A/C compressor pulling all my engine power

[SergeBMW]

Lately while running the A/C ive noticed a huuuuuge loss in enigne power. I know A/C compressors running will lessen your engines power but at this point from a stop start, the car doesnt like to move even with the pedal more than halfway to the floor.
Its not a constant problem, its more random but after about 2 seconds of holding the pedal more than halfway, it takes off

So I tried turning the A/C off, accelerated and its got great response. I have power all the way up

Anyone have an idea why this all of a sudden is sucking all my power out? Scares me sometimes when im trying to pull into traffic haha, hesitates too much

[shogun]

I do not know how it is on the 735, but when I had the compressor problem on my 750 I could see on passenger side with the hood open the clutch and pulley kick in and out while someone switch AC on an off. At that time I also found that wobbling on the pulley which was in the end cause by wear of material on the shaft of the compressor. You could also losen the belt and turn the pulley by hand to check if the bearing is making the problem, on my 750 there is also a pulley tensioner with a bearing which also could seize.

[SergeBMW]

It all seems to be working the way it should, doesnt feel hard or anything, and I just replaced it recently with a newer one from the pull a part down here (yes not brand new but it was a 94)
And I dont have a pully tensioner on the 735.
Could it be that there is too much pressure in the system? Ive checked it and it seems ok but similar symptoms to overcharged system.
I rememeber my old one seized up when I put too much pressure in the system since the guage was reading 0. (a valve was seized closed) and I ended up overcharging the sytem and it seized up on me to where the belt was just squeeling like crazy

Compressor bearings where shot anyway so I didnt lose anything on that one

[SergeBMW]

Today I went for a drive and really put down my foot on the gas pedal and after like 5 minutes of that kind of driving it seems my problem is solved!

Engine feels much more responsive now with or withought A/C. I know the engine computers adjust to driving style, but I guess I let it get too sluggish? Ive been driving real easy lately, due to gas prices and I want my baby to last lol

[SergeBMW]

Wow, this was an old thread from my old 735i. Funny enough on my 750 I am experiencing the same thing as I originally did on my 735i. My compressor just makes a whine/groaning noise as I accelerate with it on. Saw a few people had success with WD40 in the shaft but I think mine is just too worn out. I think purchasing a new DENSO Compressor will help mine run much smoother. Usually putting the foot to the floor has no effect with A/C on. With it off its far more responsive, big change.

This is what ill be buying: https://www.fcpeuro.com/products/bmw...-471-1263#desc

Should I really replace the dryer when swapping this out? I just replaced the dryer when I went to R134 less than a year ago.

[CroughtonE32]

That's a great price Serge. Last time I replaced my compressor I paid over 800 for this one. It's what came on the car. But now it's over a grand. When mine goes again, I'll have to look into a company other than Seiko.

[e30luv318i]

I noticed a lot of cars from that error with the ac on are quite sluggish, my e34 m50 is absolutely awful with the ac on. My e32 is very noticeable as well. Both are manual trans cars

[6erWEBB]

Mine is THE SAME WAY! Its been well into the 90s here lately and when that compressor kicks on you KNOW it. It hasnt bothered me too much but this weekend I had extra passengers who were also quite large people and it felt like the ol 3.5 was really struggling.

Ive wondered if my compressor was just worn out as well because mines making a crazy noise too. Id definitely swap the dryer out too no more than they are.

[shogun]

demetk makes Sanden 508 compressor brackets that will fit the m30 and s38 engines . He says the brackets allow for the install of a Sanden 508 a/c compressor using the existing a/c compressor mount. 508 clones are available new for about $115 shipped. https://www.bimmerforums.com/forum/s...tch-being-made

[htrdbmr]

Just a thought, but is your battery/ alternator doing the job at low speed, such as leaving a stop light? Low voltage plays havoc with these ECM's.

[SergeBMW]

Funny enough last week I was looking into the voltage of the alternator through the OBC, it was fluctuating a lot from 13.4 down to 12.80v, seemed like my regulator was going out. The interior lights flickered as well so pretty sure I needed a new one. Purchased one from Erich/Shogun.

With the Florida heat I never have the A/C off, its like a sauna without it. Yesterday on my way back home from work, I left the A/C off and gave it mid throttle and was amazed at what I am really missing out on this engine. I then did a WOT run from rolling and also a kick down just to test. At around 4k it really pulls HARD. Scared me a bit because I am not used to what this engine can really do. I turned the A/C back on and it was a grannys car again. That plus the horrible noise it makes when accelerating with it on has me wanting to rip that thing out and put in the new DENSO unit. Hoping it will help with the power drag too. my worry is that it does not appear to look like my compressor at all. Maybe just a stock photo?

My system also needs to be re-vacuumed completely and refilled, its not running as it should, its not really cold unless I am driving on the highway. I did fix the Aux fan low speed and it does function. When it originally was filled after the retrofit, it was ice cold no matter what, and at the time the aux fan had failed at low speed. Problem was it leaked through the site glass, it was just loose! I should have vacuumed after I found that leak, but I just simply refilled it for the time being.

[shogun]

Remember, the 750 AC compressor is a special version with lock sensor http://www.bimmerboard.com/forums/posts/1263029
http://www.bimmerboard.com/forums/posts/1263034
http://www.bimmerboard.com/forums/posts/1263030
https://www.bimmerforums.com/forum/s...58360039-issue
http://www.ow.no/index.php?option=co...d=59&Itemid=41
http://www.bimmerboard.com/forums/posts/885452 includes by-pass info by E32Fan

[SergeBMW]

That explains why my compressor cut out during a torrential downpour one day headed home from work. Got to the gas station, turned off and on the car and it worked again, had me worried something was shorted out because of all the water.

So are you saying that the new compressors wont have this feature and require a new lock module?

[shogun]

E32Fan has made some instructions to use a normal AC compressor and by pass the lock sensor, see above link. But depends on built year.
and here I posted info http://www.bimmerboard.com/forums/posts/1263029/
and here I posted differences which my wrenching buddy found http://www.bimmerboard.com/forums/posts/1221242/
read the cpl. thread on BB