,679
Thanks: 0
Thanked 2 Times in 2 Posts
Gotta bump this one. I have a problem with 94 cluster. Speedometer works find but my odometer no longer works. My cruise control also stopped working when the odometer went out. Anyone have any experience with this?
t-von is offline  
Reply With Quote
Old 07-12-17, 07:19 PM
  #36
Rotary Enthusiast
iTrader: (1)
 
Gen2n3's Avatar
 
Join Date: Jun 2004
Location: Virginia Beach, VA
Posts: 894
Thanked 43 Times in 41 Posts
VA Fix FD Odometer & FD Speedometer Circuit Board Components

t-von,

Refer to these threads to help fix your odometer. Read them to its entirety. There are a lot of good info to take in.

just got done figuring out how fix fd odometer

FD Speedometer-Odometer Circuit Board - Odometer Components

Cheers,
George
Gen2n3 is offline  
Reply With Quote
Old 07-13-17, 02:53 PM
  #37
Rotor Head Extreme
iTrader: (8)
 
t-von's Avatar
 
Join Date: Apr 2002
Location: Midland Texas
Posts: 6,679
Thanks: 0
Thanked 2 Times in 2 Posts
Thx for the links. Seems my C3 capacitor leaked.
t-von is offline  
Reply With Quote
Old 07-13-17, 04:41 PM
  #38
Rotary Enthusiast
iTrader: (1)
 
Gen2n3's Avatar
 
Join Date: Jun 2004
Location: Virginia Beach, VA
Posts: 894
Thanked 43 Times in 41 Posts
Any time. Glad to lend a hand. You may also want to use the ...fix odometer... thread for further updates to the repair.

I also recommend taking multiple angle photos of the circuit board since the speedo is removed. It may be useful on future repairs!

Cheers,
George
Gen2n3 is offline  
Reply With Quote
Old 07-15-17, 03:01 PM
  #39
Rotor Head Extreme
iTrader: (8)
 
t-von's Avatar
 
Join Date: Apr 2002
Location: Midland Texas
Posts: 6,679
Thanks: 0
Thanked 2 Times in 2 Posts
Originally Posted by Gen2n3 View Post
Any time. Glad to lend a hand. You may also want to use the ...fix odometer... thread for further updates to the repair.

I also recommend taking multiple angle photos of the circuit board since the speedo is removed. It may be useful on future repairs!

Cheers,
George
Well I changed out the capacitor with a panasonic piece from the links and still no workie.
t-von is offline  
Reply With Quote
Old 07-15-17, 03:03 PM
  #40
Rotor Head Extreme
iTrader: (8)
 
t-von's Avatar
 
Join Date: Apr 2002
Location: Midland Texas
Posts: 6,679
Thanks: 0
Thanked 2 Times in 2 Posts
t-von is offline  
Reply With Quote
Old 07-15-17, 03:16 PM
  #41
Rotary Enthusiast
iTrader: (1)
 
Gen2n3's Avatar
 
Join Date: Jun 2004
Location: Virginia Beach, VA
Posts: 894
Thanked 43 Times in 41 Posts
Tvon,
Please post your repair remarks to the fix odometer thread. That will prevent inadvertant hijacks and keep the thread relevant to the original post.
Cheers,
George
Gen2n3 is offline  
Reply With Quote
Old 08-28-17, 06:23 PM
  #42
Junior Member
 
Join Date: Aug 2017
Location: NV
Posts: 26
Thanked 11 Times in 11 Posts
NV 12V may be more than stock tacho board supply voltage...

The tacho board normally gets its power from the speedo board. I've been testing my speedo/tacho boards recently. When I apply 12V to my speedo board it only outputs around 7V to the tacho board, so 12V appears to me to be more than the designers intended for the tacho board (though 12V may be perfectly safe as evidence from all those using 12V suggests). If I remember correctly, my tacho board functioned with even 6V power supply power when I was testing the board on my bench.
ALIENR2 is offline  
Reply With Quote
The Following User Says Thank You to ALIENR2 For This Useful Post:
Gen2n3 (09-02-17)
Old 09-02-17, 08:51 PM
  #43
Junior Member
 
Join Date: Aug 2017
Location: NV
Posts: 26
Thanked 11 Times in 11 Posts
NV Partial speedometer board circuit diagram

I saw strange tacho and speedo needle glitches at first and eventually both gauges stopped working at all (needles did not move) and I got code 06 (No Speedometer Sensor Signal).

My speedo board's capacitor "C3" (1000uF) was leaking like others, but "IC4" (LM2903, comparators, used for sensor signal processing) was my main problem; it had partially failed such that "OUT2" had large noise when changing state. "OUT2" supplies processed speed sensor signals to the speedo board CPU (D751...,for the "4P" signal back to the PCME for code 06) and to the speedo motor driver chip (AN8363UBK) for making the speedo gauge needle move.

I note that the speedo board does not simply pass the TAM signal (instrument console connector 3F) through to the tacho board; connecting 3F directly to the tacho board signal screw is not what the designers intended, though I don't know if it's hazardous to the tacho board or PCME to do so.
Attached Thumbnails extremely simple FD tach/ odometer repair-fd-speedo-board-ic4-circuit-diagram-2.jpg   extremely simple FD tach/ odometer repair-speedo-board-ribbon-connector-signals-my-reference-designator-assignment-where-connect-.png  

Last edited by ALIENR2; 09-02-17 at 09:07 PM.
ALIENR2 is offline  
Reply With Quote
The Following User Says Thank You to ALIENR2 For This Useful Post:
Gen2n3 (09-02-17)
Old 09-02-17, 09:05 PM
  #44
Junior Member
 
Join Date: Aug 2017
Location: NV
Posts: 26
Thanked 11 Times in 11 Posts
NV TAM (instrument console connector 3F) reference data

I observed TAM using an oscilloscope. It looks like the PCME outputs two ~1.4ms tach pulses per output shaft revolution. The tach pulses appeared to be ~15V magnitude which seems large.
Attached Thumbnails extremely simple FD tach/ odometer repair-tachometer-signal-pcme-speedo-board-measured-fd.jpg  
ALIENR2 is offline  
Reply With Quote
The Following User Says Thank You to ALIENR2 For This Useful Post:
Gen2n3 (09-02-17)
Old 09-02-17, 09:20 PM
  #45
Rotary Enthusiast
iTrader: (1)
 
Gen2n3's Avatar
 
Join Date: Jun 2004
Location: Virginia Beach, VA
Posts: 894
Thanked 43 Times in 41 Posts
AlienR2 (Jeff), Excellent troubleshooting work and nice schematic diagram!

I believe the depth of your research exceeds the scope of this particular thread, as it is meant to be a quick fix. However, I understand your caution and equally agree with it - directly wiring the tach via the mounting screws is a hazardous proposition that could easily cause more harm than good.

Since your information is detailed, may I suggest beginning a new thread to document your progress and allow others to follow in your footsteps? There is also a good amount of detailed info here: just got done figuring out how fix FD odometer that could also provide as reference material.

How did you trace out the IC4 circuit? Seriously, that was nice work!

Cheers,
George
Gen2n3 is offline  
Reply With Quote
Old 09-02-17, 09:45 PM
  #46
Rotary Enthusiast
iTrader: (1)
 
Gen2n3's Avatar
 
Join Date: Jun 2004
Location: Virginia Beach, VA
Posts: 894
Thanked 43 Times in 41 Posts
Originally Posted by ALIENR2 View Post
I observed TAM using an oscilloscope. It looks like the PCME outputs two ~1.4ms tach pulses per output shaft revolution. The tach pulses appeared to be ~15V magnitude which seems large.
It would make sense that the +15V amplitude is used to drive the tachometer motor and its frequency determines the amount of deflection on the tach needle because the tach board also has an AN8363UBK chip (IC1 on the tach board).
Gen2n3 is offline  
Reply With Quote
Old 09-03-17, 11:20 AM
  #47
Full Member
Thread Starter
iTrader: (5)
 
Join Date: Aug 2009
Location: Wales, MA
Posts: 69
Thanks: 0
Thanked 0 Times in 0 Posts
Originally Posted by ALIENR2 View Post
I saw strange tacho and speedo needle glitches at first and eventually both gauges stopped working at all (needles did not move) and I got code 06 (No Speedometer Sensor Signal).

My speedo board's capacitor "C3" (1000uF) was leaking like others, but "IC4" (LM2903, comparators, used for sensor signal processing) was my main problem; it had partially failed such that "OUT2" had large noise when changing state. "OUT2" supplies processed speed sensor signals to the speedo board CPU (D751...,for the "4P" signal back to the PCME for code 06) and to the speedo motor driver chip (AN8363UBK) for making the speedo gauge needle move.

I note that the speedo board does not simply pass the TAM signal (instrument console connector 3F) through to the tacho board; connecting 3F directly to the tacho board signal screw is not what the designers intended, though I don't know if it's hazardous to the tacho board or PCME to do so.
I understand your concern, and you clearly went way above what I did for this since my original post.

that being said, I have been running my tach signal to the tach directly for a few years now, since I removed my speedo for a Speedhut gauge, I no longer have the factory speedo. I have had no issues with it.

Full disclaimer, I am LS1 swapped, so my tach signal is not a factory signal, either, it is from the LS1 pcm.
Attached Thumbnails extremely simple FD tach/ odometer repair-20170527_120443-large-.jpg  
jeffp is offline  
Reply With Quote
Old 09-03-17, 08:29 PM
  #48
Junior Member
 
Join Date: Aug 2017
Location: NV
Posts: 26
Thanked 11 Times in 11 Posts
NV

Originally Posted by Gen2n3 View Post
AlienR2 (Jeff), Excellent troubleshooting work and nice schematic diagram!

I believe the depth of your research exceeds the scope of this particular thread, as it is meant to be a quick fix. However, I understand your caution and equally agree with it - directly wiring the tach via the mounting screws is a hazardous proposition that could easily cause more harm than good.

Since your information is detailed, may I suggest beginning a new thread to document your progress and allow others to follow in your footsteps? There is also a good amount of detailed info here: just got done figuring out how fix FD odometer that could also provide as reference material.

How did you trace out the IC4 circuit? Seriously, that was nice work!

Cheers,
George

Thanks!

I found that backlighting the circuit board was key to following the traces. A good flashlight will work; put the flashlight right on the board on one side and look at the board from the opposite side, with magnifying glass as needed. Components attached to the board are in the way (you can't always see where the traces go), so I also tested for continuity using a Digital Volt Meter as needed for confirmation.
ALIENR2 is offline  
Reply With Quote
Old 09-03-17, 08:34 PM
  #49
Junior Member
 
Join Date: Aug 2017
Location: NV
Posts: 26
Thanked 11 Times in 11 Posts
NV

Originally Posted by Gen2n3 View Post
It would make sense that the +15V amplitude is used to drive the tachometer motor and its frequency determines the amount of deflection on the tach needle because the tach board also has an AN8363UBK chip (IC1 on the tach board).

The 15V tach pulses seemed large to me because I expect automotive electronics signals to usually be less than 12V (i.e. battery voltage, which can be closer to 13V with a healthy battery, and up to 14V when the engine is running due to a healthy alternator, but 15V? Confirmation measurements from another car/oscilloscope/human desired, though the paragraph below includes a partial confirmation). Ignition signals (much higher than 12V) are a different story, of course. I note that the crankshaft position sensor plate (shown on sheet F-166 of "1994 Workshop Manual") only has one 'finger' sticking out of it for making the "G-signal", so my guess that the G-signal (one pulse per output shaft revolution) was the source of TAM (two pulses per rev) was wrong. Of course, the PCME could have been made to use the G and NE signals to make TAM with any number of pulses per rev.

While troubleshooting the speedo board I applied digital signals to the board inputs (where the ribbon cable connects) to try to test IC4 and found that 5V(0V Low and 5V High) signals resulted in very small amplitude signals at IC4 inputs (IN1+ and IN2+); I increased the voltage in steps and eventually was applying 12V signals and still the signals at IC4 inputs were small and not triggering IC4 outputs to change state, so I was really confused (wondering how many things were broken) until I observed that TAM was even larger than 12V. For testing IC4 outputs, it was easier to apply (4V) test signals directly to IC4 inputs (IN1+ and IN2+). IC4 runs on 5V (measured 5.2V).

My tacho board has an AN8352UBK, and my speedo board has an AN8363UBK. Both are clearly motor driver chips and have the same package (Skinny DIP22, so they will not fit into a normal breadboard, unfortunately) and maybe the same pin assignments. I'm curious if they can be used interchangeably, but I'll try that experiment when I don't have an exact replacement when I need one. These chips are non-commercial (i.e. hard to find new chips or even datasheets). I've found them at junkyards in 1994 and 1995 (and maybe other years have them too) Nissan Pathfinders (same applications in speedo and tacho boards). A manufacturing date code "11/95" Pathfinder still had a AN8352UBK on its tacho board (the printed board is identical to our board but has some different component values that look to me like it might use 12V supply power), but the speedo board design had changed and no longer had an AN8363UBK on it. I only started looking for an AN8363UBK because I thought mine might be failed (it was not failed) and then picked up a couple just in case, since they are hard to find.

One puzzle is that these chips connect to the speedo/tacho motors using 4 traces, so I assumed that the motors are stepper motors, but my oscilloscope does not show Hi-or-Low stepper driver signals like I would expect when measuring the 4 traces, so I'm not sure what kind of motors they are.
ALIENR2 is offline  
Reply With Quote
Old 09-04-17, 03:35 PM
  #50
Rotary Enthusiast
iTrader: (1)
 
Gen2n3's Avatar
 
Join Date: Jun 2004
Location: Virginia Beach, VA
Posts: 894
Thanked 43 Times in 41 Posts
Jeff,

I like your approach to tracing out the circuit. That was very cool! I will try that out on the next circuit board I examine.

Regarding the I/O signals for IC4, you venture into uncharted waters with dedicated bench testing. I like your methodical approach!

Thank you for correcting me on the different motor driver IC part numbers between the tach and speedo. At first glance, they looked the same; damn older eyes. However, the photos and parts list accurately reflect the proper part numbers that you so kindly verified.

Getting back to the 15V signal, it could be possible that TR8 amplifies a logic 1 (+5V) to the desired voltage. Most of the "TRx" transistors are actually Darlington Pair transistors. They typically offer tremendous signal amplification because they are 2 transistors combined into 1. I know it may seem odd to see voltages in excess of 12V (or 14 when alt is working) on a car but (to me) it is plausible to see that 15V pulse serve as a motor driver when a Darlington Paired transistor is used. I wish I could offer more info regarding stepper motors however, I would have to research more on that electrical component.

Cheers,
George
Gen2n3 is offline  
Reply With Quote
 
 
 

Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Coochas
1st Generation Specific (1979-1985)
30
10-01-17 12:30 PM
Turblown
Vendor Classifieds
5
12-18-15 11:14 PM
PhEnX
Old School / Other Rotary Vehicles and Parts
4
11-05-15 12:36 AM
demetlaw
3rd Generation Specific (1993-2002)
6
10-02-15 07:22 PM
zephyr07
2nd Generation RX-7 (1986-1992) Vehicles
0
09-29-15 10:54 AM


Thread Tools
Search this Thread
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 06:12 AM.


All content Copyright 2007 by Internet Brands, Inc. We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: