The Stovebolt Site Forums The Shop Area The Electrical Bay 1963 temperature gauge

I have the gauge dash in my '63 . The temperature gauge has lost it's credibility . When the truck is warmed up , the gauge is in the fully (far right) hot position . I verified the engine temperature with an infared thermometer (the engine was no hotter than 200F) .
Is there any way to add a resister or something to get the gauge to become accurate again ?

I'd change out the sender first. It's not too pricey. If that doesn't fix it, it's probably the guage.

Thanks . I picked up a new Delco sender yesterday and installed it - same results as the Standard TS6 sender that was in before .
I just came in from running two new wires- one directly from the gauge to the sender and the other from the gauge directly to 12V . same results .
I also tried a variety of resistors I had , as well as a ballast resistor from an Accel Supercoil and a household ceiling fan control . Each of these attempts gave me no reading on the gauge .
I am sure the sender is good and I know the gauge moves - just too far too soon . This is beginning to stump me .
HELP

I have been working part time at a parts store & I found the temp senders are listed as the same for 60-72, although I know they changed in 67 from 30 Ohm to 90 ohm gauges/senders. I think maybe that is what you are getting, a later sender. See if you can score an original.

How can I tell a 60-66 from a 67 - later ?
The one I had and the one I got yesterday both were supposed to be for the 60-66 .

I run an aux temp guage on my 63 just because the unit in the dash doen't read the temp, just tells you cold or hot. Living in the Phoenix metro area, I like to know exactly where my temp is running. When my aux guage reads 180 (where it constantly runs), my in dash guage is just slightly to the left of the midway point. Someone correct me if I'm wrong but shouldn't you be able to tell the earlier sender by simply ohming it out when not hooked up? Or does heat need to be applied before ohming?

I also made sure there was no pipe sealant on the threads - still same results .

One way to check and see if the sender is the right resistance might be to check the resistance when it was cold (room temp) and then put it in some boiling water for a little while to warm it up. That might not give you the extreme ends of the temperature range, but I would guess that it would give you enough to determine if you have the right sender for your gauge. I would also think that you could watch the resistance change as the sender cooled off after being removed from the boiling water. I've pulled a similar stunt when trying to figure out if a thermal switch was working. Just a thought...

Thanks for the idea . I have three senders now (don't ask) , so I could try out the two that are not installed to see how they react .
At this point I am going to try to find another gauge to see if that is my problem . I believe in coincidences , but three senders giving me the same high reading on the same gauge , when I know the engine is not overheating , is a bit much to believe.

greg63,

I'm not 100% clear on the workings of your gauge, but I think it is important that the gauge has a proper ground in the dash assembly. This could affect how the gauge compares the 'in dash ground' with the ground provided by the sending unit.

With the way the gauge is constructed, it is usually a work or no-work kind of deal. Your gauge is working, but incorrectly.

If the accuracy of the gauge depends on the variable ground supplied by the sending unit, there could be a possibility that the wire leading to the sender has been damaged and is 'leaking' to its own ground.

These are just guesses on my part though. :confused:

Stuart

I wondered about that as well , so I ran two new 18ga seperate wires from the gauge ,under the dash, out the door , under the hood and to the gauge and 12V supply (completely seperate from the original wiring harness).I even took a pair of alligator clips and grounded the gauge ground post to the metal dash . None of that made any difference .

Sheesh...you're one step ahead of me!


Stuart

Well , if I ever do figure this out , I will post the answer . I am sure I am not the only one to run through this situation .

The temperature sensors are negative coefficient (NTC) style units. As the temperature rises, the resistance falls. You should be able to check your sensor resistance with an ohm meter to see if all the units you have are reading alike. If so, you may have the incorrect one. I have a 261 in my 1949 GMC with the electric sensor in the thermostat housing and it never has read correctly. Always reads low and never gets to 180. I tried resistors inline rated from 1 ohm to 10K ohm and nothing worked. The gauge would either read low or peg high. So, until someone comes up with a correct unit that'll read, I'll just watch for steam.

I checked mine today,,663 Ohms on two known good 64 senders, room temp prolly 70-75*,,Brian

Thanks Brian .
I will get all three of mine out tomorrow and see what they tell me .
I am right in the middle of getting this problem resolved . I picked up an aftermarket set-up (sender and gauge)and tried it out (wired direct to gauge from battery)). I ran the engine (327) for five minutes at 2000 rpm . The gauge never went above 195F (195F thermostat). Now I know the engine is not overheating .
I will try the gauge with the trucks wiring harness next to see if that works . If that is good ,then I will try to eliminate either the original sender or the original gauge as the culprit .

Is it possible you have the connections on the back of the gauge reversed. Iv,e fixed gas gauges before by using the resister off of a later model gauge across the terms of the gauge. All the GM gauges from about the early 70,s on up have this resister on the back. There are different colors for different values so they can be taylored to match.