Temperature Gauge and Sending Unit
Burning Brakes
Joined: Feb 2011
Posts: 850
Likes: 12
From: Shakopee MN
My WT203Z worked great for me. But with my new engine and heads I needed a smaller thread. I know Willcox will turn down my original but since it seems hard to find a good working one, I didn't want to chance that using my original as test bait for a friends friend who can also turn it down to the size I wanted.
So I went and looked for a WT230Z and apparently they aren't made any longer. I sent an email to SMP Corp who makes these and asked them why. Here is the response I got back from their marketing mgr:
So even if you found a good quality one, according to their specs, it won't be right as we need 80 ohms around 210 not 220.
Not sure if that helps anyone but I thought it was good info to share.
SL
So I went and looked for a WT230Z and apparently they aren't made any longer. I sent an email to SMP Corp who makes these and asked them why. Here is the response I got back from their marketing mgr:
Functionally the WT203, WT203P, and WT203Z are the same. The specs that I have here for all of them is 368 Ohm at 100 degrees F and 80 Ohm at 220 degrees F. The difference lies in the quality. The WT203 is our premium quality part, while the WT203P and the discontinued WT203Z are our standard quality value line.
Not sure if that helps anyone but I thought it was good info to share.
SL
Instructor
Joined: Feb 2013
Posts: 228
Likes: 67
From: Kennewick WA
I too have been through this whole issue with the temp Gauge on my 73. I replaced the sending unit with one from Ecklers but the gauge would not move. Did all the tests, show the gauge is good so I bought the Willcox variable resistor and set my gauge to be close using a temp gun reading off of the sender base. I also bought a new gauge from Willcox but didn't use it, so another new part goes on the shelf 
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
My WT203Z worked great for me. But with my new engine and heads I needed a smaller thread. I know Willcox will turn down my original but since it seems hard to find a good working one, I didn't want to chance that using my original as test bait for a friends friend who can also turn it down to the size I wanted.
So I went and looked for a WT230Z and apparently they aren't made any longer. I sent an email to SMP Corp who makes these and asked them why. Here is the response I got back from their marketing mgr:
So even if you found a good quality one, according to their specs, it won't be right as we need 80 ohms around 210 not 220.
Not sure if that helps anyone but I thought it was good info to share.
SL
So I went and looked for a WT230Z and apparently they aren't made any longer. I sent an email to SMP Corp who makes these and asked them why. Here is the response I got back from their marketing mgr:
So even if you found a good quality one, according to their specs, it won't be right as we need 80 ohms around 210 not 220.
Not sure if that helps anyone but I thought it was good info to share.
SL
As recently as two years ago, I tested each and every brand on the market. Once completed, we then cut the tops out of them to test the components (thermister) inside. (Including the one that says that it has oil in it, it didn't) We have tested each of these same brands and not one worked per the original gauge requirements.
So.. instead of trying to re-invent the mouse trap, we made the resistors! The resistor will fix the issue with any sender that is in the ball park close.
3rd Gear
Joined: Nov 2016
Posts: 3
Likes: 0
From: Beech Island SC
What does the plug look like that fits over the sending unit? I ask because the water temp guage doesn't work and I dont know what to look for.
Thank you for your help
Le Mans Master
Joined: Jan 2001
Posts: 6,743
Likes: 1,385
I installed a duralast tu66 in my "small hole" vortec heads
....and it reads about the same as my stock sensor (reads cold).
See here:
https://www.corvetteforum.com/forums...tec-heads.html
It reads about same as my original (big hole) sensor. Since I was able to read temp on my computer controls I've been putting off for years. I was ordering other stuff from Willcox and so I ordered the adjustable resistor.
I should be receiving the Willcox adjustable resistor presently. I should be able to set my temperature gauge quite accurately since I can use the EZ-EFI 2.0 to display the actually temperature(digitally) and then adjust the gauge to match that.
See here:
https://www.corvetteforum.com/forums...tec-heads.html
It reads about same as my original (big hole) sensor. Since I was able to read temp on my computer controls I've been putting off for years. I was ordering other stuff from Willcox and so I ordered the adjustable resistor.
I should be receiving the Willcox adjustable resistor presently. I should be able to set my temperature gauge quite accurately since I can use the EZ-EFI 2.0 to display the actually temperature(digitally) and then adjust the gauge to match that.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
....and it reads about the same as my stock sensor (reads cold).
See here:
https://www.corvetteforum.com/forums...tec-heads.html
It reads about same as my original (big hole) sensor. Since I was able to read temp on my computer controls I've been putting off for years. I was ordering other stuff from Willcox and so I ordered the adjustable resistor.
I should be receiving the Willcox adjustable resistor presently. I should be able to set my temperature gauge quite accurately since I can use the EZ-EFI 2.0 to display the actually temperature(digitally) and then adjust the gauge to match that.
See here:
https://www.corvetteforum.com/forums...tec-heads.html
It reads about same as my original (big hole) sensor. Since I was able to read temp on my computer controls I've been putting off for years. I was ordering other stuff from Willcox and so I ordered the adjustable resistor.
I should be receiving the Willcox adjustable resistor presently. I should be able to set my temperature gauge quite accurately since I can use the EZ-EFI 2.0 to display the actually temperature(digitally) and then adjust the gauge to match that.
From the thread posted about Rogers post above... Roger and I talked about this for a long time.... and I'll give Roger props for pushing me to make this item.
With the adjustable resistor you can pretty much run any sender you want... then just dial in the temperature gauge.
When you use the adjustable resistor you make a linear change in the gauge, the trick is getting it adjusted and you can do this with an IR gun or by knowing what thermostat you have in the car and felling the upper hose to open when running. If you have a 180 stat, then when the hose gets hot, dial up 180 on the gauge.
https://willcoxcorvette.com/corvette...resistor-77-82
We have a video on our tech page on how to install this too.
http://repairs.willcoxcorvette.com/w...able-resistor/
-Willcox
