Another inop AC

[Coastr]

While many are investigating inop heater boxes and other associated cold weather problems, I finally started looking at the inop AC which I have been putting off for quite some time.

First things:
- Vehicle 1981 911 SC, factory air
- all pieces in place
- PO removed York compressor and replaced with rotary compressor of Volvo origin (York came with car in a box of spare parts)
- Cabin fan blower works without problem
- R12 system (R12 is technically illegal here [Australia], but i'll work around that)

First check, static pressures:



Low side : around 10 psi
High side : barely registering- call it 5 psi

Ambient temp 27 Celsius

Second Check ; engine idle



Low side : no change
High side : call it 10 psi

Revving engine to ~2000 rpm makes no difference to high side pressure.

Third check : vent temp


Essentially no change : cabin ambient was 25/26 Celsius

Fourth Check : Compressor clutch function



Compressor is activated when AC switch is turned on.

Finally, for laughs, I attached the gauges to the DD just to make sure the gauges were working as expected:



That's a static check of R134 in the same garage on a car with working AC.

Conclusions/Questions

• Obviously the gas is low
• Can any conclusions about the compressor be made with the gas so low?
• Is there any risk in having run the compressor with gas so low?
• Is next logical step is getting gas topped up and see where we are at?

My aim is to get factory AC working and assess from there on the need for upgrades.

[DaveMcKenz]

Gas is low. You have leakage. Do not run compressor with low gas, as that equal poor compressor lubrication. You need to do a leak test. Not sure I'd do it with R12, but I don't use R12 myself, so others may advise. Many times the problem is just a bad Shrader valve. I have never really been that lucky. Could also be slow, gradual, chronic leakage through old hoses.
Good luck,
Dave

[wwest]

I suggest having a certified A/C shop convert your system to R-134a, not only fully legal, but actually more efficient provided you somehow limit the high side extreme pressure excursions that are more likely to happen with R-134a vs R-12

Here in the US the EPA recommends the use of a binary pressure switch both to prevent inadvertent pressures beyond the factory design specifications and protect the compressor. I would suggest going one step farther and install a trinary at the same cost with an additional function.

I would also be sure and have the shop install a new receiver/drier.

The fact that you have no R-12 left in the system might be pretty much SOP according to the notes in my '88 Carrera owners manual.

[wwest]

Originally Posted by Coastr

While many are investigating inop heater boxes and other associated cold weather problems, I finally started looking at the inop AC which I have been putting off for quite some time.

First things:
- Vehicle 1981 911 SC, factory air
- all pieces in place
- PO removed York compressor and replaced with rotary compressor of Volvo origin (York came with car in a box of spare parts)
- Cabin fan blower works without problem
- R12 system (R12 is technically illegal here [Australia], but i'll work around that)

First check, static pressures:



Low side : around 10 psi
High side : barely registering- call it 5 psi

Ambient temp 27 Celsius

Second Check ; engine idle



Low side : no change
High side : call it 10 psi

Revving engine to ~2000 rpm makes no difference to high side pressure.

Third check : vent temp


Essentially no change : cabin ambient was 25/26 Celsius

Fourth Check : Compressor clutch function



Compressor is activated when AC switch is turned on.

Finally, for laughs, I attached the gauges to the DD just to make sure the gauges were working as expected:



That's a static check of R134 in the same garage on a car with working AC.

Conclusions/Questions

• Obviously the gas is low
• Can any conclusions about the compressor be made with the gas so low?
  
  Not really.
  
• Is there any risk in having run the compressor with gas so low?
  
  Yes, don't do that anymore.
  
• Is next logical step is getting gas topped up and see where we are at?
  
  No, see post.

My aim is to get factory AC working and assess from there on the need for upgrades.

[wwest]

Looks as if you have a Seltec/Valeo TM-16 Compressor with a 5590 bolt-on manifold, most likely out of a Volvo TRUCK... 40,000 BTU capacity.

[kuehl]

Originally Posted by DaveMcKenz

Do NOT run compressor with low gas.
Dave

Best tip so far, thank you Dave

[DaveMcKenz]

Originally Posted by kuehl

Best tip so far, thank you Dave

Hi Griff,
I don't know 5% of what you know. But I do know that.
Thanks,
Dave

[Jack Stands]

Has anyone had any experience with other refrigerants like Duracool? I was told that they are a direct replacement for the R12 and works better than R134, but the legality may be a question in various areas.

[Bob Kontak]

Originally Posted by Coastr

- R12 system (R12 is technically illegal here [Australia], but i'll work around that)

If you follow the rules, it's probably technically legal in Australia, but finding the certified tech that bothers with it will be a chore.

Mind you, I state this from a quick Google search.

[DaveMcKenz]

Finding a USA shop that will service anything but R12 and R134 is pretty difficult. If you do it all yourself, less of a problem. It may not be completely legal, but hard to trace.
Dave

[kuehl]

Jack Stands,

Good Question.

Well, here in the US, you got have the EPA Regulations which briefly discuss what you can use or cannot, depending upon where you are using it, what they call SNAP Regulations:
"unacceptable, acceptable to use conditions, and acceptable subject to narrowed use limits".

Just read this http://epa.gov/ozone/snap/refrigerants/lists/mvacs.html "Substitutes Acceptable Subject to Use Conditions for CFC-12 in Automobiles", this is the list you want to check an alternative refrigerant (meaning the car had R12 and you want to explore something else).

No matter what you do, document what you have in there and do it right! Meaning, if you put in something other than R12, there should be a label clearly seen near where the AC is serviced (engine compartment by compressor) so that when somebody else works on the car..... they know what's in there; otherwise you will get them very upset.

To answer your question on Duracool http://www.epa.gov/ozone/snap/refrigerants/hc-12a.html

[Coastr]

Originally Posted by Bob Kontak

If you follow the rules, it's probably technically legal in Australia, but finding the certified tech that bothers with it will be a chore.

Mind you, I state this from a quick Google search.

Yes, this is a major problem but I have some leads.

I will not be converting to r134. We had a carbon tax for a brief period. During this period r134 was taxed to the hilt (saving the planet, one ac recharge at a time). Filling up a normal car cost about $150 in gas alone. You also cannot buy it over the counter like you can in the US. I fear the tax may come back. I will be looking at alternatives.

As for running the compressor ... Are we saying never run it, or try and avoid running it?

[kuehl]

The issue with running a compressor with a system low on refrigerant is..... you can prematurely wear out the compressor and potentially contaminate the entire system with debris (metal particles), the later can be quite expensive to repair. Hence.... avoid running the compressor in this scenario by NOT running the compressor; there is nothing to gain. So, unplug the compressor clutch wire until you fix things.

On AC in your country:
AUSTRALIAN REFRIGERATION COUNCIL Ltd Fact Sheets

[Coastr]

Yep thanks for that. So I need someone accredited to recover the remaining r12. I don't need accreditation for refilling with alternative (hydrocarbon) refrigerants, and these are perfectly legal for use in road vehicles.

I am wondering how much is actually left in the system with pressures so low.

[kuehl]

Based on your gauge readings and temperature of 27c, probably a handful of ounces at best, and some of it could be air. I'd say if you have a farm down the road, the pigs would release more hydrocarbons and C02 damage than your entire system.

I would avoid tabloids Calls-for-ban-on-hydrocarbon-retrofits/

[DaveMcKenz]

Originally Posted by Coastr

Yep thanks for that. So I need someone accredited to recover the remaining r12. I don't need accreditation for refilling with alternative (hydrocarbon) refrigerants, and these are perfectly legal for use in road vehicles.

I am wondering how much is actually left in the system with pressures so low.

I would vent the gas to atmosphere, based on your pressure. However that in itself does not really get you anywhere. You will need to fill it with something, to find leaks. When you find a leak, you will then have enough gas that you actually will need to recover it properly and then fix the leak.
Good luck,
Dave

[Coastr]

Originally Posted by DaveMcKenz

I would vent the gas to atmosphere, based on your pressure. However that in itself does not really get you anywhere. You will need to fill it with something, to find leaks. When you find a leak, you will then have enough gas that you actually will need to recover it properly and then fix the leak.
Good luck,
Dave

Noted.

I'm thinking about getting my own vac pump. For around $150, that's how much an ac tech would charge to get involved. I'm sure I'd find more uses for one down the track. I should be able to tell if it's got leaks by ability to hold vacuum? I've been reading on the use if nitrogen to find leaks...seems straightforward. Doesn't help with detection if there are any, though.

[Coastr]

Originally Posted by kuehl

Based on your gauge readings and temperature of 27c, probably a handful of ounces at best, and some of it could be air. I'd say if you have a farm down the road, the pigs would release more hydrocarbons and C02 damage than your entire system.

I would avoid tabloids Calls-for-ban-on-hydrocarbon-retrofits/

Yes, I hear you loud and clear.

I'm not the slightest bit concerned about the FUD around hydrocarbons.

[wwest]

Believe it or no, Porsche designed your system knowing the result would mean a slow leakage of the R-12 refrigerant. The owners manual for my '88, as likely does yours, states so in no uncertain terms.

It appears, according to the engineering technical white papers available from quite reputable sources, that "curing" the A/C hoses with the previous use of r-12 will actually prevent R-134a refrigerant from leaking.

So you may not be looking for an actual leakage fault as it is highly likely that the R-12 charge was lost by design.

[wwest]

Paragraph on hoses and O-rings.

Guidance on Retrofitting to HFC-134a | Ozone Layer Protection - Regulatory Programs | US EPA

More complete EPA article.

http://www.epatest.com/609/manual/609_section4.html