'93 Ford E350 - Nitrogen pressure testing and recharge

[rgnprof]

I am fixing the AC on my 1993 Ford E350 chassis motorhome (7.5L with the old FS15 compressor) - it's not been converted and I'm going back with R12 (since I have it). I have replaced everything - all new parts as my old FS15 compressor black died on me! Bought a new compressor online (Amazon) and it froze up on me during my first try at recharging. Not sure what happened as I was charging vapor only through the low side and once the compressor starting cycling on and off, after just a minute it started smoking and locked up on me. I got things shut down pretty quickly, pulled the orifice tube and it looked clean. I didn't replace the drier as I had just replaced it - hope that's alright, but a local AC shop thought I would be fine.

Bought a new Motorcraft compressor this time and just got it installed. Nitrogen pressure testing using my AC manifold gauge set and I had a leak on the hose manifold that connects to the back of the new compressor. Pulled it and re-oiled the o-rings (they looked fine) and reinstalled it. I pressurized the system to about 160 - 200psi - open the high side and then barely open the low side (low side gauge jumps to Retard and then declines to a steady reading around 90psi) - then closed off both of my manifold gauges...I think I have a leak, but I'm confused. The low gauge settles at 95psi and the high side at about 160psi - they have both stayed steady now for several hours.

Do I have a leak? I'm going to leave it pressurized overnight - since I'm going back with R12, I want to be as sure as I can that my system is leak free! I'll run a nice long vacuum after all of this...

[Tom Greenleaf]

Having trouble following you. Why are you pressure testing and happy that it falls back to 90PSI from higher?

First - Nitrogen isn't so temp sensitive and doesn't leak as easily as plain air or you add some R-22 for a leak test that would leak and be sniffed out.

Holding a vacuum is great but know you are only holding BACK atmospheric pressure - just 14.7 PSI +/- still a good bet.

You've burned up a compressor charging with gas only. Too slow to get oil moving no doubt. However you are charging, small cans, 30 lb bottle weigh in the charge liquid into vacuum should be a good amount not full just should move oil along.

Having R-12 or not are you sure you even want to? Depending on components already changed and oil in there it may not work better than staying with 134a.

It's not legal to go back if anyone cares anymore just not sure you can know it wont quickly leak out just yet. 134a will leak faster as it's a smaller molecule.

IDK - What do you really want to do that can last? I don't think you are going to know if this leaks till it's up and running with any usable gas. Static pressure testing with nitrogen alone if that's so and only that and dropped, reads different on high or low side just sitting there doesn't make any sense to me,

T

[Tom Greenleaf]

Signing off for a while or hours so back later if you are replying, Tom

[rgnprof]

I am not happy - confused would be more like it. I pressure up the nitrogen on my valve to about 160psi-200psi...open the high side on my manifold gauge and it goes to that or even a bit higher and holds. Open the low side - slowly - and it will jump to the 120+psi and then back off to 90psi and hold. System been holding at that 200psi high and 90psi low for hours. What I don't understand is why is doesn't all leak down after a while - I mean a leak is a leak - right?

First time I did this I could hear a noticeable air leak from behind the compressor - I have sprayed Big Blu all over and I see no signs of a leak (yes, I realize I have to actually see the bubble form etc. and I will spend some more time at it tomorrow). I have R22 and a sniffer and may follow up with that if what I'm currently doing remains inconclusive...I was hoping that the nitrogen pressure and the spraying around for leaks would be conclusive.

And I realize that running a vacuum is NOT leak testing...

From what I've read, charging through the low side with vapor only is the safest way - but I realize that it is slow. How should I recharge - when I get to that point?? (I didn't really follow your last sentence...)

Thanks, and good night!
Ryan

[Tom Greenleaf]

Got one eye open let's figure this out.
OK: Take that you pressured up to YOU said 160-200? Why the range? What pressure did you get to? Can't be both and that's too much for guessing.

Both gauges of a manifold set would read the same just static pressure testing or something is all wrong right away with test.

It drops on it's own to 90 PSI and holds - it could. That could like a "T" handle type tire air pump going fast hold, going slow leaks past seals type action with pressure kind of torqueing on rubber or flexible items especially.

The assorted methods for leak finding should all be used - some find leaks better than others. I just find nitrogen use (my opinion) the wrong gas. For a while a huge run on selling tire service to switch to it claiming it doesn't leak, isn't so temp sensitive so apt to stay at the correct tire pressure under all conditions - got that but if looking for a leak I want it to leak! So by the book they suggest a tad of R-22, a CFC to sniff out.

All that in the effort to not use a refrigerant you would be using in a vehicle to save the world?? You are at least saving how fast anything leaks by fixing one so why not use one known to leak faster like 134a? I didn't make the rules but you aren't supposed to intentionally vent 134a and nobody want to waste product but a failed job isn't helping either.

In short you could vacuum down till max and hold for a while - is still a check then add 134a - just a few ounces should pressure up to about the pressure in PSI as the temp in Fahrenheit. Should stay there except for temperature would raise or lower the pressure very predictably and leak sniff out, bubble out with soaps, dyes or inert tests. You could evacuate and recover what didn't leak out when found.

Can stop here as this is still in the leak finding mode not what to use to charge system and make it work yet. Don't allow mixing of gases for running a system - leave all that when it ready, leak free and everything thought ready, oil charge and all for the final charge up,

T

[rgnprof]

Good morning (and Happy 4th),

I have figured a few things out this morning - I have a range because even though I shut off my nitrogen valve at 160psi, when I go to then open the manifold gauges the psi jumps up 20-24psi. I am pretty sure this is happening because of residual nitrogen pressure in my system - I haven't been waiting long enough for all the nitrogen to leave my system before trying the procedure again...

I have isolated the leak to where the AC hose manifold assembly bolts on to the back of the compressor - I now have identical static pressure readings on my gauges and the leak is only evident at or around 200-225psi and it's a very audible leak. Right now the system is pressurized at 140 - both low/high side static pressures and it is holding right there...

This makes sense as during my prior attempt to do this, I also checked the pressures and had no leaks in the system - so I'm having some trouble getting this compressor to bolt cleanly to my hose manifold assembly...I've already removed the o-rings once, but I didn't replace them as they looked fine - but, maybe I'm missing something. I guess it's possible that I sprung a leak somewhere in my hose assembly (I did have it pressure checked at a local AC shop though)...

Any thoughts? I am really concerned about burning this new compressor up, but I'm not going to recharge until I figure out this leak...

[Tom Greenleaf]

Just this: An "audible leak" -- easy to find or should be. Bucket of soapy water or whatever it takes to find.

Plain air pressure fine for a short test not real good or suggested if PAG oil was used - know which.

Gauges jump?? Oh my. I know my own couple sets not how all have tricks or features that could hold pressure or leak down a lot just the split second of disconnecting or connecting.

Made plugs for mine if you "park" spots are not seals also so can vacuum gauges easily and you should,

T

[rgnprof]

Yes, I know where the leak is coming from - at least as close as I'm going to get without removing the AC manifold hose assembly from the vehicle and having it checked again (something I'm trying to avoid...) It is clearly coming from the manifold where the hoses mount to the rear of this FS10 compressor...I think I am going to try new o-rings first...

Any thoughts on recharging? Vapor only? Or liquid?

Thanks, ryan

[Tom Greenleaf]

Vapor or liquid charging: Weigh what you do either way - vapor (gaseous state) is safer but faster also requires knowing how fast you are adding so NO if with a running engine and system engaged.

This is a great read on charging procedures to guide you.........

http://aircondition.com/tech/questions/ ... Procedures

Know how much your aim is. You can add quite a bit of liquid quickly into the well held vacuum and system should be able to kick on and almost cool with just that so oil is moving for compressor when you do start up to finish off.

Know everything when charging - all temps, all pressures at what RPMs. Do anything not to overcharge it as more doesn't = cooler just creates problems and without measuring what you are removing ounce by ounce very difficult to back up a charge to correct.

This leak you hear - why is that so difficult to see it then with plain bubbles so you are real sure of the area no longer guessing. If the flaw is the hose manifold and not "o" rings or something else would be nice to be sure,

T

[rgnprof]

Thank you for the charging link and suggestions...

The leak is weird - right now I have 275psi in the system (I know, pretty high!!!) and it is not leaking at all. Earlier it held at 200psi for hours...I have sprayed and looked, sprayed and looked and I just can't see any significant bubbles - maybe some small ones where the high side tube leaves the manifold...but nothing that screams "here's the leak"...

I'm not sure what's going on - especially since it seems to be holding at 275psi...

ryan

[Tom Greenleaf]

That info is all in the knowledge Base right up top and lots more.

Yes - 27 PSI right now should show a leak and active. There's a pressure chart up top too by ACProf to take a look at is great info too as everything to do with A/C is what 'state' something is at what pressure, what real temperature which will be all over the place depending on exact time checked.

Just know when time comes that the only heat the vehicle knows is the exact air flowing thru the condenser not the air temp forecast or a thermo on a tree nearby type thing. Heat from surface, engine if it's been running really does kick back some radiant heat.

Rule is when you find just a static pressure anything under that chart at the given temp the system is essentially empty.

The entire system should stay tight and tolerate spikes to perhaps 350+ PSI. Think about 2.2 X temp in F. for R-12 with gauges and 2.5 for R-134a is expected high side pressure at some raised RPM.

Getting harder to find good cheap one but like the wired home type thermo you hand the wire out a window things for in/out temps. One in front of grill and one in a center vent so you can watch all temps all the time. The meat thermos are fine but don't like them myself. Fall out, too slow. Wireless too slow as well.

IR thermos are super handy but learn one's bad habits before trusting one. You don't need to spend a lot for decent ones either with laser tracer or key fob size stream along a line. NG for just air temps.

Quite the game (that isn't a game) to do this, know what's going on where right when charging especially. I also with unknown ones drive a vehicle around the block before the last tweak of charging so oils have moved around and settled in where they might puddle a bit just with starts and stops, turns and so forth - just what the vehicle would encounter anyway.

Doable but pay attention. Mistakes set you back, frequently worse off than before you did something if wrong,

Tom

[rgnprof]

After again checking the pressure and finding the system to hold, I decided to draw a vacuum and see what happens...after 4 hours in about 95 degree heat, I can only get 24" or so...first time I've had this problem as I've always been able to get it down to 29ish before. I think I have too much moisture in the system - I noticed some black, oily stuff being released from the high pressure schrader valve when I was depressurizing the system...

Is this possibly due to my previous problems with the first compressor? Should I have replaced the accumulator/drier??

ryan

[Tom Greenleaf]

First - Vacuum should hold for the altitude you are at indefinitely. It too can leak back and stop at a certain #.

What can be hard to know is if your operating gauges is proper or gauges have the leak? May only leak while hooked up and not away from a vehicle.

What oil was used in the conversion if you know? If not flushed and you are going back to R-12 (mineral oil) there will be some left somewhere in system and not compatible with PAG oils in particular. Those absorb moisture and turn acidic and be their own problem.

Black death is a name for what you see when a compressor burns out and bakes oils, perhaps metallic bit at the "O" tube. A total flush and yes the accumulator/drier should go which will be a real pest at this age if not lubed well at threads of things may be real stuck and break the next item.

I plain don't know for sure the HD truck layout for this but hunch is like most full size cars of the era and earlier - a CCOT system with spring lock "O" rings at lines. Some "O" tubes are inside high pressure hoses and not serviceable.

You may hear of compatible rubber hose and products. Virtually all sold will be 134a friendly rubber parts once only green for "O" rings, hoses marked or would be barrier hose R-12 didn't require.

It probably should be totally flushed out and start from clean and new accumulator and "o" tube again. If tube and fin condenser that can be flushed out.

Compressor if you roll the dice just spin thru new oil till clear off vehicle.

OE these were pretty tolerant systems but only to a point.

Again - know that oil if for compressors only but circulates. That and it only circulates when operating and charged enough to carry it along and around or compressor is spinning dry and can't last long measured in seconds give or take.

We haven't passed just properly holding vacuum and still confused on the pressure.

IDK - are gauges messing up the show?

If true "Black Death" is the nick-name all must be flushed out as said and parts that don't flush unfortuneatly time and time again with each failure!.

Short of cutting certain items open you can't see all possible debris if excessive or not. Just black oil isn't a good sign alone.

Where do you want to go from here?

T

[rgnprof]

My gauges do hold the vacuum, its just not getting anywhere close to the 29+ inches it should be with the pump running. Just let the vacuum pump run all night and still only to 24", and I did change the pump oil before vacuuming...

There has been NO conversion here - system was R12 and I am going back with R12, it has only had mineral oil in it. This new Motorcraft compressor did come with 7 ozs PAG oil, but I removed it all and flushed the compressor with mineral oil a couple of times...The first compressor that I tried to install (see my first post in this thread) did not come with any oil and I used 7 ozs mineral oil that time (7 ozs is Ford specs).

Seems to me there are 2 possibilities - my gauges are not working properly, all of a sudden, OR the system has too much stuff/gunk (moisture, etc.) in it from my first compressor locking up on me. I think I'm going to have to take it all apart again and basically start over!

ryan

[rgnprof]

A new development:

I double-checked my gauges again and noticed that the low pressure gauge needle was not on zero to start from - it was actually resting at 2-3 psi, so it was throwing my vacuum readings all off...think I've got it! I hope! I may try and track down another set of gauges today to triple-check!

ryan

[Tom Greenleaf]

OK - OE still R-12 never changed. You said "black died" about the compressor which IDK what you really meant - compressor or clutch froze or what yet. Black Death is a term used is mandatory to flush out everything flushable and toss anything with desiccant.

Re-read you added what my book calls for a 100% oil charge of 7oz when ready but left the accumulator on which may have had ounces still in it you can't get out and measure without drilling a hole it them, heat them up and see what comes out.

Now, no telling how much oil is in it or exactly how it failed if told you could leave the accumulator by a pro if a pro? Two type of accumulators used only difference is one is threaded fittings and the other spring lock type like this.....



If threaded items are not steel to steel an alloy will be frozen up like welded usually and bust the evaporator.

IDK - Trucks seem to put in what was ordered when new with whatever HD options changes things.

I still just can't know what type pump or gauges you are using that you can't hold a full vacuum but holds at 24? Why on earth did you leave a pump running any longer than the max vacuum it would pull and lock off system from pump - a slow one would only take 15 minutes if that long. All night you are wasting the pump. Empty is empty so running it forever does nothing more. There's no water left at 24 Hg. really unless it was obnoxiously cold out which it isn't. I don't have the chart handy but water boils at some insane low temp under vacuum, then as vapor is removed.

OK - here's a spot that could be trouble. Your pump can do a full vacuum on gauges/manifold set so we know it works. The low side fitting on accumulator may not be so perfect and not seal right in some way. Odd that it would hold and stop at 24? I can't explain that?

You could just vacuum from the high side, plug low side hose and read the vacuum. As said, zero is zero - whole system is zero (29,92 Hg.) is it for sea level minor adjustments for most by altitude. About 1 Hg. less seen per 1,000 ft. of elevation. I don't work in that so can't expound. I'm at 232 which is insignificant as things go for this for my own anything.

I'm at somewhat of a loss with both the pressure testing and now can't hold the full vacuum - refresh that you are only sealing out about 14.7 PSI of pressure at max vacuum not holding IN the operating pressures it mush be able to but is a clue if it holds a vacuum that it's likely to hold pressure - with exceptions to anything.

So if the "spring lock" connectors you need the tools to release those.........


Cheap but a must have if that type.

O tube must go and flush this out and start over. Perhaps see if compressor when turned will spit out any junk now or flush some mineral thru again and see if junk or what is in it? Run thru a coffee filter or something.

Other: Ask places like Autozone if you can rent (free for deposit) gauges and a pump as there's something not right about all that.

You do need an adaptor for high side OR if your gauges are for R-12 get the adaptors for 134a and the port adaptor for just the high side to temporarily leave on for looking, service or whatever. The adaptor to fit R-12 hoses can easily be the leak if left on.

There's just so much that isn't behaving for you I don't understand? I would be using a second set of gauges or another pump - anything to rule out why it's doing this to you doesn't make sense yet,

Tom

[rgnprof]

Tom,

You may have missed my second, follow-up post just a few minutes ago - my low pressure gauge was off, now the vacuum is down to where it should be 29+"...

Let me be clearer about this whole procedure:

I started this about 2 weeks ago - AC was empty, pulled orifice tube and it was all gunked up - clear to me that the old, original FX15 compressor had black died. Replaced everything at this point and started over - nitrogen pressure tested and then drew a good vacuum...started to recharge with R12 cans and this is when the new compressor/clutch locked up on me and the thing started smoking...shut it down almost immediately, pulled orifice tube and it looked ok. Bought a new compressor, added 3 ozs mineral oil to it - after flushing out all of the PAG oil - and that's where I'm at now...I didn't change anything else out this time. As stated above, I think I sorted out my vacuum and gauge issues and the system held 275psi nitrogen for hours, so I think I'm good - I hope!

[Tom Greenleaf]

I think I get it? So this had the nick named "Black Death" which is just a compressor that burned out. Next compressor you think locked up a clutch - IMO it hydro locked choking on refrigerant or something. Smoke was probably from it slipping at the clutch being new would be more likely to slip clutch than lock and have belt just squeal over it.

Suggests you jumped a LPCO to force in a charge of liquid which you can without system running into a vacuum then however you tap the cans of R-12 side or top with tool for those add final amounts with pierced spot UP.

That's history now. Now we need to know if compressor is OK or not. How long did it run and compressor engaged? When off it's just a pulley - nothing more - just unplug it at the clutch coil or the LPCO and it can't work.

If the bearings really melted that dang compressor was real junk - they make noises of a bad bearing or were totally messed up melted into shaft of compressor or something to go that wild. The air gap should be about .020 and hope you got a new clutch with compressor or not installing the used one properly who knows if any good easily.

OHMs just testing the two prongs should read about 4.5 or so for the coil just sitting there - everything off - not running engine or empowered anything by key even.

Now I need help from another here for ideas on knowing if this compressor is any good or not. Accumulator must go and yet another O tube after another flush if this ran any refrigerant thru it at all is was trashed.

Do you want to send part of this job out or try a claim on another compressor I don't know how to trust or could be just another replay of failing.

IDK of what quality control of compressors by any brand if rebuilt is and would always buy whole new when at all possible.

Other note on the small cans of R-12. Two types known to me were either 14oz or 12oz ones same things used for some air horns with same gas exactly.

Tapping those to get to gas never did seal and hold part cans for me for long. I drive an OE R-12 same system Ford product holds 44 oz of R-12 still all OE. Stinks for experience as it has never totally failed just on about a 3 year need for a boost and stored all off season not used in lousy weather even in Summer if I can help it.

I'd like another's opinion on how to approach this not just mine. If mine it would have a total flush, new compressor, hoses, accumulator and keep the condenser as long as possible especially if staying R-12,

Tom

[Tom Greenleaf]

Add this worth a look but not responsible for what comes off of YouTube at all - lots of mixed junk on A/C out there,

T

Click > https://www.youtube.com/watch?v=-yBRooMbIt0

[cornbinder89]

. Empty is empty so running it forever does nothing more. There's no water left at 24 Hg. really unless it was obnoxiously cold out which it isn't. I don't have the chart handy but water boils at some insane low temp under vacuum, then as vapor is removed.


Tom

According to my text book water doesn't boil until 100 deg F at 28" of vacuum. From there the boiling point drops as the vacuum approaches full. It is why it is important to have a good vacuum pump.