AC is amazing at 1200 RPM+ Compressor shuts off under 1200

More exposure here, 2013 Sequoia Limited with rear air suddenly started doing this.

Firestone parts connoned the compressor & pressure switch. That didn't work, they gave up blamed my SC.

Aamco said it's the condenser. Nope, they still have it, hoping for help.

Any ideas?

 

Any events or symptoms leading up to the HVAC acting up?

At this point, the system had been evacuated and recharged at least twice. Is it safe to assume correct charge weight and oil amount? Hard to say. They should have checked refrigerant temperatures at various points of the system to detect any restrictions that shouldn’t be there (the expansion valve should be the only restriction)

 

Both say all is well, Firestone evacuated 2x, the second to install the pressure switch, said they gave it the right fill.

Aamco said the condenser was the issue, 100%, all the rest is good, specifically said no issues with the expansion valve.

End of the day they said it's having problems, they need to keep it.

 

Your SC'd Sequoia is now being used at clandestine eighth mile flashlight drags.

And someone at double A em cee oh is racking stacks of cashish.

 

AC can be a tad difficult to troubleshoot over the internet since I can’t see the pressures when on; you might have a blockage through the expansion valve causing the problem; but since I can’t see pressures I’m not gonna 100% say that’s your problem. It runs past 1200 rpm no problem?

 

I'm paranoid. I can see the location (here and on find my) and if it's running based on voltage. It hasn't moved.

 

When they said it was the condenser I was relieved as I know the expansion valve is a center dash out ordeal, I have to assume they were certain it was ok (based on testing I hope) the valve is ok.

The damn valve is the only thing that remains so if they can't figure it out I assume they will want to do that, based on how things have gone, I'll say no & go to an AC only shop in Tempe if that is the case,

 

You do have two expansion valves because of the dual system. The main one on the firewall calls for 10.2 hours and the one for the rear calls for 4.5 (FYI)

 

The rear one would not have an impact on the front temps I assume? Also, if the rear system was not working, I would not care.

I have not checked the back seat vents, I'm never there & since the kids moved out (20 years ago) the back of the truck has had occupants 2x

Thanks

Edit, also is it plausible based on these symptoms it is the valve? I had a BMW years ago the valve was clogged after an accident caused the system to be open & it had no cold air & my 80 series died from being 35 years old. Again 0 cold air.

This happened out of nowhere with no visible cause.

 

Evaporator core is a potential problem as well. The face that the concern is tied to engine RPM suggests an incorrect charge, or abnormal restriction in the refrigerant circuit versus a mechanical or electrical problem with the HVAC system.

 

I assume if there is a leak and any of the shops filled it there would be function until it leaked out no?

It's never had cold air at idle since this started.

A friend sent me this, I printed it & will bring it with me with 33oz = 2.062lbs since they are dealing in lbs.



lol

 

Did you see if your electric pusher fan for the condenser is working? Its plausible you may have insufficient condenser airflow if that fan is not running, and the mechanical fan is running at a low speed at idle.

 

That's a really good point. Did they check the function of the fan clutch?

There's a whole lot of WTF going on the diagnostics performed. The compressor should have not been changed without confirming it was bad by observing pressures. This is really basic stuff. I would have replaced the condenser and pressure switch with the compressor, regardless, but sounds like some very basic diagnostics were overlooked.

 

I can't speak to what has really been done except for the compressor (replaced for free by Firestone because they gave it back having killed the amp/AC computer so it had no HVAC panel function or outside temp) I diagnosed it by checking the fuses and relays and verifying the voltage at the amp power wire and buying an eBay replacement.

Then I hoped it was the 13 year old pressure switch and "made" them evac the R134a and install it. Nope.

Aamco had a 2 week wait so I drove it (only when absolutely necessary) in 3rd in traffic when it went under 1200 or with my foot on the pedal to keep the air cold.

Another attempt at a bandaid was getting a tune that brought idle to almost 1400. It still needed some pedal!

When the compressor is on, the condenser fan is on, under 1200, neither are on.

The fan, fan clutch, support bearing and all of the tensioners were installed 12/25 less than 3k miles ago when I replaced the motor.

 

I wonder if with a scan tool you could see if the output from whatever is controlling it/energizing the compressor relay is present at idle vs beyond that 1200rpm threshold.

 

Those parameters are available to a scan tool that can read them, as well as refrigerant pressure. That's going to require a higher grade scan tool though.

 

I have a Topdon Phoenix Plus, I tried commanding the compressor, it said it was on but it lied.

This is the 18 month compressor they replaced, in the box from Napa, what's in there now.





This is when the truck is above 1200

 

Aamco just called, when the truck is inside or at night the solar sensors give a code, been that way as long as I have had the truck, they wanted to blame them, then said it must be the amp/ac module, I said this was happening before Firestone burnt out the amp & caused no HVAC display & outside temp, I installed a replacement & got all that back. Back to the under 1200 warm but 40 degrees at the vent when running/kept over 1200

 

I don’t think I can me much help, but just to be clear:

- The compressor turns off under 1200 RPM?

- or the ac simply gets warm under 1200 rpm?

- and even though Phoenix is like living on the surface of the sun, does the AC suddenly get warm? Or gradually warm up after it drops below 1200rpm? I realize “gradual” is relative when the street is able to boil water and cook eggs.. just trying to focus on one problem at a time.

Also, as @joseph_womack said, pressures and pressure differentials would be very telling of what’s going on. Not that I know how to read this pressures other than what I can read from a chart.

But in my limited experience with AC systems, when the compressor turns on or off can indicate a problem with pressures, then reading those pressures can indicate what may be wrong with the system (bad compressor, low charge, high charge, bad valve, restricted condenser flow, etc..).

So I’m trying to confirm compressor operation first. Is it running at all below 1200 rpm? If pressures get out of whack, the ECU or hvac controls will turn it off after a period of ineffectiveness. You can see that in the line pressures. If it simply clicks off below 1200 rpm the instant that changes, that’s a strange issue that I could only guess at being ECU/tune/HVAC switch related.

Again, I’m not super experienced with fixing AC issues so I’m grasping at straws.

One other thing that just popped in to my head - the condenser fan.. is it drawing too much juice at low engine rpm? Is the alternator not charging enough, or the fan on its way out? I don’t know for certain, but with the sequoia having an aux fan for the condenser and the ambient temps so high everywhere else on the vehicle, I wonder if it’s a safety cutoff. I don’t know if the fan has to run for the ac compressor to cycle. Perhaps the fan is cutting out and tripping a compressor safety switch/parameter.

 

Did you check the fan/fan clutch?

The secondary fan might have lost low or high speed; when you’re idling the main rad fan might not pull enough air for the condenser since it’s a dual unit. When you rev up it starts pulling enough air

 

Over 1200 it's 40 degrees, compressor & condenser fan are on, under they are off immediately vent tems go up.

Aamco called before they closed at 5, said the condenser fan is not getting power, blaming the wiring (which makes no sense, how is it "getting power" over 1200? Seems to me something is commanding the fan & compressor off under 1200.

I also feel like it is crazy I keep having to give them information (2lbs not 1.6, solar sensors error when they don't have light) etc. I suggested moving it outside or putting flashlights on the sensors they did flashlights, codes went away go figure.

Also, I never use auto which is what the solar sensors feed so how are they involved?

 

Fan and clutch are sub 3k mile, installed 12/25 OEM I didn't check them but I'd hope one or both shops did, no one is pointing at them.

I'll give them tomorrow, 3 days should be enough, no?

 

You said under 1200 rpm the compressor and condenser fan are off? There’s your problem; hot side pressure builds too much because the condenser isn’t getting enough airflow so the compressor gets told to shut off. Use your scan tool to see if you can command the condenser fan on for low speed or high speed

 

Depending on how busy they are, yes.

AC work well get done relatively quickly unless it turns into a wiring diagnostic and then it can take awhile, but from your experience it doesn’t sound like the shops are digging into it

 

I tried to command in Tech Stream & the Topdon both said the compressor was on when it was not, I have held the throttle to 1200+ & looked at the fan & compressor, they go on, vent temp is 40, pull the pole off the pedal they go off, temps rise immediately.

Sadly I don't have the truck so I can't do anything. I'm hopeful they figure it out tomorrow but I'm not holding my breath, when I brought the 4 seasons R134a spec sheet the guy said they ran out of freon & were waiting for more. I know it's not been freon for years.

 

I'm talking about the condenser electric fan; also we just use "freon" as a general term

If techstream is saying the compressor is commanded on, but it clearly isn't spinning, then you need to unplug the compressor and check for power and ground

 

Had a very similar issue with an accord once. It has the dual fans - one for the engine and one that turned on with the AC. The second fan had an issue and when you slowed down or were stopped in traffic, that’s exactly what would happen - the pressure on one side would spike, the whole system would saturate with heat, and bye bye ac. Get running down the road and AC would turn back on.

It wasn’t as clearly delineated as this instance, but quite obvious once we figured it out.

 

Neither the fan or compressor respond to the command on if the engine is not at 1200.

I may not have said this, Aamco said they gave the system 2lbs of R134a

 

If the compressor turns off immediately with the RPM and not a 10-20 second delay (corresponding to a gradual build in head pressure from no airflow) I’d tend to think this is an electrical/control issue. As RPM increases so does alternator output and system voltage. This makes me think about other likely issues such as a weak clutch solenoid coil, low coil voltage, or a poor clutch solenoid coil ground.

 

These are all in the compressor? What are the odds 2 compressors would have the exact same issues if so?