ML320 Intermittently Blowing Hot Air

[ScaryRaven]

Hello all,

I have a 1998 ML320 SUV. When I am operating the air conditioner it will intermittently and suddenly stop blowing cold air and begin blowing hot air. This air is very hot, not ambient outside temperature. It feels like the air conditioner suddenly moved from cold to the hottest setting of the heater.

There is no leak in the Freon system and the Freon levels are high. My Mercedes dealership seems to be at a loss to fix the problem. They have noted it blowing hot air, but have been unable to determine what is causing the problem.

Any Suggestions for why the AC is doing this?

Thanks

[Gilly]

More than likely one of the temp sensors is bad.
One thing you definitely need to know is that there is NO heater valve in the heater system, hot water constantly runs through the core, nothing regulates the flow. It's all done with flaps (diverting air where it needs to go).
Another possible problem could be related to the aux fan wiring update, by your description I rather doubt it though.

Gilly