F150 temperature gauge

shelby27604

shelby27604

Well-Known Member
Joined
Jun 6, 2013
Location
Efland NC
Been working on a 94 F150 lately, a couple of weeks ago the temp gauge went from reading "R" on the "NORMAL" gauge reading to reading "N". I assumed my thermostat had stuck open. I did a full flush, thermostat replacement, new temp. Sensor and radiator cap....and it still reads low on the gauge ("N" or lower).
My only real concern is that this pre-historic fuel injection system is actually using this low reading to keep the system in open loop /warm up mode and running rich all the time.
Is there anyway to confirm what the ecu is doing and / or shift the gauge back to a usable reading?

I have confirmed, at operating temp the thermostat housing sits right at 195 deg. Before the flush and fill it was running around 210 deg.
 
First thing I'd do is make sure the gauge itself is functioning.
Unplug the sending unit, not the ECT sensor, the single wire sending unit, run a jumper from the wire to the negative side of the battery.
The gauge should go full hot. If it doesn't, you have a guage and/or wiring issue.
 
The trans temp gauge in the CJ stopped working. How can I check to make sure the gauge isn't bad? Thought about switching the engine temp wire to it to see if it goes up any.

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ncsutj said:
The trans temp gauge in the CJ stopped working. How can I check to make sure the gauge isn't bad? Thought about switching the engine temp wire to it to see if it goes up any.

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Same. Ground the wire that goes from the sender to the guage. Just make sure the key is on. Full ground = full hot.
 
Well since this is now a gauge thread, same process for a factory oil pressure gauge on a cj? I measured 3ish volts on the sender wire connector at the engine side of things. Tried 2 "diaphragm" senders yesterday with no love. I didn't want to ground out the purple wire with voltage on it.
 
FWIW, my gauge checked good, I put a new sender in the truck and it runs in the "O" range....I am going to assume that is about "factory" with some wiggle room to go to "M" or worst case "R" before an owner would worry. I would have left it alone, but it went from mid gauge to low gauge.....so something had died.
 
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