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tubman · 07-27-2017, 07:43 AM

I've got my '51 back on the road and am very happy the way everything turned out except for the temperature gauge. It worked fine before I removed the old engine. A little background : About 3 years ago, the temp gauge in the car started reading very low (just off the "Cold" mark during normal driving). I followed the manual (it says the test for a bad sending unit is to replace it with a new one and see if it corrects the situation), and found the sender was bad. I had 3 other sensors, so I put the best looking one in and voila', my problem was solved. In the process, I checked all of the sensors with my multi-meter. Maybe it's just a coincidence, but all of the sensors "Ohmed out" at 14 ohms while the bad one was quite different (I don't remember the exact value). I have tried all 3 of the sensors I have left, and get the same results with all of them. With the ignition off, the temp gauge goes to full "Hot". When I turn the ignition on, the gauge goes to full "Cold". I can start and drive the car any distance, and the gauge stays right there. I have checked the "switch" sensor on the drivers head and it has no resistance (closed), just like it should. I have made sure the the passenger side sensor is grounded to the head. Also, I checked the voltage at the wire to the passenger side sensor with it disconnected and the ignition on; it reads 2.7 volts.

I have to believe that the problem was caused by something I did, but I'll be darned if I can figure it out. The wiring is so simple that it's almost impossible to get wrong (I even "Ohmed-out" the wire between the sensors to make sure there was no internal break). The fact that the gauge cycles from full "Hot" to full "Cold" when I turn the ignition on tells me the gauge and dash wiring are OK (I may be wrong here).

Does anyone have any insight to what may be going on here? I went through "JBSeery"'s post on instruments and it was quite helpful, but I still have the problem. ("JBSeery" feel free to jump in here if you feel like it.) One thing that might help me is if someone with one of these cars (shoebox) could take a voltage reading on the disconnected wire to the temperature sensor with a cold engine and the ignition on.

07-27-2017, 07:43 AM	#1
tubman Senior Member Join Date: Dec 2013 Location: Minnesota, Florida Keys Posts: 10,404	1951 Temp gauge problems I've got my '51 back on the road and am very happy the way everything turned out except for the temperature gauge. It worked fine before I removed the old engine. A little background : About 3 years ago, the temp gauge in the car started reading very low (just off the "Cold" mark during normal driving). I followed the manual (it says the test for a bad sending unit is to replace it with a new one and see if it corrects the situation), and found the sender was bad. I had 3 other sensors, so I put the best looking one in and voila', my problem was solved. In the process, I checked all of the sensors with my multi-meter. Maybe it's just a coincidence, but all of the sensors "Ohmed out" at 14 ohms while the bad one was quite different (I don't remember the exact value). I have tried all 3 of the sensors I have left, and get the same results with all of them. With the ignition off, the temp gauge goes to full "Hot". When I turn the ignition on, the gauge goes to full "Cold". I can start and drive the car any distance, and the gauge stays right there. I have checked the "switch" sensor on the drivers head and it has no resistance (closed), just like it should. I have made sure the the passenger side sensor is grounded to the head. Also, I checked the voltage at the wire to the passenger side sensor with it disconnected and the ignition on; it reads 2.7 volts. I have to believe that the problem was caused by something I did, but I'll be darned if I can figure it out. The wiring is so simple that it's almost impossible to get wrong (I even "Ohmed-out" the wire between the sensors to make sure there was no internal break). The fact that the gauge cycles from full "Hot" to full "Cold" when I turn the ignition on tells me the gauge and dash wiring are OK (I may be wrong here). Does anyone have any insight to what may be going on here? I went through "JBSeery"'s post on instruments and it was quite helpful, but I still have the problem. ("JBSeery" feel free to jump in here if you feel like it.) One thing that might help me is if someone with one of these cars (shoebox) could take a voltage reading on the disconnected wire to the temperature sensor with a cold engine and the ignition on.