[Royce 67/87/97]

• 1992 Chevrolet Suburban C1500 w/5.7L

This Suburban has seen very little miles for several years. Was seriously thinking of selling it recently, as it's had several mechanical issues creep up over the years and they have not been addressed.

BUT one major issue with the tranmission seems to have not been a big issue at all...so now I'm having fun cleaning it up and trying to tackle some of its other problems. This is what I want to try to fix next:

• Temp. gauge on dash stays completely at the far left/bottom.
• On startup (when key turned to start) the guage will briefly peg out to far right, but returns to left as soon as engine starts.

I've done the obvious things I could think of :

• checked coolant level (Overflow reservoir was empty, so I filled it to the "cold fill" line. I only had to add a little bit to the radiator itself though, so I don't think the level was low enough to be a problem...)
• checked fuses (Didn't notice anything blown, and all the other guages are working, so I don't think this would be it either.)

I tired searching but did not come across this exact issue. If there is a thread out there I missed, please point me in the right direction. I did read about a sensor located near the first spark plug. I found it, and its connector and one wire seem to be intact.

Thanks in advance for any help!!!!!:happy:

 

[stephan]

That wire that's on the temp sensor between the #1 & #3 spark plugs... Pull that wire off, leave it unhooked & turn on the key. The guage should stay to the left. Now with the key still on, momentairly ground that wire to the engine. Your guage should peg out. If it does both of these correctly, then you need a new temp sensor. If it does anything else with either of these two tests, then it's a dash cluster/guage problem.

 

[Revredneck]

Check your thermostat first! If your thermostat is bad, the engine will never warm up, and that can make it look like the gage is bad. Are you sure it's warming up properly? You can plug in a scan tool and check the readout on that temp sensor, which is much more likely to be accurate. A thermostat is a cheap and easy fix.
Good Luck and God Bless

 

[Royce 67/87/97]

@stephan - I attempted both of your tests.

• First, with the wire unplugged/key on: The gauge does stay to the left (as it has been doing when plugged in as well).
• Next, I grounded the wire to the block. (At least I think I did. Had some small solid copper Radio Shack wire that I could wedge into the plug, then hooked the other end to bare metal near the exhaust manifold.) With the key on, the gauge DID NOT peg out as you suggested it would. So...if I performed this correctly, it may not be the sensor, but the gauge itself? That would be a bummer.

I'm not 100% sure I grounded the wire properly. I feel the need to try again tomorrow in the daytime!

And just to clarify - when you say with the key "on," you do mean just in the on position, not all the way to the starting position, right? Because whether the wire was plugged in or not, the gauge will still peg out all the way to the right just while starting the engine.

@Revredneck - I am not really sure if the engine is warming up "properly." I know it gets really hot after awhile! I have not checked the thermostat. To be honest, I don't remember how to - the last time I changed a thermostat in a car was about 15 or so years ago in my '87 Cougar! I'll have to read up in my Haynes manual to refresh my memory. The only scan tool I have is for
ODBII, and this Suburban is from several years before that came around. Are there scan tools that would work with the '92 that can give me the actaul readings from this sensor that I could check? That would be more than my Actron OBDII scan tool (several years old) does for me now with the newer cars!

Thank you both for your replies. I will try to work on this problem some more tomorrow.

 

[Royce 67/87/97]

hmm...I tried writing a reply last night...but it never seems to have made it.But now I can?


Anyhoo: Tried your tests on the old sensor.Don't think I grounded it properly though. Went ahead a bought a new one from O'Reilly's yesterday. Thought I got the right one when I looked at it in the store, but after I switched them out and tried to plug new one in...my plug would not fit!

Went back and they did not have an alternate listed in their system. He was going to have me buy a pigtail that fit the other one (another $15!!) but I saw it had 2 wires...he said "cut/tape off the black on e and use the yellow one." Well that would be more $ and more work...

Counter man had gotten down a box full of different ones, so I proceed to start checking them all out. Found one that looked like my original. He looked up that part, and it was listed as having been used by GM from 1990-2002...so I took a chance and got it.

Put it in this afternoon and the gauge did begin to climb as it idled in the driveway. Looks like it is going to work! It does have a strange "twitchiness" to it sometimes though... Will try to drive around a bit more tomorrow to see what it does. A knowledgable neighbor said he would help me check the sensor tomorrow with a hir drier and a meter to make sure the sensor works the way I need it to.

Next project: spongy brakes. Going to install new master cylinder

 

[Ethan]

Replace the "temp switch". It's on the right side of the block, in between the exhaust headers, it'll have a single green wire going to it from past the alternator. They cost like $20, and it's an easy replacement.

Be sure to get the "temp SWITCH" and NOT the "temp SENSOR". They look exactly the same, but the temp switch has one pin, while the temp sensor has two pins.

 

[SUV1962]

All I have the same issue, I own a 1996 chevy pickup c1500, before I replaced the temperature gauge sensor, the gage read two lines below 210, after I replace the temp gradually climbs but the engine not as hot as where the gage reads, need advice

 

[Motor City Rick]

stephan is on point for the diagnostic procedure.

First, ...it's not a thermostat issue. Overheat - under heat was never mentioned in the original issue. Leave the thermostat alone.

Next, it isn't the computer's system engine coolant sensor (yellow / black wire connector) has no connection to the dash temp gauge operation.

On the temp sensor itself, I'm worried you don't have the proper / exact temp sending unit you should have. Temp sensors have a "calibrated resistance scale" to the system they are providing temp data to. Wrong connectors is a big red flag!!!

I'm leaving you the GM resistance scale for you temp sensor. If your temp sensor resistance values are not the same as the chart when fully warm, ...replace the sensor.

 

[S. Ramsay]

This was a topic a while back on a 1990’s Silverado…… how to test the temp sensor. I’ve tried this and it results in needing a new sensor. I’ve replaced the sensor twice and it’s still doing the same. Pegging to the hot side when the wire is in the sensor. Any advice?

That wire that's on the temp sensor between the #1 & #3 spark plugs... Pull that wire off, leave it unhooked & turn on the key. The guage should stay to the left. Now with the key still on, momentairly ground that wire to the engine. Your guage should peg out. If it does both of these correctly, then you need a new temp sensor. If it does anything else with either of these two tests, then it's a dash cluster/guage problem.