Is this a Blend Door problem?
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New User
Joined: Aug 2021
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Is this a Blend Door problem?
My 1999 F350 AC is not cooling as it used to. The blend door opens towards the engine (clockwise from above) in the AC mode and closes toward the truck’s cabin (counterclockwise from above) in the Heat position. The blend door is warped and doesn’t close completely, but that is the Heat position, so I don’t understand how that would effect the AC.
If I pinch off the heater hose line, the AC works better.
Should I go ahead and change the blend door (I already have the Dorman Blend Door kit), or is my problem somewhere else?
If I pinch off the heater hose line, the AC works better.
Should I go ahead and change the blend door (I already have the Dorman Blend Door kit), or is my problem somewhere else?
Laughing Gas
Joined: Mar 2002
Posts: 946
Likes: 342
From: Newton Illinois
There should be a vacuum controlled valve in the heater hose that closes when the heat is off, should be no hot water circulating unless calling for heat, the heater will always win over the AC.
Fleet Mechanic
Joined: Sep 2006
Posts: 1,491
Likes: 295
From: Fresno, CA
Not all trucks have the valve, it was a certain option that was required. I don't know about the 7.3 but on the 6.0 you can buy the heater supply hose with the valve already in it. There should be a vacuum line already in the area that's connected to a plug which is used to move the valve. It only closes the valve in the Max AC position BTW. It piggybacks off the recirculation door vacuum signal.
Did some digging on Rock Auto and it looks like you can buy the valve separately. It would need to be plumbed in, hopefully someone with a 7.3 can chime in and show you were it should go.
https://www.rockauto.com/en/moreinfo...t=6860&jsn=936
If your blend door is warped I think you found your problem. Dorman stuff is horrible, recommend you find an OEM Ford part.
Did some digging on Rock Auto and it looks like you can buy the valve separately. It would need to be plumbed in, hopefully someone with a 7.3 can chime in and show you were it should go.
https://www.rockauto.com/en/moreinfo...t=6860&jsn=936
If your blend door is warped I think you found your problem. Dorman stuff is horrible, recommend you find an OEM Ford part.
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