78 chief defrost not working

[jeepgirl]

Have a 78 Cherokee chief with a defroster issue. Air just trickles out of the windshield vents even with the defrost button in. Heater works great. The controls were swapped and it worked briefly but stopped again.. it worked briefly the other day but the weather turned cold and it quit again. I'm looking for suggestions.

Thank you

[Ryan]

this is a common problem. The defrost tubes themselves are sometimes the culprit, as they can rip / tear from underneath. Do you hear more air rushing around under the dash? if so, you'll need to get under there and wrap the tubes with tape, or find some decent condition used ones.

If there isn't a lot of air rushing around, then the issue may be your heater box or fan box. they get filled up with debris / leaves / pinestraw, and eventually it starts blocking air from flowing.

[Brent]

Also, make sure there is a vacuum line hooked up to the defroster switch that opens the defroster door.

Typically, like Ryan said, it will be debris that are in the way not allowing the door to open.

[jeepgirl]

The defroster worked today but it is warmer today than it has been. It doesn't seem to move as much air as it used to move though. Not sure why it doesn't work when cold but I will need check for debris anyway.