what might cause my heater grids to constanly cylce on and off? intake air temperature sensor? i did some searching, but mainly found reasons why they never come on.

 

Yes, there is a sensor near your intake horn that has two wires leading from it. It tells them to heat up I'm assuming in cycles because of how much it draws off of the batteries but I do not know for sure.

 

they should quit cycling once you get above 30 mph.

 

Also, after you pass 20 mph or so. Hows your spedo working?

 

I want to say they will cycle if the intake temps are 50* or less, and if you are driving slower than 20 or 30mph. Cant remember on the speed, but I do know the temp. is correct.

 

Don't know how they came up with this number but the grids turn off if you exceed 17 mph.
They also shut down when the intake temp exceeds 50F.

 

thanks for the info, but my problem seemed to just be corroded terminals on the air intake temp. sensor, a little cleaning and some dielelectric grease seems to have fixed it. the heaters would not stop running while the truck idled, but now they are back to normal. also put my alternator out of commission, but it was on its last leg anyhow. had it tested and all it could muster was 2 volts.