QuestionMy heater/air conditioner fan works intermittently, seeming to come on and off at will when I leave the switch in the on position. Can you give me an idea on where to start looking? It will work fine for a period, then will not operate the next time I use the vehicle. I don't think it has ever stopped working while I was driving it, just seems to happen after it has been shut off.
AnswerDale,
Looking at the wiring diagram for your truck, it is a relatively simple circuit that controls your blower motor. That is good in the fact that there is not alot of faults That could cause it.
The power is fed to the mode switch from a 30A fuse in the in-cab fuse box. From the switch it travels to the blower motor, then the blower speed switch and then finds its ground through the resistor block.
So, the first check that I would make is the ground wire on the resistor block. This is a black wire that meets up with the ground wire on the blower speed switch. If this is loose or geting a poor connection, it would work intermittently as you describe.
If this has a good connection, the next component that I would look at is the switches themselves. The first being the mode selector switch. This switch has a continuous connection that feeds the blower motor. If for some reason it has a poor connection, AND, the blower does not operate in any mode (defrost, vent, max a/c, etc.) Then this is where I would zero in the fault as being. However, if it works on some modes and not others, then I would lean to the blower speed switch as the problem.
I hope, this did not confuse you at all. I tend to start to run-on when I get going. If you need me to clarify anything, please just let me know.
Thank you for the question, I hope I was of some assistance. If I can do anything further during this process, or in the future, please do not hesitate to ask. If you found this response to be of some assistance, please remember to rate this answer. Thanks again and good luck in everything.
