Heat gauge

[steve57dodgetruck]

My temp gauge always reads hot but my infrared temperature gun gives healthy temperatures at the radiator, hoses, and head. I was at a show recently and talked to another flathead owner who said he resolved the same issue by putting a 1/4 ohm resister in between the sensor and the gauge.

Anyone done this or have thoughts about it.

I'm running a 218 block with 12v and original 12v gauges in my '57 d100.

-steve

[Merle Coggins]

I suppose that's possible. The temp sensor is basically a variable resistance to ground for the gauge mechanism. As it gets hotter the resistance changes, usually less resistance when hotter. Changing the overall resistance would adjust, or "calibrate", it.

Merle

[Plymouthy Adams]

this is basic gauges 101 here for the early system..

but I can't see where 1/4 ohms is going to make a difference..I would think that the sender is either bad in pegged mode or the wire is shorted to ground for it to read hot all the time..quick test, disconnect your wire from the temp sender, key on, use a test light..do you get a flashing light? if so and the light is about 1/2 brillance..(6.8 - 7.2 volts) and when disconnected the gauge is returning to cold..then I would try a new sender unit..not sure the ohms for the gauge simulation test..

you have to have a good CVR and it also is the same device that supplies the voltage to your fuel gauge..so rule of thumb is that if the gas gauge is working so is the CVR..

but if key on, gas gauge is working, the temp wire is disconnected and the gauge is still pegged..shorted wire.

I just went and read your profile to where you had problems with your original fuel gauge..so if you have altered your wiring and such and have deleted and or incorrectly hooked up your CVR..it is anyone's guess to what may be the cause..but ..if still stock..the above should help you troubleshoot your gauges..

Edited July 13, 2012 by Tim Adams

[TodFitch]

this is basic gauges 101 here for the early system..

but I can't see where 1/4 ohms is going to make a difference..I would think that the sender is either bad in pegged mode or the wire is shorted to ground for it to read hot all the time..quick test, disconnect your wire from the temp sender, key on, use a test light..do you get a flashing light? if so and the light is about 1/2 brillance..(6.8 - 7.2 volts) and when disconnected the gauge is returning to cold..then I would try a new sender unit..not sure the ohms for the gauge simulation test..

you have to have a good CVR and it also is the same device that supplies the voltage to your fuel gauge..so rule of thumb is that if the gas gauge is working so is the CVR..

but if key on, gas gauge is working, the temp wire is disconnected and the gauge is still pegged..shorted wire.

I just went and read your profile to where you had problems with your original fuel gauge..so if you have altered your wiring and such and have deleted and or incorrectly hooked up your CVR..it is anyone's guess to what may be the cause..but ..if still stock..the above should help you troubleshoot your gauges..

Sounds like the system used on the '63 D200 I once had: A bimetallic device with about a 50% duty cycle provided approximately 6v for the temperature and fuel gauges. For the '63 it was located inside one of the two gauges but I can't recall which at the moment.

If that goes out then both gauges stop working. If either gauge is working then it is probably okay. I did have a problem with it once but a little cleaning fixed it for the remaining time that I had the truck (several years).