AC compressor doesn't activate every time I turn the fan switch on
 

Does the ac compressor have a shut off if the system is low on freon? The car is a 1984 Porsche 911 Carrera

If it is 100% stock, no it does not. It should have one but it does not as delivered. If you ever have a chance add one.

Is your switch good? The contacts tend to weaken from the heat.

Green wire.
 

Have a look at the green wire on your compressor.

It has a tendency to get loose, or corroded.

Good luck,

Gerry

pm me as needed.

yup, check for 12 volts at the compressor. You could have a stuck AC relay or a bad switch.

afalcfan,

The system is simple.
1) Evap motor Fan Speed Switch on Right turns on the ac system in a 'ready state'.
2) Thermostat Switch on the Left changes the state.
Fully CCW (to the left) is off, or warm,
Fully CW (to right) is max cold.

The thermostat has a sensor (a metal tube filled with refrigerant gas; the tube is between a bellow in the thermostat and its end is crimped; hence a sealed unit).
The sensor goes inside the evaporator. When the evaporator is warm and the thermostat is set to a particular degree of 'cold' then power flows through the
thermostat to the compressor. As the evaporator gets too cold at that set point it turns off the compressor. The refrigerant gas inside the sensor tube expands
and contracts and tuns on and off the compressor.
Read: The AC Temperature Switch - An example in detail with a typical 911 Porsche
here: troubleshoot-the-ac-system/

Had the same issue a few months ago. Inexpensive relay in smugglers box from Advance Auto Parts solved the problem.

X2. The relay is on its way out...

I had same thing happen to me. Sometimes I got nothing and sometimes worked fine. New relay in smugglers box fixed it.

As stupid as it sounds, check the fuse. That was my issue.

Relay replacement.
 

http://forums.pelicanparts.com/uploa...1435249908.jpg
^^^^^
Replace with this.



http://forums.pelicanparts.com/uploa...1435249966.jpg
^^^^^
And add this!!!!!!!!!!!!!!!!!!

Good luck,

Gerry

Re-routing Fuse #2 electrical.
 

http://forums.pelicanparts.com/uploa...1435250056.jpg

http://forums.pelicanparts.com/uploa...1435250079.jpg


http://forums.pelicanparts.com/uploa...1435250105.jpg


http://forums.pelicanparts.com/uploa...1435250127.jpg
^^^^^
This mod reduces the current burden on fuse #2
which has a tendency to overheat & corrode.
http://forums.pelicanparts.com/uploa...1435250322.jpg
^^^^^
Here's a pic.

Good luck,

Gerry

Thanks for the all the help. It ended up being the relay that some of you advised.