Hopefully an HVAC guru can help me out here:

A couple years ago I started to notice that whenever I come to a stop, something in the A/C would turn on and the car's lights would dim.

Now that I have a manual tranny, the same situation will cause the engine to almost stall.

I now realize that the cause is the A/C compressor kicking on. When this happens, it puts a load on the engine that almost stalls it (only caused lights to dim when it was auto tranny).

I figure that the A/C compressor is having to work too hard to get the refrigerant moving. A/C has also been sucking lately, so I checked it out.

Low side pressure is lower than it should be. Weird because I thought it might be overcharged, as A/C compressor is having to work harder.

Maybe the expansion valve?

 

Hey Karanx, have ya tried the climate control's self diagnostic feature ?

If not, it may be worth a shot. Here ya go :

Turn key on, push the "auto", then the "off" button for the dash CC. Hold them in until the temp indicator display gives a letter code for the DTC error. If nothing is displayed, then the system checked out ok. To return to normal mode, simply release buttons and turn the key off. Ya never know, it may help ???

 

Also a faulty Alternator would not have enough power once the Compressor kicks in..
After you figure out if the A/C system is Okay have your Alternator check'd.

 

Switched to Type S alternator since the swap, haven't really noticed the lights dimming.

I'm thinking bad expansion valve or bad compressor.

 

It could also be an iac problem, not increasing rpms as fast as it should.

 

Beat me to it. I second that.

 

My taxi mechanic is really good with A/C, just bounced your problem off him.....

He seems to think there is some kind of restriction in the system.

One possible scenario is you pinched or kinked a line making a restriction in the system. If your high pressure is a little high, and the low pressure side is low, this may very well be your case. Inspect every single inch of the system to make sure, and if there is ANY sign of flat spots or bends that aren't factory, replace the part.

If it is your expansion valve, you may be able to 'shock' it open, run the A/C full blast and shoot the condenser with ice cold water, it may open the sticky valve, if it does, you might be in for replacing said valve if it makes progress with the cold water, then regresses into crap.

Good luck brother!