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Old 11-02-2016, 01:49 PM
coloradoluke coloradoluke is offline
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Join Date: Jul 24, 2016
Location: Sooke, BC, Canada
Posts: 10
Defroster isn't working

Hi there all.

So most the time, although I have put the switch on defroster, no air is coming out of the vents.

If I put it on air, I get air out of the ac vents, and if I put it on heat I get air out of the vent near the floor. But if I put it on heat/def or def nothing changes. It is the same air that comes out when it is on heat.

However sometimes it will just work, or randomly work after a few minutes.

I feel like this is a electrical issue, but I am curious if anyone had encountered this and has any advice.

Thanks,
Luke
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Old 11-02-2016, 02:18 PM
joe joe is offline
 
Join Date: Apr 28, 2000
Location: PNWet, USA
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If the fan is moving air even if not to where you want it, it's not electrical. The switch that selects heat or def is a vacuum switch. It draws vacuum from the reservoir in the eng bay and then routes the vacuum to the selected vacuum motors that open/close the heat/def doors. If you have a vacuum leak the doors won't work/move. The vac hoses get old with age and leak. Most common leak area is at the back of the heat def switch. Kinda one'a them replace the hoses maint items every 20 years or so. Depending on the overall conditions of the vac hoses you might buy some time removing the hoses from the back of the switch and at the vac motors and cut off an inch or so and reconnect. The connection ends are 'usually' the bad/leaking sections. Possible but unlikely the vac motors are corroded/frozen. Also check the integrity of the feed hose between the switch and the reservoir. If you've got a vac leak anywhere the heat/def air routing doors just stay in the position they're already in. Vac hose is cheap($0.50/ft)...go get a bunch.
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Old 11-03-2016, 01:21 PM
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serehill serehill is offline
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Join Date: Nov 22, 2009
Location: Mesquite Texas
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well

First of all a model would help. I agree with SIR Joe it sounds more like a vacuum problem.
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Old 11-03-2016, 03:34 PM
darylb darylb is offline
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Joe nailed this one. The heater/defrost switch is a vacuum switch which rerouts vacuum as the buttons are pushed. As the hoses age they crack and break. It sounds as if the hose from the switch to the defrost vacuum motor has a small leak that occasionally seals due to warming up or movement from vibrations of the motor running.
They are a pain to get to, but easy to change out the hoses once you do. I usually replace all of the vacuum behind the dash when I work on an FSJ. Even if it isn't leaking it will be soon simply due to age. Don't forget to replace the hose between the switch and the vacuum reservoir in the engine compartment and the vacuum reservoir and the manifold source while you are doing the others. If you have any plastic fittings either replace them or bypass them as they tend to become very brittle with age as well.
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Old 11-03-2016, 04:32 PM
ShagWagon ShagWagon is offline
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So how does the pneumatic actuator work? And where is it?

I have not seen or located this but assume it opens/closes a vent door that sends airflow one way or the other?

Would the vent door or actuator get boogered up with dirt and leaves like the heater door vent does?

Does anyone know of a product that restores vacuum hoses and or prolongs life?

Aerospace 303 comes to mind
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Old 11-03-2016, 05:04 PM
joe joe is offline
 
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Quote:
Originally Posted by ShagWagon
So how does the pneumatic actuator work? And where is it?

I have not seen or located this but assume it opens/closes a vent door that sends airflow one way or the other?

Would the vent door or actuator get boogered up with dirt and leaves like the heater door vent does?

Does anyone know of a product that restores vacuum hoses and or prolongs life?

Aerospace 303 comes to mind
The duct work has it's own door and vac motor for each heat or vac function, not just one door that flops back an forth. The vac motor for each function is right down at the door on the ducting. Yeah you can get crud inside the ducting. Do not spill crap down your heat/def vents. If the doors close but don't seal it's usually the foam seal edging is rotted out.
Don't know of anything that "restores" rubber. All rubber gases out,degrades, ages from the day it's formed, be it tires or vac hose. I've "heard" folks say wintergreen oil rejuvenates rubber(questionable at best) but go price enough wintergreen oil to soak. 10 ft of vac hose. New vac hose is a LOT cheaper and you're done/good for another 10-20 years. Last vac hose I bought a while back was 40-45 cents a foot prolly 50 cents/ft today. Don't make an easy maint issue harder or more expensive than it needs be.
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