FLYAIRWHIT

I have a 97 ES300 with 380k miles, about 350k, started having very strange AC issues. When below 80 degrees F, after about 20 minutes, the air starts to blow warmer, and you can smell and feel the air getting more humid (almost like the compressor was shut off, although I can see and hear it cycling). If the temperature is between 80-90 degrees with high humidity, it will run for about 45-50 minutes before getting warm. If the humidity is very low at that temperature, the AC will not blow cold at all, although the compressor comes on and cycles normally. In the mid-high 90's and 100's, it will blow cold as ice all day long, as long as the car is driving. Sitting still, it will stop working after about 15-20 minutes.

I am a technician (on BMW's), so I did an evac & recharge. The charge level was normal. I don't recall the pressures. Maybe I should hook it up and check again to see if that might aid in figuring this out. I am thinking it might be the evap temp sensor (thermistor??). I dont have a wiring diagram, so I'm not sure exactly how its wired, but if the sensor isn't reading correctly, matbe I'm picking up some evap ice, which would explain the loss of cooling after some time, but not the complete loss of ac with low humidity. My second thought is maybe a stuck expansion valve, which is not flowing the right amount of refrigerant for the temperature.

Anyone ever see a problem like this on these vehicles? I've heard that the expansion valves are garbage after they get old, which 380k miles, and 15 years is old. I'm half tempted to rebuild the entire system, but I'm hesitant to spend $1500 on a $300 car.

Any advice is most appreciated, and thanks in advance.

PFB

I can't provide you with much information except to mention that these cars have a humifity sensor, that amongs others determines wether to switch to recirculating air or not. It also determines how long the compressor should stay on. If however your compressor is on but not cooling than the problem is elsewhere. So maybe that's something worth investigating a bit more.

Phil

mdbrown

For starters, if you want to sell the car for $300 contact me immediately! Now, I would hook gauges to the car and see what's going on with the pressure. Since this is an automatic system it could be in the control unit as well. See what the pressures are as the system cycles (if it's cycling too much there may be a different issue.)

FLYAIRWHIT

Mdbrown, not looking to sell at this point! It's been a fantastic car, and at 380k, it still doesn't burn any oil! I am going to hook it up in a couple of hours and see what the pressures are. I'll let you guys know. I will look into the humidity sensor. There seems to be a direct correlation between humidity, and the system working or not. For example, it never works if it is 80 degrees, with little humidity, but yesterday it worked all day at 80 degrees and it was raining, then last night I went through a major downpour, and it immediately quit working. I had to turn the heat on full blast and roll windows down in order to see. That is the main reason I need to figure this thing out.

MikeLex

A plugged expansion valve is my candidate, but let's see what you find out.

FLYAIRWHIT

I agree. After hooking up the guages while the AC was working normally and blowing cold, the pressure was 190psi on the high side, and 28 on the low side. I recovered the correct charge amount (1.8lbs). After driving and getting the ac to start blowing warm, the compressor quit cycling. It just stayed engaged. The high side pressure is 90psi, and the low side is a vacuum, pulling about 20 inches.