Automotive Air Conditioning Information Forum

So the car is a 1989 BMW 325i that I bought used and the a/c always kinda worked until last summer. And yes it was converted to R-134a when I got it. I'd always just topped it off to get cooler air.

The compressor clutch went out this Spring and I took it in to a local a/c rebuilder here in Austin, TX. I expected the compressor to be toast, but he said it checked out fine, but had "black death" in it and after a good cleaning and new clutch all was well with it. I was shocked I walked away with a $140 bill!!!!!! He also said to flush the system really good (black death and all).

Armed with a compressor with a clean bill of health, I was really excited. (A/C guy told me he put 6 oz of oil in the compressor.)

I then replaced the condenser, evaporator, receiver/dryer, expansion valve. And replaced one hose and flushed out the others. Replaced all o-rings and schrader valves.

Super confident, it was time to charge the system. R-14 capacity is 2.15 lbs, so I understand with the 80% rule, I need 1.75 lbs (28 oz) of R-134a.

I pulled a vacuum for 45 minutes and started to fill. BTW, it is 100 degrees today while I did this.

I got 10 oz in, that's all!!! (Just a bit more than 1/3 charge.)

With the engine at about 1,500 rpm, the low side dropped to about 40 psi and the high side was pushing 300.

The compressor started making some clanging noise too.

Wouldn't put more refrigerant in afraid the system was going to blow up!

And the low side equalizes to the high side in about 1 second when I turn off the a/c.

I have one successful freon rebuild under my belt, but this one is driving me crazy.

Any ideas before I drive it to an a/c shop for someone to figure it out?

Here is a video of the gauges with the engine at idle and then revved up to maybe 1,500 rpm. And you can hear the compressor make some scary noise at the end.

https://youtu.be/Ugbu0RkOcIk

And a picture with static pressures (system off) included. The low side is pegged!

And the electric fan in front of the condenser comes on when the a/c is on.

Thanks in advance for any comments.

Dan Perez

Sounds like a stuck expansion valve to me.

Also, when charging the system, the interior fan should be on the low speed to have the lowest possible low side pressure to enable the charge to go in faster. Turning the interior fan on high increases the pressures on both sides and slows down the charging.

tony1963 wrote: ↑Wed Jun 28, 2023 5:05 pm Sounds like a stuck expansion valve to me.

Also, when charging the system, the interior fan should be on the low speed to have the lowest possible low side pressure to enable the charge to go in faster. Turning the interior fan on high increases the pressures on both sides and slows down the charging.

Stuck open? New one from Rockauto installed.

I don't understand those static pressure numbers being so high when the system only has 10 oz rather than the full charge of 28 oz of refrigerant.

Thanks.

With only 10 oz of refrigerant showing 150 psi on the high side, I'd suggest the expansion valve is stuck shut or there is something totally blocking the refrigerant flow.

Something is pulling away from the low side and stacking up on the high side. Nothing is circulating.

tony1963 wrote: ↑Wed Jun 28, 2023 7:04 pm With only 10 oz of refrigerant showing 150 psi on the high side, I'd suggest the expansion valve is stuck shut or there is something totally blocking the refrigerant flow.

Something is pulling away from the low side and stacking up on the high side. Nothing is circulating.

But the static pressure on the low side is off the scale, right?

Did you see the youtube of the pressures while running?

I'd be really happy about maybe just needing to put in a new expansion valve.

Dan

You're pushing 300 psi and climbing. Then it shuts off. I would think there are other issues besides an expansion device. Mist the condenser and she when the pressures do.

If that clanking noise is the compressor. That sounds horrible.

Tim wrote: ↑Wed Jun 28, 2023 7:54 pm You're pushing 300 psi and climbing. Then it shuts off. I would think there are other issues besides an expansion device. Mist the condenser and she when the pressures do.

If that clanking noise is the compressor. That sounds horrible.

Yeah, I let it idle and the low side climbs and the high side falls.

I can't comprehend that it was a pain to get 10 oz of 28 loaded in. That is just bizarre, right?

When I took the compressor in to the rebuilder, I was expecting really bad news. I was shocked when they told be they just needed to clean it up and replace the clutch. "It holds pressure" is what they said.

I'll pull it out of the garage and get the garden hose on the condenser tomorrow.

I'm not very optimistic at this point.

Also I have this schedule of pressures with temperatures. It is hotter than hell in Texas right now, so the chart is showing the high side at 315-325psi!!!

Another data point. It is 80 degrees F this morning. I hooked up the gauges to read the static pressures.

Low and high sides still equalized and each now at 100 psi.

I've understood that static pressures kinda follow F degrees, so I was expecting a little lower.

But when you figure I loaded in 10oz of R-134a when it calls for 28oz, it is a real head scratcher.

My port for the low side is on the return hose downstream of the evaporator to the compressor. The high side port is between the receiver/dryer and expansion valve.

Maybe time to tear it apart, again.

BTW, this is the old [edit] evaporator [/edit] and what came out of it.

Looks like I have an Denso 60-01159 NC. And out of stock lots of places.