Greetings. I think my AC system is possessed and I am looking for a sanity check on my troubleshooting process.

When I bought my 7 a few years back the ac did not work, it didn't hold pressure or vacuum, etc. Last year I went through the entire system (including whats behind the dash) and installed new o-rings (used AC nylog), a new expansion valve, new compressor, new pressure switch, etc. Tested the system pretty extensively under vacuum and using ES-12 + dye to verify it didn't have any leaks before having it charged with R12 + dye. That was about this time last year.

For reasons (its a long and ongoing story) I won't get into here, I haven't had the car much since September 2019. I finally got it back from a shop pretty recently and I noticed the other day that the AC wasn't cooling. Looked in the engine bay and the compressor wasn't kicking on. These are the steps I have taken

1. Jumped the pressure switch momentarily just to verify if the compressor was working and getting the on signal from the ECU. The compressor functioned fine
2. Hooked up AC gauges to both pressure ports, pressure on both lines was zero.
3. Checked all the connections with a UV light and found no trace of a leak (only connector I can't get to with the light is the expansion valve)
4. Scratched my head and hooked up a vacuum pump, pulled hard vacuum on the system.
5. System has held the hard vacuum for several days now.

I am scratching my head at this point. Can anyone give advice on what else I should check? At this point I am really wondering if someone just vented the system at some point. The only next step I can think of is to charge it again with ES12 + dye and see what happens.

It seems like if there was a leak, it should have reared its head already, but I am not an AC guru. Appreciate any second opinions so I am not chasing shadows.

Finally, mostly unrelated question. Should this AC line go over or under the bar that runs through the engine bay? I had it installed as pictured below, but the shop seems to have tried to run it under the cross bar instead, and it doesn't looks quite right to me.

 

Not that this is for sure your issue, but o-rings can hold pressure/vacuum in one direction, and not in the other. So the fact that it held vacuum does not necessarily mean it would hold pressure.

 

Totally agree. I just figured I would see the UV dye light up on the leak at least. I still have a few cans of the ES-12 stuff and some dye so I guess the only thing to do is to charge the system up and see if any dye stains start to show up.

 

^The part above in bold italics is your clue - there was little to no refrigerant in the system when you tested it. Even if it was very low on charge, and with the compressor not running, you should see at least SOME static pressure in the system. The other clue was there wasn't enough pressure in the system to activate the pressure switch. Since it's holding a vacuum overnight, my best guess is one or both of the service valves is leaky - and if they are, you wouldn't see it with the gauges hooked up. To find the leak, you'll need to evacuate & charge the system with the dye, and hunt for the leak with the A/C running.

 

Ah! I didn't even think about that. I pressurized it with ES-12 and still couldn't find any signs of a leak but of course I still have the gauges attached to monitor the pressures. I didn't see any dye there initially, but this charge had new dye so I will keep a very close eye on that. I did replace the schrader valves during the initial overhaul but I suppose it isn't crazy that maybe I didn't get them in there good enough.

 

Sure enough, it looks like the low side valve had a very small leak going on. Put a new valve in and I don't see the little bubbles anymore. Hopefully that's all it was, didn't see anything getting passed the high side valve.

 

Yep, when I started reading I immediately suspected the service ports. They are common to leak, especially since they are on the hot side of the engine bay.

There's not a lot of refrigerant in the system so a small leak can easily dump all the refrigerant in a few months.

I got some spray called Big Blu a while back that's for finding AC leaks. Even the tiniest leak bubbles like crazy when you spray it on the spot to test, it's like soapy water on steroids.

Dale

 

Oh cool. Definitely going to grab some of that stuff to keep around so I can keep an eye on the new valve. Hopefully it behaves, not sure what else to do if the new one starts leaking too. Might have to replace the actual port fitting in that case, I guess.

 

Just for an update, the new valve and new service port caps seemed to address the slow leak.

Unfortunately my fairly "new" (rebuilt) compressor started getting noisy and doing some funky stuff so I decided to swap it out before it self destructed. It was one of the 5 rib compressors that bolt to the FD (I had just swapped the original 6 rib pulley + clutch to it). I remember noticing some stuff with it when I originally installed it last year and have always been a little suspicious, but due to a lot of different reasons unfortunately I never acted on that instinct and I am sure it is out of warranty with 4Seasons at this point.

A bummer, but it is what it is. I got a "new" (supposedly not a rebuild) unit from a parts distributor in my area. It is identical to the original denso unit, but does not have the denso sticker on the back (it does have the recessed space where the sticker should be) for ~$350. Put a few ozs of oil in it and rotated it by hand to make sure it's distributed then installed it. I also put a new drier in, and replaced all 4 o-rings (2 for the drier, 2 for the compressor).

At that point I pulled vacuum and charged with 1-2 oz of enviro-safes oil charge, and a partial can of ES12 Industrial (charged as a liquid per their instructions). When I turned the car on, the compressor engaged and didn't make any of the racket the old one was making. The system did cool, but not as good as it should (~68 out of the vents at idle, ~60 at 1000 rpm). One thing that surprised me, is that the system wouldn't take even the entire first can of ES12, the low pressure line was ~40 just with the initial partial charge I did before kicking the car/compressor on.

The pressures read ~40 low side at idle and ~125 high side at idle. At "elevated" RPM (lets say 1200-1500) the low pressure side did drop to around 30, and the high side did elevate to around 150 (as best I can tell, its tough to read the gauges from inside the car and also watch the tach) so it seems like the compressor is functioning.

With my limited knowledge, this doesn't seem like an obstruction in the system or anything like that and I want to give the new compressor the benefit of the doubt for now. So my assumption is either 1.) the system was overcharged with oil when the old compressor was installed, and is still overcharged, or 2.) I didn't run the vacuum long enough (I did 30-45 minutes, down all the way to 30 on my gauge) and did not get all the moisture out of the lines. Leading to not enough refrigerant being in the system despite the pressures looking right (except the high side seemed a bit low based on ambient temperature ~94F)

For additional context I did install a new denso expansion valve last year, as well as new o-rings on all system connections.

I evacuated the system again last night (which removed some amount of oil), and I am leaving the vacuum pump running all day to make sure any moisture is pulled out (I did notice last night that after pulling vacuum for around an hour, it would rise from 30 to 20 after several hours passed and stopped, so it seems like moisture was still in there and boiling off, checked with UV and the system didn't leak under pressure so not sure why it would leak under vacuum). Will charge the system again after that, and see if it pulls the entire ES12 can in.

From what I have read, 6 oz of ES 12 should equal ~18 oz of R12. My denso system is labelled as a little over 21oz R12, so it should be taking the first can and then some.

If all that fails and the system still won't take in enough refrigerant, I guess I will need to look into the new compressor and/or a full oil flush. Not necessarily any questions at this point, but just wanted to collect my thoughts/process in case its helpful to someone else, or I unknowingly did something really stupid.

 

I know a lot of people have had problems with the ES-12. Have you considered doing R-152a (Dust-off)?

6 ounces seems VERY low.

Dale

 

Hey Dale,

Mostly using ES12 industrial to test since I have a bunch of it around and its fairly cheap/easy to charge. As you said, not sure its something I would use long term. If I was getting 55-60 out of the vents with the ES12 I would call it a day and charge it with 12 or 152A. What I have noticed in the past is that ES12 tends to fall about 10 degrees short of the other two.

But right now something seems off and I think I would have the same issue with 152A. My only beef with 152a is a stupid one, but its the clamp on side taps. The last time I messed with it they were always very leaky, and eventually the plastic handles would snap. Maybe just crappy amazon side taps? I'm not sure, but without a better way to tap the can I would have trouble charging it without an extra set of hands.

 

May just need to buy another side can tap. Those taps are a little iffy on good days though.

A proper R12 charge in a properly working FD will put 34 degree air out of the vents. That's how it should be operating. 55-60 degree air is nowhere near enough to cool down a hot car, especially in Texas.

Here is the MASSIVE thread on R-152a in the FC forum, really good read -

https://www.rx7club.com/2nd-generati...gerant-964688/

I would just try going to it, it's cheap and readily available at Office Depot.

Dale

 

The best I ever got with R12 was 45 during the heat of the summer here, but that was with the old compressor which may have had issues. ES would get around 55, and 152A was similar to 12 at the vents. That's the reason I wouldn't really use ES for anything besides testing, but I think if it doesn't cool "correctly" with ES and isn't taking the proper charge, it will have that problem regardless so I have to solve that first.

I plan to charge it with 152 or 12 once I am confident the system has no leaks, and will hold the correct amount of refrigerant. I have read most of the various threads on 152a, ES12, etc and I agree with the facts in them. My experience is that ES just can't transfer enough heat in this kind of climate compared to the other two.

 

ES 12 is absolute garbage unless you live somewhere that doesn't actually need AC. Here in the south (and definitely TX!) you might as well charge it with compressed farts.

I spent way too much time researching how to get that **** to work just to find out the distributors/manufacturers don't even know and can't keep their story straight as to how to charge. That 2nd gen thread is spot on.

Just put in a new dryer, new schraders, ditch the R134 conversion ports, pull a vacuum on it, and (IMO) throw whatever freon is compatible with your oil and be done.

You need to be careful about what oil you have vs what refrigerant you use. The Envirosafe oil doesn't even say what is in it... is it mineral, ester, pag, double capped pag?

I refilled my system with mineral like it was designed to run so I was married to R12. The BG frigiquiet double capped pag is awesome stuff if you are in the market.

 

Agreed. I find it useful just for troubleshooting/pressure testing and making sure everything is good to go. It is cheap, and it is easy to charge/discharge. The performance has never been there with it for me to want to use it as my actual refrigerant.

Regarding the oil, I use/used ester for the original AC work last year, so it should be compatible with most things I think. The reason I used ester is that the AC system didn't work when I bought the car, but it did have the 134A adapters so I was not sure what the last oil in the system was. I didn't get much of anything out when I flushed the lines at the time, but I played it safe with ester anyways. It was probably a little dumb to use the ES oil charge this time since you are correct that they don't really say what it is. Since they say it is only compatible with mineral, ester, or pag oils I would assume it is some type of ester oil as well.

I think the denso compressor calls for ND-# (forget the exact number) and not straight mineral oil, but I never looked into it much so I might be talking out my butt on that one.

If I have to do another full system flush or remove the compressor again while chasing this down, I will definitely look into that oil you recommended. Hoping my main problem was not getting all the moisture out and I can move forward with getting this done. Fingers crossed I didn't just get another bad compressor.

 

Another update.

After pulling vacuum all day today, it was holding better vacuum numbers but still appeared to have some moisture in the system. I went ahead and charged again and this time it took the whole can (6 oz, supposed to equal 18 oz of R12). Still not the right amount, but probably at least twice what it would take into the system last time. I wasn't getting the correct AC performance, but it was much improved and more in line with the ES12 performance I am familiar with. ~60F at 600 rpm, ~50f at 1000 rpm, ~40-45F at 1800 rpm

I think I am on the correct path, and will continue trying to work the moisture out of the system as best I can. Once it seems good, I will put another new drier in and charge it with a good refrigerant.

 

Don't know if this applies to you, but one other procedural step lots of guys forget to do when charging an A/C system is bleeding the air out of all the manifold lines before charging. This extra step ensures that no moisture laden air gets mixed in with the refrigerant when you charge it. Any air/moisture introduced into the system when charging can cause the kind of problems you're seeing.

 

My yellow line has a shutoff valve to hold gas/vacuum, and my gauges have the little schrader valve to purge the fill line as well. I use both just to be on the safe side.

Myself included, I think everyone has made that mistake at least once though.