Temp gauge not moving much

[76JimmyBlue]

The temp gauge on my '76 has never really moved past cold, even after driving for long periods of time. Actually the one time it got close to middle of the gauge was when it has a leak in the radiator haha. Havin trouble testing the sender but when I ground out the wire the gauge pegs all the way hot. Which I believe means the gauge works. The other option is if the thermostat is getting stuck or pushed open. It has an original "AC" 195 degree ( if I remember right) thermostat which I tried testing in hot water and seemed to open up fine. The upper rad hose immediately pressurizes on a cold start up like the rad isn't being bypassed by a closed t-stat. Also where on the gauge should the needle point/ what's the normal operating temp once warmed up? SBC 400 engine.

[Pontiac1976]

around about 195-210 depending on your cooling options if towing at warm to hot day warmed up temp.

[Wikid61]

Originally Posted by 76JimmyBlue

The temp gauge on my '76 has never really moved past cold, even after driving for long periods of time. Actually the one time it got close to middle of the gauge was when it has a leak in the radiator haha. Havin trouble testing the sender but when I ground out the wire the gauge pegs all the way hot. Which I believe means the gauge works. The other option is if the thermostat is getting stuck or pushed open. It has an original "AC" 195 degree ( if I remember right) thermostat which I tried testing in hot water and seemed to open up fine. The upper rad hose immediately pressurizes on a cold start up like the rad isn't being bypassed by a closed t-stat. Also where on the gauge should the needle point/ what's the normal operating temp once warmed up? SBC 400 engine.

Drain the coolant. Run if for a bit.

[hatzie]

1976 has the old GM 0513321 nailhead temp sensor.
Most aftermarket and even AC Delco replacement sensors do not have the same thermistor resistance curve as the originals.
If it's had the sensor replaced the gauge will not work properly.

Ecklers sells one that's supposed to work properly. https://www.ecklerscorvette.com/1957...-129200-1.html

[mr48chev]

I had that same issue with my 77 and went with a Delco G1852 sender. I think I ordered it from Amazon though. I looked it up to make sure and dang, that has been a while. The gauge works right per my heat gun though

I wouldn't trust an old thermostat and would replace it with a new quality brand one.

[truckin 79]

I had the same issue and someone put a temp sender for a light and not a gauge. I will say if you have a four core radiator the temp goes about a 1/4 of the way on the gauge but have never seen it go half. I have not towed with the truck though so who knows what temp is then

[cadillac_al]

All my trucks go up to about quarter way. If I ever see it half way in the middle I know there is a problem.

[Accelo]

All the aftermarket stuff is junk as far as accuracy goes.

Do not use any tape on the threads when installing.
After installation, I checked resistance between the manifold and the sender outer housing, and it should be essentially zero.

You can still sometimes purchase an AC part new. You can often find NOS ones on Ebay... Avoid the "made in Mexico" ones as the quality suffered when the production was changed.

One of these cheap sensors caused me a lot of headaches before I knew they were all over the map as far as resistance goes.

In my case, I checked everything and ended up replacing the water pump. Which was not the issue but it caused a big one when the casting broke with less than 50 miles on the newly rebuilt pump.
The fan went into the radiator, took out my radiator, fan clutch and fan. My assumption was the prior owner ran the pump to failure and then the re builder was too cheap to check it for cracks.
Later I traced it down to the (Piece of S) sensor. Last rebuild water pump I ever purchased.

Consumers are now the quality control department.
Probably best check is in boiling water (212 F) with a ohm reading of 78 ohms +/- 2.
Most stock gauges when inputted with 79-82 Ohms will read right around 212. This is a general statement regarding GM temp gauges. May or may not be applicable to our C10's but it's correct for the general time period.

BTW the Amazon ACDelco part says "Professional, premium aftermarket replacement".
It also says this: "Temperature Low-100 Degree F inch. Temperature High- 220 Degree F". Exactly what does that mean? No resistance at a specific temp given.
Some guys have been know to purchase three of the sensors and then use the one "closest" and return the others.
Says a lot when they vary a lot even between the same manufacture.
I never trust Amazon till I read all the fine print.

A friend of mine manufactures coffee pots. He has to trace this stuff down all the time. One time even the quality control dept measuring device was off.



Cheers.

[Willowrun]

Originally Posted by cadillac_al

All my trucks go up to about quarter way. If I ever see it half way in the middle I know there is a problem.

Same here.

[76JimmyBlue]

It does have the big four row radiator. I have to check again but I don't think it's even coming close to 1/4 up the gauge when warmed up. When testing the resistance, do I put one tester lead to the sender body or the block? I was having a hard time getting any reading. If i really have to I guess I'll replace that sensor, probably maybe the one hatzie suggested, and the thermostat because I think it's original to the truck.

[Axle]

If you don't have one, buy yourself an infrared temp gun. It'll at least give you a ballpark of temps to see how close or far off the guage is.

I gave up on temp sensors for my 81, stuck an aftermarket guage in it, at least I get temperatures that are reasonably accurate.

[76JimmyBlue]

Originally Posted by Axle

If you don't have one, buy yourself an infrared temp gun. It'll at least give you a ballpark of temps to see how close or far off the guage is.

I gave up on temp sensors for my 81, stuck an aftermarket guage in it, at least I get temperatures that are reasonably accurate.

I have one I can borrow. What temp am I looking for, and do I aim it at the sender?