Show full size 924Board.org
Discussion Forum of 924.org
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
 Technical FAQ924 FAQ (Technical)   Technical924 Technical Section   Jump to 924.org924.org   Jump to PCA 924 Registry924 Registry

AC rebuild help

 
Post new topic   Reply to topic    924Board.org Forum Index -> General Discussions
View previous topic :: View next topic  
Author Message
ted von Kampen  



Joined: 14 Oct 2016
Posts: 121
Location: Scottsbluff, Nebraska

PostPosted: Mon Aug 12, 2019 9:37 am    Post subject: AC rebuild help Reply with quote

I have a 1981 Porsche 924 that I have been rebuilding over the course of the last 2 years and am nearing the end. The last major part has been to restore the Air conditioner. This car had AC and used a Denso 6P134 compressor and R12. One of the hoses that went from the compressor hi pressure end to the condenser was broken so it has been replaced. This system uses the expansion valve.

I tore down the compressor and found the inside parts to be in good order with no metal shaving or scoring or anything. I rebuilt the compressor using a kit for new seals, gaskets, etc. I thoroughly washed the old compressor out and found no metal, etc. I did have to get a new carbon shaft seal as I broke the old one. I had a 500page catalog from Santech that listed a lot of parts and an exploded view of the 6P134. I also flushed the lines, condensor and evaporator with the pressurized flush. I used 3 cans to do the job and it seemed to clean the old oil out. I also blew out the lines with compressed air. I Reassembled the compressor with new PAG36 oil. It calls for 6 oz of the oil so I put 4 oz in the compressor and the other 2 oz into the new accumulator. The whole system was reassembled, new "O" rings and all joints tightened. A Vacuum pump was put on the system and evacuated for several hours (6). I was then ready to start the system. I discovered that my AC relay under the dash was bad and I need to replace. However, to get the system loaded with freon I by passed the electrical switch on the evaporator fan and also made a bypass 12Volt circuit to the clutch. The system calls for 30oz of freon R12 but I am converting to R134a. The various articles I have read on the subject say to use 80% of the R 12 load to when using R134a. 80% is 24oz so that is 2 cans of the R134a. So while the vehicle was running I switch on the clutch and began to load the first can of R134a into the low pressure side. It loaded slowly and there was a High side -low side pressure differential noted. A little cold air did come out the vents. After getting the first can in, I went to load the second can and found that the second can would not load. THis means to me that the suction side of the compressor (low) is not sucking the freon in and no matter what I do the high & low sides read about the same on the gauges. I cycled the clutch a few times but it stayed the same. I let it set overnite and tried again today but still says the same. The freon is not leaking out that I can tell. It holds pressure okay although it has only been a day.

The above narrative is background for where I am now. I have a few questions.
1. what does it mean when the gauges are same (beyond the obvious)? is there something else that failed?
2. Did I screw up my compressor rebuild in this processed? It is possible that I did not do the rebuild correctly. I viewed a you-tube video on rebuilding the Denso 10P compressor and the notes on the video said the notes also applied to the 6P series.

I would appreciate comments from anybody that has gone through this process on the 924. I am getting another relay although as far as I can see it just controls the fans.

Thanks,
Ted
Back to top
View user's profile Send private message
austinporsche  



Joined: 26 Apr 2018
Posts: 42
Location: Austin, TX

PostPosted: Wed Aug 14, 2019 8:00 pm    Post subject: Reply with quote

Ted, a tough one as it started sucking refrigerant then stopped.

What was the "equal pressure" when the clutch was engaged and engine running?

If low (50psi or less) maybe it's a compressing issue and not a suction one.

Post the pressure reading when running and equal, and I'll to ask a friend who is an AC tech what that means.
Back to top
View user's profile Send private message
ted von Kampen  



Joined: 14 Oct 2016
Posts: 121
Location: Scottsbluff, Nebraska

PostPosted: Thu Aug 15, 2019 12:21 am    Post subject: AC problem Reply with quote

I will get the readings and get back to you. Right now it is shoved in the corner while I wait for the relay to come in. I am wondering if the Expansion valve isn't stuck open. I'll get the readings in a few days and let you know. I think I will order a new Expansion valve as they are not expensive. Remember this car sat for 17 yrs. The discharge hose was broken and off the compressor for that time. I replaced the hose and flushed the system but who knows a little dirt may have broke loose and the flush did not get it all. Have you replaced a Exp valve? It doesn't look too hard but getting to the valve is like anything else on this car. Everything is in the way.
Let you know pressures as soon as I get.
Thanks,
Ted
Back to top
View user's profile Send private message
austinporsche  



Joined: 26 Apr 2018
Posts: 42
Location: Austin, TX

PostPosted: Thu Aug 15, 2019 12:28 am    Post subject: Reply with quote

Haven't replaced an expansion valve myself, but take pictures to share. Do you get at it thru the blower hole in the engine compartment (easy?) or thru thru the dash (harder?).

I am guessing that if the readings are low (<50psi?), the valve is stuck open, if high (>50) then stuck closed.

The condenser+valve is what creates the 150psi+ pressure differential between the high and low side, so sounds like you're on the right track.

Post those gauge readings anyhow.

AC is such black magic.
Back to top
View user's profile Send private message
ted von Kampen  



Joined: 14 Oct 2016
Posts: 121
Location: Scottsbluff, Nebraska

PostPosted: Thu Aug 15, 2019 12:33 am    Post subject: AC rebuild problem Reply with quote

Unfortunately it is under the dash. Of course the manual does not cover well. It will be hard to get to.

You are right it is black magic. I have redone a couple on newer camaro's but that is in the engine compartment. I think I like the Orifice tube type better.
I will post the reading when I can
Thanks

Ted
Back to top
View user's profile Send private message
austinporsche  



Joined: 26 Apr 2018
Posts: 42
Location: Austin, TX

PostPosted: Thu Aug 15, 2019 12:40 am    Post subject: Reply with quote

Good luck. I am so glad I didn't have to go there with my AC renewal . . . .
Back to top
View user's profile Send private message
ted von Kampen  



Joined: 14 Oct 2016
Posts: 121
Location: Scottsbluff, Nebraska

PostPosted: Wed Aug 21, 2019 6:07 am    Post subject: 924 AC rebuild Reply with quote

Well Bill the saga continues. I got the new Exp valve in and guess what it is not the correct valve. The various vendors catalog and on-line ordering guides show what is needed. All the parts are what is called an external equalizing valve system. There is a separate copper line that is supposed to attach up the low pressure line. After I got the AC unit out I determined that the exp valve I have is called an internal equalizing valve. The parts books do not show it but that's what I have. So I returned the wrong one. I went to the NAPA store and a guy did some research within their system and determined that indeed there is another internal valve that matches. NAPA said their system only shows 2 units in the country. He also gave me the 4 seasons PN. So I went back to my original vendor and he had 12 of them. I hope this fits. Price is a little less than NAPA. If this one doesn't work then I will have to go back to NAPA. What surprised me was that my old valve was rated at 2 tons while the one I ordered only is rated at 1.5 tons. Apparently no one makes the 2 ton version in that package anymore. So we shall see. Surprised that system is that big a rating.

I could not get a pressure reading on the system before I tore into it so will have to see if this solves the problem. I did locate another R12 Denso 6P134 compressor in Omaha. I am going to purchase that plus all the lines. I will pickup next month when I go down there. I wonder if you can flush the old oil out of this one without teardown. I think you told me that a POG (?) oil will mix with both systems.

Let you know how this turns out. Soon be time to put this thing away.

Oh yes, you or someone on the forum was asking about removing the old Expansion valve. You cannot do this from inside. No room for wrenches. I ended up pulling the entire AC box to get it apart. I think I can reassemble and put in whole now that I know what is going on.
Regards,
Ted
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    924Board.org Forum Index -> General Discussions All times are GMT + 10 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group