I just bought a 2002 AP1. My A/C blows hot air when not moving, and periodically decides to blow hot air at highway speeds, but is usually cold at speed. The fans and compressor run when the A/C is on. Both the low and high pressure lines are warm at idle. I have a low side pressure of around 110psi when the car isn't running, and it'll dive into the 80's if I rev it up a bit, but otherwise(at idle) the pressure is about the same as not running. I also managed to get the low side pressure to drop by splashing water on the condenser(which has a significant number of bent fins). While the condenser isn't in the greatest shape, I'm not sure if it would totally prevent the system from blowing cool air at idle. What stumps me is that the air is generally cold while moving, yet sometimes starts to blow warm when on the highway at 70mph. The high side hose on this AutoZone rental tool doesn't fit the high side port. Otherwise I would have a high side pressure to report. It's too large and just pisses r134a and oil everywhere and won't seal, so I have no idea about the high side pressure. The coolant valve on the passenger side is in the correct position and isn't stuck or anything like that. Is it possible that there is moisture in the system and a vacuum and recharge would be necessary? As I mentioned before the part that really confuses me is when I'm on the highway at 4k with it blowing cold air, and it suddenly turns warm. Ambient temperature is around 100f. Thoughts?

Thanks,
Chris

 

I would say the thing about it being weak at idle is normal (are all s2000 compressors weak?) but the part about it turning hot at speed is definitely not.

How many miles on your car?

 

100k

 

This is a longshot, but check the coolant level in your radiator - not your overflow tank. Make sure the engine is cool before pulling the radiator cap off to check.

As I understand it, the compressor will kick off if your refrigerant gets too warm and builds too much pressure. This happened to me years ago with another car.

 

Coolant level was ok. I removed some r134a from the system and it seems to blow a little cooler at idle. Half of my condenser is pretty beat up, so I'm thinking I'll get another condenser, dryer, and then vac/recharge the system. Perhaps the reason the air turning cold to warm on the highway could be from high pressure if the condenser isn't efficient enough. Maybe I should replace the expansion valve while I'm at it.. hehe.