ancdmd

My a/c won't blow cold until ten minutes after starting the car when the engine is cold. Usually if the engine is somewhat warm the a/c will blow cold immediately. Shutting the climate control off and on has no effect. 2002 with 165k miles. I had this problem 5 years ago and replaced the high pressure switch, which didn't fix it. Only when I replaced the compressor did the problem go away. After only a few years and about 45k miles how could I be having this problem again? I know the high pressure switch is activating because I can disconnect it and the a/c clutch stops. Ugh

Lavrishevo

iTrader: (1)

Are you sure you don't have a leak? There is a little glass bubble at the AC line right in front of the radiator. Do you see any bubbles swirling when looking at this glass indicator? Otherwise, I would bet it's the compressor.

ancdmd

I checked the glass and didn't see any bubbles except for an occasional small bubble whizzing by the window. For years I've had an extremely small leak that has been impossible to find, likely under the dash. I'd take the car to the shop and have the refrigerant topped up about once a year. Since the compressor was replaced, for the last few years I've just been doing it myself, and I've had to add a can of refrigerant maybe only twice. I just use a can of pure refrigerant with no sealers and a hose with a pressure gauge on it. I checked it several months ago and it was actually a little full so I didn't even add any more refrigerant. I'll reattach the gauge again and see where the needle falls, maybe it's at the low end of the acceptable range. Just would've expected to see a lot of bubbles in the window glass if that was the case.

jimbosr1

check the glass window only after you have the a/c on max then check the window.if you have bubbles the system needs r134a charge.if your compressor is cycling on and off your compressor is good.if its not then your r134a could be too low and the compressor shuts down so it doesnt burn up do to no oil.

ancdmd

I did have the a/c on max and checked the window during the initial ten minute period while it was blowing warm. I also disconnected and reconnected the high-pressure switch during this time and confirmed that it was signalling the compressor.

KING

iTrader: (1)

Did you replace with a brand new compressor or used one?

Because that does sound like a weak compressor, saying it's good bye's.

ancdmd

I replaced it with a new Denso unit.

KING

iTrader: (1)

If you have a leak in your refrigerant piping, your compressor will become weak by time. Just because it is forced to output more than what it was designed to give. Find the leak and fix it first.

ancdmd

Finally got around to hooking up my pressure gauge to the system and it shows more than enough refrigerant in the system, so I know it's not low on refrigerant. Ugh. Not looking forward to replacing another compressor.

Tom57

If it ultimately blows cold, it's probably not the compressor, especially since it's new. When my '01 didn't blow cold, it was the compressor switch.

rkw77080

Hopefully "more than enough refrigerant" is not your problem, because over-filling you’re A/C with refrigerant can diminish its ability to cool the cabin – here’s why…

The A/C system consists of a compressor and an expansion valve to continuously converting the refrigerant between liquid and vapor phases. When the refrigerant is compressed, it heats up. Conversely, when the liquid refrigerant expands into vapor, it cools down. Key thing to remember is that the refrigerant experiences a huge temperature rise at the compressor (vapor-to-liquid phase change), and a huge temperature drop at the expansion valve (liquid-to-vapor phase change).

In normal operation, the A/C compressor compresses the refrigerant into liquid phase and sends the hot refrigerant to the condenser coil. A cooling fan cools the hot refrigerant down and sends it to the expansion valve, where the warm refrigerant expands into vapor phase and cools down drastically. The cold vapor refrigerant then travels into to evaporator inside the cabin. An A/C blower recirculates cabin air through the cold evaporator to chill the air. The cold vapor warms up and returns to the compressor to repeat the cycle.

The problem with overfilling the system with refrigerant is that there’s simply not enough space within the system for the refrigerant to expand into vapor phase. So less expansion translates directly to less cooling.

ancdmd

Thank you for the info rkw. I used a gauge very similar to this one to check it, the needle hovered around the 50psi mark, near the upper end of the green section on the dial.

rkw77080

If the 50 PSI reading was taken with the engine running, then your system is over-filled. According to the repair manual (see attached, Page AC-4), the proper reading on the low side should range 0.15-0.25 Mpa or 21.76-36.26 PSI.

To confirm that your A/C system is indeed over-filled, please follow procedure #5 on page AC-3 of the attached.

KING

iTrader: (1)

Nice catch RKW, as always.

Let some out and measure at the parameters provided. Let us know if that fixed your problem.

ancdmd

Thanks for the info. I had a shop check it out last Friday and they said the refrigerant level is normal and not overfilled. The tech suggested a malfunctioning controller of some sorts that changes something under the dash from hot to cold air. I didn't quite understand what he was talking about. I'll see if I can feel the hoses and determine if in fact it is overfilled before I attempt to let any refrigerant out.