problem with heating and a/c unit

kamet · 05-13-2009, 10:28 AM

The sympton: My air conditioning doesn't work. If I turn the fan switch in the a/c unit , nothing happens, it simply stays in the one fan position. The fan only works on the defrosting mode. Any other position, the air doesn't blow. Also, the air that comes out is burning hot. Using the lever to change the temperature does nothing. When I turn the lever that controls the direction of the air, I can hear valves opening but the fresh air in the center of the dash does not open. Does anyone have any idea what the problem is? Thanks.

MPDano · MPDano's Garage

Sounds like a multitude of problems. All those noises behind your Center Console are Vacuum Soleniods that are supposed to open and close vents. Yank the center Console out and sort out the soleniods. I bet the tubes are leaking or disconnected. But this is for the early cars, not sure what are behind the console on later models.

What year is your car?

Danglerb · 05-13-2009, 11:11 AM

More info please,

US or Euro, model year, did the AC work in the recent past?

Does the heat work, as in regulated temp, not just blows hot?

Do all the fan speeds work?

What happens when defrost is selected?

Picture of the control face might help, some have an AC button

Dozman · 05-13-2009, 11:36 AM

Sounds like the many problems .. BUT betting on the fan electric unit (forget it's name ) under the hood near the low temp lock out switch.

Danglerb · 05-13-2009, 12:23 PM

Quote:

Originally Posted by Dozman

Sounds like the many problems .. BUT betting on the fan electric unit (forget it's name ) under the hood near the low temp lock out switch.

Only if the middle fan speeds don't work, just hi and off I think means the resistor pack is bad.

rjm65 · 05-13-2009, 12:33 PM

When I purchased my 79, the fan would only blow on high when the lever was placed in the defrost. A new relay fixed the problem.

MPDano · MPDano's Garage

Hey Raymond, can you take a quick phone pic of your controls, so i know what they are supposed to say in English.

psychII · 05-13-2009, 01:08 PM

http://members.rennlist.com/pirtle/svc.html

read through the HVAC section on the left side of the page. It should help you correct some of the issues.

This link will help you trouble-shoot - https://www.928gt.com/t-wallyhvac.aspx

rjm65 · 05-13-2009, 01:28 PM

I'll snap one tonight when I get home.

To the best of my recollection, going left to right it's OFF, AC, then you have symbols (triangles) showing airflow direction.

Dozman · 05-13-2009, 02:37 PM

Quote:

Only if the middle fan speeds don't work, just hi and off I think means the resistor pack is bad.

Probably correct. I know wally P has a write up. I have it on my computer, but not sure if I should post his write up with out his approval.

Rixter · 05-13-2009, 03:24 PM

Wally's writeup is on 928Specialists website
www.928gt.com
https://www.928gt.com/t-wallyhvac.aspx

devilinblack · 05-13-2009, 03:48 PM

Quote:

Originally Posted by rjm65

To the best of my recollection, going left to right it's OFF, AC, then you have symbols (triangles) showing airflow direction.

That's what mine says. Far right setting being defrost, iirc.

rjm65 · 05-13-2009, 09:32 PM

Here's the A/C controls on my 79.

MPDano · MPDano's Garage

Here's the Euro Version

rjm65 · 05-14-2009, 08:13 AM

I would say AUS is off, ECO is vent, AUTO runs your A/C depending on where you have the temp slider, the up/down arrows is bi-level (air through upper and lower vents) and finally defrost.

What does seem odd is that you don't have a setting for lower vents only. Does the temp slider have any control on where the air is directed to?

lfausty · lfausty's Garage

rjm65 figured my euro german labelling off your 79us thats a match thanks

kamet ???????

where the heck did the one asking for the info go.

kamet · 05-15-2009, 10:38 AM

Thank you for all your kind advice. I''m sure that all your suggestions and information will help me sort out my air conditioning problem this weekend. I appreciate the help immensely! My 928 is a 1982 car that came over from California to here in Finland-now that the hot Finnish summer is approaching, I might just need some cool air-ha ha!

Danglerb · 05-15-2009, 11:27 AM

Multiple things may be wrong. I suggest starting with the vacuum control system. Use a hand vacuum pump like a MityVac and check for leaks in the vacuum system and fix those. Source of vacuum is near the brake booster if I remember correctly, and the whole control system can be check by pulling a vacuum on that line.

Your heater valve is one of the vacuum devices, failure mode is heat on, and it may need replacing.