2005 Avalon XLS AC air vent temps

[Kourso]

Thanks for your help.

[JohnHere]

This^^, tbirdtbird.
I would say needlessly complex in most cases.

OP, if we can "assume" (there's that word again) that the wiring, PCM/ECM, and sensors are okay (and they probably are on a Toyota), there's really no reason why you can't tackle this job yourself if you're accustomed to working on simpler systems, as long as you have the proper tools: Manifold Gauge Set, a good electrically driven vacuum pump, a refrigerant scale, hand tools--and of course, virgin R-134a and PAG-46 oil. You can always job-out refrigerant recovery. Since cost is a factor, compare how much it would be if you DIY versus having a shop or dealer do the job.

[Kourso]

Yes I do have a good set of Robinair ac gauges & a good elect. vacuum pump.
And when it was needed, I have also flushed an auto AC system.
And I do operate an huge industrial propane refrigeration system in a big NGL frac plant.
So I know how refrigeration systems work.
I just don’t know about all of the automotive AC system complexities such as the elect. control valve using a PCM signal.
Thank you for your help

[Kourso]

I got my AC readings:
Low 54 #
High 170 #
91 degrees ambient

And the ac vent air temps were cool for a while then suddenly the air temps. changed to 78-80 degrees without any climate controls being touched?
But when you start the car very early morning at 70 degrees ambient, the vent air stayed very cold!
Prob 50 degrees.
So something is causing the warm air temps at high ambient temps.? When the variable displacement compressor should be at full refrigerant flow.
What can I test or replace?
I do have a spare air amplifier that I could try?
What about a bad comp. flow sensor or TXV valve?
I just don’t know what are the most common 2005 Toyota ac culprits?
Thank you for your assistance!

[Kourso]

I do have computer code scanners that have a live data mode but I don’t know if they are capable of reading anything on the AC system?
And I have an infrared thermometer & an infrared imaging gun if they could help with this problem?
Thanks

[JohnHere]

Special tools are available to verify electronic control valve operation. Lacking those tools, and bearing in mind the pressures you posted, replace the control valve as a first step. They're relatively inexpensive. You might (or might not) be able to access it without removing the compressor. But you will have to recover the refrigerant before removing the valve.

Then proceed as previously mentioned: 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.

[Kourso]

You think the comp. elect. control valve is probably the cause of the random vent air temp. changes?
Can you possibly send me an elect. control valve Toyota part # and where I can buy that replacement part.
I checked autozone and couldn’t find the correct part to fit the 05 Avalon.
I’ll look around & also at Amazon.
Thanks for your help.

[JohnHere]

You think the comp. elect. control valve is probably the cause of the random vent air temp. changes?

Always difficult diagnosing a system from a distance without any hands on, but I'm guessing that's the problem.

Can you possibly send me an elect. control valve Toyota part # and where I can buy that replacement part.

Suggest checking with Tim at ACKits.com first. Otherwise, visit your local Toyota Parts Department. They'll look up the part number and order it (if it's available separately from the compressor). The hard part will be installing it

[Kourso]

At 93 degrees ambient, my AC air vent temp gets cool for 5 mins. after an engine start. Then it just goes to warm with the temp setting on low & max AC recirc. on.
If I turn off with the AC button & after 5-10 sec. turn back on, it goes back to cooling again.
I know the ac comp. is staying engaged when ac is turned on. And both elect. radiator cooling fans run with the ac turned on.
Also when the outside temp is 75-80 degrees, the air vent temp. stays very cold.
The low side suction is 60 # at 91 degrees ambient.
Something is cycling the ac system incorrectly on the hot outside temps.?
Would that be the AC amplifier and/or the elect. control valve?
Thanks for all of your help on this forum!

[JohnHere]

I know the ac comp. is staying engaged when ac is turned on. And both elect. radiator cooling fans run with the ac turned on.

Right...that's typical behavior for a variable-displacement compressor setup. Instead of cycling the compressor, the PCM varies the compressor's displacement via the control valve according to heat-load demands.

Something is cycling the ac system incorrectly on the hot outside temps.?
Would that be the AC amplifier and/or the elect. control valve?

It's unusual for a Toyota A/C amplifier to go bad, although it's certainly not impossible. Chances are it's the control valve that's malfunctioning.