Fox3

Over the last couple of months, my wife's 2008 RX350 A/C has been working intermittently. At first it seemed like it quits cooling (continues to blow, albeit warm), more recently it seems like it quits cooling more frequently the hotter the ambient outdoor temperature gets.

I'm reading around 125 psi low and 160 psi high with the A/C off. With the A/C on, and the engine idling, it went to around 87-ish psi low and 190 psi high with the A/C on. I heard a "psst" when I unscrewed the dust caps from the maintenance ports, so I assume it is losing refrigerant slowly. I had a partially used can leftover from when I serviced the A/C on my SUV, so I threw that at my wife's Lexus - probably only about 3 - 4 oz of R134a left in the can. About 57 psi low and 267 psi high, approximately. Maybe overcharged now? This was shortly before dusk in the evening and ambient temperatures were probably in the 80 - 90°F range.

The only error codes were the B1421 & B1424 for the solar sensor(s) - parked in the shade. From what I could see, all the sensor readings look okay and the A/C compressor clicks in and out when commanded. Air flow dampers seem to actuate/travel okay when commanded.

Things to note: there is an "unhappy bearing" sound coming from under the hood. I ordered a cheap mechanic's stethoscope from the "jungle site" and it seems to me to be the belt tensioner. Previous owner said the transmission was rebuilt or replaced a year or two before we bought the vehicle (probably unrelated to the current issues). Also, the vehicle was the victim of a hit-and-run last year at the end of June (27th of June, 2023). The passenger side was hit at the front wheel/fender and the driver's side wheel was pushed into then up onto the curb next to which the vehicle was parked. Struts, CV axles, ball joints, brake rotors w/pads, lower control arms, and one wheel were replaced as a result. Passenger side fog light and windshield washer reservoir are both toast. A/C still worked fine after that hit. Only just within the last couple of months has the A/C issue become apparent.

Any suggestions on the A/C, aside from replacing the belt tensioner (already planned)? Thank you.



Solar sensor(s) error codes

A/C on

A/C turned off

A/C on and running

A/C on after adding 1/3 can of R134a

Approximately 64°F (17.9°C) at the evaporator, while it was cooling.

Pressure sensor reading about 262 psi (1.8087 Megapascals), within a few psi of what my analog pressure gauge was reading on the high side service port.

Mesquite77

You can ignore the B1421 Solar Sensor codes, they seem to always be set if car is in shade, and do not affect A/C operation as far as I can tell.

Adding 4 oz of R134a on an older car would not overcharge it IMO (cars of this gen lose about 1 oz per year from normal seal leakage, and valves as you noticed), and your pressures seem fine, so I think the compressor is working, and belt is not slipping on it. If all flaps are ok, then maybe check the fans are running, and/or have a pro recharge done?

evident

Looks like I too might be low on refrigerant. Is there a way to identify where the leak is coming from precisely? My car has never been in an accident and 2 years ago was the first time i needed to charge up the AC system.

rlee777

Find a reputable A/C specialist and have them evacuate the refrigerant to see if your system will hold a vacuum. Then they can inject a dye with the refilled refrigerant to identify where the leak occurs. This will also assure that the correct amount is replaced.

Margate330

In our cars please expect to have to bump the refrigerant a couple of ounces every year or two years.

Our cars are getting old and it's normal.
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I've done some experimenting and I'll drop some Intel on this, recharging is easy.

Conditions: using a meat thermometer in the middle AC vent and with the AC turned up to max

Refrigerant. bump: easy, bump the refrigerant with short squirts by cracking the valve for just a tiny bit

When it's done: you will know when it's done when you get your lowest vent temps. Give it a min to blow colder

This is the way we did it old school.

I have evac'd my AC and recharged using a scale to compare and this technique was spot on.

The manual says our cars ac runs more efficient at slightly under charged. This technique above will put you 1/2 ounce low to spot on.

evident

Yeah, dropped it at a shop today, dont have time to DIY right now.
I wonder if I replace the AC Compressor and condenser and all of the fittings between them myself next time this happens if that would make things better going forward. I've heard of the evaporator and heater core failing behind the dashboard on this board before, but no one ever said how they traced it back to one of those? that would be a royal PITA.