1988 HVAC Air Vent Problem - HotZ28 or Anyone?

[Ron AKA]

I have a problem with air flow in particular to the windshield defrost vents. This thread had some good suggestions, and in particular from HotZ28.

http://www.automotiveforums.com/vbul...d.php?t=419903

I took apart the AC programmer as suggested in a service link from this thread. I did not find any kinked or soft vacuum hoses, but I did find them mixed up. In this photo you can see a similar setup not not exactly the same as what I have.

http://www.imcool.com/articles/airco...se_harness.jpg

As found and assuming the order of the hose colors is the same on all harnesses, the red and orange were ok, but the yellow and the blue were reversed. There was vacuum on the purple hose, so it was ok. I reversed the yellow and blue, again assuming they should be in the same order as the photo above. However not much change if any when I put it back together. I did notice that the motor operated vent behind the glove compartment seemed to be working ok. When the digital electronic temp control was set to a low temp it went all the way left, and all right when set to a high temp. The main fan makes lots of noise in high and in particular when AC is set to maximum, so I presume it is fine.

So now I'm thinking that the vacuum motor that directs air flow to the defrost ducts or heater ducts is not working or the hoses are mixed up. I really don't get much air flow to either the floor heater vents or to the windshield. In AC mode there is reasonable flow from the mid dash vents (but AC is not working in any case).

So my questions are:

1. Is the order of the vacuum hoses standard and should they be as shown in the photo?
2. Does anyone know where each color goes? I know the purple one is the vacuum supply, but the rest...
3. Where are the vacuum motors and are they reasonably easy to get at? In particular the heat/defrost deflect door?

All help appreciated,

Ron

[Ron AKA]

I'm still struggling with this problem. Don't know if I have vacuum hoses mixed up, and electrical control problem, or a damper not stroking. Referring to this image:



- I have concluded the electric damper to control heat and cold is ok. I watched it stroke.
- I have also concluded the recirculation door works fine. It has a orange vacuum hose going to it and is only open when the AC is in the Max setting.
- The rest I'm not sure. The red and yellow vacuum hoses appear to go to opposite sides of a double acting diaphram. I assum that is the the one that controls air to the floor vs the dash and has three possibilities; vacuum on one side or the other, or neither
- The blue hose goes to a single acting diaphram and I assume it controls flow to the windshield or the mid level dash vents. I can see it move, but am not sure it does what it should. Here are the directions it strokes for each of the 6 possible settings:

AC Max - Down (vacuum)
AC Norm - Down (vacuum
AC Bi-Level - Up (no vacuum)
Vent - Down (vacuum)
Heater - Up (no vacuum)
Defrost - Down (vacuum)

Does this make sense or is it suggesting this hose is mixed up?

I just checked the other two hoses. The yellow one goes to the left or top side of the diaphram, while the red goes to the other side. Here is what I got for each of the positions:

Position - Yellow - Red
Max - Vaccum - No
Norm - Vacuum - No
Bi-Level - Vacuum - No
Vent - Vacuum - No
Heater - No - Vacuum
Defrost - No - No

So I think the good news is that the controller seems to be working, however still not sure if the vacuum hoses are mixed up, or if the double acting diaphram is not working. Can't see it stroke.

Thoughts or suggestions?

[HotZ28]

I think you are working in the right area and are close to finding the problem! The pic below is not vehicle specific, however, it is from a GM car with ACC. If you will notice, it shows two vacuum diaphragms to the left of the drivers side center vent. They have a rod connected to the blend door lever. Have you tried to remove the vacuum lines and move the rods manually? If a door is binding, the diaphragm may not have enough power to move the door. Try this before condemning the vacuum diaphragm. It is good to see someone with your determination to resolve an issue like this.

[Ron AKA]

Just as an update, I finally broke down and took the Delta 88 into a GM dealer. The service rep called in a mechanic who apparantly owned one. He immediately identified my problem when I described the symptoms, and what I had checked and found to date. He said it was fairly common in these models to have leaks in the AC coils. The freon leaks out of course (and my AC had died quite some time ago). However, the bigger problem is that there is oil in the system along with the freon. The oil leaks all over the coils and then collects dirt and crap -- plugging the AC coil. They were able to get in and clean the coils, and it is now like a new car. I have air flow!

Ron