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E12, E28, E34, E39, E60 General discussion and technical help for all year 5 series cars.

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Old 06-02-2007, 12:27 AM   #1
eightynine535

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help with A/C and AUX fan

I bought my 1989 535i from a second owner who himself never drove it because it was bought on another person's behalf who changed his mind.

I am letting you all know this because other from carfax I do not know the history of the car. now on to my situation....

I noticed a sticker that the A/C system was converted to r134a back in 2000. but the compressor was not turning on. I bought a cheap r134a recharge kit and the compressor did turn on. BTW i checked before and there was nothing in the lines. The air is not cold, it is bearly cool after the recharge. And the AUX fan does not turn on. I suspect it also did not turn on today while sitting in traffic on the freeway in 90+ weather. At that time I noticed the temp slowly creaping up from the 1/2 mark so I turned on the heat full blast and it went back to normal.

I asked a shop and they told me the compressor is weak/failing and needs to be changed.

now I do not have a problem with buying a compressor, I just do not know if the previous owner used the original or an r134a compatable one.
and more importantly: why isn't the AUX fan not turning on??? I changed all the fuses for the A/C system and AUX fan and still, nothing.

HELP ME!!
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Old 06-02-2007, 12:32 AM   #2
witeshark
 
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My guess to start is that the aux fan switch (likely a thermostat) isn't working
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Old 06-02-2007, 12:41 AM   #3
eightynine535

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the one on the passenger side of the radiator with three wires comming off it?
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Old 06-02-2007, 12:41 AM   #4
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Before replacing your compressor first replace the aux fan resistor (it's a ceramic resistor out on the frontside of your aux fan - you have to remove the front grills to access it) that's an extremely common E34 problem. Next have your AC system completely evacuated and recharged.
check out www.realoem.com - enter your info and check out the diagrams

Last edited by c1apton; 06-02-2007 at 12:51 AM..
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Old 06-07-2007, 09:36 AM   #5
Jimmie34

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I spend a lot of time on moble a/c units and have never seen a weak compressor. They are either good or have self destructed. If the a/c had no charge when you carged it there is air in the system and it will have to be evacuated but most of the time when there is air in the system the a/c compressor will cycle due to low psi on low side and extremely high pressures on the high side. Your fan would also be on.
For a check get in your car after it has cooled down or overnight. when you get in and start it up turn your a/c system to high as well as the fan. The fan should kick on within 3-5 min depending on the outside air temp abouve 60F. Your high pressure switch on the a/c should kick the fan on well befor your car reaches operating temp.
I would jump 12v to the fan and make sure it turns on If it does not while doing the previouse test. Your comopressor will not make a difference on 134a. The difference was the compatability of oils in the systems. They have corrected that by using an oil with 134 that is compatable with the oil used in r12 systems. It runs at a relitively higher pressure than r-12 but the difference is the coil area due to r-134a not being as efficient at transporting heat. It will not be as cold as an r12 system but should be comfortable.
Does the car overheat without the a/c on???
Sorry for the random extra info. Needed a break from studying the human body.

Last edited by Jimmie34; 06-07-2007 at 09:40 AM..
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Old 06-09-2007, 02:45 AM   #6
eightynine535

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it only started to overheat that one time while stuck on the parkway in the heat. And no the A/C was not running at the time. It was only blowing hot air at that time. i just need to address this Aux fan issue before disaster happens!
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Old 06-09-2007, 03:38 AM   #7
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the early E34s (& E36s) had multiple issues w/ceramic resistors for the aux fan. I felt the same as you, I didn't trust the temp sensors so I put in a toggle switch where I can manually turn on aux fan if temp ever did/does climb. I connected the wires to the relay (brown relay) in the relay control box (3x5" box driv side -top of wheel well) one side to blue wire, other side to green wire. I only use it when in heavy traffic and using A/C - just added insurance against overheating.
Another note - E34 engine compartments handle ALOT of heat so the more air flow the better. I had the hood louvered and that dropped temp by some 20-30 degrees, but you need not go that extreme. On the pass side just behind headlamps is a black plastic circular plug about 5"s across, pop that out and you'll notice that she'll run cooler also. (that plug is same size as air filter intake on drivers' side)
To answer your initial problem - try the above mentioned switch on relay, make sure ALL your fuses are good and evac & refill your A/C (4lbs MAX) - prior to charging system add AC oil & AC sealant (since you mentioned prior owner let it sit for long time) I'm betting you'll have cold AC without having to buy a compressor.

Last edited by c1apton; 06-09-2007 at 03:45 AM..
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Old 06-09-2007, 03:29 PM   #8
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Be careful about the amount of oil that is put in the a/c system. Check with the spec but normally 2 oz is good. If you happen to get liquid intead of vapor back to the compressor you will end up buying a new compressor.
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Old 06-10-2007, 11:41 PM   #9
eightynine535

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I am gonna try and jump the AUX fan from the harness that goes to the double temp switch in the radiator. anyone know if it just pulls off or do i need to twist then pull?
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Old 06-17-2007, 12:06 AM   #10
eightynine535

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I jumped the fan harness to 12v tonight. I can get the fan to run on high but not on low. i guess the double temp sensor needs to be changed along with the resistor?
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Old 08-15-2007, 09:17 PM   #11
Kistoni

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Any follow up on this?
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Old 08-16-2007, 01:12 AM   #12
eightynine535

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yep...sorry I forgot to post up.

I changed the fan resistor, luckly mine was Bosch type so no wires needs to be spliced. And i also changed the double temperature sensor. everything is working like it should. we had a couple 90+ days here and thee car did not overheat once!
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Old 08-16-2007, 06:08 AM   #13
Kistoni

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Thx for the update 89fivethreefive

I m guessing my resistor is also gone. With you would the fan only run on fast when you jumped either wire or was it like mine which is only triggered by the black/grey wire is jumped to the brown wire and nothing when I jumped the black/green wire to the brown one?

I asked the stealers to check the wiring on the fan and they said it all checked out fine but I don t really trust them.

Does any one know if the aux fan is triggered only by the radiator sensor or is it triggered by the engine heat sensor too?
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Old 08-16-2007, 07:29 PM   #14
eightynine535

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with the resistor broken ( mine came apart in two when i removed it) the fan will only work on one speed.

the fan is triggered by the A/C and the double temperature sensor
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Old 08-28-2007, 10:57 PM   #15
eightynine535

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*update*

So i finally took the Bimmer to have the A/C system fully checked. the culprit is the compressor itself. they put in 4lbs of R134a and lost about 1lb from the badly leaking compressor. so now its on to find a replacement.
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