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Porsche 944 with complete but not working AC

JEL on Wed July 24, 2013 12:38 PM User is offline

Year: 1985
Make: Porsche
Model: 944
Engine Size: 2.5
Refrigerant Type: R12
Ambient Temp: 90
Pressure Low: 0
Pressure High: 0
Country of Origin: United States

Greetings.

I have been off the forum for a while, as all my AC efforts from the past are working great thanks to the help I received from this forum.

Being a glutton for punishment, I recently acquired a 944 from my brother in law. The car has factory AC and uses R12. I am told the AC "doesn't work" which is true. The question is: why is it not working? I have no background info to work with so I have to start from scratch.

So my question to the group: how should I proceed? What testing should I do and in what sequence? I believe it would be best to leave this car with R12 if possible.

Thanks!
Jim

Cussboy on Wed July 24, 2013 2:50 PM User is offline

I agree to keep it R-12, available and legal to use.

First thing is find out why it's not working. I assume that it blows air, but not cold (if doesn't blow, then electrical issue). Second likely is out of refrigerant, would be to add some refrigerant (even R134a for test purposes) and find where the system is leaking and correct the leak.

webbch on Wed July 24, 2013 6:08 PM User is offlineView users profile

I use 134a all the time for leak testing r-12 systems...just make sure you don't run the compressor while the 134a is in there. A small amount of 134a, then pressurize the rest (I go to about 100 psi, 120 max) with nitrogen.

If you use an electronic leak detector, be aware that brake cleaner or similar items you may have used to clean off connections, etc will set it off for at least several days.

wptski on Wed July 24, 2013 6:55 PM User is offline

Quote
Originally posted by: webbch
I use 134a all the time for leak testing r-12 systems...just make sure you don't run the compressor while the 134a is in there. A small amount of 134a, then pressurize the rest (I go to about 100 psi, 120 max) with nitrogen.

If you use an electronic leak detector, be aware that brake cleaner or similar items you may have used to clean off connections, etc will set it off for at least several days.
Exactly what do you with the R134A/nitrogen mix after your pressure test?


Edited: Wed July 24, 2013 at 6:55 PM by wptski

JEL on Thu July 25, 2013 2:33 PM User is offline

Wondering if pressurizing a bit with nitrogen then lathering up with big blue might be useful? Where might a DIY'er like me acquire a nitrogen source?

webbch on Thu July 25, 2013 2:52 PM User is offlineView users profile

During the pressure test, you put in just a trace amount of 134a (like 1/2 oz or less) for the leak detector to pick up. The vast majority of what's in there is nitrogen.

Yes, lathering up with big blue should help as well.

I picked up a nitrogen tank from the local welding supply where you trade in your oxygen or acetylene tanks. I expect it'll last me the rest of my life. Need a regulator for it as well of course.

Edited: Thu July 25, 2013 at 2:53 PM by webbch

JEL on Fri November 08, 2013 12:39 PM User is offline

A little confused about the compatibility of mineral oil and PAG when upgrading to R-134A. I read this official document from Porsche on how to proceed:

http://www.944time.com/porsche/2005images/944_ac.pdf

If I am reading correctly, the procedure is to remove at least half of the old oil that is in the system, than adding the Denso equivalent of PAG 46. This makes it sound to me as though it is not the worst thing in the world to have residual mineral oil in the system.

Looking forward to hearing from these wise ranks.

Thanks,
Jim

Dougflas on Fri November 08, 2013 6:21 PM User is offline

For leak testing, use a trace of R134a and N2. Use about 100psi of pressure. After you find the leak, just vent the mixture. Recharge with r12 for best results. If you decide to usde R134a, you'll need to get almost all of the mineral oil out, flushing properly with the proper equipment is important. Then use Bava 100 oil. I would keep this vehicle R12 if at all possible.

wptski on Fri November 08, 2013 9:40 PM User is offline

Don't want to highjack this thread but when N2 is mentioned for pressure testing, I have to think about it would cost for a tank(whatever size) and a regulator, etc. for use.

HECAT on Sat November 09, 2013 3:29 PM User is offline

Small tanks of N2 are cheap from your local gas supply house; and an Oxygen regulator is cheaper than an N2 regulator, which works just fine for this type work.

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HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 

wptski on Sun November 10, 2013 8:32 PM User is offline

Quote
Originally posted by: HECAT
Small tanks of N2 are cheap from your local gas supply house; and an Oxygen regulator is cheaper than an N2 regulator, which works just fine for this type work.
Good as long this isn't a item that only sold wholesale.

TRB on Mon November 11, 2013 10:05 AM User is offlineView users profile

Quote
Originally posted by: wptski
Quote
Originally posted by: HECAT
Small tanks of N2 are cheap from your local gas supply house; and an Oxygen regulator is cheaper than an N2 regulator, which works just fine for this type work.

Good as long this isn't a item that only sold wholesale.

All Hecat products can be purchased via the www.ackits.com website.




-------------------------
When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

wptski on Mon November 11, 2013 1:03 PM User is offline

Quote
Originally posted by: TRB
Quote
Originally posted by: wptski
Quote

Originally posted by: HECAT

Small tanks of N2 are cheap from your local gas supply house; and an Oxygen regulator is cheaper than an N2 regulator, which works just fine for this type work.

Good as long this isn't a item that only sold wholesale.

All Hecat products can be purchased via the www.ackits.com website.

I was asking about purchasing nitrogen and tanks for purging not flushing equipment. I know that Johnstone Supply doesn't do retail. There is a Airgas location nearby but I don't know if they do retail.



Edited: Mon November 11, 2013 at 1:04 PM by wptski

Dougflas on Mon November 11, 2013 1:17 PM User is offline

Airgas does retail.

wptski on Mon November 11, 2013 1:21 PM User is offline

TRB stated that small tanks of N2 are cheap. Not sure what he calls cheap? I just looked up empty nitrogen tanks, a 40cf was just under $200 plus you need a regulator on top of that.

Scratch on Mon November 11, 2013 1:30 PM User is offline

When I decided to pressure test my A/C with nitrogen gas, I checked Craigslist for a tank. A 125 cu. ft. tank with a DruVa regulator was on sale for $80. I exchanged the empty tank for a full tank at Airgas. It cost me $30 plus tax and fees.

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scott johnson

TRB on Mon November 11, 2013 1:52 PM User is offlineView users profile

They are cheap in the overall picture.

-------------------------

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

wptski on Mon November 11, 2013 2:20 PM User is offline

Quote
Originally posted by: TRB
They are cheap in the overall picture.
Being a DIY'r I have to consider the amount of usage I'll get out of it.

There is one on CL, looks like a 40cf, half full, regulator with missing lenses but claims it still works for $110.

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