coolant sender voltage and gauge issue.

[elfbrew]

90 cheyenne 5.7 tbi 4x4



In re the coolant sender in the head, what is the voltage on the green wire that connects? in the course of tracking down a non functioning gauge. installed new sender and gauge redlines. t stat is new.
thanks

 

[Schurkey]

In re the coolant sender in the head, what is the voltage on the green wire that connects?

Not much.

in the course of tracking down a non functioning gauge. installed new sender and gauge redlines.

The sending unit grounds the circuit. If the gauge immediately goes to the high-end of the scale, you've probably got a bare spot in that wire that's grounding somewhere.

 

[elfbrew]

I have 12 volts on the green wire. The gauge runs to red over a few minutes of engine running not immediately. Maybe wrong sender.? I assume tstat is open as heater blows hot. Was just wondering if 12 v was normal. Looking at the schematics I figured it was.

 

[RichLo]

Theres two different part numbers for these sensors. Most parts shops will give you the ECM sensor in for the intake manifold unless you explain that there's another one specifically for the gauge.

 

[Schurkey]

I have 12 volts on the green wire. The gauge runs to red over a few minutes of engine running not immediately. Maybe wrong sender.?

Maybe. Maybe the engine is overheating.

I assume tstat is open as heater blows hot.

Even if the thermostat was stuck shut, the heater would be hot.

Was just wondering if 12 v was normal. Looking at the schematics I figured it was.

I thought it was less than that. Maybe I'm wrong.

 

[Das Hatt]

I have the exact same problem on my 92 350. Previous owner told me the temp gauge did not work, but no codes were being thrown in the truck ran fine. I put a new sender in the head and it does not spike right away, but as it heats up, it will keep going into the red until it's peaked out. I hooked up a multimeter to check the resistance and held a infrared gun at the sensor at the same time to monitor the temperature. The resistance tracked with the temperature very close and ended up about 190°, and the resistance stabilized. That leads me to believe there is some wiring issue between the plug and the gauge, or the gauge itself is faulty.