Now that my '60 is running I notice that the temperature gauge is running up against the 'H' mark for high temp. At the same time I laser test the engine temp. and it is running around 165 F at the thermostat housing (slightly cooler at the radiator header). The implication is that the temp. gauge is not reading correctly.
My question: doesn't the thermo-sensor in the engine block just act as a variable resistance to ground for the gauge? Are there different thermo-sensor ranges that would change the indication on the gauge? I think that the thermo-sensor that I have is just an off-the-shelf unit that could have a different resistance range causing the gauge to read high when the engine isn't that hot.
Any wisdom will be greatly appreciated. Whit
I would try grounding the wire to the engine temp sensor, and see
if the gauge goes to COLD. If so I'd replace the sensor. Bruce Roe
Whit,
First question, is your temp sender the original OEM or a new replacement? When you say off-the shelf it could well be a new replacement. ???
The original ones have higher resistance between the temp ranges with around 380 ohm at 150 degrees, while the new replacements have a lower resistance around 318 ohms at 150 degrees.
The newer ones are designed for the early year’s gauges, so to compensate for the older ones you have to make a modification to the wiring.
You can place a small resistor in series between the sender and gauge a 50 â€" 55 ohm should be fine the resistor can be either a ¼ watt or ½ watts. The added resistance will place the correct resistance for the gauge.
Good luck..!
Thanks to Bruce and J. Gomez for your input. I suspect that the temp sender is a new one with probably the incorrect resistance. I will check it out.
Thanks Whit
Another way to test the temperature is to temporarily hook up a mechanical gauge in the same hole as the hole for the electric gauge sending unit. That way the gauge reading will not be influenced by the car's electrical system, especially your own sending unit which, as others have pointed out, could possibly have some sort of problem. I don't know anything about '60 Cadillacs, but I've had to do this a couple of time with my '49 over the years.
You can buy mechanical gauges and their sending units at any parts store. They usually have adapters to allow the sending unit to be screwed into any engine's sending unit hole. You then run the capillary tube through the firewall somehow and just lay the gauge on the seat or temporarily hang it under or on the dash.
An additional point: when you re-install your electrical sending unit, don't seal it with teflon tape to prevent leaks since the temp gauge circuit is grounded at this point and the gauge reading would be affected. At least that's the way it is on my '49.
Jay mentioned what I was thinking at the end of is reply which was look at how the existing sensor was sealed. Like he said 1 wire sensors depend on getting their ground through the threads so if someone went nuts with some sort of sealer it could be insulated. For a test you could hold a jumper wire from the body of the sensor to a good ground. You would likely need an assistant to either hold the jumper or look at the gauge.
Is 49 one where 6 volt vs 12 volt could come into play?
Both the gauge and sensor can be tested, if you have a calibration station. It's a common thing in instrument shops. Hey, it's nearly 60 years old. If the motor isn't overheating, I wouldn't necessarily worry. Take the cap off and stick a thermometer in the radiator while it runs. That will verify if it's hot or not.
You can still buy the proper AC temp sensor for the '60. I think I got mine from Rock Auto. Change it and take what it gives you. Otherwise, you have to look at the wiring as well and that might be more than you want...
thanks again to all for the input. Will work it.
Whit
Quote from: TJ Hopland on February 18, 2018, 09:28:30 AM
Is 49 one where 6 volt vs 12 volt could come into play?
TJ,
'49s are 6 volts. Cadillac went to 12 volts in '53. As far as I know, the 6 and 12 volt temp sending units of that era are similar looking, so the wrong kind could be mistakenly used.
Jay
I have VG used, tested original 1956 to 1964 Temp Sending units for $15. Click on this link for details:
http://forums.cadillaclasalleclub.org/index.php?topic=145639.msg364824#msg364824 (http://forums.cadillaclasalleclub.org/index.php?topic=145639.msg364824#msg364824)