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Melting Fuse Box Problem Creates Losing Coolant


mayoslc
07-09-2004, 10:58 PM
THIS MESSAGE WAS POSTED BY Xzilla ON 5/10/04;
The fusebox melting in a 533i is a common problem. I went thru two myself before I did some research to find out the problem a few years ago. It's an undersized wire going to the aux electric fan for the radiator. Too much current is drawn thru the fuse and causes it to heat up...and melt the plastic around it. If I can re-find the fix for it, I'll post it. It's essentially just pulling a larger feed wire to the fan from the fusebox.
CAN SOMEONE PLEASE HELP ME WITH WHAT GAUGE WIRE? HOW DO YOU ROUTE THE WIRE?? I ASSUME ON TOP OF THE EXISTING WIRE HARNESS WITH PLASTIC WIRE TIES! PLEASE ADVISE, SINCE I AM CONSTANTLY BLOWING THE HI-SPEED AUXILLARY FAN FUSE AND LOSING COOLANT WHEN THE TEMPERATURE GOES 3/4 HIGH!!!!

jeffreyb4me
07-10-2004, 01:48 PM
I recommend you first address your cooling system problem ! you have one !.....the Aux. Fan circuits are actually quite reliable until the cooling system components age, wear or 'weaken' and the Aux. Fan circuit becomes 'overtaxed'.
It would help if you'd listen any cooling system work you've done recently and I'll look into your gauge question unless some has an answer for you first.......why are you rerouting the wire?...........jb

mayoslc
07-10-2004, 05:11 PM
I haver replaced the water pump, installed a new 8n blade clutch fan and checked the ballast for the high speeed aux fan, but when the fuse blows for the high speed aux fan, I always keep boiling over and dumping my coolant. Any suggestions would be greatly appreciated!! The undersized wire issue came from someone else who was having similar problems.

jeffreyb4me
07-10-2004, 05:28 PM
i shall retrun with some 'thoughts' for you 7/11, ok?

mayoslc
07-10-2004, 06:01 PM
Works for me-thanks!!!

jeffreyb4me
07-11-2004, 02:16 PM
Next suggested step would be to replace the Thermostat. USE THE CORRECT temp ['80C ?] and be careful with the housing bolts, if rusted they can snap. carefully bleed the system [easy, just open the bleeder screw on top of the T-stat housing until coolant trickles out] and recheck the system..........IF it's still running hot, check to temp. [by hand is ok] of the radiator inlet[top] and the outlet hose[bottom]........they BOTH should be HOT.......if that lower hose is cool/cold you'll need to replace the radiator [they clog over time and can't be cleaned effectively due to the alum./plastic construction....i'll be awaiting your
wonderful [hopefully] results..........................jb.

mayoslc
07-15-2004, 10:10 PM
Thermostat correct and radiator was replaced last year. Anyone know how to test resistance of auxillary fan in front of radiator?? Since it's a 20 year car, might be pulling too much resistance and blowing fuse.

i_jim
07-16-2004, 12:43 PM
I think I might have a similar problem with my 84 533i: the 25 amp fuse for the heater/AC blower overheats and melts the plastic around the fuse clip- the fuse never blows, it just falls out! It typically happens when I've been in stop & go traffic. This just started in the last few weeks, & I've been thinking it might be a wiring problem- any further info would be appreciated.

jeffreyb4me
07-16-2004, 05:16 PM
well then......how old is the fan clutch itself?? I don't think we've covered this yet, and as previously stated, these cars shouldn't be running hot enough to overheat W/O the aux. fan unless abbirnt air is, maybe, 95'F and idling 'in traffic' for a while. yes I know there are two fan switches on the radiator, but until the high temp switch closes,
the normal speed air flow does little except drop the temp. of the a/c condenser when in use [which also adds to the thermal load on the cooling system
which a proper functioning thermostat, radiator & fan clutch can handle. I've emperical evidence from working the east coast, the Denver/Boulder area and now the west coast, N/W as it maybe......

you can't directly measure the aux. fan motors resistance but with an ammeter, measure the circuit's draw, right across the fuse tabs if you like.
More to the issue however are the VOLTAGE DROPS
across the circuit. Without getting too technical here, added resistance due to bad connections, etc
don't add, wait, I'm not sure how deep to get here..
....the new local 'load' in the circuit, in a place not designed for it, has to dissipate the energy it's now consuming as a new load in the circuit, trying to share the current the designed load consumed. It does this by overheating causing furture damage.

Am I making any sense here, I'm not sure, have I answered any questions yet, I don't really know....
Make SURE the cooling system's 99-100% 'pure', we can deal with bypassing the damaged fuse box with a bit of wire, another 30A relay and a little time if anyone is "game" for that.....................jeffb

mayoslc
07-17-2004, 06:21 PM
Well the auxillary fan has never been replaced on the car....20 years old. The radiator was replaced last year, an 11 blade fan, and clutch fan was replaced last year. Thermostat is actually a cooler thermostat. When the temperature goes above 85 degrees that when I notice the fuse start to blow. High auxillary fan is set up to come on and bypass low speed. Coolant is 70% low-toxic antifreeze, topped off with distilled water to dispate heat faster. Could it or might it be the auxillary fan..I don't know other than to take a chance and replace it. The cost thru Bavarian Autosport is $350.00 plus shipping.

jeffreyb4me
07-18-2004, 07:52 PM
That's a pretty steep price to throw a dart, even one that's well aimed. Yet, I'm puzzled at your persistent problem...this may sound really silly, but have you been using BRAND NEW, OUT OF THE BOX
PELACEMENT PARTS? IT would be the first time I've seen a person spend time and money on 'Good Used' parts where NEW items were called for. That
aside, you've addressed every issue that can plague these cars when they age.....except one, if due it's years the coolant were neglected long enough, rusr/scale can build up in the engine block
though you would have noted it's presence replacing the components you have recently. As I've mentioned in other posts, when these cars were new, running hot/overheat was never a problem [unlike E12's] and your problem's 'bugging'
me as much it is you. If you've temp. tested the system as I suggested and the lower hose is good and hot, the system is simply at it's capacity, fine but why is it still overheating so badly. You've given no reason to suspect a head gasket/crack problem though they do occur. The fuse [with a damaged fusebox] might get hot but not 'blow'. I assume you've replaced the wire terminals for the high temp. switch and connected them to the low temp switch as your 'by-pass' and the Aux. Fan does run for a time until the fuse 'blows'. I'll wait 'til you write once more, perhaps having found something simple we've missed, I know I'm missing something here, just a few comments from last post
50/50 is the BEST mix...higher antifreeze will increase boiling point but DOES'T conduct heat as well [ 100% water is actually best for that ]. Distilled water IS a good idea and adding a 'water wetting agent' is also effective and are availible in parts stores - avoid 'Magic In A Can' products though..........things like this are annoying since I think with 10-20 minutes with your car, I'dve solved
it buy now, I await your words.......................jeffb

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