99 EB AC vents change when accelerating.
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Mountain Pass
Joined: Jan 2005
Posts: 222
Likes: 4
From: Richmond, Va
99 EB AC vents change when accelerating.
Over the last week, for some reason, when it's hot outside & I accelerate, my AC vents switch to the defroster vents until I let off the gas. Then the air starts blowing out of the AC vents again. I was thinking it was a vacuum leak somewhere in the EATC system, but this only happens after the dash has been sitting in the sun all day. It doesn't do it (yet) in the mornings when I first get in the truck. I don't have an issue replacing the EATC control head. .. I have 2 in the garage. I just wondered if there is something else I need to look at before I pull out the control head ??
Hotshot
Joined: Jan 2004
Posts: 19,762
Likes: 1,079
From: St Louis
Yeah, it's a vacuum leak. if could be in the supply from under the hood or it could be a leak somewhere else "downstream" including the common issues with the O-rings in the solenoids for the EATC.
A handheld vacuum pump is invaluable for diagnosing. Otherwise, you can throw your spares in there and hope that they don't have their own problems.
A handheld vacuum pump is invaluable for diagnosing. Otherwise, you can throw your spares in there and hope that they don't have their own problems.
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Mountain Pass
Joined: Jan 2005
Posts: 222
Likes: 4
From: Richmond, Va
THX !!!! I've got a vacuum pump, but honestly, wouldn't even know where to start. You can't see the majority of the damn vacuum lines. I think I'll try one of my spares first. They "should be" fine. Both were "rebuilt" by a 40+ yrs Ford technician/ mechanic (although I know that really doesn't mean squat).
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Mountain Pass
Joined: Jan 2005
Posts: 222
Likes: 4
From: Richmond, Va
Just a follow up.....
I did not find any vacuum leaks under the hood, but I admit, I wasn't able to check EVERY line. Another forum suggested the EATC control head could be bad. Luckily, I had a functioning spare, so I replaced it the other day. I've only run it for about 25 miles, but it seemed to be fixed. The real test will be this week when the temps get back up into the mid to upper 90's.
I did not find any vacuum leaks under the hood, but I admit, I wasn't able to check EVERY line. Another forum suggested the EATC control head could be bad. Luckily, I had a functioning spare, so I replaced it the other day. I've only run it for about 25 miles, but it seemed to be fixed. The real test will be this week when the temps get back up into the mid to upper 90's.
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