Automotive Air Conditioning Information Forum

I haven’t put AC gauges on the 06 Avalon to check the comp. disc. pressure. With 93 degree ambient temp. it has 37-38# suction.
I added Freon to reach 41-42# suction & there was no noticeable difference in the AC vent air temps. The driver side was still warm & pass. side was just cool, not cold. The driver side blend door is operating properly.
so it must be due to the Freon charge.
What should the AC suction pressure be at 93 degrees ambient temp.?
Thanks guys!

That is impossible to know without relative humidity. Also you need both high and low side pressures to gauge what is going on. FYI A/C performance test are also performed with Recirculated Air, High Fan speed, windows and doors closed and the readings are taken after the system has stabilize with ~10 minutes of operation at ~2,000 rpm to be meaningful. The newer vehicles are extremely sensitive to charge amount, highly suggest having the system evacuated and recharged by an accurate method. As little as a 2oz variance can drastically effect the systems operation.

Kourso wrote: ↑Mon May 27, 2024 9:06 pm I haven’t put AC gauges on the 06 Avalon to check the comp. disc. pressure. With 93 degree ambient temp. it has 37-38# suction.
I added Freon to reach 41-42# suction & there was no noticeable difference in the AC vent air temps. The driver side was still warm & pass. side was just cool, not cold.

You're going in the wrong direction with the low-side pressures—higher is not better—and I believe the system is now overcharged. You cannot recharge or "top up" an OEM system by observing the pressures.

With 42 PSI on the low side, the evaporator temperature will be about 45°F—inadequate for much of any cooling. In addition, your Avalon has an electronically controlled variable-displacement compressor.

If the car were mine, I would recover the system, replace the control valve, replace the desiccant container in the R/D, evacuate the system, and recharge it to the manufacturer's specifications—or have all of this done by a professional MVAC shop.

The specs that I have for your car are as follows (both the 2005 and 2006 model years are the same): 19.5 ounces net weight of R-134a, and 4.5 fluid ounces of PAG-46 oil.

How much mileage is on the clock?

I agree with your diagnosis’ & suggestions.
I actually lowered the low side to 35# and the comp. Immediately disengaged.
The Avalon has 159k miles.
How common is the elect. control valve going bad/not working?
Where is a good place can I buy a replacement elect. valve control valve? What brand? Denso?
Could it be any of the dash panel controls causing this problem. I can raise the climate control temp. & I think the comp. disengages when the temp. setpoint goes over 80 degrees.
I will confirm that the 2 radiator cooling fans are running as they should be with the AC turned on.

I don’t view your issues as DIY, especially with the mileage on the car. Once you get past 100K, all bets are off on the components on most cars.

“ if the car were mine, I would recover the system, replace the control valve, replace the desiccant container in the R/D, evacuate the system, and recharge it to the manufacturer's specifications—or have all of this done by a professional MVAC shop.”

John has given you excellent and appropriate advice. Please review it again.

With that kind of mileage, your Toyota is nearly broken in But the compressor might be getting a bit "tired.," as tbirdtbird inferred.

If you're planning to keep the car, consider replacing the compressor with a brand-new one. A new compressor comes with a warranty, a new clutch, and a new control valve. Ensure that you follow the compressor manufacturer's instructions to the letter to maintain the warranty.

I believe that Denso is original equipment for your car.

If you're in the USA, check with Tim at ACKits.com, this Forum's sponsor, for any parts you might need.

If you do take a crack at doing it yourself, be careful that you don't over-fill the system with oil, which for this car is only 4.5 fluid ounces (in total) of PAG-46.

Thank all of you for your great assistance!
I do plan to keep the 05 Avalon, don’t want to put too much money into the car but I really need a working AC in S. Louisiana!
I’ll have to decide what I should do.
How does the elect. control valve work & what actually controls it?

In a nutshell, the ECM/PCM analyzes various sensor input from the vehicle and sends small electrical signals to the compressor control valve depending on how much demand (heat load) is placed on the A/C system. The control valve then changes the compressor's piston stroke (displacement), via the angle of an internal "wobble plate," to meet the demand--low heat load equals minimum piston stroke/displacement and low refrigerant flow; high heat load equals maximum piston stroke/displacement and high refrigerant flow--and all points in between.

Great technical explanation!
This Toyota AC system is more complicated than the ac systems that I have worked on.
So the AC comp. can theoretically be engaged & the elect control valve not be getting the PCM signal per bad wire and/or connections?
I think I will have to find a local mechanic shop that does AC repair.
Thank you

Most auto AC systems now are more complicated than in the past. Some of us would say over complicated