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I’ve read as much as I can about getting a correct reading from the temp gauge, but I want to be sure of something.
i’m getting about 42 ohms of resistance across the two circled terminals, shouldn’t that be 90 Ohms?
car is a 1973
Last edited by 5gear; Feb 8, 2021 at 09:32 PM.
Reason: Year
I think I measured my gauge when it was out with the resister off and it was also 90 ohms. The resister and the gauge are two 90 ohm resisters in parallel which would be 45 ohms.
Edited and corrected: I just confirmed that my temp gauge with the resistor is ~90 ohms (87.7 ohms to be exact). sorry for my incorrect answer above
Last edited by Kidster71; Feb 9, 2021 at 03:29 PM.
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
It should read 90 ohms, but I would remove it from the gauge before measuring to ensure you do not get a false reading even though the connector is removed.
i was trying to avoid messing with the gauge until i test a few other things, but i guess i will have to at some point.
But if it is only 42 ohms, would that make the gauge read low or high?
Just throwing this out there and not sure if you have seen it but Willcox Corvette - willcoxcorvette.com has a TON of resources on testing and checking the gauges. Videos too.
Yes willcox has a tremendous amount of good tech info, and it has helped me numerous times. My gauge actually "works" but it reads 30+ degrees on the low side.
A friend once told me that some disreputable shops will change the resistor in the gauge to make it read lower when they can't solve a cooling problem.
I can't imagine that happens very often, but that's why i wanted to verify my resistor
If you really want to test the complete sender/gauge system you need to do something like this:
You need the gauge cluster out of the car, and the sender unscrewed (hole plugged haha) and drop it in some heated water of a known temperature. Then you can check the gauge against the thermometer. I just did this a couple weeks ago (sort of as a fun little project) and mine was off, that's why I ordered the adjustable resistor from Willcox. That's right, I ordered some beakers and a hot plate and a couple thermometers.
I bought the Willcox variable resistor and it works perfectly. Just dialed it in a few days ago. I will say this, if you buy any new sending unit today, from any vendor, it will not be correct to an original gauge, 69 anyway. I tried Lectric and Paragon when I restored my 69, and both read 30-40 degrees hot, compared to a temporary mechanical gauge. I temporarily ran a cheap mechanical temp gauge to another water port on my intake, right next to the stock sender, and when it got to 180-185, I dialed my stock gauge with the Willcox resistor to the first hash mark on my gauge, which is around 185. Works perfectly. Great product!
When I tested my resistor attached to the gauge in the car, it read 45. Pulled out and unattached, it reads 90, so I know my problem was the new sender.
Last edited by 69ttop502; Feb 11, 2021 at 09:16 PM.
Thanks for the info, that's what I wanted to hear. And thanks to everyone else for not noticing I put up a picture of my fuel gauge by mistake.
Looks like I will be buying the willcox resistor too, though for some reason shipping to the Boston area is almost $20, so I might wait until I need more stuff to make the shipping worth it.
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
BTW, I also have the adjustable resistor, just haven't installed it yet. I hear that it works ok, this post just above (69ttop502) proves that as well as others. Thank you.
Last edited by Buccaneer; Feb 10, 2021 at 04:25 PM.
From: Into the Mystic And yet, despite the look on my face, you're still talking TN
St. Jude Donor '09 thru '25
This may be a really stupid question but does the Wilcox adjustable resistor require that the center gauge panel be removed to access the back of the gauge?
I looked up my notes. The old resistor on my temp gauge was reading 86.3 ohms (not 90) and my gauge was reading low for ages(decades really). I installed the adjustable resistor and now it tracks with my EZ-EFI 2.0 digital reading up and down the scale.
I cannot recommend it enough---- it's well worth it.
You can see a pic of how mine was installed here...but just go to the Willcox website and you can see a lot more:
Originally Posted by Capt. Shark
This may be a really stupid question but does the Wilcox adjustable resistor require that the center gauge panel be removed to access the back of the gauge?
Last edited by carriljc; Feb 11, 2021 at 07:10 PM.
Capt.Shark,
Since I have no heater, I can just reach behind my center cluster and replace the resistor. What you should be able to do is to first remove the parking brake console and then the 4 screws that go from the center bezel into the right and left dash pads. Also the one on top that goes into the upper dash pad. Then the two screws which hold the center console up front. At this point you should be able to pull the center cluster still attached to the console back far enough to make the swap. Getting to those nuts that hold the center cluster to the console are about the worst job on the whole car lol.
Be careful and don’t break your cluster bezel!
Bill
Last edited by 69ttop502; Feb 11, 2021 at 09:19 PM.
All you need is the gauge, the sender, a pot of water on the stove and a cooking termometer. First test the sender for resistance readings from room temp (approx 70*F) and every 40-50 deg. jump until the pot is boiling. Now you know what resistance will be presented by the sender to the gauge at different temps. Now connect the gauge and sender and power with 12vdc source (battery...not a charger!) with the sender in a fresh pot of cold water, then run the same test at the same temperatures...this time record the gauge reading, also.
Amazingly simple process. Unless the gauge does not move at all, or the 90 ohm resistor is "toast", the fault will almost always be a sender with scaling that does not match the needs of the gauge/resistor.
From: Into the Mystic And yet, despite the look on my face, you're still talking TN
St. Jude Donor '09 thru '25
Originally Posted by 69ttop502
Capt.Shark,
Since I have no heater, I can just reach behind my center cluster and replace the resistor. What you should be able to do is to first remove the parking brake console and then the 4 screws that go from the center bezel into the right and left dash pads. Also the one on top that goes into the upper dash pad. Then the two screws which hold the center console up front. At this point you should be able to pull the center cluster still attached to the console back far enough to make the swap. Getting to those nuts that hold the center cluster to the console are about the worst job on the whole car lol.
Temperature gauge resistance
