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Blowing 30amp aux fan fuse

eaglerider94 on Wed August 07, 2013 12:04 PM User is offline

Year: 1994
Make: BMW
Model: 525i
Refrigerant Type: 134a
Country of Origin: United States

Recently blew 30amp aux fan fuses twice. The 3rd time, all of the freon blew out of the "safety" plug of the drier. Is this related to the blown fuses? What should I be looking at before refilling the system as I am concerned this had something to do with the blown fuses. Resistor going bad?

mk378 on Wed August 07, 2013 12:10 PM User is offline

Most likely, the fan motor is bad or there is a frayed wire shorting out.

Overheating of the condenser after the fan stops causes overpressure. So yes, that was related. You need to fix the fan first.

Edited: Wed August 07, 2013 at 12:12 PM by mk378

eaglerider94 on Wed August 07, 2013 5:31 PM User is offline

Thanks MK, I'll check the high and low operation of the fan as well as the resistor.

emsvitil on Thu August 08, 2013 2:12 AM User is offlineView users profile

Is the compressor coil on the same fuse?

If so, the coil may be partially internally shorted.


NickD on Thu August 08, 2013 9:30 AM User is offline

One good idea what replacing the pressure release valve that was used for years with a high pressure cut off switch. Surprised your 94 BMW wasn't equipped with that. But prior to the EPA getting involved and R-12 was something like 25 cents a pound, who cared? BMW must have tossed in an older dryer in your vehicle. Would definitely install a high pressure cut off switch in series with the clutch coil.

mk378 on Thu August 08, 2013 9:43 AM User is offline

Also stop up the hole with tape or something until you can make repairs. It's important to keep water, including moist air, out of the system.

eaglerider94 on Sun August 11, 2013 11:15 PM User is offline

eaglerider94 on Sun August 11, 2013 11:23 PM User is offline

Funny thing is, my dryer had the pressure relief valve AND the high pressure cut off switch attached to it. It must have worked because it stopped the compressor from working once the freon was blown out.

Anyway, I removed the aux. fan resistor to find out what the ohm reading was. Resistor is labeled: 85W at .5 ohm.

I set the ohm meter to 2K and got a reading of .001. Is this an open (defective) resistor?

Edited: Sun August 11, 2013 at 11:24 PM by eaglerider94

NickD on Mon August 12, 2013 7:15 AM User is offline

Not strange at all if you BMW has a cycling switch, need at least 45 PSI of static pressure before it will close to enable the compressor.

Depends on the lowest range of your ohmmeter, with a VOM 200 ohms maximum is way too high, need one with a 2 ohm ranger to read 0.5 ohms accurately, they cost more than ten bucks. You do know that its not blown open, but know that anyway, because if it was blown open, you wouldn't be blowing any fuses.

Did you try to hand spin your fan bladed? Could have a seized bearing, if it can't spin, would blow a fuse instantly, also shorted turns in the motor would do that, or a broken brush spanning two commutators. Really doesn't make much difference any way if you try to take these motors apart to attempt to repair them, redefines the meaning of throwaway. Also clarifies the meaning of that word, sh!t.

mk378 on Mon August 12, 2013 9:35 AM User is offline

It seems like the resistor would just be in series with the motor to slow it down on low speed. No matter how the resistor might fail, it wouldn't blow the fuse. Like Nick said, check the motor thoroughly. You could connect it directly to a battery and measure how much current it uses.

Leggie on Mon August 19, 2013 10:12 PM User is offline

What does the blown fuse look like? Blistered or slow melt? Obliterated? This should tell you the cause.

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