545svk

I have a new problem that, with the temperature selector set on the coldest setting, I still have above outside temp air coming into the cabin. Moving the selector to hottest setting turn the car into a sauna.

Everything worked great till I turned up the heat on a chilly evening a few days ago.

Is there an easy way to bypass all the settings and get the aircon to give me full cold until this can be attended to properly?

Car is a 1987 928s4, right hand drive.

Thanks in advance.

Ducman82

Unhook the actuator from the flap under the dash?

Bilal928S4

Or the heater valve is not closing properly.

WallyP

Feel of the AC suction line (larger line) and see if it is cold. If not, the problem is in the AC part of the system.

Tails

For a good description go onto the 928 Specialists web site www.928gt.com and under Wally's Technical Tip, he has an excellent write up on the HVAC system.

Nicole

The first thing I would check is whether the heater valve closes properly.

- If it doesn't close at all, you may have a vacuum problem.
- If it closes, it can be a variety of other things, including a leaky valve, low Freon or R-134, etc.

545svk

Thank you for the hints and tips. I spend the day poking around the car in stead of working - and I still don't have cold air.

I am thinking that as the actuator move up and down as I change the temp setting (slowly but at a constant speed) and the revs drop when I press the aircon button leading me to assume the compressor clutch work, perhaps a re-gas is a good next step.

Also looking for the heater valve and wondering how I check it when I find led me to think of a business idea for a 928 specialist. I will post it in a new thread.

FredR

Just remember:

1. Gas- do you have the right amount.
2. Heater valve- is it working correctly? Easy thing to do is disconnect the vac line [plug it off] and wire the actuator in the closed position- you will lose the heater circuit until you re-connect it.
3. Recirc flap -is it closing correctly- stick your mitt under the passenger footwell and stick your pinky through the aperture to determine if the flap is open [i.e. lowest position] or closed [more upright]. If it is open then either the vacuum actuator has failed [common] or the entire vac system is leaking creating too little vac to keep the flap open.

Remember, if you do not use the a/c system in winter time the lube on the seal face dries and you will lose gas rapidly- always keep the a/c running for a minute or two no matter if you are at the north pole if you want it to retain gas and work when needed.

Regards

Fred

Schocki

If your HVAC blows only hot air and not jsut luke warm, I would suspect a faulty temperature flap motor.
If one of your NTC sensors is bad, it would at least blow full cold air at the lowest setting (micro switch override).
The setting motor sits (in your case I´m not 100% sure) on the passenger side about wehre your right knee would be while sitting down. I´ll attach a photo of the motor.

The motor has two plugs. The two yello cables connect to the NTC sensors and should read about (disconnect before)
2,57 kOhm @ 20°C
2,22 kOhm @ 25°C
1,9 kOhm @ 30°C

If you set the temperature selector to full cold at an ambient temperature of about 20º C you should see about 3,7 kOhm. Move the slider to full warm and the resistance should slowly but steadily increase to 4,7 kOhm without interruptions.

If this is OK your setting motor is most likely faulty and is stuck in full hot. The problem with this is, that the motor moved the temeperature mixing flap to full hot AND with the arm on the motor in hot it will permanently activate the heater valve to full hot too!!!

Temporary fix: remove the setting motor and disconnect the arm. The temperature flap will drop to the full cold setting by gravity. On one of the plugs you will find a red cable at PIN 2 and a black/red cable at PIN 3. Bridge these two PINS and the heater valve is always closed. This should keep your head cool

If your resistance readings were OK, I would recommend to open the setting motor and clean it. This helps sometimes. Also take a close look at bad solder spots. The electronics inside are very simple. If everything looks OK but the motor still refuses to work, go ahead and replace the four transistors.

This worked in my GTS and is very cheap. The motor is still available from Porsche but will cost more than $ 500 new.

545svk

In this write-up, Wally suggest to feel if the coolant pipes coming out of the firewall is cold.

If this mean the two short pipes leading into a square metal block, then mine was not cold to the touch. I'll take a photo of this tomorrow.

So while I will go through all the flaps etc. I just want to make sure I actually have cold air and that it didn't dump it's gas for some reason.

WallyP

First check: Engine running, AC on, temp lever at full cold - use a good light to look at the AC compressor clutch. Is the center of the clutch spinning? If so, you probably have at least some refrigerant (not "coolant") in the system, and the electrical connection to the compressor clutch is OK. This eliminates about half of the problems. If the clutch isn't spinning, either you have low refrigerant or a problem with the electrical circuit to the clutch.

auzivision

My two cent input can be found here:

https://rennlist.com/forums/10510236-post8.html

and it looks like this:

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

Step by step troubleshooting vacuum:

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

More A/C system troubleshooting and pictures:

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

545svk

Update - I had my friendly local shop check the gas levels in the aircon.

The report is a fail, with the system not being able to hold a vacuum. JAmie recon it is not worth it to put new gas in, even as a temporary fix.

Suggest replacing the compressor and filter, which appear to not be available in Aus any more. Other option is to get it reconditioned or see if there is one in the States (will email Roger).