Just to start I want to say thank you for any advice, and or help in advance.

I have a 2002 s2000 it blows warm air at idle, but cold air above 2500rpms. This is true even when the car is sitting and I rev it to above 2500rpm, the car does not need to be moving to achieve cold air to blow form the A/C. Its been doing this since December, but I wasn't concerned with it because well... it was nice outside so top down was more than enough. However summer is here and its unbearably hot now days, and too sunny for even trying top down driving. Im not sure what could be wrong with the A/C system so I gathered some info that may or may not be relevant to my issue. I was able to record some low side pressure readings, but unable to fit my gauge on the high side port. From what I can discern from research, it might be a faulty expansion valve. If high side readings are needed ill buy a reader that fits on it to record the pressure.

90 degrees Fahrenheit outside with 62% humidity during the tests. A/C set to MAX, at coldest setting with recirculation on.

Cold start Low side pressure- 35-47psi @1500rpm
Engine temp now at 2 bars- 58psi @1250rpm
Still at 2 bars- 62psi @1100rpm

Warmed up to 3 bars 65psi @900-1000rpm
60psi @1500rpm
45-53psi @2000rpm (fluctuates a bit) the A/C is starting to cool
40psi @2500rpm (stable) A/C blowing cold air.

 

This is a chart that shows what normal readings should be

 

So your pressures on the low side are definitely high. A/c system issues can often be diagnosed by pressures however need info on your high side readings. Normally an expansion valve will cause low, low side pressure... here is a chart that shows a pressure diagnostic chart. Don’t mind the fact it had a/c dye spilled on it... unfortunately I would not be surprised if it has a failing compressor as that is an extremely common issue on almost all hondas and unfortunately s2000s aren’t an exception. As you can see from the chart if the high side is low it’s almost a guarantee

 

My A/C compressor turns on, the clutch does spin, but in your opinion even without knowing the high side pressure in your opinion the compressor is the likely culprit because its beginning to fail? Even with the accompanying symptoms? I understand this is just your diagnosis without all the info you really need, but still thanks. I might just buy a used compressor to get it done asap.

 

well based on the flow chart used by ASE for air conditioning flow charts there are 4 caused for high pressure. If you have not charged it recently then you can rule out it being overcharged. Moisture in a system generally occurs after an improper a/c charge or repair, so lets say the line was disconnected and it was charged to the correct amount without putting the system into vacuum... so if you can eliminate 2 causes immediately that leaves you with a faulty compressor or faulty evaporator function. Based on the symptoms its quite possible that its an a/c compressor despite the fact it turns on and engages however i would never condemn a compressor or replace any a/c parts without first finding out the high side pressure

is there any specific reason why you cant get a high side reading other than your adapter doesn't fit? Have you thought about going to harbor freight or a parts store and picking up a cheap set of gauges?

 

Ill buy a cheap set of gauges, Im just being impatient but compressors aren't cheap and I may as well get the readings to be certain. ill post the readings when ever I get the gauges.

 

Hi @prodigalmichael, I have the exact same issues that you're explaining. I just took my car to an AC shop, and they said the compressor is the culprit and that it's on it's way out. I still get cold air when driving above 2k RPM like you, so it's not an immediate repair, but eventually the compressor will go out completely. They quoted me $2,500 for parts and labor using genuine Honda parts, or $1,600 for an aftermarket compressor. This is in Hawaii where stuff costs more, so take that with a grain of salt.

 

OP, how many miles on the car?