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Park Ave heater problem... still no solution

I posted this a couple weeks ago and am still looking for answers. The problem I'm having is cold air out of the driver's side center vent when set to mid-range temperature, e.g. 75F. If I run the set temperature way up, e.g., 85F, it will route all air to the floor, and it's warm. I've confirmed vacuum to the system, and the coolant hoses to and from the heater are warm.

I have been searching old newsgroup postings and gotten several leads, but so far nothing has fixed it or confirmed the cause. One or two people have suggested an error display sequence i.e., simultaneously pressing Off and Warmer buttons to get codes to show up on the display. However, this doesn't work on my car, something I today confirmed after subscribing to AllData. Only way to get the codes is with a scanner, which i don't have. Also, someone said to momentarily disconnect the battery in order to cause the AC programmer to reset. No help. I got a little better understanding of the system from the diagrams in AllData, but it did not get me any closer to the answer. Perhaps I wasted $25 for the year's subscription.

I have also pulled the passenger side under-dash trim and the glove box to get a look at the vacuum lines. They look OK to me.

Only thing I found that seems to be out of order is a discovery I made with my MiteVac tester. First, I checked the vacuum at the line going to the reservoir on the firewall. It reads almost 20 at idle, which I think is pretty good. I then on the tester on the line to a vacuum actuator on the drivers side of the AC/heater assembly. It reads around 17 or so when the temperature control is very high (80F), and drops off when I run the temperature back down. That seems to show that the programmer is working OK, at least to that actuator.

However, when I hook the tester to the actuator and pump it up, it won't hold vacuum. If this is a simple actuator I would think the diaphragm is ruptured. DOES ANYONE KNOW IF IT IS SUPPOSED TO HOLD VACUUM? If so, perhaps I've found my problem. Obviously I'd like to know for sure before trying to replace it, as it doesn't look easy.

Any other ideas?

Thanks.

Ed

Reply to
Ed
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VACUUM?

I don't have a PA and you didn't put what year, but maybe the system is the same as my DeVille.

There are to motors/actuators for the air distribution system. One, w/blue hose, for the AC-Def. One is a duel-diaphram motor, w/two hoses-orange hose & tan hose. Orange controls air inlet valve, Tan controls up-down valve. All vac motors must hold vaccum when tested at the vac-motor port.

Dave S(Texas)

Reply to
putt

The actuator should hold vacuum. A small leak and it may still function. A larger leak and it won't work at all.

It won't be. Dash removal will probably be involved. I've noticed that most of the Haynes manuals I have don't detail the complete procedure either.

If there's heat from the other vent areas I would say you've found your problem..

Reply to
Michael Keefe

Dave,

Thanks for the reply.

Sorry, it's a '95. What year is your DeVille?

The one I am talking about is a dual. I noticed that but failed to mention it. In you car is the dual on the driver's side like mine?

How does that work? Do you mean there are two shafts coming out of the motor, each with it's own diaphragm?

I'm looking at the Air Flow diagram at AllData and can't quite match my symptoms to any failure mode I can see. Four doors (valves, as they say) are shown:

  1. Defrost-AC, which switches the air from center outlets to defrost.
  2. Outside air or Recirculation, which switches inlet air between inside the car and outside.
  3. Air mix, which controls amount of air that is routed through the heater core.
  4. Mode, which controls the fraction of air going to floor versus center outlets/side outlets/windshield

The main problem I'm having with this diagram is there is no door shown would cause the temperature coming out of the right side center vent to be different from that of the left center vent. It looks like any air going in the "up" direction as a result of the positioning of door 4 will go to either the side vents, center vents, or windshield, and all of these streams should be at the same temperature. Yet, when there is air coming out of the center vents the left one issues cold air while the right one issues warm air.

Is it possible that the diagram AllData is showing is not correct for my car?

That's what I figured but didn't want to believe....

Thanks again.

Ed

Reply to
Ed

Thanks, Michael. That's what I figured.

There are some diagraps at AllData that show disassembly of the dash to get at something in that area. I'll look it over.

Would you mind taking a look at my reply to Dave?

Thanks

Ed

Reply to
Ed

I have now discovered OTHER airflow diagrams for Dual Zone AC, which my car has. These newly found diagrams offer explanation for my symptoms. There are two electric motors, separately controlling heater core bypass doors for passenger and driver side air. It looks like the one for the drivers side isn't working. The car's in the shop for other problems now, but I'll see if I can verify that when I get it back. Unfortunately, the controller motor is part of the HVAC programmer, probably a very expensive part.

What I've learned from this is the stuff at AllData isn't organized very well. One would hope to see all applicable diagrams for the AC airflow doors in one place, but also that isn't so.

Ed

Reply to
Ed

If you have air flow from both sides but the temperatures are different then that is a mystery. On most cars the air is sucked from either the cabin or the outside or both and blown through the AC accumulator to the mixing door controlled by the rheostat (electric motor that runs the mix door). From that point the air is directed either through the heater core, or bypassed on to the ductwork. My only thought would be that the mixing door is not completely closing one way when the heat is on and that air is taking the easiest path through the ductwork (presumably to the left center vent). I know that most AC systems seem to blow the air most forcibly out the console vents and particularly onto the driver.

As for diagnosing this possibility, ... ??

Best of luck!

Reply to
Michael Keefe

thanks, Michael. It turns out the car has a Dual Zone AC system, i.e., the air to the drivers side is conditioned differently from that going to the passengers side. I found AllData diagrams showing that. So now it looks the motor that is supposed to control the heater bypass for the drivers side is not doing it's job. Also, i think the actuator controlling recirc/fresh is bad.

Ed

Reply to
Ed

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