on my way to work this morning at each stoplight and parking I could hear the grid heaters cycling on and off. It was about 55 degrees out and it takes me about 25 minutes to drive in. I'm guessing that they are not supposed to keep cycling like that. Any advice on what may be wrong or how to diagnose the problem?

 

Pretty normal I think. I have heard of some guys putting the grid heaters on a switch if it bugs you, but I would just let them go.

 

The heaters will cycle if the manifold temp is below a certain level. On mine it is 50 degrees, I think. They are different temps for different years and I don't know what yours is, I'm sure some one here does. I put a switch on my heater relay to turn them off when not needed and I will probably never need them here. If they will not turn off at any temp then perhaps you have a bad temp sensor. I don't have a diagram for your year truck.