Help troubleshooting tachometer or finding replacement parts (1 Viewer)

[shado]

Hello all,

I’m new to the group and have been searching all prior threads that have to do with broken tachometers. Unfortunately it looks like I still haven’t found an answer. Here is my issue: I have a 1992 FJ80 3FE (US spec) that has an inoperable tachometer. I verified that igniter signal is working (with AC reading from a multimeter) both at the diagnostic connector and at the C4 pin of the combination meter. I took the cluster apart but can find anything obviously wrong with the circuit nor can I find part numbers of items I could replace. Does anyone have experience with this? Anyone have part numbers? Anyone have a source of a replacement tachometer?

Thanks!

 

[SmokingRocks]

unfortunately the solution is usually a “replace the guage bezel”.

I dont think anyone has gone through the trouble to trace the issue, even though it is a common one.

I ended up just going with a custom guage cluster

 

[efjayatee]

Did that, tried that and ended up buying a Bosch Tach gauge.

 

[SmokingRocks]

Was it a lot of work.... Yes.....

here is the thread

Custom Gauge Cluster

Welp after loosing my tach, oil pressure gauges and trip meter (with my speedometer getting real twichy) I have decided that it is time to do a completely custom gauge cluster. I'm going to mount this in a stock housing so that I can keep the caution lights on the bottom. I've priced out the...

forum.ih8mud.com

 

[ppc]

Hello all,

I’m new to the group and have been searching all prior threads that have to do with broken tachometers. Unfortunately it looks like I still haven’t found an answer. Here is my issue: I have a 1992 FJ80 3FE (US spec) that has an inoperable tachometer. I verified that igniter signal is working (with AC reading from a multimeter) both at the diagnostic connector and at the C4 pin of the combination meter. I took the cluster apart but can find anything obviously wrong with the circuit nor can I find part numbers of items I could replace. Does anyone have experience with this? Anyone have part numbers? Anyone have a source of a replacement tachometer?

Thanks!

View attachment 2821175

Looking at the back side with the solder joints they're some that don't look very conductive. There are three at the top center and at least one near the nuts. I would start by heating every solder pad making sure they are no cold joints. Anything that doesn't look smooth and shining is suspect.

 

[shado]

Was it a lot of work.... Yes.....

here is the thread

Custom Gauge Cluster

Welp after loosing my tach, oil pressure gauges and trip meter (with my speedometer getting real twichy) I have decided that it is time to do a completely custom gauge cluster. I'm going to mount this in a stock housing so that I can keep the caution lights on the bottom. I've priced out the...

forum.ih8mud.com

Oh dang, that does look awesome though! but looking at those gauge prices i don't want to go broke trying to fix this tach lol.

 

[shado]

Looking at the back side with the solder joints they're some that don't look very conductive. There are three at the top center and at least one near the nuts. I would start by heating every solder pad making sure they are no cold joints. Anything that doesn't look smooth and shining is suspect.

yeah the corrosion or whatever was on some of the joints i cleaned up. Next task will be to see if i can fix some solder joints, but im skeptical it will work. I also tried to look up the datasheet for the IC chip on there to no avail. If possible i would like to get a hold of a working factory tachometer so i can get some voltage readings and track down the broken component. Besides the IC chip and the motor, pretty much everything is easy to source resistors, capacitors, and zener diodes.

 

[gummycarbs]

Did you check for continuity between the solder joints on each circuit? That was the giveaway for the corroded traces on my speedometer circuit board.

 

[Comet]

Top right of the picture. Brown circle coming off the negative screw lead. Is the solder supposed to be separate, together, or what? Its the only thing on that board screaming at me.

 

[William BB]

2025 update. Tachometer fixed for $2. Followed the 90s MR2 and Supra forums and found that our tachometer board has 2 capacitors that are a high fail item. My 94' has a 6.8uf at 25v and a 100uf at 25v. I replaced both. Of note the 6.8 was leaking so I had a visual sign I was close to my fault. Background. My tach would work in the heat of the day when my dashboard was warm, I knew it had to be a component that was changing value with heat. Most of the board is solid state devices and assumed another reason it was the caps. I bought the two capacitors at a local electric store and now the tach works. Hope this helps. Note: Remember, you have to match the farad rating but you can go up in voltage for the replacement capacitor. (I.e. I have a 100uf at 50v vice the 25v).