View Full Version : Aux AC fan runs all the time

11-23-2011, 10:13 AM
Fellow Sprinterites,

I have an RV which is built on an 07 Sprinter 3500 (Diesel) chassis. Beginning recently (I think), the A/C aux fan will run whenever I press the lock/unlock keyless remote (for 20 sec or so) and runs all the time when the engine is running, whether the A/C is running or not.

I understand from what I've read that the aux fan will run whenever the temp shows high AND the A/C pressure is high. It seems unlikely that both sensors would fail, which leads me to the following questions:
- could ONE of these sensors cause the fan to run all the time? If so, exactly where are they and how can I check them?
- could it be a fan relay problem? If so, I'd appreciate any info anyone could provide on where exactly that relay is and how I could check it.
- could it be something else?

I don't have any diagnostic tools to check things, but I do have a multimeter. Any hints in diagnosing this would be greatly appreciated. Thanks!

Happy Thanksgiving,

Alexandria, VA