1986: vacuum lines for climate controls

08-05-2026, 11:11 PM

Hi,
The P30 uses vacuum lines, sourced at the engine, to operate the doors that control flow of the heater and window defogger. I think my defogger last worked in 2009, and this is now the priority for me. Some of the vacuum lines have turned to dust.

Has anyone done this work, and do you have any advice or pointers? I haven't found anything in the forum history on this.

Matt

08-06-2026, 09:26 AM

billyt53

Good morning Matt, what brand is your dash AC? Back in the day there were Frigette, Acme, etc. There would have been a sticker on the evaporator housing. Worst case, post a picture of the dash control, I may be able to identify it and find a vacuum schematic.
Billy

Billy & Helen Thibodeaux

Retired from Billy Thibodeaux's Premiere RV, Inc. Scott, LA 70583 I-10 Exit 97-Our Son now owns it!
The Farm is near Duson, LA I-10 Exit 92 then N 1 mile on right
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1994 Sovereign 36' Widebody on Spartan IC (Mountain Master Lite) Chassis.
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08-07-2026, 02:51 PM

BarthBluesmobile

Billy T!

Here's what I got at the dashboard, I think it might be hardware from a Mopar factory. The identifying number seems to be 3779501 26961. That first 7 digit is smudged, it might be something different.

I don't see any identification on the evaporator housing.

Matt

08-07-2026, 02:54 PM

BarthBluesmobile

Forward of the radiator, this vacuum reservoir is mounted, with a fat hose coming from the carburetor. I would presume that the narrow hose is headed to the control panel. This unit is up above the radiator door area and hard to see.

Matt

08-07-2026, 04:24 PM

BarthBluesmobile

Top side of the control hardware.

08-07-2026, 06:05 PM

BarthBluesmobile

I traced them through. It couldn't be done with the secondary doghouse in place.

There's a black plastic vacuum line coming from the vacuum reservoir and going to the control assembly. The black vacuum tube is broken.

Coming out of the control assembly, there are red, white, and blue plastic vacuum lines.

Red: this goes to the heater control vacuum actuator, probably works a "blend door". It is in place, inside the dash.

White: this goes to the defroster/defogger control vacuum actuator. It is in place, inside the dash.

Blue: this goes to the AC control vacuum actuator, probably works a "blend door". It has turned to dust in the area between the actuator on the ducting inside the area ahead of the radiator, to where it went over the radiator.

It wasn't that bad to figure out.

Some new lines and for the black and the blue and things should be working better.

Matt