Automotive Air Conditioning Information Forum

Hello everyone,

I have a problem I haven't made sense of yet. I've never encountered this before. Just wondering if anyone has any advice.
My AC Compressor clutch in engaged. Clutch is turning.
There is pressure in the system. 50psi Low 150psi High.
But the system is not compressing. The gauges don't move. And the AC Clutch never disengages unless I pull the relay for it. Or turn the AC off.
Its blowing cold now, but apparently after awhile it stops.
This is a 2007 Toyota Sienna CE
What do you think could be causing this?

I've considered not enough pressure. Maybe enough pressure in system for low pressure switch but not enough to ever cycle the clutch off?
Maybe moisture in system making it not compress?
My condenser is clean...

Any help is appreciated. I'll see if I can help anyone with anything here shortly...

It is a variable displacement compressor, stays engaged until you turn AC off. Gauges won't really be changing much unless blower speed or engine speed changes.

What is your complaint? You said it's blowing cold??

Customer complaint. They say it stops blowing cold. I didn't get to inspect it for long, but I've never seen a AC system run like this.
I am used to older vehicles...
Normally that magnetic clutch cycles on and off.
And with gauges hooked up I can see when the clutch engages and the compressor starts compressing.
But on this vehicle, the magnetic clutch is always engaged, and I don't see any activity on the gauge set.
I've just never seen anything like it

I have to research more if this is a variable displacement pump.
But shouldn't my gauges move either way?
I didn't see any evidence anything is happening on my gauge set. And I know my gauge set is ok.

I would re-read Detroit's answer.
He can tell from make/model/year that it is variable displacement BTW

The heavy hitters here have access to all the specs for any vehicle. The newer variable displacement stuff is nothing like you are used to, forget what you already know, it will not help

If you are a mechanic in a mom and pop type shop, and not an AC specialist, I would punt this to an AC specialty shop before you get in too deep

And, BTW if "nothing was happening" it would NOT be getting cold!

It's a Denso 7SEU17C, externally (means electronically) controlled variable swashplate. What you are saying sounds like normal operation to me. Unless the conditions change, like vehicle speed, blower speed, HVAC inlet air temperature, etc. there won't be changes in the pressures.

I've never worked for Denso, but I was an AC system engineer working on control valves, control stability, hinge mechanisms, compatible evaporators, TXVs, for variable compressors for another supplier 20 years ago, and this industry has been using them ever since. I was tearing down Denso variables in 2001 to benchmark their control valves and hinge mechanisms.

If it just stops working and blows hot, I think you should be able to troubleshoot it. A good start would be to recover the charge, evacuate and recharge to the sticker amount.

Then maybe tell us what sort of pressures and pipe temperatures you getting and at what conditions, try a hot day, windows down, full blower, panel, engine RPM held high like 1500-2500 and steady. We might be able to tell if you have a refrigerant system issue or not.

Back to basics.

Customer complains that it "stops"

Check the clutch gap. Very possible it stops cooling on a hot restart with a bad clutch gap.

Check the gap. If it is out of spec, correct it. It needs to be right anyway.

Wow, thanks a lot for all the replies.
I had no idea it was normal for the needles on a manifold gauge set to stay still with the ac compressor running on a variable displacement pump.
And I had no idea it was normal for magnetic clutch to stay engaged all the time.
I was thinking there could be something I'm missing though so that's why I got on here.
I didn't want to recommend a recovery and recharge if it was possibly an electrical problem.
I think I will try and replicate the problem while driving.
And then evacuate and pressure test.

So I quickly researched variable displacement compressors, and apparently they don't use a magnetic clutch.
My ac compressor clearly has magnetic clutch and mag clutch relay.
Does this sound like a variable displacement pump still?

Yes it's a variable, some are clutchless and will just stay at a very tiny piston stroke to be "off" some have a clutch. The compressor is the same, the pulley and clutch are replaced by a pulley and hub