A/C only blowing through defrost
Thread Starter
Member
Joined: Mar 2012
Posts: 187
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From: Las Vegas, Nevada
Year: 1990
Model: Cherokee
Engine: 4.0L 6Cyl L8
Hello again everyone,
So I'm hoping to get my a/c recharged and I went to test it today and it would only blow from the defrost vents on the dash.
Blows nice and hard but only from those vents. Any suggestions?
So I'm hoping to get my a/c recharged and I went to test it today and it would only blow from the defrost vents on the dash.
Blows nice and hard but only from those vents. Any suggestions?
Senior Member
Joined: Feb 2012
Posts: 864
Likes: 4
From: Arlington, Texas
Year: 1998
Model: Cherokee
Engine: 4.0
This is a classic Jeep issue. This is almost always caused by a bad vacuum line or connection, or a cracked vacuum canister.
Behind the front bumper on the passenger side, there is a spherical vacuum canister about the size of a softball. These are prone to being hit by road debris and cracking, or just cracking over time due to heat and cold. Your problem is usually that the canister has cracked, or that the vacuum line going to it has cracked or come loose. Start at the canister and work your way back toward the firewall looking for cracks in the hose, especially at the connections, or any loose connections.
Behind the front bumper on the passenger side, there is a spherical vacuum canister about the size of a softball. These are prone to being hit by road debris and cracking, or just cracking over time due to heat and cold. Your problem is usually that the canister has cracked, or that the vacuum line going to it has cracked or come loose. Start at the canister and work your way back toward the firewall looking for cracks in the hose, especially at the connections, or any loose connections.
Senior Member
Joined: Feb 2012
Posts: 864
Likes: 4
From: Arlington, Texas
Year: 1998
Model: Cherokee
Engine: 4.0
Sorry. Brain fart. Wasn't thinking about yours being a 90. Your may look more like the one below, and should be either behind the front bumper or behind the radiator cross member just in front of the motor.
Seasoned Member
Joined: Sep 2011
Posts: 474
Likes: 0
From: segoville tx
Year: 1997
Model: Cherokee
Engine: 4.0 6 cylinder
When I drive and hit about 60 it stops blowing from my vents and blows from defrost vents but when I slow down it goes back to the normal ones
Senior Member
Joined: Feb 2012
Posts: 864
Likes: 4
From: Arlington, Texas
Year: 1998
Model: Cherokee
Engine: 4.0
Yep. Classic vacuum leak symptoms. Check for the same things I mentioned to the OP. Just sounds like your leak isn't as bad yet.
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CF Veteran
Joined: Apr 2010
Posts: 3,966
Likes: 0
From: knoxville, tn
Year: 2000
Model: Cherokee
Engine: 98 4.0 I6
Originally Posted by monstercherokee
When I drive and hit about 60 it stops blowing from my vents and blows from defrost vents but when I slow down it goes back to the normal ones
Originally Posted by macgyver35
Yep. Classic vacuum leak symptoms. Check for the same things I mentioned to the OP. Just sounds like your leak isn't as bad yet.
Thread Starter
Member
Joined: Mar 2012
Posts: 187
Likes: 0
From: Las Vegas, Nevada
Year: 1990
Model: Cherokee
Engine: 4.0L 6Cyl L8
Originally Posted by macgyver35
This is a classic Jeep issue. This is almost always caused by a bad vacuum line or connection, or a cracked vacuum canister.
Behind the front bumper on the passenger side, there is a spherical vacuum canister about the size of a softball. These are prone to being hit by road debris and cracking, or just cracking over time due to heat and cold. Your problem is usually that the canister has cracked, or that the vacuum line going to it has cracked or come loose. Start at the canister and work your way back toward the firewall looking for cracks in the hose, especially at the connections, or any loose connections.
Behind the front bumper on the passenger side, there is a spherical vacuum canister about the size of a softball. These are prone to being hit by road debris and cracking, or just cracking over time due to heat and cold. Your problem is usually that the canister has cracked, or that the vacuum line going to it has cracked or come loose. Start at the canister and work your way back toward the firewall looking for cracks in the hose, especially at the connections, or any loose connections.
I thought it was for the heater core but maybe not.

See below the overflow tank, one missing house and one barely hanging on, could that be causing the problem??
Last edited by Johnthepanpire; Jul 22, 2012 at 07:37 AM.
CF Veteran
Joined: Mar 2010
Posts: 47,923
Likes: 38
From: Broward County Fl.
Year: 1989 xj sport 2dr
Model: Cherokee
Engine: 12 hole bosch Injectors
classic leaking check valve get a in line check valve install on vacuum line going to vacuum canister it will help greatly
Thread Starter
Member
Joined: Mar 2012
Posts: 187
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From: Las Vegas, Nevada
Year: 1990
Model: Cherokee
Engine: 4.0L 6Cyl L8
Originally Posted by freegdr
one goes to vent control on dash the other goes to heater control valve .
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