Jump to content

911 SC Air Con Upgrade Project


Recommended Posts

As it is a common question I am going to document the install of the replacement airconditioning system for the 911.

The car : US market 1983 911 SC.  Came with factory air-conditioning, partial delete by previous owner (took off the compressor and plugged the lines)

The AC : I have purchased a Griffiths replacement system, in fact I purchased it almost 12 months ago and I forget the exact configuration.  It has a new compressor, a new evaporator, new hoses, a second condenser and extra air vents.  The only parts that will be original are the decklid and front condensers, plus the fan and the dashboard ducting.

I started today by replacing the factor evaporator in the smugglers box.  This isn't going to help anyone with a RHD car because it's one of the areas where the car is different.


Here's your standard LHD Smugglers box scene.  Looks like nobody else has been messing with it - mostly undisturbed which is great.

The way these work is pretty simple.  There are two inlets - a hole behind the passenger floorboard and a hole on the drivers side which has a 3 inch tube feeding into the smugglers box.  The fan sits on top of the evaporator and pulls the cabin air upward through the evaporator, then out through a single pipe at the rear of the smugglers box (you can see the exit in this photo).  From there it is distributed to the middle vents and the two side vents.  Blue wire and silver wire with red tags is amp / speakers because the amp sits over the top of the smugglers box normally.


With the evaporator box taken out, found all sorts of crusty gunk underneath.  It's probably rodent storage, can't see any other way it got in there. There''s no red or blue thread in the car and I doubt Porsche used anything like this as padding.  It didn't stink or anything, and thankfully no moisture had been getting in - wet gunk is a rust starter.   Note the opening at the back is the air intake on the passenger side for recirculating air.  The factor AC is always 'recirculate' - there's no option to cool incoming air.  I cleaned this up right down to the white factory seam sealer but somehow forgot to take a photo of my handiwork.


Here is the Griffiths Evaporator next to the factory.  The factory one shows some rust around the coils - I don't know if it every worked or the AC was removed for some other reason.  The new one is supposed to perform better with the 'parallel flow' design rather than the big tubes.  It also goes in without lots of rubber feet and sticky goo - all of which had to be cleaned off the evaporator box.


The Griffiths instructions are very specific and there are some mods that happen as you put it back together.  You can see the steel flange piece that connects the box to the drivers side intake - this is to improve over the factory plastic/steel slip fit which only has a small foam gasket (long since crumbled and ingested into the core).  The steel piece requires the evap box to be put in bottom first, then evap, then top.  This makes it super-tricky to fit the clips over the retaining tabs you can see bottom left and right and top right.  The instructions recommend drilling the tabs and putting a self-tap screw in to hold the top and bottom together.  I eschewed the advice and had a ripe old time getting the clips on but managed to do it by holding pressure with a big screwdriver and pushing on the bottom of the clip with a smaller screwdriver.   This was pretty nerve wracking as there are plenty of stories around of people breaking the tabs off and having to use resin to re-attach them.  But I got it done with no broken tabs and no lost clips.   The white plastic gasket comes with the kit and provides an air seal around the sides of the evaporator to force the incoming air through the core. 


Here's the end of the day's work with everything back together.  The AC hoses are not connected as I have left the shipping stoppers on the new evaporator.  The new hoses will replace these and will have O-Ring fittings rather than the flare fittings you can see here.  The white coiled wire is the evaporator temp sensor which works to regulate the compressor.  This goes into a brass tube which inserts into the evaporator core.  The wire has to be treated with a lot of care and not bent/broken.  The new brass evap tube was filled with some type of white grease like material which I assume is to conduct heat between the evap and the sensor wire accurately.  Putting this in was the trickiest part needing finesse as opposed to the brute clamping to get the clips on.  You can see I got all the insides of the smugglers box nice and clean.  

Not sure what is next in the instructions, hopefully I'll get time on this again soon.  Total time to get this done was about 5 hours, though it could be done a lot quicker if you weren't stopping and re-reading the instructions every couple of minutes, walking around looking for tools etc.

Link to comment
Share on other sites


I'm rather partial to a good AC in an AC car thread!

With your second condenser, are you talking about a rear wheel well setup?

Have you bought yourself a vac pump, gauge set and a small canister of HiChill Minus 30 too?

Did you oil the evaporator fan bushes while you had it out?

Link to comment
Share on other sites

Yes a rear wheel condenser is part of the kit.

I have all the vac pump and gauges.. well they are at a friends place but I’ll get them back soon.

Didn’t know about lube on the fan :o too late now it’s back together.  I tested it while out, working ok.  Also cleared out bits of foam it had ingested.  I’m not surprised these old systems don’t work well, so many deteriorated mating surfaces that let cool air out and warm air in. Like trying to keep the beer cold when the fridge seal is busted.

Link to comment
Share on other sites

The stock set up isn't as bad as everyone makes out.  Certainly not perfect but with some intelligent repairs and upgrades like a wheel well condenser could be recommissioned very cheaply .  Dry bearings in the evaporator fan is a very common problem and an example of something easily and cheaply fixed.  Good to hear your bearings are silent and OK.  The real problem with the evaporator is the lack of outlet vent area that I see you have in hand.

I like how you haven't just thrown money at everything, to replace everything.

Talking about hot air diluting cold air, suggest you check the seals on either side of the fresh air blower.  If these leak when you try to shut off the external air, your AC will be less effective.  You can make new seals easily from some 4 to 6mm closed foam sheet you can probably buy from Bunnings.

Also while we're talking fans, suggest you take 15 minute to make up a fused harness for your front condenser fan that will just slip between the existing plug connection to the fan motor.  Saves an impressive amount of under frunk wiring if this motor seizes.

Link to comment
Share on other sites

I’ll put a fuse on the front blower.  I’ll have to research besT amperage for that.  A lot of testing to go on all the electrical bits, I want to get all the hardware in place first. 

when you say seals on the fresh air blower are these accessed from the frunk?  I’ll have to check that out.  I’ve been doing some informal vent testing while driving, to see if any air is coming in.   Cold days is good for that.   I have a smoke machine and was thinking how I could test for leaks using smoke, but a little worried I might leave a smell in the system.  

Link to comment
Share on other sites

Yes, accessible from the frunk.  I think there are 3 screws that hold the fan housing to the plenum box.  The housing is held together by circular wire clips.

Couldn't find a photo but here is a whole thread! Fresh Air Blower Squeal Fix - Page 2 - Pelican Parts Forums

I'm using a 10amp fuse for the front condenser blower harness.

Link to comment
Share on other sites

I did an almost identical Griffiths install in my 1988 3.2 about 4 years ago now. I think the only difference is that I also replaced the front condenser. This was the most involved project I've ever done on a car, but came out well. I shot a lot of video while working on it, with plans to edit it and post it YouTube, but I never got around to it. If you get stuck on anything, give me a shout. If you happen to be around Melbourne I can always come by for a look or to lend a hand.

Link to comment
Share on other sites

16 hours ago, Coastr said:

Cool how does yours perform?  88 has better vents but same otherwise.

not in Melbourne though, racing against the onset of humidity in the sunshine state 

I have a black on black coupe, so basically the worst configuration for hot weather. On a 28 degree day with the car sitting in the sun for 30 minutes, I get 0 degree or colder vent temperatures at idle. Having said that, the car hasn't been driven much since I finished this project, so I haven't really gotten to put the system through it's paces on a regular basis.

Link to comment
Share on other sites

  • 2 months later...

Well i lost the race against the humidity as this weekend saw 78% humidity and temps of 29 degrees.  However progress was made as the car had a hot date with the lift, allowing all the new hoses to be run and the 3rd condenser to be fitted.

Here's all the stuff to go in


Here's the patient up on the lift


First up was pulling out the rear condenser to front condenser hose.  As the rear condenser was already removed (that's it leaning against the wall in bubble wrap) it was easy to get started.  Just lots of clips to remove and drop the hose.


The rear to front condenser line goes behind the craziness which is the plumbing of the receiver/dryer in the LHS front wheel well.  There is the fuel bowl drain hose, the rear-to-front condenser line, then the front-to-dryer line.  The receiver dryer was obviously put on with the front guard off as the screws on the clamps faced away and were rusted shut (despite being fancy benz units) so the angle grinder had to be deployed to get it out.


The front condenser had to be removed to get the hose off (front condenser is being re-used) so it was flushed out of the old AC oil and refitted with the new lines.  Here's the gap while it was out.  The AC line that runs from front to back has the right 'flare' fittings to match the old condenser, while having the more modern o-ring fittings for where it attaches to the new 3rd condenser.


Next up was the installation of the griffiths rear guard condenser, which makes the 3rd condenser on the car.  It starts by drilling the engine tin lip to mount this heat shield.  There is two other holes drilled - in the valance lip and through the inner guard to mount the brace for the condenser.


Speaking of which, here it is installed.  It mounts to the two lower valance support bars, and then a cross-brace to the valance / guard joiner (where the hole needs to be drilled).  The AC lines go in from the rear condenser and out to the front condenser, so all three condenser end up in series.  This has a SPAL fan already mounted.  It pulls fresh air in and pushes it out onto the exhaust of the car.

Then the other lines in the car had to be run - receiver/dryer to smugglers box, and smugglers box to compressor in the rear.


Here is where the old hose goes up into the smugglers box - it looks difficult but it's not that hard to finagle it up into position.


Here is the other end of that same hose going up into the engine bay on it's way along the frame rail to the compressor.  Replacing this line just means undoing all the hex-head metal screws holding it in and replacing.  This is the old hose - forgot to take a photo of the new one put in.


Here's the pile of temporarily and permanently removed parts


This is the rear guard condenser finished with the wiring in place, hoses clamped up and stoneguard fitted.

The other steps completed were to fit the rear condenser (but I need the clamp) and the in-line fuse for the front condenser fan.

Still to go:
connect hoses to evaporator
connect hoses to receiver/dryer
compressor mount & drive belt
connect hoses to rear condenser
wiring for pressure switch and fan relay
fit new supplementary dash vents
leak check, vacuum and gas up

The humidity marches is definitely beating me 😐 but I will prevail.


Link to comment
Share on other sites

On 12/08/2021 at 15:46, autojack said:

.... I get 0 degree or colder vent temperatures at idle. 


How do you get vent temperatures of 0 or less and not have the evaporator freeze up and block airflow?

How comfortable is that for the occupants with air of frostbite temperatures being jetted at them at strong but meager volumes?  Unless you have installed additional vents to provide the desperately needed extra air volume of course. 

Link to comment
Share on other sites

2 hours ago, Coastr said:

Plz no AC wars :D  

I just figured out the condenser bracket is NLA so really hoping someone has one after junking their AC system (I know there’s a lot of removed AC systems out there !)

Love not war.  We simply seek the facts.

If you PM your address, I'll post you a bracket today.

Link to comment
Share on other sites

  • 2 weeks later...

Huge thanks to Peter M for the missing bracket.  Now I need to figure out what to put between the bracket and the condenser - the PET says some type of foam.  Maybe I'll cut up a bike inner tube for padding.

When I rebuilt the evaporator I had completely forgotten that I ordered the upgraded fan blower motor.  I blew it off saying it doesn't matter but then I recalled the original reason I ordered the bigger motor (and extra vents) was because moving cold air is the weak link in the original design (along with insufficient condenser size).  So I decided to pull the fan motor out and replace it with the upgraded one.


Puling the lid off was pretty easy - the tricky clips just slid off, though one ended up on the steering rack splash cover.  Don't attempt any job in this area without a magnet-on-a-stick.

Pulling the IMG_3622.thumb.JPG.05845741cccc29a271662567ccf8cfd2.JPG

You can see the brass sensor tube sticking out of the evaporator.


This is the standard fan motor.  Purists might want to look away about now.


Disassembled fan motor and 'hamster wheel' fan.  The new motor is on the right - you can see how much bigger it is than the original motor.  You can also see it won't fit into the standard housing.


Generally I'm not one for hacking up a car.  I've already drilled two holes in the engine tin and two in the chassis lip to hold the hose clamps.  This is a pristine condition plastic fan housing and I cut it up with a hacksaw.  I rationalize this by knowing nobody will ever see it, and it will make the car better by having better AC.  Still, I don't like doing this - the population of original useable 911 parts just decreased by 1.  I suppose you could rebuild it with some glue and filler ?


Here's the upgraded fan motor installed on the fan housing, which sandwiches between the evaporator lid and the evaporator.  Note the 4 nuts held in this fan housing - if you ever take your evaporator box apart these are likely to fall into the box.  It's ready to go back together.


You'll have heard of the evaporator clips.  I was very proud of myself for finagling these back onto the evap box originally.  The replacement instructions urge discarding the clips and drilling the box and putting screws in instead.  I don't like drilling holes in original NLA parts.  So I got the clips on in the first go around.  And I was confident of being able to repeat the trick and get them back on.

But after more than an hour of straining and messing about I only had one clip on.  Taking a break from it - I had to decide on whether to keep fiddling.  The truth is they are very very difficult to get on.  You don't want to break the plastic tabs that the clips go onto.  If I have to take the lid off again it is going to be a real pain.  So I decided to take the box right out and drill it.  More purity lost.


Out comes the drill and zot zot zot screws in and clips in the spare parts box.  You have to put the evaporator in bottom first and top later. You can see the damage to the plastic from me getting the clips on and off.


In goes the evap with the bespoke evap gasket.  You can also see the metal fitting which binds the evap box to the drivers side intake.  Lines are still capped as I won't open them until it goes in place.

It's all back in and the new fan blows hard.  But how much harder is hard to measure?  I also found out the RHS center vent is blocked and not passing air.  More on the to-do list, but I over-ran my time significanly with all the messing about getting the evap lid back on.  

I'm missing the compressor bracket and the evap lines put in the previous step are not aligned close enough to the evap.  So will re-route the evap lines and get them bolted to the evap assembly, order a replacement compressor bracket and get moving.  So humid today 😓


Link to comment
Share on other sites

9 hours ago, Coastr said:

Now I need to figure out what to put between the bracket and the condenser - the PET says some type of foam.  Maybe I'll cut up a bike inner tube for padding.


Bunning's have a range of of self adhesive foam products that I find handy for remaking seals and vibration pads like Whites 50 x 5mm x 1m Adhesive Rubber Foam - Bunnings Australia .  The softer stuff is in the door seals section and the firmer stuff is in with floor protection.

Link to comment
Share on other sites

Ah all items in shop photos are not mine.  Lift and workshop borrowed for a pie, cream bun and iced coffee - plus the promise of crass humor traded freely.

No AC work this weekend was wiring up the pickup with an Australian trailer plug socket.  And loading 200 concrete pavers which actually strained the pickup suspension a bit. Unlikely to get any done this weekend either, and summer marches on relentlessly.  But will get a compressor bracket reordered.

Link to comment
Share on other sites

i have a box of air cooled 911 parts i've accumulated for air con if you're interested (i think there's a compressor bracket amongst them)

must remember to be open to crass humour and iced coffee for use of tools

Link to comment
Share on other sites

  • 1 month later...

So a bit more time found and the weather was actually half decent for a bit of time in the garage.

I've posted earlier how I am missing the compressor bracket.  There's a special bracket that comes with the griffith kit.  I didn't open my box until 12 months after i ordered and the bracket is on the invoice but wasn't to be found.  I say it wasn't packed, vendor says have to check items immediately. I get that small businesses have people trying to con them all the time but I'm never like that. So I'm cutting my losses and putting the original bracket back in (PO carefully removed it and saved all the specialist hardware to refit).  Today I worked through the 3d puzzle that is an SC compressor bracket.

Here's a linked picture of the parts diagram showing the pieces for the york compressor:


I couldn't find a single image on the internet of a 911 SC Compressor bracket, and this diagram is confusing as.  There are 6 basic pieces, this shows the bottom 4 of them mocked up out of the car ( you don't remove in one piece or install in one piece).  The alloy support at the back goes onto longer studs that locate fan shroud along the top of the cylinder head.  The front two bolts bolt onto a steel piece that is still on the car.  Note the bottom bolt is a shallow head so you can fit it on between the rear engine support.  The plated bracket goes onto the block behind the oil pressure sender.


Here's the bracket from the other side


Fitting the bracket requires attaching the two support brackets first (the plated and alloy bracket).


The stud on the case is very short so this bracket has a nut with a raised cylindrical section that fits into the bracket.  You'll never get one fitted if you don't have this special nut that fits in the hole.


Link to comment
Share on other sites

Here's the two brackets installed.  The one behind the oil pressure switch is a real bear to get in.  I had to use a 17mm socket with a variety of extensions to get it tightened up.  The alloy bracket looks different to other SC brackets I have seen photos of - I suspect this is a changeover part that was designed for the 3.2 engine and fitted to late model SCs.  It supports the back of the bracket.  You can also see the bottom most part of the bracket on the car (it was never removed as it goes under the engine tin)


Here is the bracket base installed, without the top plate (that attaches to the york compressor and allows movement for fan belt tension).


I had to squash the heater hose so I put tape on it to push the bracket against.  Next up is purchase of the sanden adaptor.  I'm also re-fitting the rear condenser as I wanted to use the original screws.

Link to comment
Share on other sites

More fidgeting in the garage today while I passed time between relatives. 
I flushed the rear condenser and while I was at it re-painted the ends of the condenser.  I've never seen this treatment but it was unpainted in the middle and someone had sprayed the end tubes, which was flaking and looking kind of ordinary.  So I did a hard paint line.


Here's where I admit to Peter that I found my original condenser clip after he graciously sent me a spare.  I have cleaned and repainted that one, I can send it back?  Or I can pay it forward to someone else who is missing one?  Anyway, the original is back in place freshly painted with the original metal screws holding it in.

While I had the spray can out I thought I might touch up the top of the compressor bracket.  But then as I cleaned it up for paint with a bit of 1500 paper, I realized it was baked on gunk coming off and not paint.  So I switched track and used carby cleaner and wet and dry to remove the gunk.  Then I got out the compound and gave it a good rub.  And, well, now I've refitted it and have the glossiest AC compressor bracket in all of porsche-dom.  I can't believe how well it came up.  Yes that is the reflection of the airbox in the top of it.  It has a bit of paint off where the bolts clamp down, but still looks better in shiny original than rattle-can.


I also got fed up with how scruffy the coil mounting plate looked so pulled that off and gave it a rub down and respray.  Then I started cleaning up the fan with metal polish.  Thankfully about then the relatives arrived and I stopped before I started on an engine drop to replace the sound pad.  More soon.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...