today I was on the way home from work when I noticed the rpms bounce a little about every 10 or 15 seconds when I was sitting a traffic lights on the way home. Almost like the grid heater is cycling on and off. When I get home I get out while its idling and about every 15 seconds I hear a loud click like its the grid heaters going on and off like when you first start the truck up even though it was just running for 30 minutes, and the rpm drops momentarily about 100 or 200 rpms? Any ideas ?

 

Un hokk grids see if it still does it if so check relay

 

I bet your air conditioning is cycling, it will engage in any position of the switch except dash and feet. Put the selector to Dash or Feet only, or to Off and see if it still cycles.
-P

 

hmm well thats a thought. It did actually sound more like the ac click as opposed to the grid heaters. I'll check that in the morning and go from there. I dont think the ac is on though but it may very well have been turned by some passenger like the ones that cant keep their hands off of controls