Compressor noise after freon added to 'blowing warm' system

[davekro]

1) Why would adding freon cause a compressor to seize (or partially?)?

2) Since compressor may be toast already, any down side to reclaiming the freon then adding some oil to the system and giving rechareg another try? (Still has original 1999 orifice tube)

Recently my AC started blowing less cool and them just ambient. I only drive it once/ month. I had an HVAC friend add some R134 as he watched the pressure on his gauges. He said he thought he'd like to see ≈ 55lbs. As the engine was running, he was adding R134 from the 30lb tank. He guessed he added only 1-2 lbs. (he started adding before I could get his scale out and check exactly what we were adding. / ). Anyway, during the adding, there was no change to the ambient 75º output from vent, BUT the compressor started making noise and we could smell burning rubber (belt), so i shut it down. His gauge read 70 lbs.

History of AC system:
5/2013 installed new compressor (measured oil from old one and added that plus 1 oz of oil) [did not install new orifice tube or accumulator]
8/2015 system warm again so installed new accumulator* (only) and added freon. worked good until this spring 2016.
7/28/16 system warm so added freon and compressor started making racket and smoking belt!


*Accumularor was actually purchased in 2013, but not installed then. The cap seals were on in it in 2015 prior to installing, but I may have opened the caps in 2013 letting air in, but I don't recall.


1999 GMC Savana 3500 box truck 350 cid A/T. There is an auxilliary AC condensor/ fan assy in the box which has not been used for years, but it is still part of the ac system. My vague recollection is thatthe oem ac system needs 3 lbs R134 and the aux system needs an additional 1.5 lbs.

Thanks for any ideas.

[mk378]

High side?

A CCOT system that is undercharged but otherwise in working order will cycle the compressor rapidly. The low side will go down to the switch cutoff (25) and cycle from there.

[davekro]

mk378,
I'm not well versed in AC so may I ask for clarification?

"High side?"
I do not understand what you are asking here.

"A CCOT system that is undercharged but otherwise in working order will cycle the compressor rapidly."
Does this mean low pressure allows/causes rapid compressor cycling and can/would wear out a compressor?
Before system was recharged, I never heard the compressor lock up when AC switch was occasionally turned on for a short time. I actually never noticed it cycling on or on/off (but I may have just noticed). I thought there would be a low pressure sensor to not allow the compressor to run below 'x' pressure because the oil carried in the (low amount of) freon would be to little lube the compressor.

"The low side will go down to the switch cutoff (25) and cycle from there."
What would this mean to a layman? ;o)

Addition info: When gauges were hooked up my HVAC buddy said the needle was bouncing around. Did he incorrectly assume that meant there was some freon left in the system? Might we have gotten a different result had we evacuated the system (into a tank), then pulled a vacuum? I'm thinking I would have liked to have done that. 'IF" a large leak had developed, might I have lost enough oil to cause immediate compressor failure? He looked under the truck an did not see any oily areas and I doubt the system developed a large leak. 11 months ago, we pulled and it held the vacuum for 30-40 mins. Even holding a vacuum that long last year, is it possible there was a very slow leak still that took 9 months to leak the refrigerant?

Thanks for the response.
Dave

[Jag987]

1 what is/was the high side pressure?

2/3 he is saying that when the low side pressure drops below 25, the compressor will cycle off. This is because the oil travels through the system with the refrigerant. When there is little refrigererant flowing, the compressor is not getting enough oil and shuts down to prevent further damage. Also, rapid cycling also wears out the clutch faster and creates more heat that can cause any rubber (like in the clutch or front seal) to melt.

[bohica2xo]

It simply ran out of oil.

Several quick fixes over the years on a leaky system. A secondary evaporator loop that is not used. That system holds 78 ounces of refrigerant, and 11 ounces of oil. Some of that oil gets trapped in the rear unit & lines. Running low on refrigerant does not return oil well. You were low on oil to start with...

HVAC guys kill MVAC systems by charging like the system has a hermetic compressor. "looking for 55 lbs" ? Yikes.
Captain "Gas 'er UP!" nailed the low side with enough refrigerant to keep the low side switch closed & the compressor running - while feeding it straight refrigerant vapor with no oil. I have seen this one done before, they lock up suddenly and the clutch and / or the belt begins to smoke. The compressor might have had enough oil in it to struggle along cycling. But that blast of fresh refrigerant washed that right out.

You need to start over. Flush back to bare metal in the evaporators. Remove & clean or replace the metering devices. Check the compressor discharge hose for any sign of compressor bits. If you find a lot of metal on the front orifice tube, consider replacing the condenser - it is the primary filter. Blow all of the oil that you can from the line sets with dry air.

Put 11 ounces of PAG 150 in the system. Some in the compressor, the balance in the accumulator.

Begin chargeing the system with the engine OFF. Charge as much of the charge as you can through the High side fitting as a Liquid in to the vacuum. Then CLOSE the High side valve on the gauge set before you start the engine. Let it idle. Charge the balance through the low side in short bursts of vapor - if the clutch is cycling, let it cycle a couple of tines between feeding refrigerant.

[davekro]

It simply ran out of oil.

Several quick fixes over the years on a leaky system. A secondary evaporator loop that is not used. That system holds 78 ounces of refrigerant, and 11 ounces of oil. Some of that oil gets trapped in the rear unit & lines. Running low on refrigerant does not return oil well. You were low on oil to start with...

HVAC guys kill MVAC systems by charging like the system has a hermetic compressor. "looking for 55 lbs" ? Yikes.
Captain "Gas 'er UP!" nailed the low side with enough refrigerant to keep the low side switch closed & the compressor running - while feeding it straight refrigerant vapor with no oil. I have seen this one done before, they lock up suddenly and the clutch and / or the belt begins to smoke. The compressor might have had enough oil in it to struggle along cycling. But that blast of fresh refrigerant washed that right out.

You need to start over. Flush back to bare metal in the evaporators. Remove & clean or replace the metering devices. Check the compressor discharge hose for any sign of compressor bits. If you find a lot of metal on the front orifice tube, consider replacing the condenser - it is the primary filter. Blow all of the oil that you can from the line sets with dry air.

Put 11 ounces of PAG 150 in the system. Some in the compressor, the balance in the accumulator.

Begin chargeing the system with the engine OFF. Charge as much of the charge as you can through the High side fitting as a Liquid in to the vacuum. Then CLOSE the High side valve on the gauge set before you start the engine. Let it idle. Charge the balance through the low side in short bursts of vapor - if the clutch is cycling, let it cycle a couple of tines between feeding refrigerant.

Sounds like the compressor is likely toast. With all recommended, it sounds like it is time to bite the bullet and invest in having the AC rebuilt by a pro.
I no longer use or need the secondary evaporator. Other than cutting and 'closing off' the four ends (to secondary), is there a reliable shut off 'valve' that could be installed in the secondary's in/out lines, should it ever be needed back in action (With a big warning to add oil and refrigerant if put back into service). SHutting off the secondary one way or the other feels like a big reduction in leakable lines, especially since the secondary was not an OEM install AND was done 15+ years ago.

[bohica2xo]

The second evaporator can be abandoned & disconnected, just remove the T fittings they used to put it in. Plug the lines to it to keep them clean.

Valves are a disaster waiting to happen.

Find the leaks now, while the system is together. FIX the leaks. Clean the system out & replace the compressor, condenser & accumulator.

A new condenser is about 125 bucks. It is the primary filter in the system, and not easily flushed without specialized equipment. It is also subject to road debris, corrosion etc. Yours is 17 years old.

[mk378]

You could replace the lines that were cut to put the tees in, with stock ones from a front air only truck.

[davekro]

The second evaporator can be abandoned & disconnected, just remove the T fittings they used to put it in. Plug the lines to it to keep them clean.

Valves are a disaster waiting to happen.

Find the leaks now, while the system is together. FIX the leaks. Clean the system out & replace the compressor, condenser & accumulator.

A new condenser is about 125 bucks. It is the primary filter in the system, and not easily flushed without specialized equipment. It is also subject to road debris, corrosion etc. Yours is 17 years old.

After looking at my system, I can see that the small tube on the left (high side) they welded an adaptor in. Does that look like a 3/8” flare would cap that? On the right side, as stated, removing the ‘T’ and reconnecting the big line back to the accumulator would do it for that side (cap & plug size for 'T' ?).

Any chance, that at this point adding oil to the compressor (or other place?) might bring this system back to life?

Short of that, I’d like to cap off the secondary system then test for leaks. How much of a PIA is it for a DIY’er to remove the orifice tube on this '99 GMC van? So blowing air and maybe some acetone/other thru the condensor is not necessarily good enough to flush out any particles?

You guys' input is extremely helpful in my choosing a good path forward.
Thank you.

[davekro]

Any chance, that at this point adding oil to the compressor (or other place?) might bring this system back to life?

Thanks,
Dave