Tachometer is under reading

[KaroriPete]

Hi,

I have a 1991 auto MR2. I recently noticed that the tachometer is reading way too low. Idle shows as about 100 rpm. Driving around town it won't show much more than about 1000 rpm, maybe getting to 1500 or so if you accelerate hard.

Does anyone have any ideas where the problem might be?

Thanks,
Pete.

[GDII]

There are 2 capacitors on the back of the tachometer that get heat damaged. My 1990 did it. Was reading 3k at redline. I replaced them with new capacitors from jaycar and its worked perfect since.

[Benckj]

^^ good to know. Might change mine out anyway when I pull gauge cluster for LED mod.

[GDII]

Yeah prefect time to do it. You will see they are a bit black where they shouldn't be. I can't remember what specs the capacitors were though.

[KaroriPete]

There are 2 capacitors on the back of the tachometer that get heat damaged. My 1990 did it. Was reading 3k at redline. I replaced them with new capacitors from jaycar and its worked perfect since.

Great, that sounds like it's probably it. Looks like the tricky part of the fix is getting the instrument cluster out .

Thanks very much for your help,
Pete.

[GDII]

No problem. Here is how to remove the cluster.
http://www.mr2.com/forums/threads/29633 ... ster-Bulbs This link is good
http://www.speedview.co/forum/Thread-In ... prox-91-92" EDIT: This link is now dead.

Here is how to replace the capacitors.
http://mr2.noegruts.com/tachometer/tachometer.htm EDIT: This link is now dead. Refer a few posts down for capacitor specs and photo.

[Benckj]

Interesting read on the HUD mod. I looked into this a year or so ago but the unit being developed did more than just speed. It had RPM, boost and a couple other sensors you could switch between. It did get quite complicated and expensive from that point of view.

[MR2SIK]

Anyone got a link that works for how to replace the capacitors?
New toys just started doing the same thing

[GDII]

I should have taken photos and added a bit more info to my project thread when I did this. Not good that the only source is no longer working.

If you click on this link the images come up on the search but they don't work in the website they are from. http://www.google.co.nz/search?client=m ... igeGo4CoBA" onclick="window.open(this.href);return false;

The first 3 photos are enough to help I think. Just get the correct capacitors or slightly higher rating. I think my replaced mine with 60v instead of 50v. Maybe someone on here knows how electronics works to confirm which number can be higher. The link I previously provided said you can get a higher rated one and it works, which I did on my car and its worked for 2 years with no issues.

EDIT: obviously replacing with what is already there would be best. Can't remember what they are but you will see when you remove the tachometer.

[JasonFriday13]

50V is the maximum voltage it will handle. Cars generally never see more than 15V, but the manufaturers play it safe and put higher voltage parts in to be 100% sure it won't fail from a voltage spike.

[GDII]

Yeah I figured that would be the case. The 50v one I think is higher than stock rating which I think was 40v. If that's the case then the 10uF is what it needs to be. The higher the voltage the larger the capacitor gets in physical size so don't over do it or it won't fit in the gauge.

[GDII]

Seeing as there doesn't seem to be any info about the specs for the capacitors on the internet, here is what I have put in my car as a fix. I did this over 4 years ago and never had any issues.

2x 10uF 25V capacitors. Keep in mind that the voltage rating for the replacements is higher than the factory (which I can't remember what it was) but that is better than lower.

[mickeyduck]

Nice info, this will be very useful to a number of folk as time goes on, as all these things will fail in similar manner, seeing as they are mass produced.

We too have an SW with naffed tacho here (Isaac's) so it'll be a common problem alright...

Thanks for the info *****

[GDII]

It's a very common problem. The capacitors get heat damaged and go black or explode/pop the their lids. It's a pretty easy fix. Hardest bit is unplugging the mechanical speedo cable of the gauge cluster.
Someone asked on the US site as their capacitors didn't have markings. I had a search and nothing comes up so I thought I would go back and pull mine back out to get that photo. I had a dead moth in my cluster that was bugging me so I had to take it out anyway.

[ansys]

are there any more clear pictures out there as to which direction to install the capacitors? The old ones on my car didn't have any clear markings on them...