99 xj heater won’t change vents but blows out the defrost

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Apr 7, 2018 | 08:25 AM

Perryrich850569

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Newbie

Joined: Apr 2018

Posts: 5

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From: Pa

Year: 1990

Model: Cherokee(XJ)

99 xj heater won’t change vents but blows out the defrost

99 xj 6 cylinder bought this as a work car runs great but heater won’t change vents it blows warm air out the defrost but when it’s really windy out I can feel cold air come in the cab by my feet it seems to be

Apr 7, 2018 | 09:19 AM

Sideways99

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Joined: Dec 2010

Posts: 1,240

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From: Rocket Country MI

Year: 1999

Model: Cherokee

Engine: 4.0

you have a vaccum leak. it controls/ powers the blend door for heat/ ac

Apr 7, 2018 | 09:27 AM

4WD4EVER

CF Veteran

Joined: Sep 2012

Posts: 1,623

Likes: 13

From: In a large sandbox

Year: 1998

Engine: 4.0

It maybe a vacuum leak. OP, does the temp control switch still function? When you turn it to hot does it blow hot air and when you turn it to cold it blows cold air?

Apr 7, 2018 | 11:15 AM

Perryrich850569

Thread Starter

Newbie

Joined: Apr 2018

Posts: 5

Likes: 0

From: Pa

Year: 1990

Model: Cherokee(XJ)

Where’s the most common vac leak located and yes thermostat works correctly

Apr 7, 2018 | 12:06 PM

4WD4EVER

CF Veteran

Joined: Sep 2012

Posts: 1,623

Likes: 13

From: In a large sandbox

Year: 1998

Engine: 4.0

The most common source of vac leak is from "the ball"/canister or the line that runs down the left side inner-fender when you're looking at it under the hood.

I would also consider the blend-door actuator.

I'm leaving for the afternoon but you can find links/diagrams on here and maybe someone else will chime in.