Troubleshooting blower motor (heat)....so I got the heat working in my car,

[audiquattrot]

but it works sporadically.

Whats weird is, it wasn't functioning at all on any settings....so I pulled the shroud open (exposing the blower), and kind of spun it a little and it started to work. It worked on all settings. I then proceeded to turn the car off, and try it again....no luck. So I pulled the resistor (which was recently replaced), and checked to make sure the values were right:

• 1.6 Ohm
• .9 Ohm
• .35 Ohm

and they were within spec. I sprayed down all the leads, resistors & brushes on the motor w/ QD electronics cleaner, and it seemed to have helped....although it seems to still work in spurts.

Question I have is, does this sound like a bad motor? Like I mentioned earlier, when it wasn't functioning....i spun the motor w/ my fingers to give it a head start....and it worked.

[emi325i]

a bad motor will set your car on fire. 30A is no joke.

[Jean]

that's what fuses are for.

[emi325i]

that's what fuses are for.

explain my melted fuse box, then..

[allwheeldrive]

Yes, the motor is bad. Your melted fuse box is from the heat caused from the resistance build up inside the wires from the motor not spinning.

Replace the motor at the very least. I would suggest the wires too if it melted the fuse block.

[Jean]

explain my melted fuse box, then..

your car has other issues / problems ?

[emi325i]

Yes, the motor is bad. Your melted fuse box is from the heat caused from the resistance build up inside the wires from the motor not spinning.

Replace the motor at the very least. I would suggest the wires too if it melted the fuse block.

I had to rebuild the entire circuit. The motor was spinning just fine. I was charging the a/c system, and had the blower on high for about 10 minutes (it was definitely running!). I came back later to find that the blower was out, and when checking the fuse found a 1inch-wide hole in the fuse box. That was so exciting.

I ended up taking the blower out, checked it out. The resistance was low. I blew the carbon dust out and the resistance checked out normal. I put it back, and it's been running just fine since then.

So what happened is that those morons in germany, back in 80s, designed the wiring and fuse box for 20A, but placed a 30A fuse on this circuit. So, the defective motor was drawing, lets say, 28-29A through wiring meant for 20A. Obviously the fuse didn't blow.

Recently, I was diagnosing a problem with my brother's e30, which had a non-functioning aux-fan. I found that someone had literally cut the harness near the fan. After reconnecting it, it still didn't work. The aux-fan hi-speed relay ground wire (from the fuse box to the ground point under the dash) was molten. I concluded that there was a "thermal" event which probably caused a lot of smoke inside the vehicle.


Conclusion: BMW can't do electrical systems.

[Jean]

I am tempted to check the current draw on the fan, I will shit my pants if I see it draws a constant 15amps to run just the blower fan.


Car in the ON position, lights off... 4.35 amp draw
Car in the ON position, lights off, acc.(a/c) fan on half speed, 10.2 amp draw
Car in the ON position, lights off, a/c fan off, blower fan on speed 1, 7.5 amp draw
Car in the ON position, lights off, a/c fan off, blower fan on speed 2, 10.7 amp draw
Car in the ON position, lights off, a/c fan off, blower fan on speed 3, 12 amp draw.

[emi325i]

Take the fan out .. check the resistance, blow the carbon out. You'll be ok.

[babychaser]

you guys DO know that 30A is only used for a few seconds? its called the 'starting current'. the more amperage. the more torque. and you need torque to make the motor go from 0RPM. to just say 100RPM. then the current lowers to about maximum 18-20A. so it makes sense that this circuit is in the 20A block cuz the 30A is only there for a second. but when the motor isnt working. then theres just 30A going thru all the wires to try to create that starting torque. and if the electricity isnt dissipated into mechanical energy (motor turning), then it dissipates in heat. causing it to melt.

[Jean]

I was just doubting that there is 15-30amp of CONTSTANT Current draw for a fan.