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Thread: Electric Fan troubleshooting

  1. #1
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    Electric Fan troubleshooting

    I'm kind of out of ideas and am not great with the multimeter, so looking for some ideas.

    So, for background, this is my setup: https://www.bimmerforums.com/forum/s...1#post29196261

    I wired the relay up by the Pac-man and the positive terminal for convenience. I have one of the switch wires going to pin #16 in the Pac-man, and the other going down to the aux fan switch. I have the two large relay wires connected to the positive terminal with a 30 amp fuse, and to the fan's two input wires. The fan ground is grounded to the horn bolt for the AC drier (the paint there I've sanded down to the metal to make good contact). The fan is supposed to draw about 24 amps when it's on high speed (which is how I have it wired).

    A couple months ago the fuse blew, so I figured the fan was dying.

    It quit working the day I finished the whole suspension rebuild I've been working on, and so I figured the fan finally died.

    I replaced it today, and nope - still didn't work. I had a new relay (I bought two before I realized I didn't ever need a low speed fan in Texas, so I had a spare on hand), so I swapped that in and violà - that was the culprit.

    Until the fuse blew 30 seconds later.

    I cleaned up the ground, checked all the other wiring, and ... nope - the fuse blew again after about 5 minutes.

    I mean, this is pretty simple. The two little relay switch wires are obviously working and also obviously AREN'T what's blowing the fuse. And the fuse isn't blowing instantly.

    The only other thing that's changed since last summer is I upgraded to a 140 amp alternator back around December. However, this is Texas, and I've already been using the AC (and therefore the radiator fans) pretty heavily for a while.

    I'll say it again - this SHOULD be pretty simple. The fan and fan wiring are all new, so a short wasn't happening there. The ground and the positive wire seem to be the only two other variables.

    I have the whole wiring harness from the other relay, so my next step is to assume there's a short SOMEWHERE in that wiring and replace it all (shouldn't even take me an hour).

    I'm kinda stumped, and also dubious that replacing the wiring that looks fine (and has worked just fine for the last 3 years) is just suddenly shorting against something (especially since I checked it all).

    Any other ideas?

    -Josh: 1998 S54 E36 M3/4/6 with most of the easy stuff and most of the hard stuff. At least twice. 271k miles. 1994 E32 740il with nothing but some MPars. 93k miles.

  2. #2
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    I wonder whether it is a resistance issue. Did you try a 40A fuse? How is the engine ground to chassis?

  3. #3
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    Quote Originally Posted by pbonsalb View Post
    I wonder whether it is a resistance issue. Did you try a 40A fuse? How is the engine ground to chassis?
    I did - the 40 blew too.

    I don't know about the ground - I was just under there yesterday and it was secure. I'm having zero other issues.

    A friend suggested checking the resistance, but I have no idea how to do that. I just got a multimeter for Christmas - I've literally never needed it.

    You up for telling me how to do it?

    At this point all new wiring (which is sitting in the garage) would take 30-45 minutes to swap, and may be faster than isolating the bad connection.

    I mean, this is a simple circuit, right? What else could it be aside from a bad connection?

  4. #4
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    Honestly a 40A fuse would scare me in that location. It shouldn't be blowing a 30A fuse, so obviously the 40A is just a bandaid and not the solution. If you have one, maybe try it out and see if it blows too.

    As Pbonsalb said, I would check the engine ground.

    Do you have a photo of your volt meter? or the model number? I can show you what setting you need for it to be on to test it.

    Yeah the fan is just a simple circuit, it shouldn't really be an issue.

    Also what do you mean with Pac-man?
    Last edited by Hova; 06-06-2019 at 11:08 PM.
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  5. #5
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    30A should be enough for added draw at startup with 23A running. I have been running 2 of these fans for years with 30A fuses. I guess I would redo the wiring. Resistance is just putting a lead in each end of a wire.

    Seems odd that fan is new, relay is new and fuse is new.

  6. #6
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    Quote Originally Posted by pbonsalb View Post
    30A should be enough for added draw at startup with 23A running. I have been running 2 of these fans for years with 30A fuses. I guess I would redo the wiring. Resistance is just putting a lead in each end of a wire.

    Seems odd that fan is new, relay is new and fuse is new.
    Quote Originally Posted by Hova View Post
    Honestly a 40A fuse would scare me in that location. It shouldn't be blowing a 30A fuse, so obviously the 40A is just a bandaid and not the solution. If you have one, maybe try it out and see if it blows too.

    As Pbonsalb said, I would check the engine ground.

    Do you have a photo of your volt meter? or the model number? I can show you what setting you need for it to be on to test it.

    Yeah the fan is just a simple circuit, it shouldn't really be an issue.

    Also what do you mean with Pac-man?
    Pac-man = the underhood diagnostic port with the little Pac-man in the middle.

    You may have missed my reply above - it blew a 40 amp fuse as fast as the 30. In fact, the only reason I tried it is because it came in the relay package from the Fan Man, so I figured it wouldn't be there if it wasn't somewhat ok.

    I'll replace all the wiring after work tomorrow. Trying to DD one of these things does catch up with you sometimes. And sometimes it catches up with you a couple weeks in a row.

    I appreciate the feedback. I really can't figure out what else it could be.

    I read up on checking resistance (omega it seems), so I'll check everything before I tear it out. Maybe I'll get lucky, or maybe I'll get new wiring.

    I don't even know what it would mean if I've still got problems after replacing everything...

  7. #7
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    If replacing wiring does not help, either the fan or relay would be suspect. You could test each. Run the fan with no relay just power and ground. Then add a relay but use another relay power and ground source not the obd port and fan switch. Also consider another inline fuse. I assume yours is water tight. Test that part as well, adding it in or putting it in from the start.
    Last edited by pbonsalb; 06-07-2019 at 06:08 AM.

  8. #8
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    Quote Originally Posted by pbonsalb View Post
    If replacing wiring does not help, either the fan or relay would be suspect. You could test each. Run the fan with no relay just power and ground. Then add a relay but use another relay power and ground source not the obd port and fan switch. Also consider another inline fuse. I assume yours is water tight. Test that part as well, adding it in or putting it in from the start.
    The OBD port is used so the switch is only hot when the car is on. Otherwise, the fan continues to run after the car is shut off until the aux fan switch cools off. My grandparents had an old 86 Accord that was like that, but I'd rather not worry about the battery running low on hot days.

    For testing I'd just tie it to the strut top or some other ground.

    I also realized I could try and just run the fan on low before I replace all the wiring and see if the problem persists - might provide some insight. But yeah, I'll likely pull it all this afternoon.

    I have a hard time believing it's the replacement fan itself when the original had the same problem (after working fine for three years).

    I'll update when I have any news.

    -Josh: 1998 S54 E36 M3/4/6 with most of the easy stuff and most of the hard stuff. At least twice. 271k miles. 1994 E32 740il with nothing but some MPars. 93k miles.

  9. #9
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    Don’t worry about switched vs unswitched for testing purposes. It’s easier to use unswitched. You want to test the fan, test the relay, test the fuse by not using your wiring. Start with the fan. Use test leads to run it — will it run for 10 minutes? Then add a relay. Will it run for 10 minutes? Then add a fuse and test again. Put the battery on a charger if you are worried about it. No need to drive the car or even turn it on. Why risk overheating?

  10. #10
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    Josh, I just read everything again, and understand your setup now. I skimmed through it at first.

    Just to be clear, your electric fan runs 100% of the time when your car is on, correct?

    As pbonsalb said, I would just run the fan with an inline fuse directly to a battery, or to the positive lead without the relay. See if it blows the fuse that way. Run it on the high setting, it shouldn't blow the 30amp fuse. If after some time passes, and it doesn't blow, then test the relay. It has to be one or the other (or a frayed wire) causing the issue.
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  11. #11
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    Quote Originally Posted by Hova View Post
    Josh, I just read everything again, and understand your setup now. I skimmed through it at first.

    Just to be clear, your electric fan runs 100% of the time when your car is on, correct?

    As pbonsalb said, I would just run the fan with an inline fuse directly to a battery, or to the positive lead without the relay. See if it blows the fuse that way. Run it on the high setting, it shouldn't blow the 30amp fuse. If after some time passes, and it doesn't blow, then test the relay. It has to be one or the other (or a frayed wire) causing the issue.
    [Edit] Forgot to answer your original question - no, the main puller fan is wired (via relay) to the aux fan switch. They always run together, either because the AC is on, or if they get hot.

    Dammit, and it ate my original reply.

    Long story short, I tried to run it just on low speed and it worked great for 20 minutes, then locked up and started smoking. 30 amp fuse and relay all in place. This is a "normal" install per their instructions.

    So it seems it was this new fan that was bad all along. (Obviously the original relay went bad first, but this mess is because the new fan was a dud)

    I'll reinstall the original fan tomorrow after it all cools down, and hope and pray we're back in business.

  12. #12
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    [Update]

    Net of all of this is that the original fan is wearing out, blew a fuse, and then the relay went.

    The replacement fan was bad and kept blowing fuses. I chased all kinds of potential other root causes, and ultimately tried just running this new fan on low speed (with the recommended 30 amp fuse), which fried the fan and tried to burn down the car.

    Since the original reason the fan wasn't running was the relay was bad, and I've replaced it, I went ahead and reinstalled the original fan when I pulled the new one to return it.

    It ran great, didn't blow the fuse, cycled a dozen times while I bled the radiator, and is operating normally. I'm sure it'll blow the fuse again at some point since it seems to be failing (it did seem to be worn out while I tinkered with it while it was out of the car), but the replacement replacement should be here within a week or two (of course Amazon is out of stock at the moment).

    I think we can call it case closed.

    Thanks for all the ideas guys!

    -Josh: 1998 S54 E36 M3/4/6 with most of the easy stuff and most of the hard stuff. At least twice. 271k miles. 1994 E32 740il with nothing but some MPars. 93k miles.

  13. #13
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    Quote Originally Posted by blckstrm View Post
    [Update]

    Net of all of this is that the original fan is wearing out, blew a fuse, and then the relay went.

    The replacement fan was bad and kept blowing fuses. I chased all kinds of potential other root causes, and ultimately tried just running this new fan on low speed (with the recommended 30 amp fuse), which fried the fan and tried to burn down the car.

    Since the original reason the fan wasn't running was the relay was bad, and I've replaced it, I went ahead and reinstalled the original fan when I pulled the new one to return it.

    It ran great, didn't blow the fuse, cycled a dozen times while I bled the radiator, and is operating normally. I'm sure it'll blow the fuse again at some point since it seems to be failing (it did seem to be worn out while I tinkered with it while it was out of the car), but the replacement replacement should be here within a week or two (of course Amazon is out of stock at the moment).

    I think we can call it case closed.

    Thanks for all the ideas guys!

    Whoa, dude that's nuts. What are the odds of two fans breaking at the same time lol. At least now you know the issue, I kept thinking weird, fans and relays are simple, there shouldn't be an issue unless a wiring short or something.

    Glad you figured it out.
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  14. #14
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    Quote Originally Posted by Hova View Post
    Whoa, dude that's nuts. What are the odds of two fans breaking at the same time lol. At least now you know the issue, I kept thinking weird, fans and relays are simple, there shouldn't be an issue unless a wiring short or something.

    Glad you figured it out.
    The only really bad thing about it all was how much wife capital I burned up!

  15. #15
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    I hope your replacement for the replacement is a different brand fan. Two out of two failures is two too many.
    '96 M3, S50B32, 6MT
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    Quote Originally Posted by M3AN View Post
    I hope your replacement for the replacement is a different brand fan. Two out of two failures is two too many.
    It does make me a little nervous.

    The original one is actually running right now - it's like nothing happened. It was the relay all along. I don't know if it's wearing out / slowly getting worse and that's why it's blowing fuses, or if there was some other electrical event that blew the fuse and killed the relay (I had a bad alternator that was charging at like 18 volts when I revved it past about 4k), and now that all that stuff is sorted (a Bosch 140amp vs the original Valeo 80 amp) I think I just need to keep an eye on it. I'm getting a replacement from Amazon, which I'll test before installing.

    I don't know if you looked at my install, but it was pretty involved and depended on this particular fan to make the mounting work (in the factory shroud). I don't buy it when people tell me to get rid of the factory shroud and mount the fan directly to the radiator. This is a street car, with AC, in Austin Texas (meaning ambient temps around 110+F in the summer, or 45 degrees C) - I am keeping the aux fan with its shroud and the radiator-side shroud, and am not interested in a "race car" solution.

    I've looked at other setups, but I've decided I'll go back to a mechanical fan before I go to a solution that requires I ditch the shroud.

    -Josh: 1998 S54 E36 M3/4/6 with most of the easy stuff and most of the hard stuff. At least twice. 271k miles. 1994 E32 740il with nothing but some MPars. 93k miles.

  17. #17
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    Quote Originally Posted by blckstrm View Post
    It does make me a little nervous.

    The original one is actually running right now - it's like nothing happened. It was the relay all along. I don't know if it's wearing out / slowly getting worse and that's why it's blowing fuses, or if there was some other electrical event that blew the fuse and killed the relay (I had a bad alternator that was charging at like 18 volts when I revved it past about 4k), and now that all that stuff is sorted (a Bosch 140amp vs the original Valeo 80 amp) I think I just need to keep an eye on it. I'm getting a replacement from Amazon, which I'll test before installing.

    I don't know if you looked at my install, but it was pretty involved and depended on this particular fan to make the mounting work (in the factory shroud). I don't buy it when people tell me to get rid of the factory shroud and mount the fan directly to the radiator. This is a street car, with AC, in Austin Texas (meaning ambient temps around 110+F in the summer, or 45 degrees C) - I am keeping the aux fan with its shroud and the radiator-side shroud, and am not interested in a "race car" solution.

    I've looked at other setups, but I've decided I'll go back to a mechanical fan before I go to a solution that requires I ditch the shroud.
    My last alternator was charging to around 20 volts. It destroyed my battery. Shocked it didn't take out anything else.

    What is wrong with just running the original AUX fan with a lower thermostat and lower fan switch? I'm in FL, multiple E36 M3's over my life, zero issues with the fan delete mod.

    The idea of no fan shroud is that when the car is going over 30-40mph, the shroud is blocking air and forcing it down the center. I run a shroud, I think running a shroud is a good idea for most applications.
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  18. #18
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    Quote Originally Posted by Hova View Post
    My last alternator was charging to around 20 volts. It destroyed my battery. Shocked it didn't take out anything else.

    What is wrong with just running the original AUX fan with a lower thermostat and lower fan switch? I'm in FL, multiple E36 M3's over my life, zero issues with the fan delete mod.

    The idea of no fan shroud is that when the car is going over 30-40mph, the shroud is blocking air and forcing it down the center. I run a shroud, I think running a shroud is a good idea for most applications.
    Ha! Yeah, I went through about a dozen O'Reilly alternators trying to find one that worked properly. I finally gave up and bought a Bosch-remanufactured Bosch from eEuroparts and it's been perfect.

    As for the extra fan, it's just too hot here when it really gets hot to run only an aux fan.

    It's around 10 degrees hotter sitting on the freeway than the actual daily temperatures. I regularly see 115-120 on my OBC when it's 105-110, which is any time from June - September.

    The lower temp switch isn't really necessary since it basically runs full time when the AC is running - and if it's over ~90, the AC is on. The same general principle applies to the thermostat, but mine is failed open, so I'll use the lower temp one when I replace it this fall/winter.

    -Josh: 1998 S54 E36 M3/4/6 with most of the easy stuff and most of the hard stuff. At least twice. 271k miles. 1994 E32 740il with nothing but some MPars. 93k miles.

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