We have a 2004 with air ride seats. We have put in three relays for the compressor. Now the compressor runs while the key is turned off and runs the battery down.. What's wrong? We've had several mechanics look at it. They replace the relay and it will work for awhile then back to the same problem. One mechanic said I had to empty the compressor to get the water out of it. But none of my friends who have these trucks do this.... Any and all advice would be helpful...

Thanks

Your mechanics aren't looking for the problem.  Air ride seats are not different than any other compressed air system.  Compressor pumps air into the system till something tells it to shut off.  The air pressure is either held or it leaks down, at which the compressor starts up again.

You have either or combination of: a leak, bad pressure switch and a miswired relay.

WOW, I did not know they had an electric pump.  My 6500 has a engine mounted pump that only works when the truck is running......

If your is running that much you should be able to hear the air leaking.  I would start at the seats, then go to the tank and follow the air lines also check the rear air bags if you have airride on the rear.

Next step if you can not find the leak is to intall a switch to turn the pump on when the truck is running...

So, you got a 4500 with air brakes..??

On our 4500, once in a great while the water drain on the tank will stick open after you drain the tank. It is wired to be only on when the key is on. We have air seats and air suspension and our compressor runs a couple times an hour when driving. Never when the key is off. Check out dieselplace.com, scroll down half the page and go to the medium duty section. They discuss the 4500 compressors a lot. Good luck.