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My temp sensor has slowly gone cold at the gauge. The aluminum heads take the smaller water temperature sensor compared to the standard 3/4" iron head sensor.
Can anyone with the same compatible year sensor that fits, let me know of the part #?
Thanks much.
Steve
I just bought one of these. My ‘76 stock heads were 1/2”, are the earlier ones different?
I have yet to install it though. I have to pull the temp sensor out of where it is now and see if the part beyond the threads will fit the ID of the fitting.
This comes up from time to time. I've never heard of another sensor that is calibrated correctly. If you do find one that reads properly. Please let everyone know.
myself, I'd drill out and retap that head.
I just bought one of these. My ‘76 stock heads were 1/2”, are the earlier ones different?
I have yet to install it though. I have to pull the temp sensor out of where it is now and see if the part beyond the threads will fit the ID of the fitting.
I thought about that.  And the problem I then ran into was that the sensor I had (was sold to work with a '73) was too long to fit into the adapter. It would only make about two turns into the adapter and then bottom out before threads got tight.
I cleaned up the cold sensor's brass. I used no sealing tape. Only a narrow bead of Permatex #2 halfway up the sensor's threads did I apply, only to find no change at the gauge (still cold).
You would think here's a sensor out there that simply threads into the head and accurately indicates coolant temp on a '73's gauge. Perhaps an inquire to Dart Technical Support should be my next move. I'll get it figured out.
My temp sensor has slowly gone cold at the gauge. The aluminum heads take the smaller water temperature sensor compared to the standard 3/4" iron head sensor.
Can anyone with the same compatible year sensor that fits, let me know of the part #?
Thanks much.
Steve
Perhps it ain't bad sender ? Perhaps gage at fault ?
Perhaps the Passenger head has another identical sender situated between cyls 6 & 8 ?
If it works OK, you can either have machine shop turn it down & rethread it to fit alum head OR enlarge alum head's hole & rethread it to fit sender.
also, Lectric Limited used to sell turned down and rethreaded senders for C3 https://www.lectriclimited.com/ call em
OR
D&M repairs, restores and calibrates gages
Suggest call em, explain your dilemma, ask em what they can do..They likely get similar calls every week.
If you send your gage & a sender, perhaps they can calibrate & match. call em
Cavu2u
i suspect you meant 3/8" and if so you could try this IF you can find a Willcox Adjustable Resistor to dial in installed gauge. This starts at the relevant steps for the proposed sender but you can go back to the beginning for more info: https://www.corvetteforum.com/forums...post1608844152
Originally Posted by Cavu2u
Thanks so very much for pointing me in the right direction! Very much appreciated.
OLDer heads have a LARGE One-wire temp sender for coolant temp GAGE: has 1/2"-14 NPT (tapered pipe thread)
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NEWer heads have a SMALL One-wire temp sender for coolant temp GAGE: has 3/8"-18 NPT (tapered pipe thread)
Last edited by Rebelyell; Dec 8, 2025 at 04:58 PM.
My 73 small block had 1990 L98 aluminum heads on it when I purchased it. The temp gage was inoperable as the 3/8 NPT sensor holes were fitted with brass plugs. I opted to go with the solution that Wilcox offered at the time which was a turned down and rethreaded brass temp sensor paired with one of their adjustable resistors to replace the bar type resistor on the back of the temp gage. As you may or may not be aware Wilcox is no longer in business but others are offering similar adjustable resistors for classic Chevys. When I installed my Wilcox sourced parts I was a little disappointed at first because the setup didn’t go like their instructional video portrayed. Their install video is still available on YouTube. It shows the gage coming into correct calibration with about 10 turns on the resistor. Mine required about 25-30 turns and I started freaking out a little thinking it was defective before I got it to respond but it did work and continues to perform as advertised to this day. Good luck in your efforts.
This comes up from time to time. I've never heard of another sensor that is calibrated correctly. If you do find one that reads properly. Please let everyone know.
myself, I'd drill out and retap that head.
Corvette America sells it....I had the Standard part number at one time.....but there is one available....Wilcox sold it too if I remember....
You can go to the plumbing section at Home Depot and jury rig it for about $2 like I did. It was supposed to be temporary until I took the heads off but it's been like that for 15 years now. You really didn't see it when I had the factory ram horns.
I do NOT see the adjustable resistor in the corvette america website. I only see the inline resistor. If somebody can point us to willcox equivalent then it would help. The inline resistor will only really correct temp reading at one value.
Here is the youtube video of the Willcox back-of-the-gauge adjustable resistor.
Mine has worked wonderfully since I installed it .....it made my original old 1/2" sender read great just about everywhere....WHEN DIALED IN WITH THE WILLCOX ADJUSTABLE RESISTOR
In the link I provided above I mention the 3/8' sender part number that works adequately in the 175 to 210 range as a substitute.......WHEN DIALED IN WITH THE WILLCOX ADJUSTABLE RESISTOR
Last edited by carriljc; Dec 10, 2025 at 12:13 PM.
I bought this one on Ebay for cheap. It's a zero to 90 ohm adjustable resistor. I bet it would work. Just turn the **** until the gauge reads correct then remove the resistor and measure across the terminals to see what fixed resistor you need to find and install.
In theory, this should work but I never got to try it. I just hogged out the small hole in the head and tapped it for the bigger sender. Hope this helps.
5/8" Water Temp sensor for the '73 needed.
 And the problem I then ran into was that the sensor I had (was sold to work with a '73) was too long to fit into the adapter. It would only make about two turns into the adapter and then bottom out before threads got tight. 
