temperature sensor question
Thread Starter
Melting Slicks
Joined: Oct 2006
Posts: 2,366
Likes: 105
From: Flower Mound TX
temperature sensor question
I have just finished putting the rebuilt motor in the 64 (pulls like a *****) and I first noticed that the temp gauge never really moved. Since I now have aluminum heads I was paranoid about the temp and replaced the sensor that screwed into the intake. Apparently, I wasn't patient enough to let it warm up and it started to move to about 200 degrees after a little driving.
After driving it some more, it went to the max of 240 degrees. I had borrowed my buddies laser heat sensor and the temp isn't even close to that so something is amuck.
I put in my old sending unit since I had no troubles prior to the rebuild and it still stays at the top of the gauge. I know the sensor grounds thru the intake, but what am I missing? I know the motor is not overheating, but it still doesn't sit well with me that the gauge isn't working.
BTW, I am now running an electric fan that works very well to cool it off. Could I still have a pocket of air in the system that hasn't worked it's way out?
After driving it some more, it went to the max of 240 degrees. I had borrowed my buddies laser heat sensor and the temp isn't even close to that so something is amuck.
I put in my old sending unit since I had no troubles prior to the rebuild and it still stays at the top of the gauge. I know the sensor grounds thru the intake, but what am I missing? I know the motor is not overheating, but it still doesn't sit well with me that the gauge isn't working.
BTW, I am now running an electric fan that works very well to cool it off. Could I still have a pocket of air in the system that hasn't worked it's way out?
Team Owner
Joined: Oct 2000
Posts: 38,897
Likes: 1,926
From: Washington Michigan
To check the gauge, with the key "on", disconnect the sender wire at the sending unit - the gauge should peg to full cold. Then ground the connector terminal to the engine, and the gauge should peg to full hot. 
Thread Starter
Melting Slicks
Joined: Oct 2006
Posts: 2,366
Likes: 105
From: Flower Mound TX
I forgot to mention that I disconnected the connector hoping to see it go low and it stayed there. That tells me that there is a voltage coming from somewhere or a gauge is all of a sudden bad?
Race Director
Joined: Oct 2005
Posts: 12,468
Likes: 1,548
From: Camp Verde AZ
C1 of Year Finalist (performance mods) 2019
2017 C1 of Year Finalist
Make sure you are shooting a flat black surface with the IR temp gun.
Unless it is a more expensive model with variable emissivity settings, it is calibrated for flat black. The upper radiator hose at the T stat outlet is a good place to measure.
For instance, my gun will read 190 on the radiator hose and 140 on the chrome polished T stat housing and 160 on the natural alum intake just below the T stat.
Doug
Unless it is a more expensive model with variable emissivity settings, it is calibrated for flat black. The upper radiator hose at the T stat outlet is a good place to measure.
For instance, my gun will read 190 on the radiator hose and 140 on the chrome polished T stat housing and 160 on the natural alum intake just below the T stat.
Doug
Thread Starter
Melting Slicks
Joined: Oct 2006
Posts: 2,366
Likes: 105
From: Flower Mound TX
OK, I just did a little experimenting.....
I noticed tonight that when I turned on the key, the temp gauge moved further to the right ever so slightly even though it was already at 240.
I had hooked up the new electric fan to an ignition source that I found under the hood and installed a break in the ground on a toggle switch. When I turn off the fan, the gauge doesn't move.
At no given time do I see the gauge move back to the left. That includes the disconnecting of the wire from the temp sensor.
Please tell me my gauge is OK.....What am I missing????
I noticed tonight that when I turned on the key, the temp gauge moved further to the right ever so slightly even though it was already at 240.
I had hooked up the new electric fan to an ignition source that I found under the hood and installed a break in the ground on a toggle switch. When I turn off the fan, the gauge doesn't move.
At no given time do I see the gauge move back to the left. That includes the disconnecting of the wire from the temp sensor.
Please tell me my gauge is OK.....What am I missing????
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Thread Starter
Melting Slicks
Joined: Oct 2006
Posts: 2,366
Likes: 105
From: Flower Mound TX
I have found the problem!!!!!!
I noticed that the top fuse in the fuse block was blown. Not knowing (even right now) what that fuse is, I replace it. I had previously taken off all connections to the fan and hit the key. The gauge jumped right back to cold. You could have knocked me over with a feather. I guess I need to see what that fuse is. LOL.
Sooooooo, I guess my next question is what is a good ignition circuit to put an electrical fan????
I noticed that the top fuse in the fuse block was blown. Not knowing (even right now) what that fuse is, I replace it. I had previously taken off all connections to the fan and hit the key. The gauge jumped right back to cold. You could have knocked me over with a feather. I guess I need to see what that fuse is. LOL.
Sooooooo, I guess my next question is what is a good ignition circuit to put an electrical fan????
Team Owner
Joined: Oct 2000
Posts: 38,897
Likes: 1,926
From: Washington Michigan
The top fuse is ignition-switched, and feeds the temp gauge, fuel gauge, fuel tank sending unit, and park brake warning light. If you have an electric fan, it should be fed from a relay that's powered from the horn relay, not directly from a fuse.
