Heater not changing from the defroster

[Dundy]

Yesterday i was driving and i turned my heat onto the vents and it blew the air out of the defroster. Every single setting does this and it's wintertime in New England so i kinda wanna fix it before it gets even colder.

-Thanks
Adam

[rredalty]

Check the vaccume line to the vaccume canister in the bumper. Usually it cracks and once you fix it you will be warm again.

[jfiscus]

Yup, probably a vacuum leak, check the following lines first:
The big line to the reservoir canister & the reservoir itself, the little line going to the heater core control valve under the hood, & the vacuum lines under the passenger side dash that actuate the controls.

[Fozzy_Bear]

That is a Fail-Safe ""feature"" designed into the system. If you loose vaccume, the system reverts to the defroster, so that the driver will have visability in humid conditions.

So, there's a leak somewhere.

Here's a clue though... If you can't find it any other way, put a long plastic hose into the throttle body and tape it up so no air will escape. then have a friend who smokes, light up a cigerette and puff the smoke into the hose. It will take a few puffs to fill the system with smoke, but after a while there will be a visible plume of smoke coming from the leak. - Works like a champ.

Good luck.

[mecompco]

Check where the vac line goes under the battery--acid can eat thru it and cause a leak.

[1985xjlaredo]

Check the Canister under the front bumper.

[zeke2230]

Winter time in New England??? You're not from here originally are you...

Give me 15 degrees ambient and a frozen lake for the sled, then you've got winter...

[xzalt]

If you've done any work with your cd player or other a/c//heater controls the vaccum connection can become undone there as well. At least that's what mine was.


gavin

[themow]

Do all the models run on vacuum or did they change to little motors in the latter years?

[Fozzy_Bear]

No little motors.

[darjevon]

If it was involved in a front end whack recently, it could be that your vac line was severed by your bumper near the reservoir under the headlight (99 xj). thats what happened to me anyway.

[xj9687]

i have had the same problem heater only blows out the defrost when im in the gas...does the same thing with the ac on. i remember when i was putting on fog lights that i drilled through the bumper and into a canister under the bumper. is this have something to do with it and if so how the hell do i get it out and change it its very cramped and small up in there...thanks for any help.

[darjevon]

i have had the same problem heater only blows out the defrost when im in the gas...does the same thing with the ac on. i remember when i was putting on fog lights that i drilled through the bumper and into a canister under the bumper. is this have something to do with it and if so how the hell do i get it out and change it its very cramped and small up in there...thanks for any help.
That might just be one of the funniest things i've ever heard. anyway, just duct taper the hole. Anyway, follow ur vac lines past the cruise control and you end up at the vac reservoir - (what you just drilled a hole into)

[Fozzy_Bear]

yeah, drilling into the canister is your problem xj9687. But you MIGHT be able to use some needle-nosed pliers to apply a small square of duct tape without pulling it out. - Of course, that would definately be a gheto-job repair. You really aught'ta pull it out and fix it right. -

[Stormwalker]

Ah ha. Vacuum. I just did a quick headgasket replacement on my 91 and I was wondering why my heat was only coming out the defroster. Time to go back and make sure I plugged everything back in, lol.

[xj9687]

thanks for the help guys i forgot to check back...i guess ill have to take that out then and fix it cuz its a bitch when u want the heat to come out the vents and its only blowing out of the defrost same with ac.