Automotive Air Conditioning Information Forum

So this is the 2nd time I replaced parts of the system.


The last one was a new China scroll type and lasted 6.5 years then exploded (hope Pic is attached).

All parts (all - every line, hose, cond, evap, comp, everything) were replaced last time. System was perfect for all that time (6.5years).

This time I elected to only change the compressor, condenser, dryer and exp valve and flush everything else. The evap seemed hard to flush, but this was my 1st time. I did get some very very fine glitter from the evap, but nothing from anywhere else.

Here's where I messed up. While running after charging. I wasn't thinking and my wife walked into the shop. I opened the low manifold valve with nothing attached, probably for like 30 seconds. I believe this sucked air into the system and caused some low pressures.

After that the system sent cool air but not cold (approx 52° @ 95° ambient). Pressure was 30-35L & 150H (psi). I drove it and didn't seem to have that chill I wanted from the vents. Clutch never cycled.

Stupidity, I added more Freon and bumped the pressure till it cycled (probably for the wrong reasons). Now at 42-52L & 275-325H. The system would cycle when RPM went up but the compressor made a low whine like it was over worked.

I decided to start over. Recovered with my homemade tank. Vacuum and left it under vacuum overnight.

Questions?

Will the piston compressor cool as well as the old crappy scroll types?
Will piston give similar pressures?
Do I need the same Freon charge?
I used the correct amount of oil as prescribed by kit instructions (almost the same as OE amounts). Is this amount good for a piston unit? The housing for the R/D was much larger and the R/D kit provided was too small. Same decant pack, larger bore filter and plug.

My plan is to replace lost oil from recovery, charge exactly what the OE spec is and retest.

Any suggestions would be greatly appreciated.

Thank you if you read my long drawn out post.
-Dave

trigger_thyme wrote: ↑Sun Jul 25, 2021 3:31 pm The last one was a new China scroll type and lasted 6.5 years then exploded (hope Pic is attached).

Very good longevity for a scroll, I'd say. I don't see a picture, though.

trigger_thyme wrote: ↑Sun Jul 25, 2021 3:31 pm This time I elected to only change the compressor, condenser, dryer and exp valve and flush everything else. The evap seemed hard to flush, but this was my 1st time. I did get some very very fine glitter from the evap, but nothing from anywhere else.

Did you remove the TXV before flushing the evaporator? If not, that's why the evaporator was hard to flush. The TXV acts as a restriction and will prevent flushing-out all the debris and old oil

trigger_thyme wrote: ↑Sun Jul 25, 2021 3:31 pm Here's where I messed up. While running after charging. I wasn't thinking and my wife walked into the shop. I opened the low manifold valve with nothing attached, probably for like 30 seconds. I believe this sucked air into the system and caused some low pressures.

Yes, you now have air (a non-condensable gas), and moisture, in the system, which will cause poor system performance, high pressures, and internal corrosion.

trigger_thyme wrote: ↑Sun Jul 25, 2021 3:31 pm Stupidity, I added more Freon and bumped the pressure till it cycled (probably for the wrong reasons). Now at 42-52L & 275-325H. The system would cycle when RPM went up but the compressor made a low whine like it was over worked.
I decided to start over. Recovered with my homemade tank. Vacuum and left it under vacuum overnight.

Did you put any oil in before you charged it the first time, and how much refrigerant did you charge? The pressures you mentioned are too high, probably due to the air/moisture in the system and an overcharge. Specifications call for 18 ounces (net weight) of R-134a and 4.5 fluid ounces of PAG-46. Did you weigh-in the refrigerant using an accurate scale designed for that purpose?

trigger_thyme wrote: ↑Sun Jul 25, 2021 3:31 pm Will the piston compressor cool as well as the old crappy scroll types?
Will piston give similar pressures?
Do I need the same Freon charge?
I used the correct amount of oil as prescribed by kit instructions (almost the same as OE amounts). Is this amount good for a piston unit? The housing for the R/D was much larger and the R/D kit provided was too small. Same decant pack, larger bore filter and plug.
My plan is to replace lost oil from recovery, charge exactly what the OE spec is and retest.
Any suggestions would be greatly appreciated.

Answers to your questions:
Probably better.
Pressures should be similar.
You should charge the same amount of refrigerant ("Freon") as the OEM specs.
I would use the oil amount recommended by the compressor manufacturer if different from the OEM specs, just as you did. Install the new desiccant bag, clean and reinstall the original filter, and re-use the original plug (replacing the o-ring, if necessary).

My last reply disappeared into the ether.

Yes, removed the exp valve. It was replaced as part of the kit.

The correct oil (per manufacturer) was added and almost mirrored the OE amount.

I originally charged with 1.5 cans 12oz cans with small loss from line purge. As for a scale designed for refrigerant, that I don't have. I did use a scale, but the accuracy is always slightly in question.
Then..... I got stupid and added more refrigerant (5-6oz). Yeah this is were I panicked and evacuated the system to start over.

New question. Do you absolutely suggest replacing the desiccant again? It was replaced with the new condenser and only had about 2 hours run. It's been under vacuum for the last 18 hours. Hope that is okay.....

trigger_thyme wrote: ↑Sun Jul 25, 2021 7:49 pm New question. Do you absolutely suggest replacing the desiccant again? It was replaced with the new condenser and only had about 2 hours run. It's been under vacuum for the last 18 hours.

Some air and moisture made their way into the system earlier. And since evacuation won't pull any moisture out of the desiccant beads, I would replace it again.

JohnHere wrote: ↑Mon Jul 26, 2021 1:52 pm

trigger_thyme wrote: ↑Sun Jul 25, 2021 7:49 pm New question. Do you absolutely suggest replacing the desiccant again? It was replaced with the new condenser and only had about 2 hours run. It's been under vacuum for the last 18 hours.

Some air and moisture made their way into the system earlier. And since evacuation won't pull any moisture out of the desiccant beads, I would replace it again.

Well, I just took it out and replaced it.

Sir, I'm not too happy with the way this new desiccant bag looked. I will try to attach a photo. It's under vacuum now. I was very thorough with my flush and it still looks dirty. Maybe I'm just thinking it should be perfect, but that's not what I expected.

I'm trying to attach a photo of the old compressor. It didn't leave black death throughout the system. Just kinda let go all of a sudden. My son and I will be dissecting it soon.

Just wondering what the dark is on the bag I just removed. Possibly the compressor was breaking in? I really hope this system lasts longer than 6.5 years.

trigger_thyme wrote: ↑Mon Jul 26, 2021 5:36 pm I'm trying to attach a photo of the old compressor. It didn't leave black death throughout the system. Just kinda let go all of a sudden. My son and I will be dissecting it soon.

That's a pretty impressive compressor failure. Could be that something broke internally causing the case to rupture, excessive pressure, or even metal fatigue. Let us know what you find after you take it apart.

trigger_thyme wrote: ↑Mon Jul 26, 2021 5:36 pm Just wondering what the dark is on the bag I just removed. Possibly the compressor was breaking in?

I don't see any identifiable particles, which is good. The staining looks like very fine aluminum dust that possibly remained in the evaporator after the first compressor disintegrated. Some small amount of residue might have been left in the new compressor during manufacturing or, as you mentioned, sloughed-off from breaking-in. It's hard to tell, but at least the desiccant bag absorbed it.

Just wanted to say a huge THANK YOU to you Johnhere.

It's guys like you on forums like this that truly help people by sharing knowledge. I always have and always will pay it forward sir.

Back in the early 2000s at Honda school (French Camp CA) they had some amazing modules on automotive A/C. That created the basic understanding for me, which is enough to be dangerous. Our shop had a really nice duel A/C machine that made the work almost effortless. I converted about 20 NSXs from R12 and had no comebacks. FYI, the evaporator on NSXs is most likely the leak.

All that being said I'm rusty and your guidance is very much appreciated.

Heading to the shop in a few hours with a better scale (one I use to weigh gun powder for reloading) and a clear head.

I'm expecting all to go well.