Re: New Guy 1997 7.3 CCLB
Probably a defective temp sender.
The sender is on the front of the engine at the top of the water pump, next to the hot-hose outlet.
You can test the gauge as follows:
The sender is a variable resistor, so it sends a variable signal to the instrument cluster (gauge). The sender is grounded on one side (yellow/red wire) and sends the sig on the other (red/white) wire. Disconnect the wires from the sender, and momentarily short the two wires together, then turn ON the key. The gauge should jump upwards to full-scale. Don't leave the key ON with it shorted for any period of time, only long enough for the gauge to read.
If the gauge reads up to full-scale (or pegs out), the gauge is good, and the sender probably nfg. if the gauge DOESN'T read full scale, then you likely have a wiring or instrument cluster/gauge issue.
ON EDIT: The wire colors noted above are for my 2000 Superduty (from wiring diagram). Yours might be different colors. But the principal is the same: one side is ground, other side is signal to gauge.
HOWEVER: Are you sure your T-stat is good? Maybe the gauge is reading just fine, and your engine isn't getting up to temp...? After you test the gauge, maybe run the engine until hot, and confirm it's reaching proper operating temp.
Just a thought...
Al in SoCal
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