Question about 1999 GMC Safari

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A/c comes out of front defroster. I also found a vacuum hose lose near the front firewall and I cant find out where it goes.

My a/c iis coming out of the front defroster and I cant switch it to the other settings. I found a vacuum line lose near the firewall.

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  • Richard Scordino May 11, 2010

    blend motors under dash are vacuum're on the right track...find where the hose attaches and you should be fine.


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Vacuum hose over top of engine attaches to vacuum outlet port on intake manifold by pcv outlet port. this line is vacuum supply to heater controls.

Posted on Jul 10, 2009

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I tried to give you a vaccum diagram but the manufacture will not release that info to outsiders. you need to find where the hose goes to.if you loose vac to the controls it goes to defrost mode.

Posted on May 27, 2009

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Have a 96 safari had same problem, has hard plastic tube running and laying all over the motor got hot and brittle kept breaking. tracked it down to other side of engine used rubber vacume line to splice the good ends and routed so as not to lay on the motor

Posted on Jul 02, 2009

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Most common problem is the vacuum line broken off at the rear of the intake .you will need to take the doghouse off to get to it ,other common issues is the vacuum ball below the right lwr side of the radiator is cracked or line has broken there older vans are bad for the plastic lines cracking in the loom that runs across the engine compartment you can trace it back fron the heater control valve on top of the heater core/evaporator, I have found that they also split at the firewall behind the battery .Here is a Safari Vacuum line diagram from the controller out under the dash .Hope this helps you .

Posted on Aug 08, 2009

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May 28, 2012 | 1997 Ford Ranger SuperCab

1 Answer

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1 Answer

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Dec 20, 2009 | 1997 Chevrolet Lumina

2 Answers

Air flow wont change from defrost to other positions.

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Jul 01, 2009 | 2002 Jeep Wrangler

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Ac blows from defrost and not front vents on 2002 cadillac deville is there a switch to change this flow

I'm pretty sure the door that directs the air between the defroster and front vents is vacuum actuated. Check the vacuum lines in the engine compartment that go to the firewall. Find an approx 1/4" rubber hose that goes into the firewall around the center of the firewall and trace it back to the motor and make sure it hasn't come loose.

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Good luck.

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1 Answer

A/C coming out of defroster and will not go to any other settings

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May 27, 2009 | 1999 GMC Safari

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