[DML] Re: Proper operation of mode switch

["content22207" <brobertson@xxxxxxxxxxxx>]

I believe you're seeing the defroster vent linkage.

Disconnect each line at the HVAC mode switch and use a vacuum pump to
manually activate its diaphragm. You'll be able to feel the effect at
various vents. There are only three to check (vacuum opens): dash
vents (red), defrost vents (blue), and foot vents (brown). Remember to
cap the supply line to prevent a vacuum leak to the engine (unmarked,
tied to a big 1/4" hard plastic line under the console with a step
down connector). If your pump has a built in gauge you'll also be able
to watch the diaphragms hold vacuum. Orange line has a Tee in it to
operate both the inside/outside air supply flap and the heater core
shutoff valve -- shutoff valve linkage is visible in the engine
compartment but air supply is burried inside the heater/evaporator
core box. Be sure to check this one because the original hard plastic
heater core shutoff line is prone to crack in the engine compartment.

DeLo temperature control flap is not vacuum operated. It is attached
to the knob with a cable. Turning towards "Hot" opens the flap over
the heater core. This is very common in cars of its era.

Again, I urge you to check the whole assembled HVAC system for vacuum
tightness at the Tee in the engine compartment (right after the
takeoff barb on the passenger intake rail). See the pic of my vacuum
leak damaged plugs in #5939's photo album. A crack in the big 1/4"
supply line did that to me. Am very lucky not to have melted the
pistons or warped the valves. Other side of that Tee goes to the brake
booster -- check it too.

Bill Robertson
#5939

>--- In dmcnews@xxxxxxxxxxxxxxx, "ryanpwright" <yahoo1@xxxx> wrote:
> 
> 
> Thanks Bill & Dani. Appreciate your replies. I'll go pick up a hand
> vaccum pump, and checkout that section of the workshop manual to
> ensure my lines are setup correctly. 
> 
> I can't help but wonder if one of my diaphragms isn't working. How can
> you tell whether they're working? I know there is one of them in the
> dash that moves a metal bar. I can clearly see it move, so it's OK,
> but I can't see if the others have anything similar (I can see the
> diaphragms themselves, but don't see any actuators coming off of them
> looking from underneath the driver's side).
> 
> Also -- Is the hot/cool knob supposed to change the location of air?
> For instance, I get air out the vents when it's on one setting, but
> change it and the airflow from the vents stops. I've never had a car
> work this way before.
> 
> -Ryan
> 









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