Airco upgrade - questions

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Remco
Posts: 4
Joined: Sat Mar 15, 2025 1:36 pm

Airco upgrade - questions

Post by Remco »

My airco is not working at all, i bought the car a few weeks ago and after some more urgent issues now it is the turn of the AC. When switching it with the controls to where it should start cooling i can hear the revs go down. Also does the blower work. Just no cool air. I learnt that the oem compressor is not good, i should change to a Sanden. I learnt for that that i need an adapter which i found together with the aluminium support from an E28 which i found as well. As from here, my questions. I am quite experienced on working on cars, engines, etc. but i don't have any experience with AC. Who could give me step by step instructions for how to proceed? What else should i change, what can i keep. Assuming the actual system is empty, can just start dismantling? What compressor would be the simplest? Thanks!
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Mike W.
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Location: Sonoma County

Re: Airco upgrade - questions

Post by Mike W. »

I disagree on the compressor, the stock swashplate, assuming that's what you have, is quite good. Quiet, smooth and long lasting. But it doesn't like to be overcharged, that can cause failure.

Most likely your system is out of refrigerant. Hoses are highly suspect, especially if you have any of the red cloth ones, but after 45 years anything and everything is suspect. The condenser sitting out front is at risk of damage. First step would be to pressurize it with air to find any obvious leaks, and repair them. Next it gets more complicated. Making hoses isn't terribly complicated or difficult as long as you can find A/C barrier hose. I don't know where you're at, but if you recharge it with R134a, performance won't be particularly good. There are other options, but it can get complicated.
Mike W.



02 525ita. Wife's, aka grocery getter
02 530i. New to the fleet, 3 pedals.
03 QX4, AKA the Datsun. Finally got the 4WD vacationmoble to stop smoking.
07 Xterra. Still on the DL, a purchase from hell.
Remco
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Joined: Sat Mar 15, 2025 1:36 pm

Re: Airco upgrade - questions

Post by Remco »

I am in France... I am not afraid for complications as long as I can get it to work well. I guess I better find a good place that is specialized in working on AC´s and see how negative they are.
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Mike W.
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Location: Sonoma County

Re: Airco upgrade - questions

Post by Mike W. »

I didn't like my first reply so here we go again.

If you want to do it yourself I would go in the following order, and it assumes factory A/C, I know in Europe aftermarket systems were popular, but we never saw them here..

Pressure test with air, run it up to 100PSI, er, 7 Bar or whatever, as much as you can. If no obvious leaks I would replace any of the red, fabric covered hoses, they like to leak, they get porous. I've made my own before using one size larger A/C hose. Or you can buy them or have them made. Then fill with air again and leak check, leave it pressurized for a while. The hot compressed air will probably contract a little bit, then hopefully it will be stable overnight.

If it holds, you can then try to evacuate the system and charge it. Guessing you will only have R134a to work with, which doesn't do a particularly good job on these systems originally designed for R12. The compressor should be up to the task, but if you want decent A/C, you will need an improved condenser, a parallel flow type. Also, the auxiliary fan is an absolutely essential part of a working A/C system on these cars.

Automotive A/C on these cars isn't very complicated, any decent shop should have no problems figuring it out.
Mike W.



02 525ita. Wife's, aka grocery getter
02 530i. New to the fleet, 3 pedals.
03 QX4, AKA the Datsun. Finally got the 4WD vacationmoble to stop smoking.
07 Xterra. Still on the DL, a purchase from hell.
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528i-1981
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Joined: Wed Feb 07, 2018 5:50 am
Location: Franklin, TN

Re: Airco upgrade - questions

Post by 528i-1981 »

Salut Remco,

I found the Hack Mechanic book "Just Needs a Recharge" VERY helpful when I renovated my A/C system. As Mike said, the system is straightforward. You'll spend most of your time figuring out fittings and hoses and then chasing leaks. It's available on Amazon.fr.
(oo=00=oo) Eric
1981 528i Manual
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