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Old 12-04-2017, 08:07 PM   #1
84C10EC
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AC Vacuum Harness - Please Help

Looking for a new AC/Heat Vacuum Harness. Mine has dry rotted and needs to be replaced. I've looked on several truck part sites and ebay but cant seem to find one. Any help in the right direction would be appreciated.
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Old 12-05-2017, 11:10 AM   #2
RotaryRocketeer
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Re: AC Vacuum Harness - Please Help

You looking for the adapter, or the lines? The adapter can be purchased through LMC. I imagine you'd need to get the right size line by the foot and cut to fit.
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Old 12-05-2017, 01:48 PM   #3
84C10EC
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Re: AC Vacuum Harness - Please Help

Thanks for the reply. The harness itself is fine. Its the line that goes through the firewall and to the engine (gray stripe) that is dry rotted. I will attempt to see if I can get the line out of the harness and repair it. One more question if I can. Because the line is dry rotted I do not know where on the engine it attaches. If anyone could share that knowledge it would be much appreciated. It appears to go somewhere near the distributor.
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Old 12-05-2017, 01:56 PM   #4
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Re: AC Vacuum Harness - Please Help

I think it goes to a vacuum canister just above the fan, and that canister has a line running to the intake manifold or carburetor (really, any vacuum source will work, but I don't suggest the ported vacuum)
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Old 12-05-2017, 02:00 PM   #5
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Re: AC Vacuum Harness - Please Help

Maybe, and I'm just guessing here, it's the one that should connect to the vacuum canister/ball in the corner on the passenger side of the firewall?
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Old 12-05-2017, 02:25 PM   #6
SunSoaked
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Re: AC Vacuum Harness - Please Help

I just swapped manifolds and was cleaning up the firewall on my 85. I was wondering myself last night where that vacuum line went to inside the cab. On the firewall side it goes to the vacuum ball. My ball is below and next to my master cylinder.
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Old 12-05-2017, 03:07 PM   #7
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Re: AC Vacuum Harness - Please Help

Sounds like we're on the same track. Must be in a different spot on the later models. My knowledge is limited to my own '76.
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Old 12-06-2017, 10:01 AM   #8
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Re: AC Vacuum Harness - Please Help

Looking through pictures of engine bays, the vacuum balls all look similar, but they're mounted in different places. Many are attached to the heater/AC housing, I believe mine is attached to the firewall itself on the passenger side, and it sounds like SunSoaked has his more driver's side.
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Old 12-06-2017, 05:32 PM   #9
84C10EC
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Re: AC Vacuum Harness - Please Help

I only have one and its on the firewall on the drivers side. Looks like the cruise control is the only thing accessing it. I'm going to "t" into the line above the check valve. I suspect that will work. Thanks all for the reply's.
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