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Re: engine temp. and fan question (archive)

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Posted by James Lee on July 28, 2000 at 00:53:26:

In Reply to: engine temp. and fan question posted by Doug on July 21, 2000 at 12:42:07:

I installed a toggle switch in my old 6er, I'll hopefully help you do yours. Before I get started, I will state that the fans are probably much the same on our cars, but there may be differences. Feel free to let me know what you might find - we'll (the board and myself) see if we can figure it out. With that out of the way...
Note that on the left (drivers) side of the aux fan there is a plug with three male terminals. This is likely where you noticed that the fan is unplugged. Get some heavy wire, make sure it can handle heat and about 30 amps @ 12VDC; heat resistant because it will pass by a hot engine on it's way to the cockpit.
Back to that plug up front: as I remember, the rearmost plug is the negative ground, and the front two are for the two speeds (positive). Jumper your fan to a battery to test and identify the three terminals with certainty. Also make sure it's going the right way - if it's going backwards, the other fan speed won't do anything (if I remember right - but just make sure it's going the right way to direct air toward the radiator and not away from it.
Now, run a ground to the negative. Then run the two positives back to the firewall, through it (on the 6er there's a grommet which delivers wires under the steering column in the cockpit). Also, run a positive supply line from the positive post to the cockpit. Remember to get an intermediate 20 amp or 30 amp blade-style fuse holder; make a fuse holder right off the battery, then run the wire to the cockpit.
Now, get a toggle switch. Radio Shack carries one, part number 275-711, good for 20 amp at 12 volts. The center terminal on the switch is for where the line from the positive post connects. The two others are for the positive lines to the fan motor.
The switch attractively mounts where the speaker balance is. I don't adjust the balance that often, so I strapped it up and out of the way behind the lower panel and put the switch in it's place. It looks amazingly stock because the balance control has a recessed area, framed in black plastic trim. Mount the switch as you like; mine is down for slow fan and up for fast fan - center is off.
Install a fuse of 20 amps in the fuse holder, and go have fun on even the hottest of days.
Combined with a new fan clutch, my old 6er can't even dream of overheating. If you need it, now would also be a good time to do a flush, hose replacement, radiator clean out or recore, and water pump. Just remember the Air Force's IRAN actronym - Inspect and Repair AS NECESSARY. Mine just needed the clutch and aux fan.
Hope this helps you out, lemme know how it works if you do it.
James Lee
88 535i
85 M635CSi
82 633CSi with new fan clutch and manual aux fan
[email protected]

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