Temp needle pinned

[oldchevy]

guys.

My temp needle is pinned at max all the time now. Not over heated, just looks broken. It only goes down when there is no power. What should I look for first to trouble shoot this? Will the problem be one of the sensors on the block or the gaugue in the dash being bad? (truck specs at the bottom)

[bigcoconut]

The fact that it moves is good. Those gauges are pretty "dumb", they only do what they are told to do. Check your water temp sensor. You didn't give a year so I can't tel you where it is at. I have'nt had to look for it yet on my 92.

[cboyfan2020]

you will need to find out what kind of sensor you have...probably a single wire neg coefficient...that means resistance decreases as temp increases so you will need to check the resistance on the sensor and compare it to a chart for your specific truck( dont know what year so cant help you there) if resistance is not in line with the gauge then gauge is bad...if it is in line then replace sensor....should be located very close to thermostat area. hth

[oldchevy]

1991 is the year. I replaced the temp sensor with the single lead right next to the thermostat about three months ago. I will try that one again most likely.

any other ideas.

[jocat54]

On my 93 350 the sending unit for the the gauge is on the drivers side head between the #1 & #3 spark plugs.

[tempfixit]

Originally Posted by jocat54

On my 93 350 the sending unit for the the gauge is on the drivers side head between the #1 & #3 spark plugs.

check this site; http://www.autozone.com/servlet/UiBr...d0.jsp#hd1-1-1

There is a coolant temperature sensor in the intake manifold and a temperature switch in the head. autozone.com shows them both for your vehicle under engine management.

Hope this helps

[oldchevy]

Any other ideas? I tested the coolant temp sensor and it is accurate via an OHM meter.

Tested the engine temp sensor and it reads 1.295 on the ohm meter. Does anyone know what the reading should be??

The gauge stays all the way up at all times now. key on, off, sensor conncected, sensor disconnected.

Would the gauge read that high and stay there if the sensor is bad? Meaning due to a possible bad sensor, until the gauge sees the correct resistence from the sensor it will always ready all the way??

Just to make sure...Which sensor controls the dash board gauge for temp...the coolant sensor, or the engine temp senso on the head? I'm pretty sure it's the engine one, and the PCM reads the coolant sensor...but I could be wrong.

[oldchevy]

i replaced the engine temp sensor today with a GM sensor ($32). Still no change. The temp gauge is still maxed?

Any ideas?

Any ideas where i can get a replacement? GM does not make them any more, LMC does not have the same style or unit for the 91.

Its a 115 degrees today here in Vegas..can't keep running it without knowing the temp. I hate to put in an after market gauge..I don't even know where I could put it...plus i am trying to restore it to factory new.

[oldchevy]

well.

I replaced the engine temp sensor with a GM sensor. No help.

GM no longer makes the gauges.

I searched all of the Las Vegas salvage yards for a 1991 Moonie style guauge.

After a week of looking I found only one..it came in to the yard only a week ago and everything was taken already...excpet the entire cluster.

I pulled it today and instead of switching out the entire cluster I just swapped the temp gauge. And...it worked. I have temp again. The gauge was bad.

Now my temp is reading higher than before, but still under 200. I think it now is reading correctly where in the past it was showing too cold. Where do all of your temp needles hit?? Just under the 210 (195)? and do they stay there and not move?

just wanted to update you all on the problem incase you come across it on your own.

[bigcoconut]

Thanks for the update on your fix.