Don't know If this is the right section to post this or not but just as the title says. I have a 1996 Cherokee. I will heat up my car in the morning and it will get warm but when I start driving my heat just starts to blow colder air. I don't know what the problem is so if you guys can help me out that would be awesome. I'm new to the jeep scene but not to cars. Oh and of course air just blows threw the defrost :/

Ps. I NEED TO FIX THIS ASAP! Going up to the mountains this weekend

 

If it blows only through defrost vents, its a vacuum leak, the same for the cool air. As you idle, there is good vacuum, load it up by driving you loose some vacuum.That said, look on the pass. side of the front bumper there is an "egg" (vacuum canister) follow those lines and find a leak, or broken line. Vacuum controls the blend door to allow heat from the heater core into the HVAC system, with out good vacuum signal, the door closes.

 

Maybe in heater core. A thorough flush (and back flush) of the system could help.

 

Thanks guys for the fast replies. I'll check the lines first. That's the first thing that came to mind. Anything else to look for

 

X2