2000 Jeep Cherokee stuck in defrost mode

PAM SMAWLEY

MEMBER
2000 JEEP CHEROKEE
6 CYL
4WD
AUTOMATIC
17,700 MILES

This is a right hand drive jeep I use to deliver mail in, recently the air conditioning only comes out of the defrost vents and actually the heat as well. My husband took apart the dash to try to fix it, but was unable to see where the vacuum system was. We need a diagram of the vent system in order to fix what seems to be stuck shut. Sometimes the fan won't work at all, then if I hit a bump it will come back on

Saturday, September 5th, 2009 AT 2:15 PM

5 Replies

MERLIN2021

MECHANIC
17,250 POSTS

This sounds like the vacuum supply line is either broken, or the reserve tank is checked that supplies vacuum during periods of low vacuum(accelleration.)

Recheck the electrical connectors for the fan problem!

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Saturday, September 5th, 2009 AT 2:44 PM

PAM SMAWLEY

MEMBER
3 POSTS

Where do we find the junction box in the diagram?

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Sunday, September 6th, 2009 AT 10:29 AM

MERLIN2021

MECHANIC
17,250 POSTS

This diagram shows when vacuum is applied to which setting. Your problem is the supply line(black) vacuum hose comming in from the firewall. Or the reserve tank, both are under the hood, the supply line comes from the intake manifold on the top of the engine, goes to a check valve then to the reserve tank, and into the control head inside the car. This or the control head is the problem, do you have a vacuum tester? It's a hand held pump with a vacuum gauge on it. Attach it to where the black supply line is, pump it up to 18-22 hg, system should now switch to any desired airflow output, if not the control head is NG!

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Sunday, September 6th, 2009 AT 9:36 PM

PAM SMAWLEY