Just the other day i jumped in the truck and the AC fan worked great and i cut the truck off and when i got back in it didn't work at all.I checked the fuse and it's fine.The next morning i started it and the fan worked again and it's been doing this for the past few days now.It will work when it wants,i did notice when it does work it will slow down the longer it's on.The truck is a dodge 2500 with the 5.9L in it,2002.I know there are 3 things that might cause it,or should i say that i can buy to replace,the fan/relay and control resistor panel but,you add them up just to replace and not know which it is cost over $300.Any thoughts on which part could be the main issue?????

 

I'd bet my money on the resistor pack. One way to check is when it starts acting up, turn the fan to the highest position. This does not go through and resistors and straight to the fan. If it was a relay issue it would happen on all speeds.

 

it happens at all settings......where is the relay located???....

 

Under the hood on the driver's side there is an electrical box with fuses and relays. Once you open it up, on the inside of the cover is a diagram of what's what in there. The Blower relay just happens to be the same part as the one next to it (trailer, I think), so you can swap the two. If that doesn't fix the problem, the relay wasn't the problem. My wife's '99 blower was working sometimes, and sometimes not. Now it has gotten to the point it never works. Easier to troubleshoot that way!!
Cheers