North American Turbocoupe Organization



HR980 compressor (and general a/c) questions
anasazi4st Offline
Senior Member
#1
I'm in the midst of converting my a/c from R-12 to R-134a. I have read and studied Matt St. Denis' how-to article found here, as well as the Haynes and Ford shop manuals. I've also combed through pages on the Internet.

The HR980 compressor locked up on the way to Tucson, AZ (about 100 miles away) in early June 2014. Needless to say, driving in the desert in the summer without a/c is really not acceptable, but so is working on the car in the heat...so I put it off until Thanksgiving.

Here's what's going on: I rounded up all the parts, tools and supplies I thought I would need (including manifold gauges, air compressor, vacuum pump). Replaced accumulator, liquid line (with orifice tube), and found a used compressor on eBay that was local (!!) and that I was able to examine and do some testing on before I bought it. Flushed out all the other parts, added POE oil and new green o-rings, bolted up and attached the compressor. I vacuumed the system down to around 29" Hg for 2 hours, after 1 hour it held steady--after 12 hours it had lost about 1 inch.

Started the recharge process...it took hours to get the first can of R-134a into the system (engine off), even while heating the freon can upside-down in a warm water bath. (The can was connected to the low side by the accumulator.) It was about 65 F that day in the shade...after about 7 hours I gave up, shut off the gauges and came back the next day.

Next day I got the second can started, decided to fire up the a/c (started the car). Closed the high side manifold valve, jumpered the clutch cycling switch connector wires so the clutch engaged, upped the RPMs to about 2000. It seemed to work, but sloooowwwwwlllly. The compressor was making that dull sound and the vibration that it makes when it's operating...but after a while I noticed it had stopped that. I disconnected the jumper wire, and the gauge readings did not change--about 120 on the low side, about 150 on the high side. Stopped and closed everything up to end the day.

Came back the next day, discovered I had lost all the (admittedly small) amount of freon I had gotten in there...removed the compressor. Attached high- and low-pressure lines to it, vacuumed just the compressor down to about 28 Hg for two hours--it held for an hour, then overnight.

Turning the compressor shaft by hand, I can feel good suction on the center port, and good air discharge on the exhaust port.

My questions are: Does it normally take this long to recharge the system? And, despite its apparent failure during this process, is the compressor at fault, or could something else be the culprit? There are no strange sounds or vibrations coming from it...it seems to be okay and I would trust it--except for that one occurrence.

Thanks in advance for your help.
Another proud dues-paying member.

1987 Turbo Coupe w/T5OD, 8.8 axle, grey smoke; most options. Got it in 1991 with 41K miles: 3 turbos, 2 heater cores, 1 T5OD full rebuild, 5 clutches, 1 head gasket, 2 Teves II ABS units, etc. later....
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TurboCoupe50 Offline
Posting Freak
#2
You'll not have much luck charging a non operating system, the compressor must be turning... Sure you can get a small amount into it from the vacuum in the system but the refrigerant expands almost immediately so pressure in system and can will soon be equal... With compressor operating, low side will be much less(in the 30-35psi range) than can so system will readily accept the charge...

A high low side pressure generally indicates a restriction or weak compressor(especially if H & L are close in pressure)...
1988 Turbo Coupe331 AOD

1972 Comet GT

1969 Fairlane Cobra 428CJ 4-Speed
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anasazi4st Offline
Senior Member
#3
TurboCoupe50 Wrote:You'll not have much luck charging a non operating system, the compressor must be turning... Sure you can get a small amount into it from the vacuum in the system but the refrigerant expands almost immediately so pressure in system and can will soon be equal...
That's pretty much exactly what I thought. Still, the article suggested that you could get the first can in without the compressor running.

TurboCoupe50 Wrote:With compressor operating, low side will be much less(in the 30-35psi range) than can so system will readily accept the charge...
That explains much. Nothing I read mentioned the low side being that high.

TurboCoupe50 Wrote:A high low side pressure generally indicates a restriction or weak compressor(especially if H & L are close in pressure)...
So, is there a way to test the compressor short of hooking it back up and trying it out?

A few years ago I had a guy I worked with and his brother recharge the system with some R-12 I had purchased in the early 00s. I didn't have the tools or the incination to attempt the R-134a conversion myself, although I had been thinking about it since 2003, when I last replaced the compressor. It only took a few hours--the brother worked for an auto a/c garage--and it cost me the agreed-upon standard unit of measure for off-the-clock auto repair work, which was a case of beer. The co-worker has since moved to Colorado, and I've lost touch with the brother, else I'd just have them do the work.
Another proud dues-paying member.

1987 Turbo Coupe w/T5OD, 8.8 axle, grey smoke; most options. Got it in 1991 with 41K miles: 3 turbos, 2 heater cores, 1 T5OD full rebuild, 5 clutches, 1 head gasket, 2 Teves II ABS units, etc. later....
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anasazi4st Offline
Senior Member
#4
Here's an update on the HR980 question I posted before.

As it turns out, the interior valve portion of the R-134a Low Pressure Schrader Valve Adapter that I got from NAPA had become bent somehow during installation. This effectively prevented the refrigerant from entering the system. While I was able to get one can in (and that took literally hours), I was stuck there, even with the compressor running.

I discovered this after I had purchased another compressor and installed it, only to have the same problem. After poking around a bit here and there I tried to release the low pressure valve to test it, and it wouldn't budge. I removed it and saw that it was badly bent, so I replaced it with a spare from an old hose.

I started to recharge the system...but while disconnecting the High Pressure line from its connector (as a safety precaution), the entire line somehow pulled loose from the suction fitting--obviously despite my best effort it wasn't fully connected. I lost the quarter can of refrigerant that I had already put in...but there was also the minty smell and all this foamy liquid, which I recognized as the flushing liquid I used to clean out the evaporator and condenser. Obviously I had not gotten all of it out despite using lots of compressed air.

I finished recharging the system, got the vent air temp down to 41 degrees. But later on it occurred to me that I had never really vacuumed the low side, as the valve was restricted...so I had a friend recover the R-134a I'd already put in, and I hooked up the vacuum pump. Lots of smoke (water vapor) poured out of its air vent and it made some different-sounding noises, but several hours later I had a fully-cleaned-out system. I recharged it from cans (I had no way to filter the recovered refrigerant) and this time got it down to 38 degrees!

So this means that the first compressor is probably okay, which is great news!
Another proud dues-paying member.

1987 Turbo Coupe w/T5OD, 8.8 axle, grey smoke; most options. Got it in 1991 with 41K miles: 3 turbos, 2 heater cores, 1 T5OD full rebuild, 5 clutches, 1 head gasket, 2 Teves II ABS units, etc. later....
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