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Alternator replacement

I recently replaced my alternator. I thought I was very careful not to make anything worse but now when I’m driving I have temperature issues. When stopping or slowing down my temp. gauge goes all the way to cold, then as I accelerate the temp gauge rises to the middle. It has not gone past the middle and has never done this before the repair.

Also, the truck has never overheated or had any thermostat or cooling issues before.

Please help,

Perhaps the best place to start is to remove your temp sensor and test it. All you need is a hotplate, a lab vessel, a multimeter, a lab thermometer (or thermocouple with meter). and water. Oh, and the specs for the sensor, which you may have to ask for at the dealer’s parts department.

Jbird, does the drop in the temperature reading at idle correspond with a reduction in the cabin heat? Does it still feel hot at Max heat setting?

What I’m wondering is whether the problem is low coolant temp (from a bad thermostat, perhaps) or an electrical gremlin causing a faulty reading.

meanjoe75fan, it happens with the heat turn all the way off or cranked all the way up. It is still pumping hot at every setting. I’ve never replaced a thermostat, hope it is something simple

Well, if the heat’s still very hot as the temp gauge drops, there’s a good chance the problem is a bad gauge reading.

The temp gauge, like all dashboard indications on a modern car, is electrically controlled. Since the alternator was recently replaced, it’s possible you have an electrical issue.

Additionally, an engine full of coolant is a fairly large heat sink, and “dropping temps as I idle only to return to normal with RPM increase” sounds suspicious.

At least verify coolant temp is actually dropping before swapping out parts.

To see if this problem is related to the alternator you can do a simple test. Remove the connector on the rear side of the alternator. That will disable it and cause a warning light but then see if the the temperature problem goes away. If it does then the output of the alternator is bad. If there is no change then I would suspect something is happening with the coolant flow. Have the coolant checked to see if exhaust gases are getting into it. If they are then you have a head gasket problem.

What is truck? Year, model, and so on. Alt has wire harness. It may be close or tied to temp sender harness. Things get jostled when u change parts.