Author Topic: A/C Aux fan (Read 6728 times)

oldtimer · « **on:** July 08, 2007, 09:46:33 PM »

The temp. has been high around southern Maryland in the last few days. Today my A/C was not as cold has it has been even when it was 90 degree and 80 percent humidity. So I thought I would check if the Aux fan if comes on when the A/C is on. It does not turn on at all. After long trouble shooting I discovered that this "chocolate" bar looking thing with a "Black" wire coming out of each end. So I bypassed it and the fan worked as advertise. My question is. What is the function of that things. http://www.realoem.com/bmw/showparts.do?model=1374&mospid=47315&btnr=17_0073&hg=17&fg=10

The link above item #14 indicates it's a resistor. Someone educate me as to what's a resistor does to the Aux fan, for the time being I cut it off and connected the two "black" wires together. Tracing one of the "Black" wire it was spliced to the "Red" wire.

Wise Old Dog · « **Reply #1 on:** July 08, 2007, 10:03:50 PM »

It is the resistor that makes the fan a 2 speed fan. The low speed circuit runs through it. That's why the temp sensor switch has 3 pins.

oldtimer · « **Reply #2 on:** July 09, 2007, 10:03:33 AM »

What action have I done by cutting that off and connecting the two wires from it together?

Wise Old Dog · « **Reply #3 on:** July 09, 2007, 10:10:59 AM »

You have eliminated the low speed function of the system. It will still work, but you will hear it more than before. Low speed is not very noisy.

FL318is · « **Reply #4 on:** July 09, 2007, 10:35:03 AM »

I LOVE THIS PLACE!

First I want to publicly thank OT for all his help on a recent trip to MD. He went out of his way to accomodate my son and I. My only regret was that i was not able to buy him lunch. OT, thank you very much. BTW, post some pics of that amazing E30 I saw.

Now back to car talk. My ac is not blowing cold at all. The aux fan is not rotating either. It does spin freely by hand.

I tried to trouble shoot and "jump" 2 of the 3 prongs on the sensor (item 6). I probably did not do it correctly. So my question is this, when you connected the 2 wires, did you just wire them together and did the ac blow colder? Right now I have no ac.

http://www.realoem.com/bmw/showparts.do?model=AF93&mospid=47305&btnr=64_0516&hg=64&fg=55

The heat down heat sux and I am about to lose the E46 to college.

oldtimer · « **Reply #5 on:** July 09, 2007, 11:43:52 AM »

Glad I was able to particepate with your plan with you son. I know this is probably not the place to admit this but it's okay. I had my cell with me when we went sailing which means I don't have you number and for some add reason I can't open the PM's from you. PM me. Okay car talk. When I first got the car naming the 91 318is the A/C did not work. So I immediately coverted it to the R134. Had the system vacuumed out and then induce some oil moments after, then re-charged with the R134. the original fan did not work it was frozen. so I took a after market 14" fan and wired it in, it stopped working two days ago which prompted me to troubleshoot the system. My discover was that "resistor". I cut the wire from each end and just used your standard wire connector. having done this, the fan is not all that loud sound the same as the 1984 318i.

scottiesharpe · « **Reply #6 on:** July 09, 2007, 01:06:04 PM »

I bypassed the resistor on an e28 I had once like you did. Like you, I figured, hey why not run it on high all the time so I can stay cool inside. Well I ended up melting some wires in the fuse box. Apparently BMW did nut put enough wire guage into the low speed circuit to handle the draw of the fan on high speed.

If you want to run the system on high, I recommend swapping the sensor wires so that the low speed sensor turns on the high speed fan circuit. You can disconnect the high speed circuit (or put it on a light inside the cabin).

FL318is · « **Reply #7 on:** July 09, 2007, 01:12:45 PM »

Quote from: scottiesharpe;29292

I bypassed the resistor on an e28 I had once like you did. Like you, I figured, hey why not run it on high all the time so I can stay cool inside. Well I ended up melting some wires in the fuse box. Apparently BMW did nut put enough wire guage into the low speed circuit to handle the draw of the fan on high speed.

If you want to run the system on high, I recommend swapping the sensor wires so that the low speed sensor turns on the high speed fan circuit. You can disconnect the high speed circuit (or put it on a light inside the cabin).

DANG IT!

I seem to recall our cars take the R12. A friend of mine suggested they may be a certain head pressure needed for the aux fan. All I know is the AUX fan DOSEN'T blow and with the ac button pushed in there is no cold air.

oldtimer · « **Reply #8 on:** July 09, 2007, 02:58:20 PM »

As for the sensor you speak of. Are you talking about the one mounted on the side of the radiator just above the lower radiator hose.

Gary:

have your system vacuumed out at least 30 minutes any shop with the A/C system tool can do it. I had mine done at Midas. Since your system was never opened up, I mean new compressor or new line there's no need to induce oil. Just buy one of those conversion kit. the one I use was 40.00 at Auto Zone. With the system at negative vacuum it should suck up the new R134. If I re-call correctly it takes about 2.5 lbs. The kit should contain 3 lbs. but the guage that comes with the kit will tell you the system is charge.

FL318is · « **Reply #9 on:** July 10, 2007, 07:31:11 AM »

Quote from: oldtimer;29299

As for the sensor you speak of. Are you talking about the one mounted on the side of the radiator just above the lower radiator hose.

Gary:

have your system vacuumed out at least 30 minutes any shop with the A/C system tool can do it. I had mine done at Midas. Since your system was never opened up, I mean new compressor or new line there's no need to induce oil. Just buy one of those conversion kit. the one I use was 40.00 at Auto Zone. With the system at negative vacuum it should suck up the new R134. If I re-call correctly it takes about 2.5 lbs. The kit should contain 3 lbs. but the guage that comes with the kit will tell you the system is charge.

yppm

Vladi · « **Reply #10 on:** July 10, 2007, 05:05:00 PM »

Quote from: scottiesharpe;29292

I bypassed the resistor on an e28 I had once like you did. Like you, I figured, hey why not run it on high all the time so I can stay cool inside. Well I ended up melting some wires in the fuse box. Apparently BMW did nut put enough wire guage into the low speed circuit to handle the draw of the fan on high speed.

If you want to run the system on high, I recommend swapping the sensor wires so that the low speed sensor turns on the high speed fan circuit. You can disconnect the high speed circuit (or put it on a light inside the cabin).

That's what i did also and after a couple of months ended up with a part burnt fuse box. I soldered a wire on the back then to make it work but now i'm going to replace the whole thing and run it normally. :mad:

tjts1 · « **Reply #11 on:** July 10, 2007, 05:12:01 PM »

I installed a larger more powerful puller fan as my main fan to replace both the AUX fan and the clutch fan running off the existing low and high speed relays and circuit for the AUX fan. It runs fine and so far no melted wires. We shall see.

FL318is · « **Reply #12 on:** July 10, 2007, 08:54:18 PM »

I discovered today that the magnetic clutch is not spinning. I am now suspect of a switch or relay.

oldtimer · « **Reply #13 on:** July 10, 2007, 10:18:07 PM »

I was having a chat with another Bimmer lover at a local parts store today and he informs me that there is a way to "bypass" the low pressure switch to see it the clutch will engage without charging the system. I'll probably investigate this week end and will post result. Other than that the only way to determined it the clutch is gone, in this case the compressor is to re-charge it and if you still have the old R12 in it it would be a waste to do so if you find out the compressor is no good. If you have a good relationship with your local a/c shop one can have the system charge just to have the correct pressure and run the a/c. If the compressor does not engage with the pressure. They can always suck up the charge without loosing anything.

FL318is · « **Reply #14 on:** July 11, 2007, 07:29:32 AM »

Would it then be logical to assume that without the ac system being fully charged (head pressure) the fan and mag clutch would not engage?

OR

If the system needs a charge, can you charge it without the mag clutch engaging?

These questions are a direct result of, "a little knowledge is dangerous!"

The OBC indicated 97 degrees. Today I plan to drive home windows down and wear swim trunks. LOL