KCG

iTrader: (1)

Could anybody give me a heads up on what might be happening with my gauges...
89 IROC, both the temp and fuel are pointing straight up. Never move. My tach jumps around but mostly stays around 6-7000. The voltmeter may read 8 or it may read 13. Battery voltage with my meter is 14.5 at the time.

Temp - I pulled the wire connector off the temp sensor in drivers side head and grounded it and the gauge didn't move. I pulled the IP out and looked at the traces to figure out which connection this wire was. I have continuity from the sensor to the in-dash connector.

Fuel - I have replaced my sending unit in the fuel tank with a new Dorman unit. It reads 0-90 at the connector at the rear of the car. Have not traced any further forward yet.

Do you think I have individual problems or something going on with the cluster?
I'm going to try and clean up the in-dash connectors and put it back in first, unless someone has any testing I could do to the gauges since they're out.

tglennon11

iTrader: (2)

assuming your car is stock and never been modified you are on the right track by cleaning all of the contacts, take it one step further and pull each gauge out individually and clean the contacts and resistor bar on the backs. A little grease will help here.

Look at the wiring, IIRC the gauges ground is next to the steering column under the dash, the steel frame right under the idiot lights, take it off, clean it etc.

While the gauges are out CAREFULLY move the pointers off of the "stuck" position, these gauges were supposed to slowly sweep on start up, as they get older they speed up and get stuck.

If your car is no longer stock, swapped engine, pulled the ECM out, etc, your wiring could be a basket case and we would need lots of info to help you out.

While the gauges are out you can use your DMM to check the signals going to the gauges, i forget where i saw the information, maybe austinthirdgen? but search for the gauge readings, you can probe the contacts and see what your DMM does. I know that information is in the Chiltons Manual. Let me know if you cant find it and ill dig mine out.

mikeceli

iTrader: (2)

Listening in w/ similar problem.

KCG

iTrader: (1)

I purchased this car, 89 IROC, not running recently. It appears to be stock except someone had set a carb/intake on it but left all the TPI stuff in the car. I've got the TPI re-installed and running pretty decent. Its supposed to be a rebuilt 86 305.
Time to get the gauges working..
In case anyone wants to see, here's a pic of the gas gauge pulled out. You can see the studs sticking out of the rear of the gauge that make contact with the spring-like looking connector on the IP. This is before I took a scotchbrite pad to them.





I believe you're right...
With the steering column lowered, you can see the bolt and grounds. Took the scotchbrite to it too.



Here's also a before & after cleaning pic of one the connectors the IP connects to.





So, after doing this, the voltmeter now works and the temp gauge is also working. Progress!
Still not working are the tach, its buried at max rpm, and the gas gauge is still past full.

The Temp gauge does this. At startup, it swings fast and gets stuck. I can tap the needle and it will drop back and start reading correctly. Whats the fix? Some kind of stop

So back to the gas gauge, it's not stuck. Its just at full sweep. I have a Haynes manual that has a schematic for the IP. Checking the connector shown above coming from the tank, I get no reading. I assume this should be 0-90 ohm, just like at the connector coming out of the tank. I know this because I dropped the tank and put in a new pump, sock and complete Dorman sending unit and measured it while it was apart. The tank was disgusting inside and I had to replace it. So I started with everything new.

Didn't attempt anything with the tach yet. I'll check the Haynes manual and test for continuity out to the coil.

tglennon11

iTrader: (2)

Good im glad i could help. I also had to clean everything to get them accurate again.

I had the same problem with the oil pressure gauge, RockAuto has the coolant temp gauge as a GM restoration part for ~$37. Mine was hitting the plastic cover, so i spaced the cover off the gauges a little bit, a little searching around here should give you an idea of what other ppl have used as a stop

I would check the connectors at the dash for the 0-90ohms, if its at full sweep you have too high of resistance somewhere as 90ohms is full. if the gauge is still out try putting a 90 ohm resistor, a 47 ohm resistor and shorting the leads together, 90 full, 47 half, 0 (shorted) empty.


IIRC the tach comes off the dizzy through the C100, a white wire in D6, check along the firewall to see if it was reconnected. im not sure how its connected on the TPI motors as I swapped to an LT1 and mine comes out of the PCM now.

KCG

iTrader: (1)

Yeah, thanks again for the info...I have no reading at the dash connector for the gas gauge so I'll have to figure out how it gets to the back of the car.

Tach - come to think of it, the larger connector on the dizzy has a broken retaining clip. Its not flopping around but its not tight either. I'll check it out.

itsfnchris

Any update? I'm kind of having the similar issue with the gas gauge and the tach being pinned. Wanting to see what others have done to get it to work! Just recently became a member after a few weeks of lurking and searching and reading after purchasing an 88 Camaro strictly for the T-Top factor (Had a 2010 Camaro that was totaled on me a year ago and I miss having a Camaro).

tglennon11

iTrader: (2)

you have to find out where its getting pinned. If its getting pinned between the plastic lens cover and the gauge, space the clear plastic off the gauges with some small washers.

When i bought my car there was a small piece of electrical tape by the oil pressure gauge that acted as a stop. kinda ugly if you ask me, so i spaced out my lens.

KCG

iTrader: (1)

I traced wires for the Tach...These voltages are with the car running.
There is a white wire in the right side connector that runs out to the coil. I have continuity on this wire from the dash to the coil 2 pin connector. I measure 13.5v at the dash connector. Sound correct?
There's a pink/blk wire that supplies voltage to the gauge. I'm reading 14.2v here with the car running.
And from what I can trace on the back of the IP, the ground is shared with others and its good on a blk/wh wire in the same dash connector.
Now, my tach still pins itself at 7000 when I start the car. Maybe my tach is just bad or does 13.5v=7000?

Haven't worked on the gas gauge anymore yet.

I did take a few minutes and look thru the wiring diagrams on austinthirdgen but nothing on the IP

KCG

iTrader: (1)

Another update with some progress,
My car is an 89 IROC. I found this thread. At least one person here said they also performed this "fix" on their 89. So I tried it, and sure enough, my tach is working now and it seems pretty accurate by ear. I'll hook my laptop up at some point to compare to the ECM but i think its good and I'm pretty excited it worked!

https://www.thirdgen.org/forums/elec...meter-fix.html

KCG

iTrader: (1)

Also got another problem solved with the gauges. A new replacement,

KCG

iTrader: (1)

And lastly, my fuel gauge problem was at the rear of the car where the 3 wire plug from the sending unit connects to the harness under the back seat. 2 of the pins didn't seat correctly and pushed backwards out of the connector. Surprised I did feel or notice it when I put together the first time.

tglennon11

iTrader: (2)

im glad you were able to figure it all out.

Gibbyzracing

I was about to say the Ground wires on the column but someone beat me to it. Glad you figured it out

Galaxie500XL

iTrader: (1)

I've been looking for a new temperature gauge for my '88 IROC, but wasn't able to find it on RockAuto's site..do you have a part number for them? Every other one I've found is much more expensive.

KCG

iTrader: (1)

GM RESTORATION PARTS 25034460 [Coolant Temperature Gauge]

tglennon11

iTrader: (2)

Yup, this one. Out of stock on RockAuto. Its in the interior category as is the voltmeter.