Plenum vacuum motor
 

I don't know if the heat is the cause of this but I'm having an odd problem with the vacuum motor that controls the plenum panel-door for the registers.

I first noticed this one day after the Sun was blasting through the back window of my truck. Every part of the interior was HOT to the touch. AC was coming only from the defrost-vents, which is the 'default' for no vacuum. Going through the various settings of the Function switch did nothing to resolve. Eventually the panel-door motor got vacuum and closed that door. This has happened a few times, even when the interior isn't in the Sun. What I'm looking for is a source for that single-port vac motor. SM doesn't list the part number. RA doesn't have and I haven't found anyplace that does have it. It should be a fairly common motor for many model years and maybe even other manufacturers. Any ideas for a source would be a big help. The Ford part number would be a big help also. Thanks

Paging NumberDummy to the white courtesy phone ...

??? Is that 'a help'?

Bill was a Ford partsman for 38 years before he retired.
He has tens of thousands of posts on this board.
He can tell you the number without fail, cross applications, dealer stock, and what - if any- obsolete parts dealers may have it.

If PM'ed he will check this thread and reply...

oh, ok. A man named Bill is "Number Dummy"? Is that the search query I use? Thanks Jim. Hope Irene wasn't too bad there. We here in Texas would have taken all that rain.

Dave,
I've PM'd him to bring his attention to this thread.

I feel for all of you down there dealing with the drought.
I'm sure it is bad for crops, livestock and citizens alike.

Here in Connecticut there were only a couple of deaths attributed to the storm.
Some houses and bridges were washed away but right now it's a matter of clearing downed trees to make roads passable and restoring power to 800,000 people.
We're very fortunate that Irene's winds died down and her speed increased.
If the storm had hung around longer the already saturated ground would have turned to soup.

Dave are you sure it's the vacuum motor at fault?

Often the seals in the heater controls themselves fail.
Do you know if the A/C was factory, or dealer, installed?

I need to know a coupla things before I post the part numbers/sources that have them if obsolete.

Which blend door are you having the problem with? There are several different motors, depends on which blend door they operate.

Is the A/C factory or dealer installed?

And, are these parts for the '81 F100 in your sig?

btw: If the A/C is factory, the problem may have nothing to do with the blend door motor, because there is something else that "runs" the show, this little charmer:

A/C Vacuum Control Selector Valve Assy. Once I know all the particulars, will type a thesis :-X04 on what this valve does...and how it affects the blend door motors.

What I am sure of is that it is a heat problem. I will try to solve the problem by an old-fashioned method: parking the truck with the windshield into the West afternoon Sun (use the front of the truck as a heat-sink). If the problem still occurs, I'll wire the panel-door closed to the defrost/floor plenum and deal with it when it is much cooler out. Too darn HOT for me to fool with now....maybe by December it will be cooler. The past number of weeks the ambient temp has been in the triple-digits. I believe about 600° or so...but a dry heat.

Factory AC: I'm intimately familiar with the plenum system/AC & Heater systems. Over the 30yrs I've owned this vehicle, I've operated on various illnesses the plenum contracted; The dreaded blend door hinge failure/temp control cable break/function control replacement and a number of other old-age problems. This latest problem does not occur when the interior isn't over-heated by the outside ambient temp.

Most likely it is a plastic-hose fault. I've only experienced this problem lately due to my 1-car garage being occupied by my Harley. Cadillac is relegated to the driveway and the truck parks in the street (East/West facing)

Thanks

Thanks Bill. If you can get the part # of the single-stage vac motor that controls the register panel-door, I'd be obliged. I understand the Function control switch.....huge pita to deal with....btdt.

Thanks

Could it be that the plastic blend door is either swelling or warping because of the triple digit heat and binding up on it's pivot?

There are three different vacuum motors with factory A/C / There's also the A/C Vacuum Selector Valve I mentioned in post #9.

1) D9AZ-18A318-C (Motorcraft YH-350) / Obsolete

A/C Heat Door-Located on Plenum Chamber-One Port.

1980/86 F100/350 & Bronco / 1979/89 LTD/Crown Vic/Mercury Grand Marquis.

20 available NOS from FoMoCo Dealers/obsolete parts vendors.
------------------------------------------------------------
2) EOTZ-18A318-A (Motorcraft YH-362) / Obsolete

Recirculating Fresh Air Door located on Evaporator-One Port.

1980/89 F100/350 & Bronco.

29 available NOS from FoMoCo Dealers/obsolete parts vendors.
------------------------------------------------------------
3) EOTZ-18A318-B (Motorcraft YH-363) / Obsolete

Defrost Door-Located on Plenum Chamber-Two Ports.

1980/89 F100/350 & Bronco.

21 available NOS from FoMoCo Dealers/obsolete parts vendors.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
EOTZ-19B888-B .. A/C Vacuum Control Selector Valve Assy (Motorcraft YH361) / Obsolete

This little charmer (a notorious POS!) mounts to the backside of the A/C Heater control panel, all the vacuum hoses connect to it.

When you slide the lever on the control panel, this valve opens one blend door and closes another.

This valve also has the A/C 'kicker switch' mounted to it. Turns on the A/C (an audible CLICK is heard) by sliding the lever to A/C.

1980/82 F100/350 & Bronco.

139 available from FoMoCo Dealers/obsolete parts vendors.
--------------------------------------------------------
Pick the part(s) you want, let me know, I'll list the sources closest to you.

Check the ends of the vacuum hoses where they connect to these motors. When they age, they crack, allowing vacuum to escape.

Check the vacuum hoses to make sure none are kinked.

No. When it 'defers' to the defrost, the air is plenty cold. Now it could be the register panel-door acting that way tho (sticking closed)... When it get to sweater-weather (80s) I'll fool around under the dash and determine what's what, assuming my old-time fix didn't work.

Thank you very much Bill for the part numbers. Big help! Printed them out and put the info in my SM. Very nice of you to do that!.