<HR style="COLOR: #ffffff" SIZE=1> <!-- / icon and title --><!-- message -->
I just replaced my heater core in my '88 f150 4x4 5.0 and now my temp gauge doesn't work. Could there be an air pocket. If so, how do I fix that? Also, I know there is a way test the temp gauge to see if it works, but how do I do that? Any help would be apppreciated. Also, I replaced the thermostat 6 mos ago, so I know that's not the problem.
<!-- / message --><!-- edit note --><HR style="COLOR: #ffffff" SIZE=1>

 

Factory gauges aren't all that accurate, but you can see if the gauge itself is working by grounding out the sending unit wire.
When grounded the gauge should sweep all the way to hot.

 

I grounded it and the gauge pegged to hot. I was told if it was an air pocket my gauge would read hot when driving. Mine don't read nothing at all. Could it be a temp switch or sensor?

 

I would take rad cap off and let idle for 10 or 15 minutes (till hot).
Some suggest to raise the truck's front end a few inches to help air escape.
I have never had a problem with air, but some have.

If that doesn't solve it, I would suspect the temp sending unit is bad.

 

I took my truck for a little drive on Saturday and noticed my temp gauge is working again. It went to the "R" on "NORMAL", then dropped back down to the "N" after the t-stat closed. Do you think there was any corrosion build up on the connection that made it not work?