deeznuts94

Someone on here that has done this repair with some success should start charging to do other members clusters. I would be willing to pay to have mine done. I bought an entire cluster off of another member on here and it worked fine for a few months, then back to the usual problems. With all of us that have this problem, I'm sure I'm not the only one that be willing to pay someone for this fix.

Chevy86 IROC-Z

iTrader: (17)

In order for that to happen, the repairer would have to become a vendor since he would be making a profit here on TGO. I don't know how much the vendors fees are, but that's what would need to happen for that repair service to occur.

cliff1970

Probally just a solder broke loose. Ive repaired a many of them. Sometimes vibration breaks them loose.

BigBadLou

iTrader: (3)

I have offered my help in the past but have never had take me up on that offer.
But if the new TGO owners want to make money of their members, that would be sad.

xavier_pr84

Another tach fixed use to read at 3500-4500 now on warm up it was about 600 on idle yes it's fixed America f*** yeah! Thanks guys

CuriousPrimate

I have a 91 Z28 305 TPI manual.

My tacho was around 1600 out and I used a 200 resistor.

Its now saying 800 or so (might be high idle problems cause I have sticky holley that refuses to close 100% when the engine is on, push it back with hand and idle drops a little)

My question is...what should my car idle at anyways?

Also my Tacho is fixed but my shift light still comes in at crazy times. Is this fix meant to fix the shift light also?

Thanks again

1991z28........

my rpm dont move at all what would that be?

1991z28........

should i put resistors on mine? but the thing is that my rpm needle dont move!!

dads old blue 9

hey z see you found the repair board if you feel up to the task go for it if not read the pm I sent you . repair takes about an hr or so . so $50 is an hrs worth of electronics work. This fix will repair whatevers wrong with your tach . you can buy resistors and soudering gun solder flux and snipsome legs but if not done properly you could fry your board just be carefull and take your time if you try it your self.

Free91z28

Well new to the site guys but already fixed my tach 30mins ago can't believe it's working again. It only reads 250rpms low compared to my crappy sunpro tach which will be removed now.. Many thanks to the guys that made the knowledge available to us to fix this problem.

BigBadLou

iTrader: (3)

Amen to that!

CuriousPrimate

Anybody else still have problems with the shift light coming on at wrong times after the tacho fix?

Free91z28

My car is auto (for now) so don't have that problem.
I don't know much about how the shift light works tho but it should be controlled by the ECM not that tach gauge. The ECM would determine the rpm vs speed vs throttle position to give u a upshift light if I'm correct..

BigBadLou

iTrader: (3)

You are correct. The shift-up light is controlled by the ECM.

CuriousPrimate

Could the shift light be out because TPS is not set correctly?

I just had my throttle body changed to a holley 52mm because the old one was sticking.

The new one is also slightly sticky when the engine is running (push it closed with hand and it drops revs) but that's a whole different story.

The dude claims he set the TPS but my guess is he didn't.

For this to make more sense my car is in Australia and I live in Hong Kong, I go back once a year and drive it then, other guys work on it in between.

BigBadLou

iTrader: (3)

I would recommend you start a new thread for your problem. Let's leave this thread for its original purpose.

Elephantismo

One option could be to take a few pages of relevant tech from the thread with you to a good customs / performance shop or a small electronics repair shop along with your cluster and have them cut the original resistor pins and solder in new resistors at the proper resistance.

Elephantismo

1991z28...., I would go ahead and trim pin 4 and 10 and solder in a 195k resistor and see what happens. It may be that you also have a bad capacitor or even stepper motor in the cluster. Checking the resistance across pin 4 and 10 on the white and black resistor chip will help to get you started in the right direction.

Unless you had a small fire on the tach board, it should be salvageable.

TraviZ

iTrader: (2)

please delete, posted in wrong thread.

plum92_camaro

Another repaired tach! used two 100k resistors in series. father-in-law did the soldering. resistance came out as recommended. Haven't been able to check for accuracy but it looks right. also added some red bow ties to the speedo and tach for a subtle custom look.

tbarneski

Does this resistor fix also cure the issue in earlier models ? My tach is shaped different but looks to have the same components.

tbarneski

My 87 had the same issues as most here. The tach would peg on start up. Thinking that I could simply go to the junk yard and find a donor car that would actually work was a laugh. I now have a total of 4 tachs, all them did not work. I followed the steps in this thread and put two 100k ohm 5%+- resistors in series that after joined together ohmed out to 189k. With the 5%+- it put me within tolerance to 196k as stated in previous posts. Also in my opinion if you are looking to cure any linear errors go ahead and pick up a 500k potentiometer and put this in instead.

mikenj73

Just a great big "thank you" to all of you guys who took the time and the effort to figure this tach issue out. I followed your advice and cut the #4 and #10 pins, soldered wire leads to the board, put in two 100K ohm resistors (in series), and it fixed my tach. I have a 500K potentiometer on the way that will be replacing the resistor, just so i can fine tune it as i need to without removing the dash again. I can't tell you how nice it is to have a tach that doesn't bury the needle at anything over idle speed! Thanks again, guys!

HowardC

This page is extremely useful! Even though I'm an electronics guy I've never seen resistors in a chip used like that. Must be some old-school thing.

I've got a really dumb question though and I was hoping somebody could help me out.

I've got a 92 and the tachometer just started acting up but I can't figure out how to get to it. There is a black plastic bezel that just pops off, but it won't come off completely because of the headlight **** and the cigarette lighter and defrost switch. How the heck do you get the **** off? I've tried pulling as hard as I can but any more and I'm afraid I'll break it.

CuriousPrimate

If you pull it you will break it.

The switches unclip from behind.

Take the dash pad off and look down, you will see a button with a spring on it on the top of the headlight ****.

This must be pressed in fully, then keep pulling and turning the headlight switch until it pulls right out.

The button MUST be pressed or you WILL break it.

HowardC

Can you confirm this for a 92 Camaro? On this site and on the net I've yet to see a pic of this being done and every article I read says the button is in a different place or is non-specific about the location. I've seen people says it's on the bottom, people say it's on the side(non specific) and ect... but never on the top.

If I have to take the dash pad off then this is going to have to wait until I get a new pad.... that thing is a pain in the butt and every time I take it off I get a new crack it's so brittle at this point.

CuriousPrimate

I have a 91 Z28.

They should be same up to 92.

Its will be really really obvious when you see it as it looks like the head of a nail with a spring under it.

You could reach it with the end of a long flat bladed screw driver but its nearly impossible to hold it down hard enough and wrench the switch around to the right spot where it pulls out.

I figured I was going to have to break mine to get it off so i ordered a spare switch just in case and after playing with that a bit worked out the sweet spot.

It might be on the bottom, my memory might be off but for SURE when you get a visual on it you will know as i said. Looks like head of a nail with a spring under it.

With the dash out it goes from dam near impossible to semi difficult.

I have big hands and wrists so maybe it might be a little more easy for others to reach.

http://htsmall.rickscamaros.com/asse...0/sku/SW-1.jpg

Not sure if that link will work but that shows you what the button looks like.

From the orientation I guess its the bottom possibly. Just pull the bezel cover thingo back far enough to shine a light in there and look around till you see it on the big box thing the stalk goes into.

It might be possible to do it with the dash pad in but i almost broke down in tears after about 25mins solid of trying to push it in with the blade of a screw driver while working the shaft with the dash plastic cutting the *^&% out of my arm.

It wont pull out first push of the button, it seems the shaft needs to be at just the perfect orientation before it pulls free and it comes out pretty easy when you get it just right.

Spin it all the way left and try, then all the way right and try, then anywhere in between.

Good luck.

CuriousPrimate

Oh that photo is really bad quality I know but its only one i could find showing the spring. Its DEAD CENTER on the bottom of the steel frame with a little ledge to the left and 3 little circles to the right of it. Hope that makes more sense.

CuriousPrimate

http://images.stylintrucks.com/produ...bc108903_7.jpg

Much better image of the switch.

HowardC

Thanks a bunch.... I couldn't find a good pic so I couldn't understand where I was supposed to be looking for the button. The fact that it's behind a ridge explains a lot.

I can get my fingers back there, I just can't see anything, so I was working blind.

As nice as these cars are, sometimes I've gotta shake my head at where things are placed. Replaced my bumper a few weeks ago only to discover that the hangers for the exhaust tips are right below the bolts to the bumper.

I look at the pcb we are supposed to fix for this and wonder why it wasn't mounted to the bottom of the assembly, so you could just take the kick plate off underneath and unplug it.... oh well.

Anyway thanks for the info, I'll keep at it.

CuriousPrimate

Just remember there is a real sweet spot for it to pop out with the button depressed. I cant recall exactly where it is but I think its somewhere between the clicking on and off full lock one way.

Its funny, I drive my car maybe twice a year since its in another country to where I am now and the barrel lock is messed up but because of the Vats I cant replace it locally.

There is an exact point I need to jiggle the barrel with the button down to get the key out of the ignition which takes me ages to find when ever I get back but after a day I can almost do it one handed.

The headlight switch is sort of the same. Takes ages to work it out but once you get it a few times it seems easy.

Reaching the button is 95% of the battle, good luck

welterracer

Has anyone figured out a fix for the tach?

Mine goes to 7000 rpm and stays there all the time

Chevy86 IROC-Z

iTrader: (17)

A word of advice. Reading will help solve your issues.

levi3

Well, 7 years later I just fixed my Tach thanks to this thread. 92Blue, thanks, all you other guys that contributed I really appreciate it.

HENZOR350TPI

Plus one tach fixed , thank you guys ! Charles from Brazil

dimented24x7

iTrader: (2)

For those with the older tachs see here: https://www.thirdgen.org/forums/elec...-89-tachs.html

The circuits are the same for both tachs, an LM1819 with associated driver circuit. The difference is that the older tachs have the board integral to the tach. In either case, the ceramic resistor IC is identical on all tachs, so follow the instructions outlined. My method of fixing was slightly different, and used nominal value resistors rather than high value ones. Both the method in this thread and mine will fix all year third gen tachs.

dimented24x7

iTrader: (2)

Also another quick tip for those replacing R4. If you know exactly how high your tach is reading and you have a DVM, you can quickly determine what resistance you need. Im my case my tach was reading over by 1.33 x true RPM. I measured R4 to be 255 kOhms "as-is". The replacement resistance would then be 255/1.33 or 192 kOhms.

dwillis

iTrader: (6)

OKkay so I posted back in 2008 and just read through the thread again since then and did a search but come up empty handed.I'll ask the question again 5 years later and see what happens haha...Is there a fix for firebird tachs?I have a 1991 305tpi T-5 car and the tach will move up to about 700 rpm or so but thats it.I cant find a fix anywhere for this unless I'm overlooking something.Can someone hook me up and point me in the right direction if you know of a source to repair or even to replace the tach.I have a cluster out of a v6 car that I think worked(with the v6)so if there were something to put in it from mine to make it work with a v8 car I'd do that too.Thanks guys

arrocha87

So I have an 89 rs. Pulled the tach and checked r4. O ohms so it was bad. Soldered two 100k ohm resistors as described on here. Put it in and it was a 0 when I turned ignition on. As soon as i started the car it pegged and stayed there again even when off... any other thing it could be?

So an update: went back out to make sure everything else worked and put the dash together as I had given up. It pegged again then started working its way down. When I shut it off it was at 4000 rpm at high idle. Could it be the amp needs to adjust itself since it's probably been years since it has worked?

maxjivi05

Fixed my 91 RS was R4 had to bump it to around 299k to read properly on tach.. before it would peg out and stay pegged...

BCdawg57

iTrader: (1)

I'm having a strange issue I hope someone can shed some light on. My tach was reading similar to tach#3 the op posted. So I snipped pins 4 and 10 and got some resistors trying to get as close to 196k as possible.
Here is the issue, I'll solder the proper resistors in series, and they will measure out properly before I attach them to the board, but one I solder them to the board, the resistance I measure drops significantly. For example, currently I have 2 100k ohm and a 22k ohm resistor soldered in and the resistance measures about 185k. The tach is currently reading 100rpm low give or take. So I believe the measurement is correct. Why the drop?

BCdawg57

iTrader: (1)

This is what I ended up with:
2 100k, 1 10k, and 1 1.5k for a grand total of 211.5k plus or minus 5% lol.
My tach reads as follows,
Tach. Actual
950. 850
2000. 2000
3000. 3000
4000. 3975

That doesn't really seem right because the idle reads 100 higher and the rest is almost exact. I don't know why but I'm willing to live with that!

I may take away the 1.5 to keep it from getting too far off at high rpm, since that is what I need it for.

Gunnyj1

OK, I,ve read the entire thread. Heres my situation. I have a 91 RS 305 TBI auto. My tach does not move at all and it sits below 0. I removed the board and measured pins 4 and 10 and I got 192.6k, then I switched the leads and got 66.2.

1 Should I measure AFTER cutting pins?
2 Does it matter which lead touches pin 4 or 10 when measuring because of the different values that I got?
3 Is there something else I should be looking at instead of the tach chip?

Hope someone can help.
Thanks,
Gunny

midias

Please forgive me if I missed this somewhere in this thread. Here are the freq values that should correlate to a specific RPM for a V8 tach.

Joe Tag

iTrader: (4)

Will a 1/2 watt resistor be adequate for this? I have found 196k 1/2 watt +/- 1% resistors so there is no soldering multiple resistors together.

BigBadLou

iTrader: (3)

Yes, even a 1/4 watt resistor will work, np.

Joe Tag

iTrader: (4)

Awesome. Thanks to all who put their effort into figuring this one out.

brat747

When I read across pins 4 and 10, my meter said 191.... So does that mean mine is not messed up? The tach def reads wrong. I am not electronically inclined at all, but hve been trying to follow what this thread has said, but now I'm stuck. Help? Please?

Chevy86 IROC-Z

iTrader: (17)

No man. You got it all wrong. Solder in a pot and turn on. Dial in the pot to match the actual rpms. This is better done if you have a aftermaket seperate tach or with a timing light that reads rpms. Then turn off and remove pot/pots. Then measure the pot and note the reading. Them solder in some resistors to match the resistance on 4 & 10.

blp226

My tach is always maxed out when the key is on. All I need to do is replace this board? Where do we find one?