Vacuum bulbs???
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Joined: Aug 2007
Posts: 77
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From: Mesa Az
Vacuum bulbs???
I have an '86 that blows hot air through the vents no matter what my settings are on. Ive been told that the problem is a leaky vacuum bulb. Can anyone elaborate on this ? Where could I find the replacement part? And exactly what is the part called??
Racer
Joined: Nov 2010
Posts: 460
Likes: 1
From: Oliphant Ontario
Never heard them called vacuum bulbs 
There is a diaphram that opens and closes the 'blend door' to adjust the amount of hot mixed with cold. Could be that diaphram. Search "blend door" on this site, lots of hits.
That is assuming you can change from say vents to defrost to floor OK, if not, different problem. Most of the articles you'll find here related to blend doors sticking, not vacuum issues. Good luck! Blend door sucks to get to!
There is a diaphram that opens and closes the 'blend door' to adjust the amount of hot mixed with cold. Could be that diaphram. Search "blend door" on this site, lots of hits.
That is assuming you can change from say vents to defrost to floor OK, if not, different problem. Most of the articles you'll find here related to blend doors sticking, not vacuum issues. Good luck! Blend door sucks to get to!
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
....I see this and memories of my dads ham-radio room came to mind...vacuum bulbs? tubes? huh?
then I realize that this is a geographical reference to the vac diaphrams/servos.
I've heard them refered to as "vac pots" also.
regarding the problem, the one that meters hot/cold is in the very corner of the passenger side footwell by the firewall. If the vents operate as they should, look at that "bulb"...
if all the vent functions are bad, then go to the cabin vac and the a/c programmer thats over the gas pedal. This is the junction and distribution controller for vac signals to the servos..(bulbs) assuming its elec a/c control opt-68.
Be sure there is cold air to be blended...
Last edited by leesvet; Apr 20, 2011 at 02:28 PM.
Le Mans Master
Joined: Oct 2008
Posts: 9,758
Likes: 49
From: Houston Texas
....I see this and memories of my dads ham-radio room came to mind...vacuum bulbs? tubes? huh?
then I realize that this is a geographical reference to the vac diaphrams/servos.
I've heard them refered to as "vac pots" also.
regarding the problem, the one that meters hot/cold is in the very corner of the passenger side footwell by the firewall. If the vents operate as they should, look at that "bulb"...
if all the vent functions are bad, then go to the cabin vac and the a/c programmer thats over the gas pedal. This is the junction and distribution controller for vac signals to the servos..(bulbs) assuming its elec a/c control opt-68.
Be sure there is cold air to be blended...
I once told a customer his "electronic actuated vacuumed resistor" went out.
He said "wow will that be expensive"
I said "No, light bulbs are cheap."
