My MY 02 does the same thing. Last week took it to the dealership, they took out the freon and put it back in to make sure it was full and it still does the same thing. I really don't like this b/c when it is hot I like to stay cool, not ride with the top down and get baked. They were suppose to call the honda rep, but you know how that is. Haven't heard anything yet.

 

[QUOTE]Originally posted by R C
[B]Compressors must cycle but what surprised me was how long the S2000 compressor remains off before cycling back on.

 

Originally posted by R C...

Compressors must cycle but what surprised me was how long the S2000 compressor remains off before cycling back on. Initially the air conditioning system provides excellent cooling, but once the compressor begins cycling it remains off for an extended period while the fan circulates air from the duct. Once the compressor runs again, the air temperature drops nicely.........

That sounds exactly like the experience which prompted me to start this thread. It's very easy to keep a monitoring finger in the neighborhood of an air duct. The average cooling effect seems to be adequate, especially in view of the non-insulated black cloth top and our sunny South Carolina climate, but the temperature swings of the duct air are more than I have ever noticed. The S2000 does have a very unusual drive belt setup, which may be a part of the problem. Perhaps the accessory drives for the alternator and compressor have to be designed differently to avoid problems at extremely high rpm's. As we all know, there are no other vehicles out there in which the accessory drives are in danger of being spun at 9000 rpm.

 

The compressor cycles mainly because of the pressure sensor (secondarily from the thermostat on the condensor). Perhaps our sensor range is set too wide.

I agree the system might be made to operate differently because of the high redline.

 

My system operates as well as any other I've had, and about the same as any other I've had. AFAIK it's operating right.

A fix would be to remove/relocate the thermostat that's in the coils to somewhere else, or insulate it. This would be no easy task, and would probably cause the coils to freeze up (no fun, either).

I suggest anyone who doesn't like their AC move to Texas. You'll start loving it regardless, soon enough.

 

I think the thermostat only shuts off the system when the evaporator (I mispoke before) gets to the temperature where ice will form on the coils. Mainly the pressure sensor seeks to maintain the system at peak operating pressures despite varying compressor speed (which is directly related to the crankshaft speed).

Your home system works with a compressor that operates at a constant speed, therefore the system doesn't need to turn the compressor on and off while it runs. In this case, the thermostat on your wall does all the logic.

 

As someone who designs air condtitioners for a living, I know a little about this. Don't worry - your A/C is functioning as designed. A car A/C is very different than your home A/C. It has variable capacity (heat removal in BTU's per hour), as the compressor operates at speeds that vary with engine RPM, vs the compressor in your home that has a fixed capacity (the compressor runs at a single speed). A car also has many different fan speeds, vs. your normal home A/C with a single speed fan. When running at low fan speeds or high RPM's, the A/C system has a lot of capacity which it cannot reject to the interior of the car, so the evaporator gets very cold and could freeze up - hence the temperatur probe on the evaporator which releases the clutch on the compressor if the coil gets too cold. Cars also usually have a dual pressure switch which also cycles the compressore is the pressures get too high or too low. The pressure switches and temperature probes also protects the system if it gets low on refrigerant. Overall, it's amazing that a car A/C works as well as it does - it has to operate at extreme temperatures (the interior can get over 120 degrees and less than 0 degrees - the A/C operates when you use your defroster). So, the bottom line is that yes, the temperature of the outlet air will change as the compressor cycles. It does seem like Honda set the ranges of the pressure switches and/or evaporator temperature probe fairly wide so that the compressor has a longer off-cycle than normal. This could be due to the high RPM nature of our car. But, it is easier on the compressor, as the pressures equalize more before the compressor re-starts.

So ends your class on A/C 101.

 

Originally posted by txst
As someone who designs air condtitioners for a living, I know a little about this. Don't worry - your A/C is functioning as designed. A car A/C is very different than your home A/C. It has variable capacity (heat removal in BTU's per hour), as the compressor operates at speeds that vary with engine RPM, vs the compressor in your home that has a fixed capacity (the compressor runs at a single speed). A car also has many different fan speeds, vs. your normal home A/C with a single speed fan. When running at low fan speeds or high RPM's, the A/C system has a lot of capacity which it cannot reject to the interior of the car, so the evaporator gets very cold and could freeze up - hence the temperatur probe on the evaporator which releases the clutch on the compressor if the coil gets too cold. Cars also usually have a dual pressure switch which also cycles the compressore is the pressures get too high or too low. The pressure switches and temperature probes also protects the system if it gets low on refrigerant. Overall, it's amazing that a car A/C works as well as it does - it has to operate at extreme temperatures (the interior can get over 120 degrees and less than 0 degrees - the A/C operates when you use your defroster). So, the bottom line is that yes, the temperature of the outlet air will change as the compressor cycles. It does seem like Honda set the ranges of the pressure switches and/or evaporator temperature probe fairly wide so that the compressor has a longer off-cycle than normal. This could be due to the high RPM nature of our car. But, it is easier on the compressor, as the pressures equalize more before the compressor re-starts.

So ends your class on A/C 101

...........

Thanks a bunch, Professor Freon!! I guess I will stop worrying.