We have a '67 326 with original rally gauge cluster. We have been unable to get the temp. gauge to register correctly. We've put maybe 4 different sending units on with no accurate reading. One read consistently 20* low, the others read consistently 20-30* high. I just changed it out (again) with a new Standard sending unit and have a 20-30* high reading. All of the sending units have come from different sources, and all were for gauge clusters.
I am comparing the gauge to an IR thermometer measured on the intake manifold next to the sending unit. The car has never, and does not run hot - although the gauge reads otherwise. It is uncomfortable driving with the temp gauge reading so high. We are trying to stay with a stock appearing interior, or I would simply get an aftermarket gauge.
Anyone have this problem and resolved it? A sending unit for a different application? A resister wired inline? I also recently added a "ground strap" to the gauge cluster as the wire above the high beam was being problematic. TIA - Cal
From what I understand sends nag units and gauges need to be calibrated for each other. If I were you I'd install an after market into the same port and see how far off one is from the other. Then just adjust you thinking when you read you stock gauge. I'm doing the same thing these days. My stock rally gauge consistently reads 20* higher that my TCS is reading thru the EFI readout.
Thanks Robert. Interesting that your stock gauge is also reading about 20* high. As for simply making the mental calculation while driving it; that is what we are doing. It is just a bit unnerving to watch that needle climb into high territory. I found some info today regarding the change in resistance as the temperature climbs. It may give me a starting point to conduct some experiments if I do not get some definitive answer. Cal
Doing some additional looking through the interwebs and I came up with the name of LectricLimited. Has anyone here used any of their products, especially the temp sending unit? I've read a few posts on other sites that make the claim this will provide a correct reading. How about it folks, anyone tried one? https://www.lectriclimited.com/electrical-devices/temperature-sending-unit-86960
Yeah my rally temp gauge reads 210 when it's really only at 190. Big difference when youre driving around. I tend to believe the modern temp readings from the ECU so I rarely look at the rally gauge anymore.
Posting an update. I got the new sending unit from LectricLimited installed and took it out for a test drive. We are now reading about 20-30* low. I plan to call LL next week and see if they might have other options. Hopefully, if they have the data on these sending units there will exist one which will give an accurate reading. In the meantime, if you have an LL unit, please post your results up. Cal
You need to get your temp gauge calibrated. I sent mine in along with the sending unit, cost about $80 and you'll have an accurate temperature reading.
I don't see taking the instrument cluster out and separating the temp. guage in my future... I would likely install an aftermarket gauge first.
I did call LL today and had a good talk with a tech. When I gave him the resistance readings that I had recorded the other day he immediately said they were too high and indicative of a bad sending unit. They are sending a replacement out tomorrow. I will report the new findings next week when the new unit gets here and I get it installed. Cal
Getting back with a post regarding our resolution. The second sending unit from LectricLimited came with the same false low readings as the first. While I can fault their product (this one anyhow); I sure cannot say anything bad about their tech support. Out of the blue one day a tech called me to ask how the second unit worked. When I relayed that it was also giving a false low reading he told me that they had conducted a test with the one I had returned and found that it was out of specs. I had a lengthy discussion with him and he suggested that I purchase a resistor to use with one of the sending units we purchased from the auto supply. Which resistor? That is the big question. The auto supply sending units did not have enough resistance, theirs - too much resistance, but it would be a guess as to how much to add. The suggestion was to find a variable resistor, a potentiometer.
Hooking it up was simple enough. I did not want to splice into the wire going to the temp sending unit, so I rerouted that wire into the cabin and used a new (green) wire from cabin out to the sending unit. It took about a day and a half. A couple hours to solder up the potentiometer and find a suitable case for it and run the wire and swap out the temp sending unit; about a day and a half to correct the broken vacuum line to the heater control switch that broke clean off at the firewall while I was searching for a place to route the wires through...
I took the bird out for a run today and when we were at operating temp I dialed the gauge back down to the half way mark. I plan to do a bit more testing with the IR thermometer before zip tying the whole package up under the dash. I am pretty happy to be looking at 180* on the gauge and feel confident that it is pretty much correct!
Edit, when I returned from the test drive I put a multimeter across the potentiometer. It read right at 13 Ohms resistance that was added.
Last edited by Cal H; 02/13/1910:24 PM. Reason: To provide multimeter test result.