Goofy Instrum. Panel Problems

Hi everyone,

I'm new to this forum and I just searched though all 8++ threads in the Sierra forum and I didn't see my problem so here goes. I've got a ,90 GMC 2500 2wd sierra w/ some instrument panel issues. When I use the turn signals the voltmeter pulses in time with the turn signal. Is that normal? I doubt it is. The voltmeter is reading higher than it should as well. I checked the output with my meter at the back of the alternator and it's fine. Another issue is that the engine temp gauge will increase up to the 210 as the engine warms up and then will fall back to the first mark and stay there for the rest of the time your driving. Does all this sound like I have a short somewhere. Anyone seen this or have any ideas?!

TIA - thanks in advance, Rick

Doc:

the temp gauge issue is normal, what you're seeing is the engine warming up then once it reaches a certain temp (210), the thermostat opens up and allows water to circulate, cooling the engine.

The voltmeter issue also sounds pretty normal. Alot of factory meters will not read accurately so I wouldn't worry about it unless the reading is above 18vdc. Above that, I would check the voltage at the battery and have the alternator checked (regulator built into it). This could burn up your battery.

The meter fluctuating when your turn signal is on may be an indication that the contacts at your battery terminals may be dirty. This just causes a larger voltage drop than normal as is a common issue with batteries with side terminals. The best remedy to this is to switch to a battery with top posts and to replace your cables. It's up to you. I just clean my terminals whenever I see that they are dirty

Doc, you're all good. Mine does the same thing and never been an issue. As blab pointed out, your temp gauge is doing exactly as it should. However, you may need to look at a cooling system flush and replacement of the thermostat. I would replace it every time you change antifreeze. I have a 5.7 liter and my thermostat is a 195 degrees. Check with your local part shop or dealership and they can tell you what temp thermostat you should have.

As far as the turn signal goes, that is normal. I don't know how many amps the flasher draws, but it's plenty to pull the gauge down. Shouldn't have anything to worry about here.

One thing to remember is that gauges aren't always accurate and they do go bad. If you feel you are having an issue, look to get an alternate set of gauges.

Thanks blabhern. Does the temp gauge usually rest at that 1/4 mark (165 deg F roughly) though after the thermostat opens. You would think that the coolant leaving the engine is hotter than this. The truck will not idle at the proper rpm either. I'm pretty sure that I have no vacuum leaks, the temp sensor is okay. That's why I was wondering if a short somewhere is causing the computer to get the wrong signal. The battery is clean also.

Does anyone know if there is a website that show all the locations of all the connectors, and grounds like in the service manual. The chilton manual I have doesn't tell me where they are exactly.

Thanks, Rick

Thanks to you too astralepic. Any ideas on way I've got a high idle. I can drive the truck for an hour on the highway and it will still idle around 1000 rpm. All the gaskets are good.

Let me know, Rick

Mine idles somewhat high until the motor gets warm. This is part of the emissions system. Do you have a SES light on?

What does SES stand for? I don't have one on though. Sometimes the engine will get down to the right idle speed but only during the warmer months and then it's not that often.

SES = service engine soon

If I were having this issue, I might would look at flushing cooling system and changing thermostat. Given how it seems to idle better in the warmer months makes me think it is something related to temps. I'm no mechanic though. You might see what GMMerlin has to say.

A high idle can be caused by a vacuum leak. The TBI gaskets are a common problem on the TBI engines. Spray some TB cleaner at the back of the TBI while the engine is running. If the idle changes, you have a bad TBI gasket.

//2000CAYukon

Yeah, I tried that and it didn't do anything. I also rebuilt the throttle body so I know that all the gaskets are okay. The other day the idle was a lot lower but it was hunting around, going high than low, so it makes me think that it is some sort of electrical issue somewhere. The idle air control is okay so I am looking for other issues. I may try to replace the engine temp sensor just to see if that helps.

Rick