Temperature Sending Unit Wiring

jim brock · November 17, 2007

Just a quick question about the temp. sending unit wiring on my '94 Suburban 2500 w/350 CI power. Plug wires on left bank shorted out with eng. temp. sending unit and burned up wiring and connector. New sending unit pigtail has two wires. One apparantly goes to a green wire but haynes manual schematic does not show second wire. Please tell me if you can the proper wiring for this sending unit. I sincerely appreciate your help. Thanks. Jim B.

Nytemare · November 18, 2007

If you could post a couple pics of the place it goes and the new pig tail that may help a bit.

But I don't think it matters which wire goes where. The sender is a thermistor, (a temp dependent resistor, if you will) as temp goes up the resistance changes. That resistance change is the signal to your gauge, since a resistor has the same resistance backwards and forwards you would be fine.

But post pics so I can tell you for sure.

jim brock · November 18, 2007

Thanks for taking the time to respond. Sorry, I do not have the means to post any pics right now. The pigtail plug off of the sending unit has two wires. I can only locate one green wire which was feeding the old sending unit. This wire gets 12V with the ignition on and the other if I could find it probably goes to the gauge. Do you think that's right? Jim B.

Nytemare · November 19, 2007

the 12V it gets, is dropped over the thermistor, the voltage drop is measured and thats what the gauge reads. The 2nd wire probably connects to ground, as does the gauge.

threearmsinjune · November 24, 2007

THERE ARE TWO DIFFERENT TEMP RELATED SENSORS!!!

1. The temp sending unit is single wire located in the head. This is typically a dark green wire about 16 ga or so. This is info to dash gauge or light.

2. The coolant temp sensor is two wire located near the coolant inlet/ thermostat housing. Black is input 5v in circuit after the TPS. The yellow is signal back to the PCM.