Ninespub

My rear air never worked worth a chit in the 19 years I've had my 928. Hell, the front air doesn't work either now and so I'm gonna replace the whole system, probably even the condenser with the system from Griffiths. I have a nice leather factory rear storage compartment that looks better than the useless rear AC system that I removed when my car was being stripped inside and out for my repaint. I cant find any info on how to cut the lines properly so I don't destroy the new system. I've done enough (but tasteful) mods on my 928 that it will never be original again and so I'm not particularly concerned with any potential value drop if I ever sell it. I just want cold AC up front. Any help out there? I know its been done, just not how and by who.

The Forgotten On

You have to replace the hard lines in the engine bay with non rear air ones (need to pull the engine) or go under the car and cap the lines going to the rear evaporator.

There is a risk that the oil in the system will settle in these capped hoses and starve the compressor of oil.

You can also run soft lines parallel to the original hard lines.

It truthfully makes much more sense to just leave it in place.

jeff spahn

I left mine in place and just run it now and again to keep stuff circulating. It is a nice recirc option on the system. Turn front on low and rear on high. Seems to work well this way,

77tony

Performed a rear seat delete mod on the 94 GTS along with removing the rear A/C. Capped off the hard line just under the the pass seat under the car. Maybe it's in my head but the A/C seemed to work better after removing the rear A/C. T
more here: https://rennlist.com/forums/928-foru...928-gts-4.html

worf928

It's not in your head. All the rear A/C does(*) is steal condenser area from the front A/C and accumulate compressor oil. And it has more places that can leak refrigerant.

* My rear A/C was appreciated exactly once: when I had two small humans in the back for an extended road trip during the summer. Otherwise. Meh.

I bought front-only A/C hard lines, but decided that I couldn't install them with the engine in the bay. So, I did what you did: I cut the hard lines at the Y. Then I tapped the holes and JB-welded Alan-head threaded plugs into the holes.

worf928

It's not a 'risk.' The under-car hard lines do accumulate oil pretty much all the time unless you religiously operate the rear A/C. However, they will not accumulate so much oil that they - by themselves - will kill the compressor. Killing the compressor happens when people repeatedly 'top-up' the A/C without adding some oil.

That, and the OE compressors will survive fine with a shockingly-low amount of oil in them.

chart928s4

Seems like plenty of rear AC deletes out there and I haven't seen anyone who regrets it.

On replacing the system with Griffiths, I would be cautious on that. There are major access issues, and the soft lines can leak, but those are primarily labor costs that I suspect would be similar with the Griffiths. Other than that it's the same as any other system. A new 91 S4 Denso OEM compressor is $320 IIRC and they are still making them. Used condensers are available but hopefully not needed. Under the dash can be a lot of work so hopefully no problems with those parts.

After my engine pull by worf928, the AC (and everything else) is fantastic.

BTW - can you please take a few photos of your full-leather dash for DIY upholstery purposes?

Bigfoot928

I did a rear seat delete. I left the lines and the lower blower housing. I removed the blower and upper fan housing. AC worked fine for years. Its not back on the road but still holds a charge.

928 GT R

I concur with the rear unit delete being a great option. I simply pulled it and capped the lines.

One additional item: I fashioned a rubber block with holes in it to keep the capped lines from bouncing/vibrating.

Ninespub

Thanks everybody for the current responses. Was not able to get the time to be online for a couple days. Years ago I had heard various horror stories about having to pull the engine and if not, oil pooling in the lines would lead to your compressor exploding. Not knowing my *** from a hole in a compressor line, I wondered if you didn't cut the lines but re-connected them them (in somewhat of a circular routing fashion) without an ever-leaking expansion valve, wouldn't everything just recirculate as if the system were constantly on? The end result being that you could re-install the worthless parts if you wanted to.

worf928

Replacing the condenser on the under-oil-cooler cars (MY90+) is not as easy as you may think and more involved than with the pre-
90 928s. It's not something I'd *want* to do unless the OE condenser is leaking or blocked-up. Certainly the 928's A/C system is 'condenser' limited, but it's not clear to me if a bigger condenser would justify the effort without some additional airflow.

When working as-intended, the 928's front A/C is adequate - cold even - for all climates except the high desert (LA in traffic, death valley, etc.) 28-35 degree center vent temperatures when the car is moving (condenser air flow) and RPM > 2000 (compressor speed) are to be expected from a healthy 928 A/C system.

I have no experience with the Griffiths' condenser. However, I've not been impressed by the Griffiths' replacement compressors, primarily, because they are not able to pull low-side pressure down as far as a healthy ND. The lower the low-side pressure the colder the A/C gets. Since 'new' NDs are available for short money, I don't use anything else.

There is a minimally-invasive way to block the rear A/C. Rather than cut the lines, remove the under-car lines and plug the ends of the under-car lines closest to the Y on the engine bay lines and then re-install the under-car lines. It's easier than cutting the lines - it's all 'bench work' after removal - and if for any reason you want to reactivate the rear A/C, all you have to do is replace the relatively inexpensive under-car lines.

Bigfoot928

worf928

Tony

Just putting my my own plan B together...in case I do delete it all.

how did you block ..plug the lines...a cap or something internally between the joint.?

I thought about picking up a sacrificial used set and just cutting them where I show here and have them welded shut.

worf928

I was going to answer this in your other thread after dinner. It’s now after dinner...

what I have done on clients’ 928s (upon request) was tap threads into the ends of the under-car lines where they join to the engine bay lines. Then, I JB-welded hex-socket grub screws into the threaded holes. This is the reversible mod.

Edit: then re-install the rear lines with four new o-rings to moisture seal the remaining rear a/c components.

On my ‘91GT which can never have rear a/c again, I did the above, but to the engine bay lines after the split to the under-car lines.