Hello all, I could use some help troubleshooting my A/C as it just recently stopped cooling. The A/C was working fine just a couple weeks ago before I left for a trip. I came back to notice the car would not defog or cool down with the A/C on.

The car is a 2003 Lexus IS300 with 185k miles, original A/C system that has never been repaired or serviced. (I jinxed myself by posting in another thread how problem free this car has been. )

When I turn the A/C on, set the fan on high and set the temperature at minimum I observe the following:

The interior blower motor is working, and hot/cold air mixer door is working properly, but the air will not cool or remove moisture for defogging.

The compressor clutch engages and stays engaged as it should. I can hear it engage, the RPMs dip, and I can see the clutch engage and stay engaged to spin the compressor when I look at it in the engine bay.

Accessory belt is in good shape and is not slipping.

The radiator fans turn on as they should.

With the A/C engaged, an oil change tech put a pressure gauge on the low side and the gauge reading went to the “red” area indicating the low side pressure was much too high.

With the A/C engaged, I do not see any refrigerant flowing in the sight glass by the high side port, I do occasionally see some bubbles, no change when I rev the engine a bit.

After several minutes of the A/C running the high side lines aren’t getting warm and the low side lines aren’t getting cold.

Is my R134 charge too low, is the compressor toast, or is there something else I should look for? Thanks a bunch!

could have a small leak, my truck did that this summer, stopped cooling but the compressor clutch kept cycling on and off, did one of the store cooling kit fixes and it's been ice cold since.

similar age and miles. Got me through the summer months, and it's still cool, those cans have some leak preventative in them.

For $30 it's worth a shot.

Shoot a can of R134a in it and see what happens.

When my compressor stopped working, the check ball had rattled itself down so small it was ingested by the pump.

The charge may be low. It happens on older cars.
IIRC, the newer R 134 has a dye in it, neon/booger green I think. This way, when you recharge it, you'll find the leak.

Thanks guys. I was of the impression that the pressure switch would not let the compressor engage if the R134 charge was too low. Do you think it's possible that it leaked down enough to not cool, but not low enough to trip the pressure switch?

Yes. You can do this yourself with a self-charge can of R134A from auto parts store. It is amazingly easy.

Don’t add any more charge to it yet! If the low side is reading high pressure while the compressor is running, it means you’ve got refrigerant in there. Let me think about this for a bit... Meanwhile, check the wiring to the compressor to make sure it’s not damaged.

Does the low pressure line get hot?

I would not add any refrigerant as there is refrigerant present. The compressor would not engage with little to no refrigerant in the system. I would have a good set of gauges hooked to see what both readings are, and to see if the readings change any when the compressor clutch engages.

My first question, does the compressor clutch stay engaged when you turn off the A/C? I believe some compressors are internally regulated and the compressor will appear to be running at all times because of the internal clutch. If the compressor clutch can be seen to turn off and turn on with the switching of the A/C or defrost on and off, then I’d suspect a possibly failed compressor.

My guess is you have a blockage in the system. There are usually inline filters in the system. I certainly wouldn’t add any more R134.

quote:

Originally posted by jezsuiz:
My guess is you have a blockage in the system. There are usually inline filters in the system. I certainly wouldn’t add any more R134.

Typically when there is a blockage, the high side will have higher pressure and the low side will tend to go low and even into a vacuum and will turn off the compressor clutch.

quote:

With the A/C engaged, an oil change tech put a pressure gauge on the low side and the gauge reading went to the “red” area indicating the low side pressure was much too high.

Although it would have been more helpful to also know the high side pressure, this is a red flag for the compressor.

Sounds like the valves in the compressor are shot!

Listen to this. I would get a second opinion. The "readings" don't make sense. You also said "lube tech" which doesn't sound confidence inspiring.
You need to know what the system is doing with proper gauges.
All auto a/c systems will leak a little over the years and eventually need to be recharged.
The correct way to make sure the system is properly charged is by evacuating and recharging the system to the proper weight.
Doing it by pressures when part of the refrigerant is a liquid and part gas in the system is guessing.

quote:

Originally posted by Shifferbrains:

quote:

Originally posted by jezsuiz:
My guess is you have a blockage in the system. There are usually inline filters in the system. I certainly wouldn’t add any more R134.

Typically when there is a blockage, the high side will have higher pressure and the low side will tend to go low and even into a vacuum and will turn off the compressor clutch.

This is going to sound silly, had a similar issue with my 2013 f150. Would not heat and cool. My engine coolant was below the cool line when cold.

Now it is working like normal.

I topped off the coolant, 160k with never having a coolant issue. So now i am watching the engine coolant levels.

I had an a/c issue recently, where everything was cycling properly (well low pressure switch cutoff), but not cooling.

Borrowed a set of manifold gauges, bought a can of r-134a with dye and a sixer of the regular variety.

Apparently there was a leak, but I couldn't find it.

Pulled a vacuum, tested pressure, injected the dye/stuff, and found nothing.

It's been working fine ever since.

Odd.

I had a similar problem in my F250. The coolant travels through a path of tubing and there can be leaks at several places along the way, not always in places that are readily visible. After putting dye into the system looking for leaks, the auto AC specialist I use tracked it down to a leak in the evaporator core inside the cab.

Hooking a set of gauges to the system and on a static system(one that has been sitting for a while and not turned on) both high and low pressure should read the same. On R-134a refrigerant, if the readings are close to ambient outside temperature, you have a close to correct charge. This should be a starting point from which to go.

Thanks for all the advice guys. I haven’t yet been able to find a shop who will do a simple diagnostic with gauges without needing the car for a day and charging me an arm and a leg.

I went to advance auto to see if they had gauges to rent. No go but I was able to hook up one of the AC Pro refill kit gauges on the low side. It showed ~90 psi with both the engine off and then 90 psi again with the engine running and the AC engaged. Much too high to even consider “topping off”. Yes I removed the gauge to reset back to zero between the 2 tests. And yes I’m sure the clutch is engaging and disengaging when I turn the AC on/off. So far still looking like the compressor may be toast since it didn’t pull down pressure on the low side while running at all. If I can’t find a shop to help me out I’ll order some of my own gauges to get better numbers and go from there.

I used to be a tech and have done my own work for years but I never really had to work on AC so I appreciate all the ideas.

quote:

Originally posted by Brett B:
Thanks for all the advice guys. I haven’t yet been able to find a shop who will do a simple diagnostic with gauges without needing the car for a day and charging me an arm and a leg.

I went to advance auto to see if they had gauges to rent. No go but I was able to hook up one of the AC Pro refill kit gauges on the low side. It showed ~90 psi with both the engine off and then 90 psi again with the engine running and the AC engaged. Much too high to even consider “topping off”. Yes I removed the gauge to reset back to zero between the 2 tests. And yes I’m sure the clutch is engaging and disengaging when I turn the AC on/off. So far still looking like the compressor may be toast since it didn’t pull down pressure on the low side while running at all. If I can’t find a shop to help me out I’ll order some of my own gauges to get better numbers and go from there.

I used to be a tech and have done my own work for years but I never really had to work on AC so I appreciate all the ideas.

Based off of this, it's looking like the compressor is done.

Should the compressor indeed be bad and you are going to have it replaced, have the system flushed. Also have the dryer and filter replaced. These are both in the passenger side of the condenser.

Do yourself a favor and have this work done at a reputable shop that knows A/C work. One very important thing to have done is to have the correct amount of PAG oil installed. Many shops invariably put too much oil in which reduces the efficiency of the system. There won't be enough refrigerant in the system.

It looks like Toyota has used a variable displacement compressor on some models. I am not sure about yours or whether they also had a clutch as well.
If there looks to be a set of wires going to a solenoid on the compressor in addition to the wires going to the clutch then it might.
If the pump is destroked it wouldn't be pumping any refrigerant.
This would probably still leave you replacing the pump unless it was a wiring or control issue.