Temp gauge reads low on '94 5.7L

[Reluctanse]

If the gauge moves fairly smoothly and gradually from "cold" to "warm/hot" as the engine temp gradually increases, you've got the correct style of part--a sending unit not a switch.

If the gauge goes from "cold" to "suddenly" warm/hot, you've got a switch. NORMALLY a switch would go from "cold" to "overheating--far end of scale". But if there's enough resistance in the wire harness, it might only go to some mid-point.

So there's the difference: Does the gauge needle creep up in synch with the increasing engine temp? Or does it suddenly jump from cold to warm/hot?

First Guess: You have the correct unit. But it's possible that they sold you a sending unit for some other application that has a differently-calibrated gauge. Or potentially a defective sending unit. Maybe someone put the wrong sending unit into the correct-part-numbered box.

As I've said before--the most likely (but not guaranteed) reason for the gauge not indicating hot enough, is excess resistance in the wire harness.


WHAT VEHICLE???

When the gauge goes too high, but the sensor for the computer shows reasonable temperatures, my first thought is that you've got defective insulation on the temp gauge wire, and that bare spot is intermittently grounding. When it grounds, the gauge goes up, and when it moves away so that it doesn't ground, the gauge reads "normal".

With gasoline V-8 or V-6 in a GMT400, it's almost impossible for "air bubbles" to cause problems. As soon as the thermostat opens, they're transferred to the radiator where they show up as "low coolant level". I don't know about Diesels in GMT400s.

OTHER applications may trap air in the cooling system somewhere. I've got Luminas that have cooling system bleeder screws to eliminate air pockets that won't purge on their own.

It's a 2000 K3500 with the 7.4. Thanks for the reply..

 

[name]

If the gauge moves fairly smoothly and gradually from "cold" to "warm/hot" as the engine temp gradually increases, you've got the correct style of part--a sending unit not a switch.

If the gauge goes from "cold" to "suddenly" warm/hot, you've got a switch. NORMALLY a switch would go from "cold" to "overheating--far end of scale". But if there's enough resistance in the wire harness, it might only go to some mid-point.

So there's the difference: Does the gauge needle creep up in synch with the increasing engine temp? Or does it suddenly jump from cold to warm/hot?

First Guess: You have the correct unit. But it's possible that they sold you a sending unit for some other application that has a differently-calibrated gauge. Or potentially a defective sending unit. Maybe someone put the wrong sending unit into the correct-part-numbered box.

As I've said before--the most likely (but not guaranteed) reason for the gauge not indicating hot enough, is excess resistance in the wire harness.

The gauge does creep up as the engine warms up , so I am pretty confidant from what everybody has posted that I do , in fact , have the correct part for my application regardless of the wording on the box.

Many Thanks to all who have posted and helped me out .

 

[Georgiabigfoot]

The gauge does creep up as the engine warms up , so I am pretty confidant from what everybody has posted that I do , in fact , have the correct part for my application regardless of the wording on the box.

Many Thanks to all who have posted and helped me out .

NAME,
Im currently dealing with a similar coolant sensor problem you faced. It’s now been 15 months since you started this thread, did you ever find a concrete resolution to your problem ? My grounded temp gauge maxes out. 2 different brands of coolant temp sensors with the correct one wire plug both consistently read 120 even though the engine may be at 180 or higher. I have a 96 burb with a vortec, as warmer temps are approaching I’m getting worried about engine temps. I purchased this vehicle in Sept 23, and have since hung 5,000 miles on it. The coolant temps have never registered right on the idiot gauge. It’s a real joy to drive, and completes a wish I’ve always had to get one just like this after a chance meeting with Bill Jordan of Realtree who was driving a burb just like it in 1998. I’ve wanted one ever since. I plan to hang another 100k on it. Thanks GB

 

[name]

NAME,
Im currently dealing with a similar coolant sensor problem you faced. It’s now been 15 months since you started this thread, did you ever find a concrete resolution to your problem ? My grounded temp gauge maxes out. 2 different brands of coolant temp sensors with the correct one wire plug both consistently read 120 even though the engine may be at 180 or higher. I have a 96 burb with a vortec, as warmer temps are approaching I’m getting worried about engine temps. I purchased this vehicle in Sept 23, and have since hung 5,000 miles on it. The coolant temps have never registered right on the idiot gauge. It’s a real joy to drive, and completes a wish I’ve always had to get one just like this after a chance meeting with Bill Jordan of Realtree who was driving a burb just like it in 1998. I’ve wanted one ever since. I plan to hang another 100k on it. Thanks GB

I did not find anything else that may have caused this issue with the temp gage and have just "lived with it" after my last post 12/3/22 . That being said I am starting to have other issues with the oil pressure, Tach and fuel gage jumping about "2 lines" at will. But I will start another thread if needed after reachrining these problems .