temperature sensor
Thread Starter
Cruising
Joined: Jun 2020
Posts: 11
Likes: 1
From: Elk River, MN
temperature sensor
I believe the temperature sensor in my engine is bad. The gauge hardly moves after the engine is started and runs up to temp. I have tested the gauge and it does work per the trouble shooting guide. My question is that when I went to replace it I noticed that the new one has about a 3/4" across the threads and the one in the drivers side of the engine between spark plug 1 & 3 is about 1/2". The parts house ordered a different one and it has the same size threads. What am I missing?
1978 C3, 350 engine, 4 speed - this is not the original engine and I know nothing about the engine other than it is a Gen 1 chevy 350.
Thank you in advance!
1978 C3, 350 engine, 4 speed - this is not the original engine and I know nothing about the engine other than it is a Gen 1 chevy 350.
Thank you in advance!
Race Director
Joined: May 2006
Posts: 18,604
Likes: 2,541
The engine temperature gauge sensor is on the drivers side head.
Are you sure you dont have a thermostat stuck open?
Have you rented a IR gun to confirm reading?
Are you sure you dont have a thermostat stuck open?
Have you rented a IR gun to confirm reading?
Last edited by MelWff; Nov 15, 2020 at 06:47 PM.
Thread Starter
Cruising
Joined: Jun 2020
Posts: 11
Likes: 1
From: Elk River, MN
Not sure if the thermostat is stuck or not. I am not having issues with it over heating, I just want the gauge to work.
No, I haven't rented an IR Gun. Didn't know that is possible and will in the future.
Safety Car
Joined: May 2004
Posts: 4,340
Likes: 1,566
From: los altos hills california
This "sender" is about the simplest device you could imagine, just a temperature sensitive resistor. Have you tried removing it, tested that its resistance does indeed change with heat. Cleaning the threads to get a clean electrical contact and reinstalling it might be all it needs. My experience with the newer "senders" is that they are calibrated differently and as I remember don't fit all that well even after you finesse the difference in diameter.
As far as renting an IR detector, these are really cheap. Handy in the kitchen as well, you should have one in your toolkit as well as a multimeter to measure electrical stuff.
As far as renting an IR detector, these are really cheap. Handy in the kitchen as well, you should have one in your toolkit as well as a multimeter to measure electrical stuff.
Last edited by ignatz; Nov 15, 2020 at 10:20 PM.
Team Owner
Joined: Jan 2006
Posts: 39,294
Likes: 171
From: Into the Mystic And yet, despite the look on my face, you're still talking TN
St. Jude Donor '09 thru '25
If you have the original temp gauge in the dash there is no sender available that will work correctly with the gauge. Ask me how I know.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
The average Joe will install a new temp sensor with a gob of thread sealant. This action keeps the unit from grounding itself to the head. Or in laymans terms, denies a complete circuit.
Two options when installing. Only use sealant on the bottom few threads. Or use sealant tape. The threads will cut the tape for good contact, yet seal-in coolant.
If your name is not Joe, you don't have to worry about it.
Two options when installing. Only use sealant on the bottom few threads. Or use sealant tape. The threads will cut the tape for good contact, yet seal-in coolant.
If your name is not Joe, you don't have to worry about it.
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Thread Starter
Cruising
Joined: Jun 2020
Posts: 11
Likes: 1
From: Elk River, MN
The average Joe will install a new temp sensor with a gob of thread sealant. This action keeps the unit from grounding itself to the head. Or in laymans terms, denies a complete circuit.
Two options when installing. Only use sealant on the bottom few threads. Or use sealant tape. The threads will cut the tape for good contact, yet seal-in coolant.
If your name is not Joe, you don't have to worry about it.
Two options when installing. Only use sealant on the bottom few threads. Or use sealant tape. The threads will cut the tape for good contact, yet seal-in coolant.
If your name is not Joe, you don't have to worry about it.
Le Mans Master
Joined: Jan 2001
Posts: 6,656
Likes: 1,357
Go to the Willcox website and order the temperature adjusting resistor.
Don't struggle with other solutions.
Order the adjustable resistor and in dial your gauge in with your present sender.
https://willcoxcorvette.com/corvette...resistor-77-82
I *think* your original post states that the sender you have installed at the present time is 1/2"? If so, then you can just order that from Willcox also...... but your local parts store should have one..... not rare.
Don't struggle with other solutions.
Order the adjustable resistor and in dial your gauge in with your present sender.
https://willcoxcorvette.com/corvette...resistor-77-82
I *think* your original post states that the sender you have installed at the present time is 1/2"? If so, then you can just order that from Willcox also...... but your local parts store should have one..... not rare.
Last edited by carriljc; Nov 16, 2020 at 11:01 AM.
Thread Starter
Cruising
Joined: Jun 2020
Posts: 11
Likes: 1
From: Elk River, MN
I was given some advice to use the same one that goes into an '82. They have the smaller hole that I need and it's the same gauge. I'm going to try it and if it doesn't work I'm only out $30
Thread Starter
Cruising
Joined: Jun 2020
Posts: 11
Likes: 1
From: Elk River, MN
Go to the Willcox website and order the temperature adjusting resistor.
Don't struggle with other solutions.
Order the adjustable resistor and in dial your gauge in with your present sender.
https://willcoxcorvette.com/corvette...resistor-77-82
Don't struggle with other solutions.
Order the adjustable resistor and in dial your gauge in with your present sender.
https://willcoxcorvette.com/corvette...resistor-77-82
Melting Slicks
Joined: Sep 2004
Posts: 3,217
Likes: 665
From: Northeast
Contact Willcox and inquire if this will work. :https://willcoxcorvette.com/corvette...79-3-8-npt-new
Thread Starter
Cruising
Joined: Jun 2020
Posts: 11
Likes: 1
From: Elk River, MN
Contact Willcox and inquire if this will work. :https://willcoxcorvette.com/corvette...79-3-8-npt-new
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
Yes, that was a shock that my new aluminum heads would not adapt to the stock sender. Luckily, I caught that before installing the heads. A quick trip to the machine shop, drilled and tapped ($30) for the old sender.
Team Owner
Joined: Jan 2006
Posts: 39,294
Likes: 171
From: Into the Mystic And yet, despite the look on my face, you're still talking TN
St. Jude Donor '09 thru '25
Contact Willcox and inquire if this will work. :https://willcoxcorvette.com/corvette...79-3-8-npt-new
Le Mans Master
Joined: Jan 2001
Posts: 6,656
Likes: 1,357
I understand. I couldn't decipher your original comment about 3/4" and 1/2". I see now that you have a 3/8" hole.
Nevertheless, call Willcox and they'll set you up with what you need.
PS- I actually have a 3/8" sensor installed so I can see if I can dial it in to work with my 68 gauge---- I just haven't done anything since I was able to dial in my 1/2" sensor that is now installed on the intake manifold next to the thermostat housing. Works like a dream.
Nevertheless, call Willcox and they'll set you up with what you need.
PS- I actually have a 3/8" sensor installed so I can see if I can dial it in to work with my 68 gauge---- I just haven't done anything since I was able to dial in my 1/2" sensor that is now installed on the intake manifold next to the thermostat housing. Works like a dream.
Team Owner
Joined: Jun 2001
Posts: 23,353
Likes: 1,054
From: Virginia USA
When I installed my ZZ4 the head location on it was the small diameter hole. I bought a sender to fit there but the calibration resistance was different. I put my original on the intake right next to the thermostat housing the used my IR temp gun to see the difference in temp at the head location vs. the intake location. Of course the intake was 10 to 15 degree cooler so I just keep that in mind when looking at my water temp. I would get one of Willcox's adjustable temp resistor (or make my own) but I don't feel like ripping the dash apart.......again!!!!
Le Mans Master
Joined: Jan 2001
Posts: 6,656
Likes: 1,357
Yah... I lived with my inaccurate gauge for decades. I don't even mind tearing it apart any more.... I recommend doing the adjustable resistor.... I did mine like 3 years ago and I'm still happy when I drive it and the gauge reads appropriately. 
Le Mans Master
Joined: Mar 2004
Posts: 7,424
Likes: 1,458
From: Little Rock AR
The specific bore required for the larger pipe thread tap is actually very close in diameter to the existing tapped hole minus the threads. If you just grind the existing threads out, you are ready to retap the new hole for the larger size pipe thread. Saves a trip to the machine shop.