Vacumn cuts off A/C fans

[rtcraver]

So, I'm sure this happens to others...
Is there a way around the issue of the A/C fan/duct closing when accelerating? When I start out, the A/C blower stops until I let up on the Gas... Any comments on getting around this?

Thanks,

TC

[DMCMW Dave]

So, I'm sure this happens to others...
Is there a way around the issue of the A/C fan/duct closing when accelerating? When I start out, the A/C blower stops until I let up on the Gas... Any comments on getting around this?

Thanks,

TC

Bad check valve (or missing if someone took it out and forgot about it.

http://store.delorean.com/c-365-7-3-...-controls.aspx item #28 on this page. Should be right behind the ignition distributor, at least in that general area.

[TTait]

My check valve is fine, any other likely causes?

Tom

[Ron]

Vacuum leak.
Bad mode switch.
Vacuum line or port for air tank blocked.

[Bitsyncmaster]

Vacuum leak.
Bad mode switch.
Vacuum line or port for air tank blocked.

I just thought of a way to test the tank and the check valve. After shutting the engine off, see how many times you can switch from one mode to another and stop hearing the actuators and flaps work. One of us will have to test that to see how many times they work on a good car. Probably selecting something like floor heat and vent may work.

[Rich]

Interesting experiment, Dave. I'm volunteering. Results here:

Returned from a drive an hour ago. Restarted it just now, then ran your test immed. after shutdown beginning with mode switch at VENT.

Toggled the mode switch back and forth between VENT-HEAT positions. A toggle in either direction counts as 1 cycle for now.

Result: 7 such mode switch cycles with what sounded like full flap movement each cycle followed by 1 slower flap cycle with the sound of partial movement, then nada.

A/C condition: Mode switch rebuilt and silicone lubed ~10 years ago. Does not hiss. A/C works fine including under full accel.

I just thought of a way to test the tank and the check valve. After shutting the engine off, see how many times you can switch from one mode to another and stop hearing the actuators and flaps work. One of us will have to test that to see how many times they work on a good car. Probably selecting something like floor heat and vent may work.

[Ron]

I just thought of a way to test the tank and the check valve. After shutting the engine off, see how many times you can switch from one mode to another and stop hearing the actuators and flaps work. One of us will have to test that to see how many times they work on a good car. Probably selecting something like floor heat and vent may work.

Good idea!

[TTait]

After a prolonged absence from driving the car which included a new fuel pump installation and brakes, I'm able to come back to this thread today with a notable update.

While the problem persists, I now know more.

I did the test suggested above (great idea!). My actuators are quiet but I got 9ish full cycles, and could still hear something happening until 11, so I think I have plenty of vacuum stored and no major leak.

What's more telling happened on my test drive. The heat of summer has passed in Los Angeles and I noticed no problems at all running in Vent, so I tried AC, again no problem. Hoping it was solved, I switched back to Max AC and the problem immediately returned (and I was really cold).

So what I am REALLY seeing in my car is that in MAX AC only, on hard acceleration something is closing, or failing to stay open, and choking off the return air being drawn in from the cabin. This is happening after I pulled the Plenum box this spring and rebuilt it with lots of new foam insulation and neoprene etc. so its very well sealed and insulated.

I'll go over the diagrams to refresh my memory as to what opens to let air into the box in MAX and see if I can figure out what's going on there, but perhaps some of you have seen this particular thing happen before?

By the way, aside from this, I'm pretty happy with how the car is driving for the first time in a long time (or maybe ever with this one - I'd have to think about it).

[dmcnc]

I spoke with Rob Grady about this same issue (mine has it as well), and apparently automatics have had this behavior since they came out of the factory. I don't think anyone has figured out why.

[TTait]

Well that's worth thinking about... Yes, I have the auto.

It's not because of the high G forces when accelerating with the Auto. I doubt the cross gate cable is holding something something open, so that still seems to leave vacuum.