Normal ac vs max ac
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Laughing Gas
Joined: Mar 2009
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From: long island
Normal ac vs max ac
So i know that the normal ac setting uses fresh air, and max ac recirculates the air. When i switch from normal to max, i dont really notice a difference. After a few minutes of driving on max ac, the air starts to come out of the defrost and i have to switch it to normal ac to get it back to the dash vents. I assume this is vaccume related, but i dont see any broken lines and im not sure where to start
Logistics Pro
Joined: Nov 2013
Posts: 3,922
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From: Mojave, Ca
So i know that the normal ac setting uses fresh air, and max ac recirculates the air. When i switch from normal to max, i dont really notice a difference. After a few minutes of driving on max ac, the air starts to come out of the defrost and i have to switch it to normal ac to get it back to the dash vents. I assume this is vaccume related, but i dont see any broken lines and im not sure where to start
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Laughing Gas
Joined: Mar 2009
Posts: 1,028
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From: long island
That line appears to be in tact. The servo that it leads to is what switches from outdoor air to recirc air? This truck sat for a while and maybe that servo is locked up. Im going to try and manually apply vaccume to it from another source. I assume it should be very visually apparent when it switches over
Fleet Owner
Joined: Oct 2005
Posts: 20,784
Likes: 1,751
From: Kentucky
Yes you can visually watch that vacuum servo move when selecting Max AC versus regular AC. If that white line is intact the whole length (very rare these days) you could have a cracked HVAC reservoir, on the evaporator/heater core/blower case, or another common issue is a missing check valve for the HVAC system.
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Laughing Gas
Joined: Mar 2009
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From: long island
Yes you can visually watch that vacuum servo move when selecting Max AC versus regular AC. If that white line is intact the whole length (very rare these days) you could have a cracked HVAC reservoir, on the evaporator/heater core/blower case, or another common issue is a missing check valve for the HVAC system.
Tuned
Joined: Jul 2007
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From: Vacaville, California
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Fleet Owner
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Laughing Gas
Joined: Mar 2009
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From: long island
The white line seemed compromised outside of the loom. I cut back the loom and spliced in a new rubber line from the area where it meets the firewall. The lines under the dash are in absolute perfect condition. I dont see where i could be losing vaccume. I wired the recirc actuator closed manually for now.
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galaxie223
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
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Jul 31, 2003 09:20 PM