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AUX Auxiliary Fan not working but its not the FAN!
HELP! My electrical Aux fan doesn’t work and my car overheats now in the summer. HAVING WIRED IN A NEWTEST FAN – I KNOW IT’S NOT THE FAN ITSELF. CAN’T FIGURE OUT WHAT’S WRONG – HELP PLEASE! I did NOT remove the existing fan. Thank god - an awful job. I just tested a new one. My repair steps: Here are paths I’ve taken: Tried laying a new fan on the engine (uninstalled) with pos and neg wires. Didn’t work. I assume that the third little black wire in that cluster of 3 (sensor wire from the DME) is holding me all up. (Might be wrong, but it’s my guess.) Have not tried to test that 3rd wire as it needed an oscilloscope or something. Also, I have a hole in my cat, not sure if that’s contributing. My Bentley manual says that Cat temp could be a factor, but not sure. Final Stage Resistor inside under dash – I replaced this last year, but it could be bad. Fuse – 50 amp is not blown in Glove fusebox A/C pressure switch on A/C line– jumped the pos and neg posts for continuity and while car off, there’s continuity. Did not get any continuity from the 3rd terminal. I think it's a combo high/low sensor. Both cooling temp sensors in the hoses were just replaced 3 months ago. Assume, correctly and good, but may not be true A/C does blow cold once the car moves. But, if standing still, A/C gets warm and the engine gets dangerously hot. I have to turn engine off when hot. The A/C gets cold slowly even if I am driving at higher speeds. I have to toggle the snowflake switch once or twice to get cold. I’m at the point of trying to figure out if it’s the ECM (engine control module, located in the engine EBox) or DME or a sensor. ANY THOUGHTS? How to know? HELP! I can’t figure out how to get this to work! Anyone know? |
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#2
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Sent via Telegraph Wires using my Morse Key. 2015 X5 xDrive35i MSport 2013 X5 xDrive35i |
#3
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The fan (new or old) won't spin with just positive and ground connected - the signal wire controls the speed. You would need a function generator and know what sort of pulse width modulation BMW uses to manually operate it. It is better to plug the fan in and use software to force the fan on. A generic scanner won't do it, but there are several BMW specific software tools that will.
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David.X5 2001 X5 4.4i Sport SOLD! at 160k miles |
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2006 Infiniti G35 2001 BMW 3.0I E53 X5 Build date 08/2000 SOLD Lotus Europa 1970 Destroyed by fire Lotus Europa 1970 S2 Renault Powered Lotus Type 52 1970 Twincam Webers Powered PORSCHE 911 Targa 1982 The Garage Queen Audi Avant donated to Kars for Kids BMW 525IT Sold Audi 4000CS Quattro Sold Jensen Healey Lotus Powered Sold Opel 1900 Sold Triumph Spitfire 1971 Sold Triumph Spitfire 1968 Sold Plymouth "Cuda" 340 Six pack SOLD |
#5
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Thank you for all your responses.
Just to be clear: I tested the pos/neg on the harness leading to the fan. Voltage was 12V. Did NOT test the thin control signal wire. Read enough here to stay away from that. Got a brand new fan and plugged it into the harness. All 3 wires. Nothing. FSR, temp sensors, hoses just replaced (curiously this started shortly after.) Did that indy in Morris plains, NJ do it right? Some doubts. What I don't know is what's coming out of the signal wire, and IF there's a signal to activate the fan. Upallnight, you make a good point about that. But already took it to the BMW dealer in Suffern who said I "need a new aux fan." RIGHT. So, now to find an indy with diagnostic gear capable of testing the signal wire and more. This is a pretty pervasive problem. A lot of complaints, few solutions. Some replaced the Aux fan and that did it. Others never seemed. To find a solution. I just want to use this resource to get some clues about what it might be to talk to a shop. Why reinvent the wheel? |
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zulu95, thanks for the diagram. I saw that before too. Looking at that, I wonder about the A/C pressure switch (3 leads, 2 of them do give continuity, probably the high side. I think it's a combo high/low switch). Or a radiator temp sensor (as I said, just replaced both with all hoses and tank.) hard to test the temp sensors, other than with BMW software, so off to a GOOD indy in North Jersey. Any reco's for n indy or ideas? Thanks.
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#7
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At start up the DME will command the fan to turn on and turn off power to the fan and wait for the fan motor to send back a voltage through the signal wire back to the DME that then fan did turned on and is now producing a DC signal. The IKHA module is also responsible for turning on the fan. If you have BMW scanning software you can verify this.
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2006 Infiniti G35 2001 BMW 3.0I E53 X5 Build date 08/2000 SOLD Lotus Europa 1970 Destroyed by fire Lotus Europa 1970 S2 Renault Powered Lotus Type 52 1970 Twincam Webers Powered PORSCHE 911 Targa 1982 The Garage Queen Audi Avant donated to Kars for Kids BMW 525IT Sold Audi 4000CS Quattro Sold Jensen Healey Lotus Powered Sold Opel 1900 Sold Triumph Spitfire 1971 Sold Triumph Spitfire 1968 Sold Plymouth "Cuda" 340 Six pack SOLD |
#8
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Strange- replacing the fan again actually worked!
I had plugged in the new aux fan several times without any movement. And frustration, I tried it again yesterday before sending it back and it worked!
Took it right over to an auto body shop and in one hour and $100 later I was back in shape. I have no idea why it didn't work for this time. I cleaned the connectors. BMW gremlins!! One thing that the auto body shop guy told me that's important was that you really CAN NOT run this car without the aux fan. The reason is that the AC condenser when running IS HOT and blows hot air into your main radiator. (that's why, when you turn on the AC the engine will run hotter.). In the summer it only makes the situation worse when the aux fan is inoperable. Thanks to everyone for their help. |
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OK, IT *WAS* THE AUX FAN
Can't believe it, but I plugged in the new Aux fan one more time before sending it back. Just laid it on top of the engine, the old one still installed.
Damn! It worked this time. So, I took it to a local cheap body shop and for $100, they slapped it in as I watched. IT ALL WORKS NOW. No overheating. Keeps on when I turn it off. Can't believe it. Not sure why it didn't work before, but who cares (until the next time it doesnt work!) BMW GHOSTS.... |
#10
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New Aux fan worked when plugged in but doesn't after install
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I spent the extra money on the OEM BEHR fan to be sure it would not go bad. Could something be shorting the fan out, or maybe it will suddenly start working like yours did? I do not have much time as I will need to uninstall the fan and return it soon if it did actually fail. Any input would be greatly appreciated. |
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aux, auxiliary, dme, ecm, fan |
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