Hey guys. Yesterday when I turned on my heater in my 98 ram, it would only blow out of the defrost vents on every setting. No floor or dash vents. Heater, a/c, and just the fan will only blow out of the defrost. What would cause this?

 

Ok I had the same situation, on the passenger side engine compartment there is a check valve in the vacuum line coming off the firewall. About as big a quater, you more than likely need to replace it if none of your lines are broken. You can pick it up at autozone or orielly's in their help section in a red box should be no more than 5 bucks

 

mine was a cracked line i fixed it with a heat shring butt connector

 

The vacuum lines on the passenger side need that check valve if its not there.
Do a search on Wild Vents.

More than likely though either the cable behind the climate control has slipped off, or the valve in the vents that that cable controls is stuck.
Good luck
(Do a search on this issue too there are a bunch of threads that cover it.)

 

my truck does the exact same thing, only the air blows out fine, but when accel hard or pulling up a good size hill air stops blowing out the vents or floor where ever i have it setting and blows out the defrost. Im thinking its vacuum leak somewhere, cant seem to find it. Doesnt really bother me, just annoying when I first got the truck but now am used to it. Id like to fix it someday, anyone ever had that problem? truck is a 99 regcab 4x4 5.2 auto

 

Thats caused by an either bad or missing check valve on the H-VAC system. Do a search for Wild Vents. I made a thread on it a while back that had before and after pics of the valve.

 

A broken vacuum line was my problem. I also didn't have a check valve either.

 

I replaced the check valve by the manifold and then the one on the line closer to the firewall (updated one looks nothing like the old one, looks line a small vacuum canister) as I couldn't find a vacuum leak. I ultimately found a leak in the metal vacuum lines under the vehicle for the CAD.

Anyway, I'd look for a vacuum leak. Check the line going into the cruise control unit in front of the battery, apparently that one rots through at times.

Vacuum_leaks_are_fun!!!

 

Hey guys my heater nor ac will blow out any vent. It jus stopped working. I got in and drove down tha road and tried to turn it on and it wouldnt do nothing. I looked at the fuses, they were fine. Couldnt see one for the heater/ac tho. I also looked at the vacume lines, didnt see nothing wrong there either. What would be tha issue im having? I have a 1997 dodge ram 1500 4x4 with a 318 and automatic.

Thanks,

 

There is a resistor on the heater box by the fan motor. Check it.