dmw 85 Euro S A/T

I have an 85 Euro that can't quite keep the interior cool enough during the hot Texas summers so I'm considering installing a rear A/C console. Has anyone installed a rear A/C console in a car that never had one? I have a rear blower/evaporator with some refrigerant lines but not the rear console, electronics, or remaining lines to connect it to the front system. It might be more trouble (and expense) that it's worth even if I do all the work.

Tom in Austin

Welcome to the board. 928 A/C is one of the long-running issues discussed around here. There are mixed opinions about how valuable the rear A/C is. I never bother to turn mine on, but some people think it helps.

Since you're in the metroplex you might want to go by Sean Ratts' place in Denton and have him check out your system. He's got mine working quite well now.

dprantl

Installing rear A/C into a 928 that does not have it is not easy. The most involved part is the replacement of the A/C hard lines in the engine bay. The lines for rear A/C have a Tee at the firewall, and those are almost impossible to remove/install with the engine in the car.

Dan
'91 928GT S/C 475hp/460lb.ft

jeff spahn

I have rear AC. I find that my front AC temps don't get as cold when the rear AC is on. I just use the front AC.

Bill Ball

If that is true, the system is probably undercharged.

That said, I only switch the rear AC on one in a long while just to keep its seals from drying out. Otherwise, I never feel the need to use it, even in Texas-type heat. It's intended for the rear seat passengers to get a little additional direct cold air as they are in the blazing sun under the rear hatch. The front AC should be able to chill your bones in the front seats very nicely.

MainePorsche

When on long highway drives I turn the rear on to the second click (once sufficiently cooled via the front) for the front AC gets to cold. Cools the entire cabin and doesn't freeze my right arm.

Rich9928p

What I've found works well is:

a) aim the rear vents to the front, set rear on fan speed II or III (as needed)
b) aim the front center vent straight out to slightly low, set on fan speed 2

The rear air blows up towards the windshield cooling the entire car. The front air blows downwards to keep the immediate front area cool. If the front center vent isn't lowered, the rear cooling stream doesn't make it up front.

On long trips the fan noise is lowered and the whole car is cooled well.

YMMV
Rich
'93 GTS with rear air
'87 S4 with rear air
'79 with very weak air
'79 Euro 5-liter track beast with "air delete"

GregBBRD

Really difficult.

Actually, not too bad with the engine removed....but virtually impossible with the engine in the vehicle.

The reason the rear A/C works so poorly, in the stock designed system is simple. There isn't enough condenser to make enough liquid to allow a solid stream of liquid to reach the rear expansion valve. The little bit of liquid that is made, flashes to a gas, long before it reaches the rear expansion valve. That is why there is very little cooling capacity, from the rear A/C unit.....and why turning on the rear unit usually increases the temperature from the front unit. The rear system "robs" liquid from the front A/C system....making neither work well.

I've now got a kit that bolts onto the late 928s which adds an additional condenser and a condenser fan on that condenser. This allow more heat to be removed, which thus allows a considerable more amount of high pressure gas can be converted to a liquid. This allows so much more liquid to reach both the front and the rear expansion valves, that the A/C system then works amazingly well (like a later model GM car with great A/C).

As a matter of fact, the system works so well that the kit also comes with a fan motor (and wiring) that allows about 20% more airflow than the stock fan motor.

And, as an additional (not planned) benefit, the extra condenser (which is plumbed to have the Freon go through it, first) removes such an incredible amount of heat that the radiator temperatures drop significantly (there's considerably less heat being pulled from the stock condenser, through the radiator, by the stock cooling fans.)

This turns out to be a really magnificent addition to these cars. High volume very cold air from the front, a rear A/C that blows very cold air, and reduced radiator temperatures.

I'll do a "New Product That Has Been Throughly Tested And Works", next week, with pictures and more information.

ALKada

Me thinks you might have a lot of fans in Texas and Arizona when this gets released!

77tony

Pulled the rear A/C out of the GTS and installed a rear seat delete. Do keep a reflective screen in the windshield when parked and tint the windows. Front air works great and it's hot here in So TX. T

Spun

Big. Ill take one for sure.

dmw 85 Euro S A/T

Thanks for all the replies! I think I'll just concentrate on making the front A/C work better. In fact, yesterday I left the car running with the A/C on while filling up with gas and noticed cold air coming from a small gap in the rear hatch weatherstripping. The gap appeared to only be about one millimeter but was probably a about a foot long. I think that when I get the interior sealed better, the interior will be much cooler because the front vent blows pretty cold air; it just isn't staying inside the car.

Alan

Remember though - if you seal the car up too well you won't get any airflow at all in fresh air mode - it all has to go somewhere...

I agree that the rear air adds little total cooling capacity to a correctly working system. It only adds more evaporator surface. If you actually have rear passengers its good for them to have local cool air. Your front system should be able to eventually cool the car adequately for any temperatures in the USA. For the hottest locations - you are best with front only for initial cooldown of a hot vehicle. You get direct air (feels cooler) and the rear does not compromise the front temps - your system limit is the compressor/condenser capacity. In much less than max heat - switching on the rear may help cool the cabin a little faster because the limit may be evaporator capacity at that time.

Given the hassle, expense and additional reliability issues (esp. leaks) - I would suggest its a poor trade off - expecially if your front system isn't working right - then adding on rear air may make it worse still...

That you are here asking suggests your money would be better spent totally going though the stock front system - it should work very well

Alan

dmw 85 Euro S A/T

I crawled into the rear of the car this morning and saw that about 1/3 of the rear hatch seal had about a 1mm gap so I used a putty scraper to lift the seal up until it touched the surface of the hatch. Then I went for a drive and the car seemed to cool better and much faster. I'll drive it again this afternoon to see how it does during the hottest time of day.

fraggle

There are a lot of bits in good working HVAC system - and a lot that can go wrong. I'd do as you said, focus on the bits you have. the install is nearly impossible as a retrofit.