The Stovebolt Site Forums The Shop Area The Electrical Bay Temp Gauge Issue

I am still unable to get my stock temp gauge to work on my 57 Chevy.
All wires, temp sensor at engine and temp gauge installed in instrument panel has been replaced. When I take a test light to the (green wire) sensor at the engine, the light comes on as well as the gauge. There is also power at the pink wire on the other pole at the gauge.
According to the after market wire diagram, the green goes to the outer pole and the pink to the inner pole closest to the amp gauge.
If the wires got crossed would this blow the guage?
I have been unable to find any info in the assembly manual showing the correect set up.
Any ideas?

are you saying that when you hook the test light from the sender to ground that when the light comes on the gauge also registers? if that's happening then the sender has to be bad, or else you've got a bad connection at the sender or you've used some thread sealer [or teflon tape] on the sender so it's insulated from ground

if there's power through the gauge to the sender, the gauge can't be blown, but it may be that you got those gauge connections shorted out, make sure the cardboard piece is insulating the pegs from the case - normally when you first turn on the key the gauge will jump at least slightly up off the peg [cold]

if you look at the factory schematic, the position of the wires is indicated by location on the diagram, note that the layout is just like in the truck and there is a line on the diagram labeled "front of dash", top is right side [ign sw], bottom is left [lite sw], and it shows the sender wire [grn] closest to the ign sw, and hot wire ["ign"] to the lite sw side, so you seemingly do have them reversed

if you short the green wire to ground at the sender, the gauge should read full hot, but you might try that with the wires reversed from your picture

Bill

Is the gauge not marked + and -? Have you checked for 12V at the pink wire?

The sender is a variable resistor to ground. You'll need a meter to check it. As it warms there should be less resistance.

To test the gauge: Remove the wire from the sender. Connect a jumper wire to the sender side of the gauge. Turn on the ignition. The gauge will do nothing. Ground the jumper wire. The gauge will go to full sweep.

If all that works and it still doesn't work hooked up make sure the wire from the gauge to the sender isn't open.

Taking a closer look
I see the back of the gauge says IGN (right) SENDER (left)
I hope it will be just this simple to just switch the two wires

How long does it take for the needle to come up from cold??

Thank you Bill and Charlie!

Jon

should just take a few minutes, but an easy check is just short the sender terminal to ground

Bill

It works! It works! It was the wires!
i did the gauge test and the needle jumped over.
Then started the truck and in a few minutes the needle started to rise!
Now I need to fix the leaking oil tube at the back of the oil pressure gauge...never ends!

Thanks guys!

Jon

OK,
I let the engine run for almost 5 minutes and I noticed the temp gauge going almost all the way over to right (over heating).
I checked the top hose and it was very very hot. The bottom radiator larger hose was cold....
Is the thermostat not opening or closing?

Thank you

Jon

Sounds to me like the radiator is clogged.

I had the radiator boiled and went through. Is there a quick way to check if clogged?

bad stat or an airlock there - pull the stat right out and see how the engine acts - check the stat operation by putting it in a pan of hot water, check with a thremometer temp it opens ... if it works and the engine doesn't heat up without it, drill a small hole in the flange outside the moving part

Bill

OK,
Will check the thermostat out...what does drilling a hole do?

Thank you much

Jon

allows just a dribble of flow to let out any air, insures there's no air bubble trapped under the stat preventing it from reacting to water temp .... could be other things, but checking how it reacts with the stat out should give a better idea - could even be a bad water pump

Bill

OK,
Took stat out and placed in 180 degree water. It did open.
I started the truck with out it in and it ran fine and the temp gauge needle was between the left dot and middle dot.

What does that show?

Thanks!

Jon

must have been air locked, the water needs to be in direct contact to make the stat react, air temp doesn't work - happens when you put it all together with little or no water in the engine and then fill it after it's all closed up - don't drain the rad below the level of the top of the engine, just enough so removing the housing doesn't flow tooo much out, having run it now there should be no air in the engine, so if you don't introduce any it should work fine - if you don't wanna drill the hole, make sure the engine is right full of water when you put the stat in, enough so putting it in causes some to overflow and there shouldn't be an airlock problem

Bill

Hi Bill,
Yes, when I removed the 2 bolts on the stat cover, to pull the stat out, a whole bunch of water flowed out. I did not refill the radiator when I ran the engine.

On installing the stat, do I put the spring down or up?
I forgot to look when I pulled it out.

yes, spring down, don't think it'd fit the wrong way ... you let out as much water as was in the rad above the stat - when you refill it, leave it an inch or 2 down for expansion and let it find it's own level, when it doesn't push any out the overflow when hot, that's where it likes to be

Bill

Id go along with what Bill says.

Dan Bentler

Thank you!

sorry to hijack a thread, but I picked up a set of gauges cheap and when removing they cut the thermostat sender between the engine and the gauge head. Is there some magic to that wire, or does it just conduct heat to register temp? Could it be soldered back together or is the whole gizmo shot?

Jon - if you mean the "mechanical" gauge, with a fluid/gas filled capillary tube, it's not easily DIY repairable, although there's some instructions here and there are places around that rebuild them, or useta be .... so no, it can't be soldered, and while it's not necessarily ruined you'd prolly be better off trying to find another unmolested gauge

Bill

I inspected my "wire" or "tube" and I see no hollow center. It simply appears to be a piece of metal wire, not sure of the metallurgic properties, but not copper.

I am at a loss. It also looks to be an aftermarket guage, as it is the only one in the pod that is aged differently.

It actually still looks really good. I cut a little more back very carefully and there is no hollow core, it is solid through and through.

sometimes ya just hafta prove things to yerself, solder it up and watch it not work

take a look at gauges at auto parts places, all mechanical temp gauges have the same type of sealed tube/sender, the opening for a gas pressure operated bourdon tube gauge is miniscule

Bill

Thanks Bill. Didn't know that the hole I was looking for was only visible via a hand lens. Never dealt with these before.

Put stat back in and let engine run. Temp guage shot back up to hot. I also left the radiator cap off and watched the water. I had a temp gauge and the water was running at 180 degrees. Now, if the stat opens at 180 would I be able to see the water start to move?
If the needle is pegged all the way to hot,,would the engine be boiling over?
After I turned the engine off, I felt the top hose as well as the 2 hoses to the heater. All three were very hot. The larger bottom one (bottom of radiator) was warm but not that hot.
Is it possible the temp sensor is rated for a different engine? It looks like the old stock ones. Bought it from NAPA.

What I am really not getting is when I ran the engine with the stat out...the temp gauge was fine..I think I will change out the sensor and then run engine that way and maybe run without the stat.
UPDATE: Changed out the temp sensor. The gauge needle runs now just above the middle dot.


Thanks all!

Jon

That is better. I was going to suggest using an infrared thermometer on it to see if it was really over heating. I suspected it might be the sender.

Charlie,
What about the stat? If I have the cap off and the stat opens will I start to see water moving?

Just to make sure..."normal" running on the temp needle is half way or just above half?

Thank you as always!

Jon

normal will vary between trucks on these ol gauges Jon, might be anything from say 1/4 to 1/2 or a bit above, and it depends on the rating of the stat, 160 or 180 etc - what's best is to warm it up and check the temp in the rad and compare to what's on the gauge so you know that particular trucks "habits" ... you might be able to see movement, but don't panic if you can't really tell, there's a baffle in the top tank - the temp is what matters, and an infrared thermometer is useful as you can check the temp on both sides of the thermosat at the housing, the temp of the top and bottom hoses, etc

Bill

Regarding seeing water moving in the radiator top-tank: rev the engine while looking into the tank (stand back, on first try).

Hi guys,
Sorry to open this one back up again. Took truck about 200 miles last weekend end and it did just fine...except for the smoke at a stop light and the temp gauge. The gauge needle is running just below the "dot" for hot.

Is there a way to adjust the gauge needle?

Thank you!

no adjustment other than the sender, which could conceivably be faulty ... did you check the actual temp with an infrared thermometer? still have the 180 thermostat? might try a 160

Bill