AC blows cold and slowly gets warm

[Chris85310]

I have a problem with a 1990 240sx I just got...

The Air Conditioning blows pretty dang cold for about 5 minutes. At that point the compressor seems to turn off and the air warms up pretty quickly.

I also noticed the AC makes alot of noise beyond 2000 rpm, not sure yet if its squeaky belt or a noisy compressor yet.

The AC vent controls are also stuck , it barely wheezes out the face vets even though the blower motor is pumping out full blast.

I think I have somewhat of an idea of whats going on but I thought id ask 240sx owners for pointers on what to look at first for the problem.

Thanks!

[navysnail]

is it coming out of the floor vents too? maby its not switching correctly

the compessor may be on its last leg, or it may not be filled correctly

[Dano]

go to autozone and get an A/C pressure gauge...some look like tire pressure gauges, see if u need to recharge your system.

-Dan

[Chris85310]

Hmm.. figured something out.

AC stays cold if I only put the blower motor on setting 3 IE not on high. Odd.

Now I guess I just have to tackle the floor/face blowing problem. Yeah it comes out both the floor and the face with the selector set on face only.

It will switch to only floor and defrost just fine though. Hm.

[Dano]

maybe your control unit is bad?

-Dan

[Nismo_Freak]

Check the HVAC (control unit), tighten the belt, and also you might want to clean out and fix the bent fins in your condensor (radiator looking think in front of your radiator).

It's possible the electric clutch is dying out too on the compressor.

[Chris85310]

Yeah I think I have a bad control unit. ANy way to test to be sure before I fork out for another one?

[cvex]

1) compressor relay2) low on freon3) ac fan4) ac dryer

I notice you said that the compressor turns off after 5 min. seem like theres not enough freon. i would check that 1st since it dont cost that much to get a gauge($10), can of freon($4). Since your car is a 90' and its a r12, i guess you have to buy the r134 retro-kit(around $30-40). a pound of r12 would cost double the retro-kit.

[Chris85310]

I got the compressor kicking on/off figured out.

Like I said it doesnt do it if I have the fan set to speed 1, 2, or 3. If I start it with 3 then move it to 4, it will also work fine. For some reason if i crank it straight to 4 the compressor will shut off after 5 minutes and the green light never turns on (the ac button light) It all works fine on settings 1-3 though.