aux fan blues - PeachParts Mercedes-Benz Forum

JHZR2 · #1 07-10-2002, 01:04 PM

Hi,

Lately it has been relatively hot (mid 90s), and I have been driving my 83 300D between 80-160 miles per day. What I have noticed is that when it is over 90, and Im driving on the interstate at 65-75 mph with ac on and the fan on low, my temperature creeps up to 100 and sits there. if it is below 90 or so, it will sit at around 90.
I dont like it so high when driving, and have had past problems with the aux fan. It seems to sieze up and then cause the fuse to blow. On a few occasions I have forced it free, replaced the fuse, and then gone on with life for some time, only for it to sieze up again and when I have my hood open and check, I find a blown fuse.

I would liek to know how difficult it is to replace the aux fan. since everything else related to it works fine, it should be no problem, except that I am somewhat unsure of the wiring for the fan. I can trace it down to the drivers side of the radiator, and then feel that it is connected to something, but I cannot get to it or see it. Before I go spending $180 for the fan, and go screwing something up, Id like to know what is involved with the wiring, and if its possible to attach a new one without taking off parts on the front to get to the connections.

Also, since I was mad that my fan was screwed up and decided to mess around with it and trace the wires, I mistakingly didnt put the screws for the fuse box cover back on, and closed the lid between the black relay box above the drivers wheelwell and the hood. Now I have two small upward dents in my hood. Not too noticable, but I notice them, and my car had no dents at all previously. Is there anything I could try to get them out? pushing on them didnt work, but Im afraid to take a small hammer or anything to them without a little instruction first.

Thanks for your help.

JMH

RG5384 · #2 07-11-2002, 01:57 AM

on my 300SD it wasn't too hard at all, you just remove the bolts and take the old one out. YOu may have to remove that front "crossbeam" that the horns attach to though. Another thought for you if you are very mechanically inclined. The old fan can be fixed for about 4 bucks if you do all the work yourself. It involves drilling out rivits, taking apart a motor, and lubing everything up. If you think your interested reply back and i'll give a detailed how to on it, but if your just gonna get a new one i dont want to take the time to type it all out since it will be rather long, and the repair is failry involved. let me know if you want the write up,
Ryan

RG5384 · #3 07-11-2002, 03:55 PM

i'll go ahead and post how to fix these buggers for the benefit of anyone else in this position. It has been a few months, so it's kind of fuzzy, but it should be clear enough. you need to take the aux fan out of the car, so you have to take out that cross bracket in front of the radiator. Once the aux fan is out the real fun begins. (to get it out you just remove 3 or four bolts placed in the "corners") you have to get the fan out of the metal surround, so you remove the three bolts in back, as well as the plastic cover in the front. YOu will have to cut a zip tie to allow the wire to come out, once you do those three things the fan should slide out forward. next thing to do is to remove the big bolt on the front of the actual fan. you have to bend down the little retainer metal strips and then unscrew it to the right i beleive(i'm pretty sure it loosens the way most bolts tigten, just play with it and youll get it). once you have that off you can unbolt the remaining three bolts from the back of the motor, keep in mind which bolts go where for re-assembly, some are "taller" than others. once that is done you can pull the fan halves apart. If your fan was like mine the front bearing will be completely shot, and there will be metal shavings everywhere inside the fan. Use some strength(it WILL take it) and pull the motor assembly away from the other half of the fan assembly. do your best to clean out all the metal shavings(it's kinda hard, a strong magnet helps here) and look at the oil-lite bushing in the back. try to wipe off all the old grease/oil and re-oil it. this next part is the fun part. the one metal plate that once has the bearing in it, you have to drill out the three rivets in order to get to access the bearing. Once i got this far, i took that plate to a local bearing shop, and they pressed out the old one, pressed in the new one, and glued in the new one. The place i took mine to was a place called "terry bearing". If you dont have one of these shops your kind of SOL on repairing the fan. re-assembly is the same as dis-assembly. My fan works great now with the exception that it seems to be a little more "wobbly" and when it winds down it hits the plastic protective screen. Both of which i can live with for the price of a replacement. BTW, total cost to me was four dollars and twelve cents! if any clarification is needed just reply back and i'll be glad to help. Hpe i save someone $175.82

Jeff72_220d · #4 07-14-2002, 12:01 PM

I just cleaned up my aux. fan yesterday.

I discovered that I (or, the previous owner) had mistakenly installed an 8-amp fuse instead of the required 16-amp fuse. The fuse had blown twice before I did the OBVIOUS THING and checked the chart in the fuse box.

I also removed the aux. fan assembly, which comes out very easily on my 300SD. You can check the motor first by jumpering the two wires that go to the high pressure switch (red or green), which is mounted on the top of the a/c dryer. Just slide back the insulators on each of the two wires. With the ignition ON, and the wires jumpered, the fan should go ON if it is functioning. If the motor works, no need to replace the aux. fan unit.

The fan shroud cover just pops off, using a small flat-blade screwdriver to pry it off at the three quarter points from the shroud.

To remove the motor for bearing lubrication, just bend the tabs on the center hub nut with a small screwdriver. Loosen the nut with a 20 mm socket or wrench - NOTE THAT THIS IS A LEFT-HAND THREAD. Hold the fan blades in place with something as you turn the nut CLOCKWISE. Once the nut and lock washer are off, just pull the blade assembly off. Now you can see the bearing on the front of the motor. I removed the motor in order to clean out the debris buildup behind it. There are three 5/16" screws holding the motor in place. I used a few drops of ATF to lube the bearings, then replaced everything. The fan unit comes out by loosening the cross-member bolts (you don't need to remove the cross-member). The only reason to loosen it is to free the wiring bundle enough to bring the motor away from the radiator for the cleaning and lubing.

This is an easy DIY job.

240 Ed · #5 07-14-2002, 12:10 PM

As I recall on the 300D, when you remove the fan, you can see the electrical plug...

If you can take the bearing apart, you could perhaps use a bearing grease rather than ATF. If you can't get it apart, use some synthetic engine oil from the bottom of the oil bottle or from your dipstick.
(FWIW, I drain the oil bottles and get enough to fill a pump oiler with synthetic, very handy and great oil!)

Jeff72_220d · #6 07-14-2002, 03:49 PM

The bearing is a sealed unit. Experts on the diesel list recommend using atf to loosen up and lube the crusty grease that is left in the bearing after a couple of decades of use.

On my car, the electrical plug is held (clamped) into the side of the radiator frame. The cable is folded a couple of times, and bound with an electrical band (whatever you call those plastic straps that you buy by the bag-full).