Temp Gauge Not Moving
Thread Starter
Instructor
Joined: May 2018
Posts: 234
Likes: 57
Temp Gauge Not Moving
Fixed the fuel leak on my recently acquired C3 and finally drove the car about 6 miles and noticed the temp gauge was not moving off of 100. I read that could be normal as the engines take a while to warm up. Any opinions on this? Or, do I have an issue that needs to be fixed? Thanks!
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,361
From: At my Bar drinking and wrenching in Lafayette Colorado
350 Chevy engines do not "take a while" to warm up - in 6 miles of driving any 350 Chevy will be well above 100 degrees if everything is operating correctly.
Assuming you have verified that the cooling system is full, and you have verified that your thermostat is not stuck open, pull the wire off the temp sending unit on the engine and turn the ignition to the "on" position. Your in-dash gauge should peg out in the "cold" direction. Now, insert a jumper wire into the disconnected wire and ground it to any part of the engine. With the ignition "on" your temp gauge should now peg out in the "hot" direction. If it does not, you have a bad gauge. If it does, your gauge and wiring is good, and you should replace the temperature sending unit.
An IR temp gun is an invaluable tool to troubleshoot and verify cooling system problems. Beg, borrow or steal one (or buy one) so you can verify the problem and the numbers your seeing.
Lars
Assuming you have verified that the cooling system is full, and you have verified that your thermostat is not stuck open, pull the wire off the temp sending unit on the engine and turn the ignition to the "on" position. Your in-dash gauge should peg out in the "cold" direction. Now, insert a jumper wire into the disconnected wire and ground it to any part of the engine. With the ignition "on" your temp gauge should now peg out in the "hot" direction. If it does not, you have a bad gauge. If it does, your gauge and wiring is good, and you should replace the temperature sending unit.
An IR temp gun is an invaluable tool to troubleshoot and verify cooling system problems. Beg, borrow or steal one (or buy one) so you can verify the problem and the numbers your seeing.
Lars
Last edited by lars; Apr 3, 2021 at 11:39 AM.
Instructor
Joined: Feb 2019
Posts: 201
Likes: 48
From: Detroit
350 Chevy engines do not "take a while" to warm up - in 6 miles of driving any 350 Chevy will be well above 100 degrees if everything is operating correctly.
Assuming you have verified that the cooling system is full, and you have verified that your thermostat is not stuck open, pull the wire off the temp sending unit on the engine and turn the ignition to the "on" position. Your in-dash gauge should peg out in one direction. Now, insert a jumper wire into the disconnected wire and ground it to any part of the engine. With the ignition "on" your temp gauge should now peg out in the opposite direction. If it does not, you have a bad gauge. If it does, your gauge and wiring is good, and you should replace the temperature sending unit.
An IR temp gun is an invaluable tool to troubleshoot and verify cooling system problems. Beg, borrow or steal one (or buy one) so you can verify the problem and the numbers your seeing.
Lars
Assuming you have verified that the cooling system is full, and you have verified that your thermostat is not stuck open, pull the wire off the temp sending unit on the engine and turn the ignition to the "on" position. Your in-dash gauge should peg out in one direction. Now, insert a jumper wire into the disconnected wire and ground it to any part of the engine. With the ignition "on" your temp gauge should now peg out in the opposite direction. If it does not, you have a bad gauge. If it does, your gauge and wiring is good, and you should replace the temperature sending unit.
An IR temp gun is an invaluable tool to troubleshoot and verify cooling system problems. Beg, borrow or steal one (or buy one) so you can verify the problem and the numbers your seeing.
Lars
what if when you ground it goes 3/4 of the way. I had this issue.
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,361
From: At my Bar drinking and wrenching in Lafayette Colorado
You'll get an accurate indication of actual engine temp if you shoot the intake manifold water crossover at the base of the thermostat housing. This will be the temperature of the coolant below the thermostat. You can also shoot the temp right at the base of the water temp sending unit - this will tell you what your gauge should be reading.
Lars
When you ground the wire to the temp sending unit, the gauge should peg out in the full "hot" position. If the gauge does not go to full hot "pegged out" when the wire is grounded, you have a gauge problem.
Lars
When you ground the wire to the temp sending unit, the gauge should peg out in the full "hot" position. If the gauge does not go to full hot "pegged out" when the wire is grounded, you have a gauge problem.
Last edited by lars; Apr 3, 2021 at 11:41 AM.
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Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,361
From: At my Bar drinking and wrenching in Lafayette Colorado
Remove it and check it.
-or-
If you have an IR gun, you can "shoot" the engine temp below the thermostat housing and on the housing itself as the engine warms up. If the thermostat is closed and working right, the temp below the thermostat (manifold water crossover) will rise up to the opening point of the thermostat, while the temp of the housing and the hose going to the radiator will remain low. If the temp below and above the thermostat rise at the same rate and are roughly the same as the engine warms up, the thermostat is stuck open.
-or-
If you have an IR gun, you can "shoot" the engine temp below the thermostat housing and on the housing itself as the engine warms up. If the thermostat is closed and working right, the temp below the thermostat (manifold water crossover) will rise up to the opening point of the thermostat, while the temp of the housing and the hose going to the radiator will remain low. If the temp below and above the thermostat rise at the same rate and are roughly the same as the engine warms up, the thermostat is stuck open.
Thread Starter
Instructor
Joined: May 2018
Posts: 234
Likes: 57
Update: Thanks to all for the advice. Problem fixed. The OHM line(I think that is what it is called) was not connected to the temp sending unit. Was kind of a pain taking the cover off to be able to plug it it; BUT all is good. Thanks again. You'll see another question as I went to replace coolant...
Thread Starter
Instructor
Joined: May 2018
Posts: 234
Likes: 57
Last edited by bearcatfan9; Apr 10, 2021 at 11:18 AM.
Le Mans Master
Joined: May 2007
Posts: 5,008
Likes: 1,115
From: North tonawanda NY
Remove it and check it.
-or-
If you have an IR gun, you can "shoot" the engine temp below the thermostat housing and on the housing itself as the engine warms up. If the thermostat is closed and working right, the temp below the thermostat (manifold water crossover) will rise up to the opening point of the thermostat, while the temp of the housing and the hose going to the radiator will remain low. If the temp below and above the thermostat rise at the same rate and are roughly the same as the engine warms up, the thermostat is stuck open.
-or-
If you have an IR gun, you can "shoot" the engine temp below the thermostat housing and on the housing itself as the engine warms up. If the thermostat is closed and working right, the temp below the thermostat (manifold water crossover) will rise up to the opening point of the thermostat, while the temp of the housing and the hose going to the radiator will remain low. If the temp below and above the thermostat rise at the same rate and are roughly the same as the engine warms up, the thermostat is stuck open.
Last edited by augiedoggy; Apr 10, 2021 at 09:15 AM.
Heel & Toe
Joined: Mar 2021
Posts: 21
Likes: 2
From: San Diego
I was able to ensure that my green wire led to the temp sensor and was connected. I disconnected and got full left deflection with ignition on and full right deflection when I grounded the sensor to the block. So I guess this means the gauge is good according to guys on this thread. However, temp needle still shows just right of the 100 degree hash mark when up to temp and the IR gun reading at TS housing is around 160. TS is working, hoses good, new radiator, etc. I had already replaced the temp sensor a few months ago with one recommended on the CorvetteBen YT channel: https://www.lectriclimited.com/tempe...ng-unit-115879
So, any other ideas of what to check? Try another brand of temp sensor? My mech recommends just to live with it and use the current mark as indicated on the gauge as a baseline reading. I tend to agree with him, but I can't seem to leave well enough alone...
So, any other ideas of what to check? Try another brand of temp sensor? My mech recommends just to live with it and use the current mark as indicated on the gauge as a baseline reading. I tend to agree with him, but I can't seem to leave well enough alone...
Team Owner
Joined: Mar 2002
Posts: 44,626
Likes: 1,826
From: Huntsville AL
I was able to ensure that my green wire led to the temp sensor and was connected. I disconnected and got full left deflection with ignition on and full right deflection when I grounded the sensor to the block. So I guess this means the gauge is good according to guys on this thread. However, temp needle still shows just right of the 100 degree hash mark when up to temp and the IR gun reading at TS housing is around 160. TS is working, hoses good, new radiator, etc. I had already replaced the temp sensor a few months ago with one recommended on the CorvetteBen YT channel: https://www.lectriclimited.com/tempe...ng-unit-115879
So, any other ideas of what to check? Try another brand of temp sensor? My mech recommends just to live with it and use the current mark as indicated on the gauge as a baseline reading. I tend to agree with him, but I can't seem to leave well enough alone...
So, any other ideas of what to check? Try another brand of temp sensor? My mech recommends just to live with it and use the current mark as indicated on the gauge as a baseline reading. I tend to agree with him, but I can't seem to leave well enough alone...
Drifting
Joined: Apr 2007
Posts: 1,970
Likes: 45
From: Cameron Park CA
I was able to ensure that my green wire led to the temp sensor and was connected. I disconnected and got full left deflection with ignition on and full right deflection when I grounded the sensor to the block. So I guess this means the gauge is good according to guys on this thread. However, temp needle still shows just right of the 100 degree hash mark when up to temp and the IR gun reading at TS housing is around 160. TS is working, hoses good, new radiator, etc. I had already replaced the temp sensor a few months ago with one recommended on the CorvetteBen YT channel: https://www.lectriclimited.com/tempe...ng-unit-115879
So, any other ideas of what to check? Try another brand of temp sensor? My mech recommends just to live with it and use the current mark as indicated on the gauge as a baseline reading. I tend to agree with him, but I can't seem to leave well enough alone...
So, any other ideas of what to check? Try another brand of temp sensor? My mech recommends just to live with it and use the current mark as indicated on the gauge as a baseline reading. I tend to agree with him, but I can't seem to leave well enough alone...
When I replaced,the original heads with aluminum heads, the temp sending unit hole was too small for the original sending unit. I tried several sending units, but could not get the temp gauge to read correctly. To fix it, I mounted the original sending unit in the intake at the water crossover. The gauge reads correctly.
Le Mans Master
Joined: Jan 2001
Posts: 6,687
Likes: 1,364
Just get the Willcox adjustable resistor and dial it in. Works like a dream. I lived with my inaccurate gauge for years (decades?) and got it dialed in promptly. Follow this for more info.
https://www.corvetteforum.com/forums...post1593637352
https://www.corvetteforum.com/forums...post1593637352
I was able to ensure that my green wire led to the temp sensor and was connected. I disconnected and got full left deflection with ignition on and full right deflection when I grounded the sensor to the block. So I guess this means the gauge is good according to guys on this thread. However, temp needle still shows just right of the 100 degree hash mark when up to temp and the IR gun reading at TS housing is around 160. TS is working, hoses good, new radiator, etc. I had already replaced the temp sensor a few months ago with one recommended on the CorvetteBen YT channel: https://www.lectriclimited.com/tempe...ng-unit-115879
So, any other ideas of what to check? Try another brand of temp sensor? My mech recommends just to live with it and use the current mark as indicated on the gauge as a baseline reading. I tend to agree with him, but I can't seem to leave well enough alone...
So, any other ideas of what to check? Try another brand of temp sensor? My mech recommends just to live with it and use the current mark as indicated on the gauge as a baseline reading. I tend to agree with him, but I can't seem to leave well enough alone...
Last edited by carriljc; Apr 14, 2021 at 01:39 PM.
Le Mans Master
Joined: Mar 2001
Posts: 6,231
Likes: 1,009
From: Watkinsville, GA and Glen Cove, NY
I had Lectric Limited’s sender and it was not accurate. None of the new ones are. Either get the variable resistor mentioned above, or use the original sender. I am using the variable resistor and it works great.