A/C blows warm for ten minutes after starting car
#1
Lexus Test Driver
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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
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#3
Lexus Test Driver
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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.
#4
Pole Position
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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.
#5
Lexus Test Driver
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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.
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#9
Lexus Test Driver
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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.
#11
Lexus Champion
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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.
Last edited by rkw77080; 11-09-15 at 12:50 PM.
#12
Lexus Test Driver
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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.
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.
![](https://cimg3.ibsrv.net/gimg/www.clublexus.com-vbulletin/400x400/gauge_c2cf2b495b8d396f1e02f5a5f5b994bf3c3c5f65.jpg)
#13
Lexus Champion
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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.
To confirm that your A/C system is indeed over-filled, please follow procedure #5 on page AC-3 of the attached.
#14
Lexus Test Driver
iTrader: (1)
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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.
To confirm that your A/C system is indeed over-filled, please follow procedure #5 on page AC-3 of the attached.
Let some out and measure at the parameters provided. Let us know if that fixed your problem.
#15
Lexus Test Driver
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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.