Hi There,

I have a 1993 3500 5.9 cummins and heater is stuck on hot. I noticed when i first start out there is steam coming out of the vents and windsheild would fog up a little, After awhile it would clear up. The previous own had the hearter core replaced about 1 1/2 year ago? Suggestion where to start of a fix? I do need heat in the winter but not now.

Thanks

 

The heater control valve might be bad. But that wouldn't explain the steam that is usually a bad heater core.

 

When you start he truck have someone watch your A/C compressor, does it cycle on for a minute or two? I know the newer cars the A/C cycles to clear the humidity from the heater and A/C cores.

But I can't see it being steam when the truck isn't even warm yet.

Not sure on the 92/93's but doe they have a cable control for the temperature blend? I know when I got my 87 ram it had a cable control and the cable was seized on wide open heat. Replaced the cable and all was well.

 

Not sure if it is cable control I haven't had a chance to take apart.

I might have to agree on heater core for the steam. I have heard of guys placing a shut off valve for on hoses prior to the heater core but would rather get the proper fix.

Thanks