vespa50sp

2001 Cherokee. I have heat, I have air flow out the vent but maybe not enough. I have to turn up the fan/heat more than I think I should and light fog forms on the upper half of the inside windshield.

Thoughts? Plugged vent somewhere?

carbuff

Assuming your blend doors are working properly, and you dont have air coming out of the other vents when in front defrost mode, I can say this. When I replaced the radio in my 2000, I noticed there was a big gap between the defroster duct and the heater box. There is a foam ring that looks like its meant to seal this area but there is still at least a half inch gap. I was worried that my defrost might not work all the way up the windshield but it seems to be ok so far. If it gives me problems this winter I will pull the radio out and try to seal the gap. Its possible that the foam is gone on yours and youre losing all the air inside the dash. It might be worth a look.

vespa50sp

Not a bad idea, it would be an easy fix. I'll take a look.

vespa50sp

There was a gap, I duct taped it and it didn't make a difference. Rats.

carbuff

At least it was free to try. Are you sure that youre getting all speeds with the blower switch? Sometimes that resistor breaks and you lose your high speed settings. Does the flow increase a lot if you move the heat setting to cold? If so, its possible that the heater core is clogged with leaves or some other debris.

vespa50sp

The resistor is fine, I'm probably going to have to track down the air flow.

Were does the outside air come into the xj exactly, under the hood or by the windshield? I might be recirculating moister cabin air.

Snakejumper

Does the air heat up hot enough when the heater/defroster is running? I have the same moisture problem but I've noticed the air temp seems low even though the engine is running hot enough. I plan to flush the cooling system and see if it helps. (It worked with my wife's car.)

If not, I suspect air leaks or heater coil issues.

jakecarder

Fog on the windsheild is moisture. Means moisture in the air outside. When you turn the heat on all it does is pull air from outside meaning air that has water content in it. When you select defrost your air condition actually clicks on to dry the air so your not just putting more wet air on the windsheild.There's no reason it shouldn't clear up after time. Hope your understand that

vespa50sp

I'm not convinced of the air conditioner coming on argument. I have no air conditioner in the 63 ford and it defrosts just fine. It defrosts if I put the fan on high and hot. But I get hot.

Maybe it could be the blender door, but I think that requires major surgery.

carbuff

If your ac does not work then your defroster will not work as well as it should. Even when the air is hot, the ac acts as a dehumidifier and blows dry air onto your windshield as opposed to "wet" air. I know that older cars without ac seem to work ok but they tend to have simpler airbox designs that allow for more flow. I know that the ac does not work in my mustang and it can be a pita in the rain. One of the reasons that its off the road for the winter and I bought the jeep.

vespa50sp

Figured it out, there must be a small leak in the heater core. I put in two containers of Bars stop leak powder ($1.64 each) and no more foggy windshield.

I should have known this, I was probably just in denial because at some point I'll have to tear my dash apart to replace the core. Then again, I added condensed milk to the radiator of an old farmall to seal a cracked block, we drove it that way for a decade, then sold it running for more than we paid for it.

It might hold for awhile.