Max AC always works, Normal AC hit or miss

[content22207]

Like most cars of their era, DeLoreans use vacuum to operate various HVAC ductwork flaps (outside air, face level vents, floor vents, etc). The mode switch routes vacuum to the diaphragms that open and close these flaps. It also switches electricity to the A/C compressor and the blower motor. Page N:08:15 of the Workshop Manual has two charts that show what is activated at various mode switch positions.

The only differences between Max and Normal A/C:
- Outside air flap is closed for Max, open for Normal
- Heater core water is closed for Max, open for Normal
Otherwise flap actuation and blower motor operation should be identical between them.

The temperature control knob moves a cable that opens and closes the HVAC ductwork flap over the heater core.

Bill Robertson
#5939

[Ron]

It might be worth noting that it is normal for the mode switch to momentarily make a hissing sound immediately after changing modes (depending on the selection) while it vents diaphragm(s).
The younger you are, the louder it will sound

[john 05141]

Well well,I had the EXACT same thing last year. I just could not figure this out, no logic.
It happened the first time while I was driving on the highway, and I could not hear the wind from the vents, but felt the car heating up.

So later on standing still, I noticed ony the max AC worked

As I usually deal with those things in the winter time, I did not bother to look at it right away as I had a werking AC.

But as problems have dissapeared before by itself on my car, It did so again this time.... Spooky....

John

[stevedmc]

Top Roman Steve aint stupid but that was the closest thing to a "what he said" smiley I could find....

Thats pretty bad when the site admin can't even navigate the new smiley menu.

[sean]

Thats pretty bad when the site admin can't even navigate the new smiley menu.

Oh, I can navigate, I just don't think we have it. Im liking the "Im with stupid" even more now.

[orbitron3000]

So last week I installed the new "rebuilt" switch kit. As far as I can tell, the car will switch each mode properly with an occasional hiss between modes.

However, no matter what I try, the vents in the center console will not open. I have put the car in Max AC and turned the fan speed to four as per the instructions, but nothing doing. Is there some step that I am missing? Another failure point (like a vacuum leak or something along those lines)? The side vents and floor vents still work as they should.

[DMCMW Dave]

The arm breaks off the actuator. Usually caused by a car stereo installer. The actuator is just to the left of the glove box.

[jawn101]

The switch isn't supposed to hiss. Rebuild the thing and the problems should go away, unless there is something else that is broke.

Basically there is a rubber diaphram that needs to be replaced. It is pretty simple to do but I decided to let Hervey rebuild it. I'm not sure what DMCH sells the part for but they do have detailed instructions on their support site if you choose to use their part.

www.delorean.com/pdf/modeswitch-rebuild.pdf

Mine only hisses when switching between modes. For example, A/C to Off - there will be a low clunk as the doors close, and a moment of "pssshhh". No noise when the system is operating or turned off. Is this abnormal?

*EDIT* just saw Ron's post above. Guess this is normal as long as you're not a young'un like me

[orbitron3000]

The arm breaks off the actuator. Usually caused by a car stereo installer. The actuator is just to the left of the glove box.

What should the actuator arm look like? Where is it on the diagram? I can't seem to find it.

[DMC5180]

The Vacuum actuator and arm assembly is located just left of the glovebox insert. You can probably see it with a flashlight if you can get your head under there.

It opens and closes the center ducts.

I tried posting a link to the delorean.com parts page. but something is not working right I could not get past the sections list.