robertw

Long story short, I drove my 1989 928 from Portland Oregon to the Santa Ynez valley to live at our new vacation home. On the drive down, the compressor decided to self destruct (bearing froze, cracked housing). I took the car to a local German car specialist and they replaced the compressor and I asked them to convert to R134a. That was probably my biggest mistake! Should have stuck with R12.

I returned the car twice due to leaks, the second time they bypassed the rear air since the sniffer detected a leak in that area. At least the A/C worked for about a month until the freon leaked out.

I don't know what to do. Do any area members recommend an A/C shop that can permanently correct this problem? I would love to drive the car around the Santa Ynez valley and Santa Barbara, but its starting to get pretty hot now during the day. I've thought of getting a recharge kit myself to get by, but maybe thats not a good idea either.

sstrickstein

Start looking for leaking dye that is green. A fluorescent light will help I'f it's dark. I did this job recently. After replacing every o ring I found a leaky liquid/high pressure hose in the engine bay behind the engine brain. Pulled that line and had it repaired and recharged . Now all chilly.

Randy V

robertw
New User
Join Date: Sep 2002
Location: Portland, Oregon
Posts: 4

I'm just amazed you've been around here for 11 years and only have 4 posts!

dr bob

Or....

Everything's been fine until now.


Rob (RL: Bronto) is in the area and likely knows a good shop.


OP:

Converting the car correctly means swapping ALL the o-rings and seals to material that survives the oils used with R134a. That includes the rear air system, so your shop's plan to try and isolate the rear system is just a way to avoid doing what they should have done originally. The rear system taps from the front system at the firewall forward of the passenger's feet. There are o-rings there, at the bulkhead fittings where the lines pass through the floor under the passenger seat, at the solenoid valve under that seat, at the lines connecting to the rear expansion valve (should have been replaced along with the front valve), and the connections to the rear evaporator. If they didn't have the passenger seat out of the car and the rear center console apart when they did the original "conversion", they didn't do a conversion. If they didn't rebuild the hoses, it's not a conversion. If they just put R-134a in to replace the leaked-out R12, they stole your money.

The selection of oil used with R-134a is extremely important in "conversion" cars. Unfortunately, the most popular choice is PAG. Between the PAG and R134a it self, any remaining mineral oil (used with the original R-12) will turn to jelly. The oil in the system needs to circulate with the refrigerant, and jellied oil won't do that. Result is the grenaded compressor.

When the compressor was replaced, the Good News is that they flushed the old oil out along with the debris from the compressor. Right? The drier and the expansion valves were replaced (again).


The 'charge it yourself' are meant to allow you to top off a system that still has refrigerant in it, and is otherwise working correctly. If the system had leaked to the point where there was vacuum on the suction side with the compressor running, you have likely drawn air in through the shaft seals and need to completely evacuate the system with a vacuum pump, an charge correctly from scratch. Good Idea to fix all the leaks first of course, and give yourself a fighting chance for system performance and survival.


Data Point: I spent a long day doing the R-134a conversion on my car over 15 years ago now. Evacuated overnight, charged it the next day. Still working great. If your 'conversion' took much less time than my first long day, they might be bullwinking you on the quality of the work they did originally.

Good luck in your quest!

Bilal928S4

Dr Bob,
Can you give some more insight on the location of the refrigerants pipes entering the compartment for the rear AC? I am in the process of changing out all the O rings in my 91 and did not realize that the seat has to be taken out. Also any thing else to keep in mind?
To the OP, sorry for the hijack.

dr bob

Bilal-

Look under the car under the passenger seat, and you'll see the two steel lines from forward. They pass through the tub. Run that passenger seat full forward and pull the rugs and mats from the rear foot well, and you'll be able to see/feel the lines and the solenoid, plus the line routing going back to the rear expansion valve and the connections to the rear evaporator.

Got the Morehouse CD set? The parts supplement for 924-944-928 has a routing and o-ring location drawing that shows all this stuff.

Rob Edwards

Here's a photobomb of all the rear A/C-related pics I have, should show some of the routing:


Rear AC schematic:



Rear AC control ***** at the dash:




Rear lnes passing thru floor:




Rear AC vent grille tabs


Solenoid under seat:











Screw holes for mounting rear ac console cover:



At rear evaporator:




Blower resistor:

stolarzj

I would visit Schneider in Santa Barbara, they should be able to sort out the issues.

Bilal928S4

Thank you for the pictures and schematics. I have the cd's but did not find that particular part supplement.
I will look for it.
The connector under the car, how do you take it apart? From below?
So inside the back there are O rings at the solenoid and 4 at the expansion valves?
Where are the connectors located under the car? Are the accessible easily from below?
Thanks

robertw

Wow! Looks like a fun project but I don't think my body would like going through the procedures. Great pictures by the way!
The original compressor had blown while still running the R12. It was a catastrophic failure, after looking at the repair the front clutch had broken and bolts backed out from the compressor mount and into the pulley while driving down the freeway. Funny thing, I hadn't had to recharge the system for about 14 years! The original compressor just decided to let go.
I think I will check with Schneider in Santa Barbara. Too much of a project for me these days, I'll stick with minor projects that aren't under the car.
Thanks for the tips!

dr bob

robertw--

The 'undercar' portion is the piping from the main sections to the bulkhead fittings, all under the floor under the passenger's seat. All the rest is inside the car. Access necessitates removing the passenger's seat, 4 bolts at the rails plus the electrical connector. The rest is screwdrivers and hand wrenches while sitting where the seat was. It's not rocket surgery, just needs the parts and some patience, plus care when taking things apart and reassembling so it all stays clean.

bronto

Indeed, Schneider Autohaus on De La Vina knows 928s, and they know AC issues. I talked with them about doing a conversion a while ago but haven't done it yet.

GregBBRD

As long as R-12 is readily available (and it still is....since this whole "Freon and the ozone" thing is complete bull**** and only about money), it's completely absurd to convert to R134. When you are all done changing the O-rings, the oil, and the compressor, and the expansion valves to R-134, you still need to change all the hoses to barrier hose.

Do yourselves a favor. Use R-12 until there is no more. At one point in time, R-134A was much cheaper. Now it is only slightly cheaper....as the "Freon makers" play "this hand of poker" to the end.

Try to always remember: Once the gasoline makers got away with ripping off the American public, there's no reason that everyone else who makes necessary things can't do the same thing.