Single wire temperature sensor versus two wire sensor

[Kirk T]

I bought a new coolant temp sensor (it is a two wire connector) and went to put it in and realized the sensor in the truck only had one wire. If I use the new sensor which wire do I use and what happens to the other wire. Should I just take it back and try to find a one wire sensor?

 

[chengny]

I bought a new coolant temp sensor (it is a two wire connector) and went to put it in and realized the sensor in the truck only had one wire. If I use the new sensor which wire do I use and what happens to the other wire. Should I just take it back and try to find a one wire sensor?

Did you miss this:

Don't even try to use that coolant temp sensor. Coolant sensors with two leads are used to provide coolant temperature to the ECM. It won't drive your dash temp gauge.

 

[75gmck25]

One wire sensors are grounded through the threads in the head, and the terminal is where you connect the sensor wire. You can't substitute a two wire sensor and get it to work.

GM also changed the sensor/gauge combo a few times over the years, so its critical to get the correct sensor for your year of instrument cluster. If you get the wrong sensor it will still work, but the gauge will be off. There are also two types of terminals on the sensor wires: button type, where you slide the insulated wire connector on at a right angle to the sensor, and spade type, where the terminal sticks straight out from the top of the sensor.

Bruce

 

[Kirk T]

Thank you that is good to know. My old sensor was what you called a button type where the wire attached at a right angle. I'll try to get on of those.

Thank you again

 

[bucket]

Did you miss this:

Don't even try to use that coolant temp sensor. Coolant sensors with two leads are used to provide coolant temperature to the ECM. It won't drive your dash temp gauge.

I've got one being used as a gauge sender, it was cobbled by the last owner. One wire just gets grounded out. It has always seemed to read properly.

But the correct sender makes more sense.

 

[chengny]

I've got one being used as a gauge sender, it was cobbled by the last owner. One wire just gets grounded out. It has always seemed to read properly.

But the correct sender makes more sense.

Yeah, I was pretty sure it could be done...but I didn't want to confuse the issue

 

[C10MixMaster]

COOLANT TEMPERATURE GAUGE PARAMETERS

For Truck Years: 1967 - 1973
The Temp Gauge Needle Should Point to:
Left Line (Cold) when sender resistance = 350 Ω
Middle Line when sender resistance = 76 Ω
Right Line (Hot) when sender resistance = 51 Ω

For Truck Years: 1974 - 1978
The Temp Gauge Needle Should Point to:
Left Line (Cold) when sender resistance = 350 Ω
Middle Line when sender resistance = 68 Ω
Right Line (Hot) when sender resistance = 46 Ω

For Truck Years: 1979 - 1990
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

as you can see there are three different ohm ranges depending on the year. there are also 1/2" and 3/8" pipe threads so you need to match the size.

 

[Matt69olds]

Not all 2 terminal sensors are for the PCM. Some car/trucks have a temp gauge, and a temp light. One terminal is for the gauge, the other terminal is for the light.

 

[bucket]

Not all 2 terminal sensors are for the PCM. Some car/trucks have a temp gauge, and a temp light. One terminal is for the gauge, the other terminal is for the light.

The GM 60* V6 was one application for those, in various models. They had a pigtail with a plug on it, rather than having the plug right on the sender body.

 

[Matt69olds]

I have owned many G body cars over the years, mostly Olds. If they had the rally pac gauge setup, it had the light and the gauge. I’m sure I probably have a spare sensor and connector somewhere.

I’m really surprised GM (or other manufacturers) didn’t include a warning light in addition to the gauges. Most people don’t pay attention to any instruments other than the fuel gauge. A warning light is a little harder to ignore. I’m guessing it cost too much to have both.