AC questions

Urotrsh

Urotrsh

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I have a 74 3.0CS that had AC originally. A previous owner installed a 3.5 engine from an 88' 735.
I bought a new modern compressor, mounting bracket and a dryer from AC Solutions.
The condenser, fan and dash unit are still in my car. There are two tubes coming through the fire wall with fittings on the ends.
I don't find any modern hose fittings that fit these. Does anyone know what size they are or where I can find fittings for these?

Also, The dryer I got has a module with two double wire connectors. I assume its the pressure sensor. I'm trying to sort out how to connect these to the existing controls.
 
You'll probably want a modern cross flow condenser. Your original evaporator and expansion valve may be questionable also

There are two mounting brackets needed for your Sanden type compressor.

KF6TRG

Thread 'Snapped off A/C compressor bracket bosses on my 3.5L M30B34'

Hello all! I have this unfortunate situation of snapped-off A/C compressor bracket bosses on my 3.5L M30B34 engine in my 1973 E9. I am told that a forum member has made custom brackets that use the side-facing bosses to attach a modern Sanden compressor - I hope that is true? Please advise me. Thanks, Alex

Here's some reading to get you started.

Blinkling

Thread 'DIY - Aftermarket Evaporator Installed In A Coupe'

Hi Team. I set out this year to find a replacement evaporator for the AC systems in our E9s and E3s (and E12s and E21s).

I found one (originally made for a 2007 Land Cruiser). It fits in the original box pretty well and it’s in my car working now. I’ll show you how I did it and then update you at some point in the near future as to whether there’s any advantage to it over the original parts. This is a work in progress and you are joining me in the experiment!

I want to emphasize that many members on this board have made their AC systems work pretty well using the original BMW...
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Lots more AC help and expertise available on this forum. Good luck with your project.
 
From the shameless plug department. It just so happens I’m in the middle of reading @thehackmechanic Rob Siegel’s book on vintage AC upgrades,“Just Needs a Recharge” as I prepare to upgrade the AC in my e28. Will serve as a practice should I decide to tackle an AC upgrade in my coupe. He goes deep into every AC system component, refrigerants, fittings, tools and a lot more. It’s easy reading and vintage BMW specific. I highly recommend it to anyone going the DIY route in upgrading their AC or just for a better understanding of how AC systems operate.
 
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Urotrsh said:
I have a 74 3.0CS that had AC originally. A previous owner installed a 3.5 engine from an 88' 735.
I bought a new modern compressor, mounting bracket and a dryer from AC Solutions.
The condenser, fan and dash unit are still in my car. There are two tubes coming through the fire wall with fittings on the ends.
I don't find any modern hose fittings that fit these. Does anyone know what size they are or where I can find fittings for these?

Also, The dryer I got has a module with two double wire connectors. I assume its the pressure sensor. I'm trying to sort out how to connect these to the existing controls.
Click to expand...
I understand you are doing a partial upgrade only:
-Compressor and drier are new, and will be using o-ring fittings
-condenser and evaporator core are original and will use flare fittings

as mentioned b HBChris you will need adaptors to mate your two hard lines (flare) to the the new appliances.

like these:

You will also new all need soft lines - and two more adaptors for the condenser if you keep the old one.

see below a very simple schematic of the system:
the hard line #10 from the evaporator will go to your compressor
the hard line #6 to the evaporator will come from the drier

It would be recommended to upgrade the condenser as well now, go with a fresh set of soft lines all with o-rings, and just use the two adapters on the flanges for the evaporator.

the modern dryers come with a pressure switch, you need to update your AC wiring harness to accommodate these. See a diagram below.
The pressure switch gets energized via the temp switch. Depending on pressure between a hi-lo threshold it then passes on the energy to the compressor (preventing compressor damage due to too high or too low pressure). The second wire passes on the signal to the AC fan relay, so the AC fan comes on if the pressure is high enough.

You could post some photos of what you have so we can guide you further.

1779686524156.png


1779686857169.png
 
I found a place online that made up new lines for me. Original flare fittings to mate with the evaporator lines coming out of the firewall on one end, and newer o-ring fittings to mate up with the drier and compressor on the other.

Your entire system will be much more efficient if you change to a modern condensor, and because the condensor mounts in front of the radiator, it is not visible. Also, I used a SPAL electric fan with the new condensor. https://e9coupe.com/forum/threads/new-member-long-time-e9-fan.37853/post-404907
 
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