just wondering what the clicking sound coming from under the hood could be. sounds like a relay opening and closing when the truck is idling. doesn't seem to make a difference idf truck is cold or warmed up still here it when parked and idling.

 

How fast/often does it occur?

 

Is the heat/AC on?
If so, it's probably the compressor clutch cycling in and out.

 

seems to happen around every 20 seconds or so and also seems to be a very slight change in rpms when it clicks. kind of thinking it may have something to do with the grid heaters but once the engine comes up to temperature and the outside temperature is 80 shouldn't the heaters be off.

 

If the AC/Heat is on, the AC compressor will cycle on all vent positions except Face only(non-AC).

 

AC

 

thanks

 

It's the AC. The old ones used to leak oil and freon so they have added them to the computer to cycle on and off so that they stay lubed and sealed.