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73-87 Chevy _ GMC Trucks => Interior & Equipment => Heating, Ventilation & Air Conditioning (HVAC) => Topic started by: 75scottsdale on February 27, 2014, 10:18:08 pm

Title: HVAC vacuum hose size?
Post by: 75scottsdale on February 27, 2014, 10:18:08 pm

hey guys what size is the small vacuum hose for all the heater box controls under the dash?
or is there anywhere to buy a full kit?

Title: Re: HVAC vacuum hose size?
Post by: bd on March 02, 2014, 02:46:02 pm

IIR the control head accepts 1/8" hose that increases to ~5/32" at the vacuum actuators.  Plastic splices should be available to join the two sizes of hose, but you may have to search for them.

Title: Re: HVAC vacuum hose size?
Post by: 75scottsdale on March 02, 2014, 10:24:07 pm

cool thanks bud

Title: Re: HVAC vacuum hose size?
Post by: 75gmck25 on March 07, 2014, 06:39:49 am

The stock HVAC vacuum hoses have soft plastic fittings on the AC controls end and on the actuator end, but in between they use the GM hard plastic lines.  I have seen sections of hard plastic lines sold at the parts store, and I'm sure you can get it from online sources. 

In my truck I used short pieces of regular vacuum hose to splice some breaks in the hard lines.  They also sell small packs of splices in the Dorman or Help! carded parts section.  I considered switching to regular rubber vacuum line, but it is much bigger around and harder to fit back under the dash.  The hard plastic lines are thin and smooth so they "snake" very well behind the dash.

Bruce