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Battery dead?
Maybe left ignition on, doors open a couple days, etc?
You got battery voltage and grounds on the IP connectors but can't really see them getting together to drain your battery or causing any other problems.
If nothing that obvious, may be better to start a new thread in Tech/General engine forum.
I'm in the same boat as you although it's not nearly as bad. I took mine out to fix the tacho last summer and when I put it back the speedo stopped working.
The best I can tell is the membrane on the back of these clusters is super fragile. You may have a trace that has come loose. Gluing them back in place might solve it or perhaps soldering any broken points.
Also it might be an issue with the security chip on your key/ignition. Last month the repro set of keys for my car stopped starting it. When I used the original set it started right up, so I guess the resistor inside the key went bad.
I'm in the same boat as you although it's not nearly as bad. I took mine out to fix the tacho last summer and when I put it back the speedo stopped working.
The best I can tell is the membrane on the back of these clusters is super fragile. You may have a trace that has come loose. Gluing them back in place might solve it or perhaps soldering any broken points.
Also it might be an issue with the security chip on your key/ignition. Last month the repro set of keys for my car stopped starting it. When I used the original set it started right up, so I guess the resistor inside the key went bad.
Is there a way to test if the key is bad? It's still the stock key so it's possible.
Also, would the film on the back cause me to lose all power from it coming loose? I could see losing power to the cluster but not the entire car.
What do you do when all the Radio Shacks are gone?
Anyone have a part number or code for the resistors?
Just type in the ohm reading you want, 1/4W should be plenty but 1/2 watt will work fine if you want to try to fit in in. Any of these places will have it. You can even get them prime
Differences between V6 & V8 are one thing.
But also the signal scaling will be different on the 90-92 tach's -vs- the 89 and older tachs, since the 90-92 tachs sweep only 180 degress of movement for full range and the 89 and older tachs sweep a full 270 degrees.
I was looking into this since I have to retune my 89 V8 tach and have noticed that has been drifting up over the last couple of years.
Reads about 150% high. Resistor drying out, but not completely open yet...?
Thanks to everybody who contributed information to this sticky. About ten minutes of reading and five minutes of soldering fixed a problem I've had for years. Fantastic work!
About ten minutes of reading and five minutes of soldering fixed a problem I've had for years.
thanks to all who provided the tech contributions to this post. I'm a little slower than IROCBOY. spent hours reading through all the details in this post. I also wanted to remove the air bag lightbulb, since air bag not present, so I needed to pull the cluster out anyways. took me about a couple hours to drop the column, remove the knee pad, trim surround, light switch ****, connectors for driving lights, cigarette lighter.
Originally Posted by PurelyPMD
What do you do when all the Radio Shacks are gone?
bought my resistors off of ebay for about $6. went with metal film resistors since they were such a low cost item, came in 10-packs. got 100k, 91k, and 5.1k. then used the ohm meter to find the best triple combo that gave me 196k since there was some variances in the lots.
Originally Posted by Ikes 91Z
So I took my cluster out to fix my tach issue as well as my speedo issue (following another post for the speedo), put it all back in, turn the key and nothing. The battery doesn't even click on. No clue what I could have touched that would make it not want to even get power. Any suggestions??
since I had it all out, and read about other contributors having other stuff not work upon reassembly, I cleaned the cluster contacts, and the dash contacts, applied some dielectric grease for longevity.
based on the advice of this posts contributors, I did put the 3 resistors in series on the back side of the ckt board. I clipped the pins on the GM resistor pack, and used a solder sucker to suck the solder out of the pin holes, was then able to insert my resistor leads into the pin hole and solder up, had to take extra care that the resistor lead didn't contact the clipped GM resistor leads, or that solder didn't flow over to contact the adjacent pin.
got it all buttoned up, reconnected the battery, and started it up. voila! success! I am so impressed with myself. but actually, all thanks and praises go to the pioneers that discovered and documented the fix.
I did realize that in my haste to reassemble, i didn't center the steering column relative to the cluster, so had about another half hour of follow up work. still good though.
Cajun Tach Shop was the original designer and producer of the new tachometer circuit boards for 82-92- Camaros. They are a veteran owned business that doesn't outsource parts and manufacturing. They offer a lifetime warranty and are much more reasonably priced! I called them on a Saturday and Greg walked me step by step through the installation process. I mean, what other company would do that! Very nice people and very professional.
Cajun Tach Shop was the original designer and producer of the new tachometer circuit boards for 82-92- Camaros. They are a veteran owned business that doesn't outsource parts and manufacturing. They offer a lifetime warranty and are much more reasonably priced! I called them on a Saturday and Greg walked me step by step through the installation process. I mean, what other company would do that! Very nice people and very professional.
You should definitely get this pinned up top of the board with a quick run down explaining the issue as an overall summary and fix for this issue. Thanks m8 for the info. Will be scheduling this fix very soon myself.
Just wanted to drop a line to say thanks to you guys for the good information! I used this data to fix my 1993 Buick Roadmaster cluster (I think it's the same chip).
For the record, I had to use a higher overall resistance ( can provide data if desired).
Lastly, individual parts can be sourced from mouser.com and digikey.com if a Radio Shack isn't available.
As many of you guys know... barely anyone has a 90-92 gauge cluster with a tachometer that reads properly. They almost always read too high. There has been a multitude of posts regarding finding a solution or a fix for this, but to my knowledge, no solutions so far.
For those of you wondering about calibrating an 89 and earlier tach, Morley has an old post that outlines the repair, which is a simple capacitor change.
ANDYZ28 has been nice enough to mail me a couple of tachometer boards. I have done some research with his boards as well as a couple of others that I have picked up from a local junkyard.
Before I get into what I have found, here is a little background info:
A tachometer works by converting pulses received from the vehicle's ignition system into needle deflection on the gauge. A pulse is generated each time a spark plug fires. On an 8 cylinder engine, there will be 4 pulses per revolution. On a 6 cylinder, there will be 3 pulses per revolution. Inside the gauge cluster, there is a small circuit board which is responsible for controlling the tachometer's needle deflection. Naturally, there are some differences between a 6 cylinder tach board and an 8 cylinder tach board. The 6 cylinder board needs to consider 3 pulses to be equal to one revolution, while the 8 cylinder board needs to consider 4 pulses to equal one revolution.
According to this articleTachometer System by Oliver Sholz, the calibration for the tach board depends on one resistor and one capacitor, both located on the tach board. Calibrating a tachometer that reads high would just be a matter of locating the resistor and capacitor on the board, identifying which has failed, and replacing it.
With that in mind, I've attempted to find the location of the resistor and the capacitor on the board. I am fairly confident that the resistor is part of the "thick film resistor chip", or "resistor network" across pins 4 and 10. This is the large white chip with black markings on the top left of the tach board. The capacitor mentioned previously would be the one on the top right of the board.
I can't see where it tells you where to repair the tach can someone send me the link?
I can't see where it tells you where to repair the tach can someone send me the link?
Here are some good posts to get you started. They’re all in this thread. Also look at the pictures that other users have posted here. They’re immensely helpful. I ended up soldering in a potentiometer, adjusting that until my gauge read what my ecm was seeing, and then measured the resistance that I had the potentiometer set to. Then replaced the potentiometer with whatever resistors I needed to meet that value. (I think. This was over a decade ago)
Originally Posted by 92blue
Those of you that want to fix your tach.....
Take your cluster apart, and gently remove the tach board. It will be the circuit board located underneath the tachometer. You will see a large 14 pin white and black chip on the tach board. This is referred to as the resistor network.
Take a look at how the pins are numbered in the picture below...
Originally Posted by 92blue
Disregard the picture above, the numbering for the pins is too hard to see. This one should be better....
The picture also shows the tach board with the newly added resistor.
Originally Posted by 92blue
Grab a voltmeter, and set the scale so that you can read over 100k ohms. Check the resistance across pins 4 and 10. If you have infinite resistance (no continuity), then the fix will be easier.
Infinite Resistance:
All you will need to do is solder a resistor across pins 4 and 10. I used a 150k ohm resistor, and the tach reads 7-8% lower than actual RPM. I believe the proper resistance will be close to 180k-190k ohms (More resistance makes the tach read higher, less resistance makes the tach read lower). Trim the resistor ends a bit to shorten the length, and then bend it in a U shape. Be sure not to get solder onto the adjacent pins. If you are not comfortable soldering, practice a little first before trying it on the tach board. Once you solder the resistor on the board, you can reinstall it into your gauge cluster. You might need to bend the resistor slightly to the side for adequate clearance once you go install it. Start your car, and you should notice your tach reading properly now.
Finite Resistance:
If you have resistance across pins 4 and 10, you will first need to isolate a portion of the resistor network. Using nippy cutters (available at Radio Shack), cut pins 4 and 10 very close to the circuit board. Carefully pry the pins upwards, away from the board. At this point, you can solder a resistor (again, I used a 150k ohm resistor which reads 7-8% low, a 180k-190k ohm resistor will be better) onto the contacts on the board which used to attach to pins 4 and 10. Be very careful not to get solder onto the adjacent pins. Also, the pins that were cut/bent out of the way must not touch the resistor that you installed. Once you soldered in your resistor, you are good to go. Install the tach board back in the car, and enjoy having a tach that actually works.
Note: The resistor values mentioned will work for a V8 application. I don't know what the proper values will be for a V6, but the fix should be the same.
Originally Posted by edman87k5
take a while and read this thread in whole, there is a lot of knowledge to be gained.
In simplicity:
-remove guage cover clear plastic and pull the board in the bottom right corner out- there are some pics earlier in the thread.
-Get out your digital voltmeter and check the resistance on the pins of the white and black 14 pin chip.
-Pin 4 and 10 are the ones to be concerned about- see earlier pics for pin #'s
-Your tach is pegged upon startup, prolly infinate resistance(open)
-cut or unsolder the 4 & 10 pin and solder in a pot or correct value of resistors betweeen the 2 pins( if you aren't pretty good with a solder gun, don't even try unless you have a spare board, get someone else to do it)
=if there is infinate resistance, it is easier because you do not have to cut the pins, just solder to them
-you have 3.1l, so read back and find what someone said the correct resistance is, and if you trust that value, use that amount of resiatance, if not, use a pot to find the correct amount- the correct resistance for a v8 is about 200k give or take 5% depending on who you talk to
- reinstall and check it out
- connect to a scanner or somthing to read the true rpm of the motor and compare against your tach at several diff rpms, if you used a pot, dail it in until correct and either glue the stalk on the pot or measure the resistance and replace with correct value of resistors
Total cost= less than $5
Here are some good posts to get you started. They’re all in this thread. Also look at the pictures that other users have posted here. They’re immensely helpful. I ended up soldering in a potentiometer, adjusting that until my gauge read what my ecm was seeing, and then measured the resistance that I had the potentiometer set to. Then replaced the potentiometer with whatever resistors I needed to meet that value. (I think. This was over a decade ago)
So after testing r4 for resistance I assume it's infinite because the meter just keeps climbing there's no consistent value like the other pins
That being said I also assume from reading all these posts that the correct fix would be to soldier an 180 to 200 k ohm resistor between pins 4 and 10?
Sound right
Here are some good posts to get you started. They’re all in this thread. Also look at the pictures that other users have posted here. They’re immensely helpful. I ended up soldering in a potentiometer, adjusting that until my gauge read what my ecm was seeing, and then measured the resistance that I had the potentiometer set to. Then replaced the potentiometer with whatever resistors I needed to meet that value. (I think. This was over a decade ago)
Where is the best place to get a resistor can't seem to find them anywhere?
I put a pot on mine so it was adjustable. been 10 plus years since I did it thou and the cluster went with the car sadly. but I remember starting it and adjusting it to match a scanner
I put a pot on mine so it was adjustable. been 10 plus years since I did it thou and the cluster went with the car sadly. but I remember starting it and adjusting it to match a scanner
09-08-2016, 07:15 PM
