Civic temperature issues

I own a 1992 Honda civic ESi 1.6.
The car has aftermarket air-conditioning installed. (Genuine).

For a while now i've been having problems with the cars coolant temperature.

What happens is this.

When I turn on the airconditioning the car runs fine but the temperature indicator rises up to the red line. The problem begins when I turn on the airconditioning but does not stop when I switch it off. The temp remains high.

My coolant levels are steady and normal, the water pump is brand new, and the thermostat also. I also checked and replaced the relay for the fan.

Another weird thing is this.
When I first noticed this I got home and left the car idling. I opened the hood and monitored the coolant fan. It was not working although the temperature indicator was almost near the red line. Then I stoped the engine and then started it again. Still nothing. What I noticed though was that when the car key wah in the MAR position (the position that where oil and battery lights are on) the fan was working. But it stoped when I started the engine.
another strange thing is:
I let the engine cool down and started it back up.
when the temperature reached the normal iddling point, the fan started but continued working (normally it works for a short time then goes back off again). The temperature dropped a bit but then started rising again while the fan was working (!).

The problem presents it self almost every time I use the airconditioning ever since.


Any ideas of what's wrong would be appreciated since I am getting really frustrated with this problem.

thank you!