Please help diagnose my AC problem. I have searched and read many threads with similar issue. This seems to be a common problem, however I cannot find a resolution. What should I try next?
The car is a 2002 LX470 (with rear AC) with about 144k miles, it has been in my family since new. It spent time in Nebraska and New Hampshire before coming to south Texas in 2018, so unfortunately there is some moderate rust on the undercarriage, however it has been a very reliable vehicle and I acquired it for really cheap. There has not been any work done or other service on the vehicle (i.e. timing belt) that happened around the time of these AC system failures.
Here is the summary of the AC troubles:
Summer 2021 – on occasion the AC light would blink and the system blew warm air. Pressing the AC button a few times would normally bring the system back to normal. A few months later, the system completely died on a long road trip to Florida in November. The compressor had seized. The system still held full pressure, there were no leaks. The compressor had about 1-2 oz of oil upon removal. I replaced the compressor (with an aftermarket unit), dryer and expansion valve. I refilled the system to spec and everything worked perfect for about 16 months.
Spring / Summer 2023 – AC light occasional blinking starts again. Sometimes pressing the button will bring it back on, sometimes it won’t turn on at all. This issue happens randomly – on cold starts, warm starts, in the middle of a drive, etc. Sometimes the screen flashes “check air conditioning system”. I do not recall seeing that message displayed when the system failed in 2021. When the system does work, the vent air is 45-deg or less. This time around, I have inspected the following parts:
MG-CLT relay: I have done a simple 12V test and confirmed it works.
Serpentine belt & pulleys: great condition, no issues found
Fan clutch: looks and feels normal, engine cooling system works as normal even in hot traffic. The fact that the AC problem can happen at cold starts leads me to believe it’s not related to the engine cooling system.
Electrical connectors on AC compressor and front pressure switch: all are normal, fully seated and not damaged.
Battery is normal, no excessive corrosion or trouble starting the engine.
Let me know what I should try next. The car is not a daily driver, so there is no rush. I have a fair amount of experience fixing car AC systems, so I’m willing and able to do a full tear-down if necessary (however I’ll wait until the winter months). In recent years I have done full system replacements (including dash-out evap cores) on an old Suburban and a Dodge Magnum.
Thanks!
The car is a 2002 LX470 (with rear AC) with about 144k miles, it has been in my family since new. It spent time in Nebraska and New Hampshire before coming to south Texas in 2018, so unfortunately there is some moderate rust on the undercarriage, however it has been a very reliable vehicle and I acquired it for really cheap. There has not been any work done or other service on the vehicle (i.e. timing belt) that happened around the time of these AC system failures.
Here is the summary of the AC troubles:
Summer 2021 – on occasion the AC light would blink and the system blew warm air. Pressing the AC button a few times would normally bring the system back to normal. A few months later, the system completely died on a long road trip to Florida in November. The compressor had seized. The system still held full pressure, there were no leaks. The compressor had about 1-2 oz of oil upon removal. I replaced the compressor (with an aftermarket unit), dryer and expansion valve. I refilled the system to spec and everything worked perfect for about 16 months.
Spring / Summer 2023 – AC light occasional blinking starts again. Sometimes pressing the button will bring it back on, sometimes it won’t turn on at all. This issue happens randomly – on cold starts, warm starts, in the middle of a drive, etc. Sometimes the screen flashes “check air conditioning system”. I do not recall seeing that message displayed when the system failed in 2021. When the system does work, the vent air is 45-deg or less. This time around, I have inspected the following parts:
MG-CLT relay: I have done a simple 12V test and confirmed it works.
Serpentine belt & pulleys: great condition, no issues found
Fan clutch: looks and feels normal, engine cooling system works as normal even in hot traffic. The fact that the AC problem can happen at cold starts leads me to believe it’s not related to the engine cooling system.
Electrical connectors on AC compressor and front pressure switch: all are normal, fully seated and not damaged.
Battery is normal, no excessive corrosion or trouble starting the engine.
Let me know what I should try next. The car is not a daily driver, so there is no rush. I have a fair amount of experience fixing car AC systems, so I’m willing and able to do a full tear-down if necessary (however I’ll wait until the winter months). In recent years I have done full system replacements (including dash-out evap cores) on an old Suburban and a Dodge Magnum.
Thanks!
