Unidentifiable Part
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Mountain Pass
Joined: May 2004
Posts: 201
Likes: 1
From: El Paso, TX
Unidentifiable Part
Hey guys I need your help here. I was under the hood of my 89 F150 4.9l and noticed a white vacuum line that went from a taped bundle to what appears to be a switch in the back corner of the engine compartment on the passenger side. The line was deteriorated so I replaced it, but my question is what is this "switch" and what does it do? I have always lost my vent setting on the a/c when going up a hill or something similar; could this have been the cause? I can find no mention of this part in the Chilton manual. Thanks.
Post Fiend
Joined: Mar 2002
Posts: 19,402
Likes: 38
From: Bonita Springs FL
There's a vaccuum line going from the vaccuum tree on the intake manifold to the MAPS sensor in about the same location you describe. If you unplug it, and the truck dies immediately, that's probably what it is.
Posting Guru
Joined: Jan 2001
Posts: 2,358
Likes: 3
From: Nebraska
The vacuum line to the MAP sensor is a black hard plastic line. The white line you describe goes to the fresh/recirculate air door vacuum motor. It's supplied with vacuum when the a/c switch is in "max a/c" and "off".
