Learjet-1

Does anyone have a 1996 C-1500 350 CID gauge temp to ohms reading chart. Tamp Gauge started reading low so I replaced the gauge sending unit in block by #1 plug with not much change. Gauge will read 210 degrees F with 100 ohms input. Sensor is reading 220 ohms when engine is at temp apx 200 Degrees F which has the gauge at apx 130 degrees F. Did they give me the correct sending unit or is the stepper motor bad in the dash

mountainmanjoe

Troubleshooting sensors and how to test

Irish_alley

those readings are for the sensor for the ecm. not sure if the temp switch are the same or not, never got around to finding those numbers or verify if theyre the same. but the numbers should be about the same

alpinecrick

I had my instrument cluster checked/reconditioned to factory specs (which are not all that precise) and even then the temp gauge reads in the neighborhood of 170-175 degrees. My scanner says I'm running 195 with everything warmed up properly. I replaced my temp sending unit with an AC Delco and it made no difference in the indicated temp on the gauge. Unless you have a hotter thermostat your engine shouldn't be running 200 degrees under normal driving condition.

The temp sender for the gauge is located on the drivers side near the exhaust manifold and the wire gets hammered with heat. Given your ohm reading it's possible the wire is working but well cooked and creating higher resistance.

Learjet-1

The wire is new as the pig tail came with the sender unit. The Truck has a 195 Thermostat and as I said the gauge is reading 130 degrees with the truck at temperature. I can find what the ohms readings for the ECM sensor should be but I can not find them for the gauge sensor. You can buy a stepper motor off EBAY but I don't want to go to all that work and money if I can't test it first and if I don't know the ohms reading for it I can't really test it. Maybe I will just put a resistor in parallel with the sensor.

Irish_alley

ive found these numbers for the gauge for the 79-91 gauges. on another spot someone referenced the 1365 as 100° mark


The Temp Gauge Needle Should Point to:
Left Line (Cold) when sender resistance = 1,365 Ω
Middle Line when sender resistance = 96 Ω
Right Line (Hot) when sender resistance = 55 Ω


anyway even if its not the same with the sensor unplugged the gauge should peg out to the coldest position and if you ground out the wire it should peg out to the hottest position

Learjet-1

Thanks, your numbers make more since than anything so far. I ran the gauge with a pot and the numbers were very close to yours.
Cold Line was 1200 ohms
1/4 Line was 208 ohms
1/2 (210 degrees) was 100 ohms
3/4 Line was 65 ohms
Full Hot (260 degrees) was 59 ohms
I think I am going to look for another sending unit as this new one is at 220 ohms at 195 degrees.
Thanks for your help.

Irish_alley

even if you buy a new switch from a parts store they shouldnt have an issue with you returning it as long as its not installed. the one you did install i would return as faulty

Learjet-1

I am having to put this project on hold as I need to drive to Iowa tomorrow as I just found out that a family member just died suddenly. Thanks for the help. I will post when I solve the problem.