924Board.org

[maireeka]

Nothing happens when I play with the switches on my '77s AC system. Anybody have a good idea how to start troubleshooting this?

sorry for the vagueness.
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1977 Porsche 924 red and READY!

[Johno]

I am taking a guess that the 77 is similar to the 79, mine has a fan swich which I also belive runs the A/C, my switch turns on my fan but nothing else. So if your switch does not turn the FAN on - I would start by looking at the fuses, and possibly relays to ensure they are there and not blown.
I will be watching this post as I will soon begin this journey. Good luck

Somewhere in the back of my mind if the fan runs you have power to the unit. if it is low on Freon the compressor won't kick in. In my case I do not have Freon and my compressor belt is off. That might also be something for you to check - compressor belt.
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79 924 NA

[maireeka]

I know the belt is on there.

Is the blower fan the same fan that I hear when my car's warm and I turn the key to 'on'? If it's the same fan, then I know that works as well.
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1977 Porsche 924 red and READY!

[Paul]

Near the dryer you will find a low pressure switch with 2 wires. Disconnect them and hook them together and see if the system runs.

Do not try this for long as one of the purposes of the switch is to shut the system off if the pressure is too low since low pressure can mean that the system is leaking and all the compressor oil has been lost.

[Roger]

[Ozzie]

If the switch has an meter put on it with the system off it should read ok. (Indictate zero ohms.) However.....

Minor low on gas.
When the system is on and motor running the compressor draws gas into itself to compress..... This reduces the operating pressure and if the system is low on gas the switch open circuits. The compressor clutch releases.
As the pressure rises again the compressor engages and the cycle repeats itself.

Major low on gas
The switch will read open circuit at all times.

Check fuse 6 on the aux fuse board
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Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

[gohim]

The 77 does not have a highly integrated ac system like the later model cars, since all ac systems on 77 MY cars were dealer installed.

Does the car have dealer installer VWofA ac with the control panel replacing the central air vents, or Non-Dealer ac system with addition vent panel that is mounted under the dashboard?

The 77 MY cars do not have an aux fuse panel, so the fuse for the ac system will be in a different place.

The 77 MY cars do not have electronic idle stabilization, so if the ac clutch is engaging when the proper switches are set to activate the ac system, the engine idle should drop when the ac clutch engages. If the ac clutch is not engaging, and the interior blower fan is not ont, I would guess that the system is not being turned on.

If the ac clutch is not engaging because of low refrigerant level, the interior blower would still engage.

If the interior ac blower is running, but the engine idle does not drop, and the ac clutch is not engaging, you could try locating the low pressure switch to try jumpering it to see if you can force the ac clutch to engage.

Since the owner claims that nothing happens when the switch is operated, I would start by making sure that the correct switches are being flipped to operate the ac system. Then, I would check for the fuse and the ac relay.

[maireeka]

You confused me a bit there, I'll get some pics and maybe you'll be able to tell me what I have.
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1977 Porsche 924 red and READY!