If the non-cooling pressures are as you state, then the most likely causes are


Compressor clutch not engaged (unlikely as A/C amplifier detects compressor RPM and generates error if incorrect)

A/C amplifier not sending correct PWM signal to compressor solenoid (measure with scope)

PWM signal not reaching the solenoid (wiring or connector issue--wiggle the wiring and connector to see if correct operation comes and goes)

Solenoid not responding to A/C amplifier (bad solenoid--disconnect PCM harness, and apply 12v directly to solenoid and verify it clicks sharply)

Compressor swash plate mechanism sticking (does tapping firmly near/around the solenoid area with a large screwdriver handle suddenly make it work?)
Compressor piston rings sticking (unlikely)
Expansion valve sticking open (tap sharply on the refrigerant lines going through the firewall for front A/C). Note than there are two expansion valves for HL's with front and rear A/C. If that's yours, then a sticking EV would cause only front OR rear A/C not to work.



What are the system pressures when working correctly?

 

AV, man thanks chiming in! I was losing steam on getting to the bottom of this one. When it's working, I get 30PSI low side, 200 high. I'll rip the cowl and wipers off first thing tonight to reach the TXV. Hadn't thought of it sticking open, makes sense on the wobble plate too. I confirmed the sol. pwm signal from the ac amp, will try to wiggle the cables and scope the valve side too. Just changed the valve, but I'll hit it with 12v to be sure.

I've read some other AC related threads on this forum today. Hats off, u really know your stuff!

 

Re: given the small 30 PSI pressure offset LOW-HI, I'd focus on the compressor and make sure it's not some wonkiness with the swash plate control/operation, before moving onto other suspects.

I've never had manifold gauges connected, and then disconnected the solenoid to see what the pressures do (assuming the PCM doesn't sense the connector removal and disengage the clutch). Maybe other members have, or some Toy tech can chime in.

As for the TVX, you didn't confirm whether your HL has rear air (e.g a rear TVX and evap). Either way, my intuition is that the compressor would struggle or lockup as significant liquid refrig might be flooding the evap and making its way to the compressor intake, and the HI side pressure much higher, if the TVX were stuck wide open. This is where an experienced A/C tech would come in handy.

That you mentioned the issue was intermittent, made me suggest the tappity-tap on various components and refrig lines.

 

Haha. At this point I'm in the mood to give it more than just a slight tap. That's right up my alley.

With half the dash out and alligator clips strapped across the compressor solenoid's wire. I'm more than happy to conduct that experiment next time it's ruining cold.

 

I forgot for a second time... it's the single expansion valve version

 

Update on my end- no luck with the calibrated hammer which is a shame.

I did find out that with just a 30 psi difference I can turn off the AC and the hi/low will take 10+ minutes to stabilize. Now wondering if that may rule out the expansion valve?

I followed the FSM to check the solenoid circuit and solenoid. I put 12V direct to it also while running, no change. The only thing which is out of spec is probing the harness disconnected from the compressor to ground .3M ohm low. but it's a harbor freight meter FWIW.

I couldn't get the AC going but with 30psi difference, unplugging the solenoid while running the low side only raised 5psi. I'll see about getting it cold tomorrow and report back.

I'm leaning toward making a $300 gamble on a new denso pump at this point.

 

If I were rolling the dice, it would be on the compressor-cheaper than getting rid of the car! If I get time this weekend, I may measure my HL with the compressor solenoid disconnected--am now curious how "low" the variable capacity feature goes.


Did you tappity-tap pretty firmly all over the compressor body?



As for resistance readings, unless one has a DVM with a "relative feature", you need to subtract the lead resistance for low resistance measurements. Hold the meter lead tips firmly together and note the reading.

 

I think I followed the tappity-tap trade secret OK. I hammered by way of a long ratchet extension on top of the compressor both toward the back face and toward the pulley. Did the same after removing the plastic on bottom. Also left some dents in the expansion valve body.

You lost me on the electrical talk, but to be sure I got tiny connectors and went straight from the battery to the two pins at the valve body this morning. Tedious, but got the same results as last night fidgeting behind the dash. I was able to hear the valve clicking with engine off this way.

If the compressor is the most likely culprit, any advise on the swap? New desiccant bag, but should I worry about the expansion valve too at this point?

Thanks for your help, I'm in Houston and it's sure to be a warm summer!

 

I can't advise on on the specifics of removing the compressor on the HL, but the general principles for the DIY is to bleed off refrigerant slowly from the LO port, using a can tap and hose, but without the can. After that remove the belt, refrig lines, elec connections and unbolt the compressor. Plug the exposed refrig lines right away to prevent significant humidity ingress.

Install the refurb compressor in reverse.

At this point hand it over to an AC shop to vacuum down and refill, or rent a vacuum pump from Autozone, vacuum for an hour. An hour vacuum pull ought to boil off most of the moisture. I wouldn't bother with a new drier/desiccant.

As you have probably already read, modern A/C system are pretty fussy about refrig charge levels. Mark your refrig cans to get the recommended charge within 4 oz.

 

None in stock locally, so there's a week I'll have to sit it out in suspense. The four bolts are loose, not terrible to access with short extensions and u joint adapters. Looks tight but I think the fan and radiator can stay in place. Keep em crossed!

 

Success! Couldn't have done it w/out your help. Wish I'd have gotten here sooner. Too many Toyota AC threads leave you hanging regarding the fix... not mine! New AC compressor and it runs like new. It's important to note that just changing the compressor control valve with these symptoms was not the fix, so hopefully this can save time and money for others in the future.

 

Fantastic! As Yogi might have said "50% of time a 50/50 chance works out".:grin:

Did you vacuum and recharge yourself?

Can I suggest you edit the original title and add [SOLVED] or whatever admins recommend on this thread.

 

Truer words were never said. I had a cheap vacuum pump around so was able to DIY the install. Had the tools, just a lack of know-how.

I actually ended up changing the condenser too - broke a tap off after a bolt extraction attempt... shade tree mechanic's special. Had to un-bolt the AC lines to it, and loosen the radiator to make room to lift the AC compressor out as it would not fit between the frame below. Even with the setback it was a very simple job (as far as modern cars go) and I have a new appreciation for how these highlanders are put together. I hope to get another 10 years out of it! Cheers AV.