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2000 ML320
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Discussion Starter #1
Hi - new to BenzWorld. I have a 2000 ML320 that keeps blowing the F44 fuse. The garage told me that I have to replace the entire fan assembly, as there is too much resistance. I can spin the driver's side fan freely, however the passenger side fan has a LOT of resistance. Is this normal?

Unfortunately I don't know if the wiring harness was ever upgraded, but I believe it wasn't since it's still using 30amp fuses.

I'm currently on a long drive vacation, and I only thought this fan (or should I say, two fans) was used for the A/C. However, while driving through the extremely heavy traffic in Boston (is it always this bad?), my ML started overheating.

Does anyone know if there's a quick and easy way to disconnect the passenger side fan temporarily so that at least I have 50% of my extra cooling? This might help for the rest of the trip.

I've discovered that buying lots of 30amp fuses is futile, as they blow almost immediately. I don't know if I should attempt to put in a larger fuse due to the risk of starting a fire.

Thanks.
 

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2000 ML430 (Sold)
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1,209 Posts
Welcome Abby, Please update your profile with year and model of ML you have for future posts.

The aux fans you are talking about are activated by the AAM, by readings of a pressure switch. This mostly has to do with A/C, so is yours working properly?
The other time these fans will come on is if the engine temp reaches 102 degrees C (dont quote me on that number)
The fan run by the serpintine belt is the primary source of cooling.

As for it being hard to turn, im not exactly sure. I would assume that if it is asd hard as you are decribing, the bearing is seized up and that would cause the fuse to blow.

If you put in a new fuse, and the truck has sat for a while, does it blow immediately? If so i would assume something is wrong with the relay controlling the fans, or the pressure switch circuit telling them to come on.
 

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2000 ML320
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3 Posts
Discussion Starter #3
The A/C works... provided that I'm moving. If I am idling at an intersection for more than a minute, it blows warm air.

If I put in a new fuse and the truck is cool, it blows after approximately 2-3 minutes of turning on the A/C.

I do believe the bearing in the one fan is the problem, but I wasn't sure if there was a way to disconnect the one fan. I figure one fan turning is still better than none at all. At least until I can have the unit properly replaced.

Thanks for your help.
 

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99 ML430, 00 ML320, 05 E500 4matic Wagon
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22,146 Posts
MB sells the setup as one entire two fan assembly, however I have seen them at bone yards for a fraction of the price of a new one at dealer pricing.
Before replacing it may be worth it to make sure the fan motor is dead and you do not have a wiring
fault that is causing the fuse to blow.
 

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1999 Ml430
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351 Posts
Not that it helps you but my fans blew at less then 60k and had to be completly replaced. No problems since then
 

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2003 ML 320: Engine:112942 31 305548, Transmission: 722662 03 807606, FrontAxelAL431020714752162233
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128 Posts
Yes the Boston traffic is bad almost all the time, depending on how far in you are and the time of day. I am local to you so if I can help you let me know.
What I would try first is see if you can lessen that resistance in the fan turning. Perhaps give the bearing area or where is attached to the spindle a shot of spray silicon. If it works great if not you should keep the spray silicone for other things like rubber door seals and hinges. I spray a can once a year to keep the rubber parts like new.
 

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2000 ML320
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Discussion Starter #8
Thanks for the help. Tried the silicone spray, but I can't seem to get in at it. Seems like it's a sealed unit.

I tried removing the bolts in the diagram (#18) to see if I could remove the fan assembly, but they are extremely difficult to turn, and after turning a few turns, don't feel any looser.

The green and tan wires appear to run all the way up the harness to the plug, but I can't see behind the fan to tell which green and tan wires are from which fan.

I think I'm going to have to wait until I can get a garage to look at it again. For now, I'm okay as long as the Benz is moving.

Thanks for all of your help, everyone!

Btw, just an aside question if anyone knows - despite the fuse being labelled as "auxiliary A/C fan", I would assume that these fans also would turn on electronically even if the A/C is NOT turned on? ie for cooling the rad? My A/C has been acting up for a long time, and I'm surprised that I had the overheating problem now even though there appears to be a large fan behind the radiator... and it appears to work. Not important, but just curious. Thanks again all.
 

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2000 ML430 (Sold)
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Btw, just an aside question if anyone knows - despite the fuse being labelled as "auxiliary A/C fan", I would assume that these fans also would turn on electronically even if the A/C is NOT turned on? ie for cooling the rad? My A/C has been acting up for a long time, and I'm surprised that I had the overheating problem now even though there appears to be a large fan behind the radiator... and it appears to work. Not important, but just curious. Thanks again all.
By "large fan behind the radiator", im assuming you mean whats called the Viscious Fan. Its belt driven, and is the main source of cooling. But if the a/c is on or the outside temp is too much, the secondary or AUX fans will come on.

*Thanks to 43sqd for the PDF's
 

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87' 190E 16V / 93' 600SL / 02' G500
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I had the same issue with my Aux fuse blowing so this is what I did...
1- Spun and listened to each fan as it spun(fans sound good)
2- With the ignition off I disconnected the Aux fans (large connection at the fans)
3- Using a pair of wires with gator clips or similar I hot wired one fan at a time and let it run for a few minuets, then the same for the other. I used a spare auto battery I had on the shelf to do this.

Result was fans now running properly, why? Well my theory was I initially wanted to find out which fan was the culprit for continually blowing the fuse so I could, like you disconnect it and run the single. What I found was by running the fans with a fresh battery freed up the offending fan. Hope that helps.
 
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