Car: 1995 Olds Regency Elite
Full load.
Automatic AC.
Problem: recently the AC started cycling from the upper vents to the defrost and back. Pressing the upper vent controls has no effect, it just blows air where it wants to. What causes this? The temp is fine-it blows cold air, just not where I want it. Is this due to a faulty circuit board in the AC controls or something more nefarious? Any help would be appreciated.

 

And the ghost of Comfortron still roams Oldsworld...

 

FWIW: I can't be sure about your specific car/year, but I know the "old School" A/C vents and switches are all vacuum powered. If there is not enough suction or a diaphragm/connector was leaking, the vent springs would overpower the diaphragms and reset everything to the default route (ie. the Defrosters)

I would like to think that newer cars don't use vaccum systems to control the vents anymore, but what you are describing sounds indicative of a vaccum setup. If so, diaphragms, rubber connectors, and plastic vent switches are common sources leaks.

 

The newer GM cars still use the vacuum controled air doors. You might have to make sure you don't have any vacuum leaks.

 

does it do it at any particular time, like on acceleration, or if you are idling with no change in accelerator would it do it? sounds like a vacuum leak to me too if it's on acceleration, but if it's just random at idle, sounds electrical like a controller

 

Jeffrey,
That's what I was wondering too. It's totally random. It can change while the cars idling, driving at expressway speed, or if you open a window, or hit a bump. On startup, the car will go into normal AC, then about a minute later it defaults to DEF. When I press lower (floor) mode, it shifts there. On Bi Level it splits between DEF and lower. Wierd.

Also, you can be driving for 20 minutes with it working perfectly and then it changes. So, I pulled out the controller module on the right hand side of the dash and looked to see if there were any visible issues with the solder joints or other electrical do dads that I wouldn't normally touch. (Been my experience you don't have to be a rocket scientest - but God knows it would help to be one - to find a melted spot on the board, or a weak solder joint.) Couldn't find squat. So I went and got another controller from the boneyard. Quick replacement (10 minutes including R & R dash trim. Seems to be working ok for now. The test will come this afternoon or tommorrow. It's supposed to be a scorcher (89 degrees both days) - that's when I noticed the most problems with the AC. That would also tend to support the theory of an electrical overheat problem on the circuit board causing the system to fail to DEF. In the morning when it's cool outside (around 45-60) I don't need the AC obviously, but the controls function just like they're supposed to. I'll let you know in a couple of days.

 

a scorcher of 89??? we find that not a bad day here in South Florida LOL... I have some strange things happen when I get into a hot car parked in the sun, been driving the Toronado for a few days while the wagon is in the shop, and when the Toro is hot, I get noice though the speakers (over bumps or banging on the dash) that go away after the car cools from the hot hot temps it's been sitting in

 

Um...yeah..well it's a scorcher to us!! We're mostly used to getting a high that's close to uh....let's see.....gotta check the window.......ok, there's no snow yet so I'm ok with saying we're used to temps that are quite a bit less than a scorcher of 89!!!

If I remember right about Fl, 89 might not seem so hot because you have the wind coming in off the ocean, right?

Know what you mean about the strange noises. I think the stuff the dash and trim is made from is probably designed for temps around 70 or less. The really hot days seems to make it get funny noises. You're right, once the car gets to a normal temp inside, its like being in a new car. Anyone else notice that too? My wife doesn't because she's parked in the garage and it's always a pleasant 68 in there. One of these days...I'm gonna build a double decker 3 car garage with a built in bar and big screen or something.

 

Ok, its not the controls. Still doing the same thing. The controls are all hooked up to a electronic pinset pigtail. I guess what I'm going to have to do is trace the wiring back from the control to whereever the vacuum motor is that changes the air flow. From there it looks like I'm chasing a loose connection or a bad vacuum line. I'm thinking a bad or loose connection because the AC will change when the car hits a bump. Any of you have ideas?

BTW Jeffrey, it got up to a barn burning 92 degrees today. C'mon, you gotta admit that's pretty darn hot.

 

Finally got this fixed thanks to 70Cutlass S. It was a vacuum line under the engine shroud going to the firewall that got pinched. New hose, reroute the line. AC and heat both work fine now.

BTW Jeff, I'm wishing it was 92 today. Outside right now it's about -25 and we have a couple of feet of snow. Windchill is -34 (I know you don't have that down in FL).

 

it's a very nice 80 deg here today, in Dec!!!

 

But humid I hear! Ted and Jeannie just got back from FL on Sunday morning. They said temps all last week were mid 70's to low 80's. Almost melted their popsicle legs off! Ted looked like a lobster....next week he'll look like a banana or an orange cause he'll be......peeling...

Jeff, like I said I'll trade ya....doubt if I gonna get any takers.