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De-frost is always on (when air is on)

B

bigblueishness

NAXJA Forum User
Location
Winterville, NC
Its getting cold now, and I want my heat to work well

So when I turn the heat on to the just feet switch, I only get heat out of the De frost air vent and a little out of the driver side foot vent

Same with the upper vent switch, I get the heat coming out of the De frost vent more than the face air vents

how can I fix this
 
Most likely you have a vacuum leak. The mode door in the HVAC box is vacuum operated. When it looses vacuum, it goes to defrost. Check if vacuum lines are disconnected under the dash or under the hood running to the vacuum reservoir in the front bumper.
 
winterbeater said:
Most likely you have a vacuum leak. The mode door in the HVAC box is vacuum operated. When it looses vacuum, it goes to defrost. Check if vacuum lines are disconnected under the dash or under the hood running to the vacuum reservoir in the front bumper.
Click to expand...

Winterbeater is dead-on, fix the vacuum.
 
bigblueishness said:
alright Ill check it out, I guess a trusty old hanes book will show me where all the vacuum stuff is

thanks
Click to expand...

Vacuum reservoir under the front bumper, passenger's side. Vacuum line runs up and under or behind the battery along the passenger's side fenderwell.
 
there is also one of those one way valve things (i forgot what there called) and if they are turned around backwards it has no vacuum. mine was near the heater control valve iirc
 
Picture.jpg

traced the hose from behide the bumper and found this
 
beraad44 said:
there is also one of those one way valve things (i forgot what there called) and if they are turned around backwards it has no vacuum. mine was near the heater control valve iirc
Click to expand...

I thought I was the only one with a backwards one.
 
a check valve?

Friend of mine with a ZJ installed one of those backwards in his transmission while rebuilding it. Long story short, he ended up rebuilding it again shortly after that...

Glad you managed to fix it!
 
kastein said:
a check valve?

Friend of mine with a ZJ installed one of those backwards in his transmission while rebuilding it. Long story short, he ended up rebuilding it again shortly after that...

Glad you managed to fix it!
Click to expand...
yea thats it a check valve. mine wasnt one that was inline with the trans just from the intake to vac ball one. good thing!
 
94HOCHEROKEE said:
My vac. ball got ripped of in a ft. end collision and now i have the same prob w/ my heater, can I get a new vac. can???
Click to expand...

Yes. Personally I would just grab one at the salvage yard. They are still available new, and you really can use about any make model of reservoir. I relocated mine from the front bumper to the passenger's side firewall. Gets rid of about 4' of useless vacuum line, and protects the reservoir.
 
I wouldn't expect it too have that much of an effect.

Slightly high idle, loss of floor/dash vents under acceleration (air would shift to defrost vents--default position).

Is your brake booster out? Engine off, pump the brake pedal 4 times then hold it to the floor, start the engine and if the pedal drops then your booster is working.

If you don't like your stopping power you can always upgrade to the later dual-diaphragm boosters of the 95-96.
 
I have been running with out a resevoir for years in alaska, just have the lines connected and I have not had any issues that I am aware of. However I do not have that vacuum crap on niether my axle nor my transfercase, when I engage 4H or 4L I am in 4.
 
I've seen guys solder a nipple to a soupcan and bolt that to the inner fender along with a check valve. There's all kinds of fancy aluminum stuff out there too. My Comanche has a large vacuum tank to keep some power brakes despite the 6" of vacuum at idle.

Some sort of reservoir is good to have especially with a disco front axle, you don't want it trying to unlock halfway up a steep climb.
 
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