confusing AC gauge readings

[88911coupe]

Some added details. this was the first charge attempt after all new hoses and new evap went in. All three condensers had been thoroughly flushed and been baking in the sun for days and periodically i'd blow air through them to make sure they were dry. I connected the r/d in about 3-4 minutes after breaking the seal It was the last thing I did before hooking up the vacuum pump. The pressurized gas is a good idea, just not sure where to get it and how to do it. I'll do search on that.

[Pazuzu]

Originally Posted by 88911coupe

Some added details. this was the first charge attempt after all new hoses and new evap went in. All three condensers had been thoroughly flushed and been baking in the sun for days and periodically i'd blow air through them to make sure they were dry. I connected the r/d in about 3-4 minutes after breaking the seal It was the last thing I did before hooking up the vacuum pump. The pressurized gas is a good idea, just not sure where to get it and how to do it. I'll do search on that.

One option is a nitrogen tank, but the normal person wouldn't/shouldn't spend money for something like that.
another option (and the one I will be using) is a CO2 tank. I have a kegerator, so I have 2 CO2 tanks around, and getting one filled costs about $12. A 10 pound tank at 500psi will last a long time backfilling automotive A/C systems...

You might find a 5 pound tank for $30-40 used if you check craigslist.

Now, backfilling is probably more work that needed, but it is an option. If you're dryer was clean (and it sounds like that's the case) then maybe you just need to pump more. Try a 3 hour pull, let it sit overnight, then another 3 hour pull.

[88911coupe]

Adding a can of r134 to circulate around is a good idea I will try that, thanks!

[kuehl]

Originally Posted by Bob Kontak

Maybe just putting in a pound of R134 in and circulating for a bit and then vacuuming can sweep additional cooties away?


Ignore wwest.

Bob, yes, using R134a rather than nitrogen is easier to raise the system above 0 and push out ambient gases and moisture.

And, if you ever read some of Porsche's factory manual charging instructions their machine flushed the system with refrigerant prior to charging.

Ignore wwest

[Pazuzu]

Originally Posted by Bob Kontak

What I don't understand are the plumbing hookups. I would love to have this as a tool.

I don't have a compressor, so I use my tank as compressed air, to blow flush through the system, to backfill, etc.

1) Tank
2) Regulator. 1 or 2 gauge, around $40-50 new, much less used

The output of the regulator is a standard thread shared by, well, looks like everything. So, unscrew the barb connector that comes with beer regulators, go to harbor fright, buy an air tool accessory kit, and screw the standardized threaded adapter into the regulator.

Magic, you have a standard air chuck QD on a 0-60psi regulator that you can carry around the garage. Toss your coil up airline on it and you can do all sorts of stuff. not enough to run air tools, but plenty for everything else.

I picked up a used kegerator and used the cheap air tank and single gauge regulator that came with it, while buying a nice aluminum 10 pound tank and 2 gauge premium regulator to use with the beer.

[tirwin]

Originally Posted by kuehl

Bob, yes, using R134a rather than nitrogen is easier to raise the system above 0 and push out ambient gases and moisture.

And, if you ever read some of Porsche's factory manual charging instructions their machine flushed the system with refrigerant prior to charging.

Ignore wwest

I have been consumed with my regular job lately so I haven't had time to get back to the car. I finally got some time yesterday. The replacement deck lid condenser came in for the one that blew out and I swapped it out.

I followed Charlie's instructions. Pulled a vacuum to 28.5 in Hg @ 1000 feet above sea level. No leaks. Put in a static charge from 30 lb R134a tank for 20 minutes. Evacuated and pulled vac for 2 hours. 30 minutes later, no significant leak. Charged the system to 258psi @ 95°F ambient temp in my garage. Initial charge done by weight to 36 oz. Fine tuned the charge by temp/pressures.

Have a few more things to do before I can take it for a test drive, but I'm extremely pleased with the results so far. I can't wait to see how it performs on the road.

Oh and as soon as the car was shut off the high side pressure started dropping.

In summary, listen to Charlie. Ignore wwest.

[Ronnie's.930]

^^^

Bob, it looks like you had the "Five Stone Breakfast" today!

[tirwin]

As much as I like the added bonus of having a CO2 tank around for a kegerator, why wouldn't you just use a little R134a for this purpose?

Of course, if you're a Guinness man you need both CO2 and Nitrogen.

[88911coupe]

So...my takeaway from all this is to get a kegerator...awesome! Nice IPA on tap would make all this work more fun.

[wwest]

Discseven's "final"....

High side still "fluctuating".

Low refrigerant charge. Factory R12 = 48 Oz, R134a "recommended" =36 Oz.

With Kuehl fender condenser/fan..... 40 Oz..?

"Proper" charge, 40 Oz, idle vent temperature = driving?

One would think with extra condenser/fan one would get better idle temperatures vs factory with 2 Spal fans.

Post #6, near bottom

My AC burns me up --- Summary of fix

[wwest]

Originally Posted by Pazuzu

??
Evaporated WHERE? Once he stopped pulling a vacuum and sealed the system, any moisture inside, iced or not, will remain...INSIDE. It won't evaporate away anywhere!

Want to remove ice? Pull a vacuum, then backfill with an inert gas to some pressure (maybe 30, 40psi?). Rinse, repeat. Backfilling with gas under pressure will keep the system clean, but allow that ice to melt and move around a bit. You need the mean free path of the water molecules to be long enough that they can actually fall into the pump, otherwise, they ain't going anywhere no matter how good the pump is or how long you pull vacuum. Deep vacuum systems don't work the way anyone thinks they do, and vacuum pumps do not "pull" stuff out of a system.


Hard chemical flush of system. This is doing most of the water removal.
Backfill with gas to check system under pressure (might leak under pressure even if it doesn't under vacuum)
Pump down for hours in high temp environment
Backfill with gas
Pump down for hours.
Maybe repeat again

THEN you might have a clean dry vacuum in your system. Also, adding heat at any point helps, you can activate molecules to jump off of the inner surfaces that they are stuck to with heat. That's the real problem, deep vacuum systems are essentially empty space and lots of crap sticking to the walls refusing to move. It doesn't matter how clean the empty space part is if you have lots of crap stuck to the walls.





Hey OP, how long did your system remain exposed to air? Is there a chance that your new dryer might be charged with moisture, and loading your system with water even after you pump it down?

In 14 hours, especially at those OAT levels, the vacuum level would have degraded if ice or even water had been present.

[88911coupe]

Decided to try adding one can (12 oz) R134 and let that cycle through to see if it will help fully evacuate system. I noted the pressure for the record and was seeing 15/260 at around 2k RPM, at idle it was 40 on the low side with the high side rapidly fluctuating between 250-300. Air from vent was barely cook at all, which I guess should not be too big a surprise.
Not driving the car much not but may take it out later to run it some and then evacuate again tomorrow. Hopefully it will work better.
One thing I noticed, which I'm pretty sure did not hear before, was a distinct "clackity" sound from the compressor when the engine returned to idle speed...maybe replace it before something more serious happens?
Thanks

[wwest]

Originally Posted by Bob Kontak

Aside from the not wildly fluctuating high side coupled with far in excess of factory performance this post is misleading and grossly off topic.

Perhaps starting a separate thread would be in the best interest of the original poster's needs.

My point is that at CG's advice, insistence, Discseven put a LOT of time and effort, with no small expense, ascertaining that his charging process was not introducing air into the system.

Only to accept, in the end, that the fluctuating high side gauge reading had to be accepted as being from another causative factor, unknown.

Plus, it should be noted, a refrigerant charge level very close to half that widely recommended for r134a retrofits.

[wwest]

Originally Posted by 88911coupe

Decided to try adding one can (12 oz) R134 and let that cycle through to see if it will help fully evacuate system.

I noted the pressure for the record and was seeing 15/260 at around 2k RPM, at idle it was 40 on the low side with the high side rapidly fluctuating between 250-300.

Those HIGH pressure readings with a seriously low refrigerant charge???

Air from vent was barely cook at all, which I guess should not be too big a surprise.
Not driving the car much not but may take it out later to run it some and then evacuate again tomorrow. Hopefully it will work better.
One thing I noticed, which I'm pretty sure did not hear before, was a distinct "clackity" sound from the compressor when the engine returned to idle speed...maybe replace it before something more serious happens?
Thanks

Low refrigerant charge results in high pressures in that range?

"maybe replace it before something more serious happens..?"

<12 Oz, 2000 RPM...how long? Quite possibly something serious just happened.

I don't think there is anyone that would advise you to run the compressor with a KNOWN low refrigerant charge.

[wwest]

Originally Posted by 88911coupe

Some added details. this was the first charge attempt after all new hoses and new evap went in. All three condensers had been thoroughly flushed and been baking in the sun for days and periodically i'd blow air through them to make sure they were dry. I connected the r/d in about 3-4 minutes after breaking the seal It was the last thing I did before hooking up the vacuum pump. The pressurized gas is a good idea, just not sure where to get it and how to do it. I'll do search on that.

Ounces of lubricant?

[Ronnie's.930]

I can't figure out how to find that thread statistics page that shows who has posted in this thread and how many times they've posted, but at a quick glance, it appears that the person with the most posts here is the the guy that does not do his own a/c system evacuation and charging - makes zero sense.

[88911coupe]

Added 6 oz ester oil to compressor after it had been thoroughly drained while cleaning condensers and installing new hoses.

[wwest]

Originally Posted by 88911coupe

Added 6 oz ester oil to compressor after it had been thoroughly drained while cleaning condensers and installing new hoses.

[wwest]

Originally Posted by Ronnie's.930

I can't figure out how to find that thread statistics page that shows who has posted in this thread and how many times they've posted, but at a quick glance, it appears that the person with the most posts here is the the guy that does not do his own a/c system evacuation and charging - makes zero sense.

Many years ago I taught army recruits how to maintain and use the Hawk missile system.

Never fired one.

[Ronnie's.930]

Originally Posted by Bob Kontak

I give him a thumbs up today.

Have you been drinking excessively?!?!?!