On my '98 Ram 3500 Van (it's an RV conversion but that shouldn't be relevant):

The A/C is only supposed to run when the heater control is rotated to the two leftmost (counterclockwise) positions with the snowflake icon. But it actually seems to be running in *all* of the switch positions, cycling the compressor clutch on and off. I have fiddled with the temperature control (trying not to make it too warm instead), but that's a workaround. I don't remember that it was always this way, and I'm pretty sure it is costing me in gas mileage.

My Haynes and Chilton van manuals are no help at all. Does anyone have a schematic of the switch and wiring (including relays) for this model year so I can do some troubleshooting?

Many thanks for any assistance!

Richard in Toronto

 

Look here at R10, and swap it with another relay to rule out a bad relay. You might get lucky.

 

Compressor will also run in any Defrost setting as well.

 

Actually I believe the compressor runs in ever position except heat(floor only) and vent(no snowflake).

 

Hi Busted;

Thank you, but those schematics in the video must be for the pickup. My van looks quite different.

But see my confession below...

 

Hi alloro;

You and HeyYou are quite correct. After some further experimentation today, I dug out the original owner's manual. It is in pristine condition, almost as if nobody has ever looked at it... The A/C is indeed supposed to run in the high/low position as well; it's just that my selector dial is missing the snowflake at that position, which is where I leave it most often when we're travelling. And yes, it does run in defrost as well, to dehumidify the interior.

Aaargh. Of course I feel like a bit of an idiot now for wasting everyone's time. But my sincere thanks to everyone who responded.

 

No idea why they didn't put the snowflake there as well, my truck is the same way.