Hi! I've got a 1999 Ram 3500 Van. AC is working, but heater is not - making for a very cold ride in the winter.

I don't have a manual on the vehicle. Any idea on the troubleshooting process? Thanks!

 

Do you think you might be a bit more descriptive as to what exactly isn't working?

 

Is this for the rear unit or the front unit?

For the front unit, check the water valve vacuum actuator.

For the rear unit, check the electronic actuator that moves the cable that controls the in-line water valve in the rear unit.

If it's the rear unit, twice a year, I move mine manually. The reason being, there is no real control to send the heated or cooled air to both the feet (floor vents) and the head (ceiling vents) at the same time. So, I rigged the rear acutator to sit in the middle door valve position and turn the rear water valve manually to open or closed.

 

Thanks for the help. As far as more descriptive, the heater isn't working - doesn't blow hot, warm or lukewarm air. It blows...but just whatever the temp is outside.

Neither the front unit or the back unit seems to work - again, blower is working, but temperature is not in terms of heat. AC works fine.

Hope this helps. Thanks!

 

Is the dash gauge up where it normally goes to?
Are the two heater hoses going to the heater core both hot?

Since the problem is with both the front and rear units, you'll want to look at components common to both, like the engine temperature, making sure the coolant is full, etc.

 

Follow the hoses to the heater cores and make sure they are connected. Sounds to me that they are not connected. Possibly they were bypassed because of a leaking hose or heater core.