Aux fans blowing Fuse 44 (ML series) - PeachParts Mercedes-Benz Forum

blueeagle289 · #1 04-04-2004, 06:21 PM

Per a note on the forum that the aux fans blow the #44 fuse, and that there is a wiring change fix which can avoid that, my question is:

Can I replace the 30A fuse with a 40A and avoid the problem?

If I do that, is there any risk to the fans themselves or the creation of a possible fire problem, etc.etc. ???

Both of the ML320's in my family blow those fuses, and the Merc
garage wants over $250 just to perform the wiring mod.

99ML430 · #2 04-04-2004, 11:59 PM

that switching the amp to a 40 would not work........l had the Fuse #44 wiring harness upgrade performed...l know it's pricey, but l haven't blown a fuse since...

Gilly · #3 04-05-2004, 09:05 AM

In the work instructions it states:

"NOTE: The larger line diameter of the auxiliary wiring harness allows installation of a 40 Amp fuse."

It would be a bit of a gamble to just go for the installation of the fuse only. My take on it is that the smaller diameter wiring harness may get too hot. I can't say for sure if it would just damage the one harness, or other harnesses, or maybe start a fire. These are definitely all possiblities. Possibly it would be fine also, but I would really tend to think that if it were really safe to swap out the fuse that MB would have just said to install the correct fuse.

The star bulletin I have says it was issued Sept. 3 2002. If you are the original owner of the truck, I would think that they should be able to get this under warranty for you, even though the truck is out of warranty, especially if you have documentation showing that you've had this problem dating back to 2002.

If you are mechanically inclined you may be able to do this mod yourself. NOT a beginner-type job though, depends on your experience level.

The harness part number I have is 163-540-00-35, plus a fuse 910153-000000 (should be able to buy at a parts store also)

Gilly

Ron in SC · #4 04-05-2004, 07:46 PM

I'm doing this install right now.

I've had no problems with installing the harness and all. I have the green wire with the female connector routed into the fuse box. But the question is where to connect it?

I've got access to the box of the fuse board (the relay and fuses are inserted from above). But where do I connect the female connector.

This does present a problem, at least right now.

Edited:

Well I've gone ahead and put everything back together without connecting the green wire, it's in the fuse box waiting to be connected when someone tells me were it goes or I figure it out for myself, which seem like a longshot.

Gilly · #5 04-05-2004, 10:12 PM

Ron
You need to remove the original lighter gauge wire from the bottom of the fuse box and plug this new one into it.
I can't remember if the info is actually printed on the bottom side of the fuse box or not, but it's a blue-colored connector with a call-out number of ML/B. If you look at where fuse #44 is, just realize that ML/B is roughly underneath where this fuse is located. The wire you need to remove is more than likely the same color as on the new harness, so that may help you find it. From the lousy picture I have on the DTB, it looks like there are only 2 wires going to this connector. You should be able to simply pull the connector out of the fusebox, then the connector comes apart so you can remove the one wire you need to remove. Look on the fusebox itself for a marking that says "ML/B".

Gilly

Ron in SC · #6 04-05-2004, 10:52 PM

Gilly,

Ok, I took the fuse box apart again. Here's a photo looking towards the bottom of the board, ie. fuses and relays on the top. There are all these multi-wire connectors on the bottom. So would it be one of these? I'm just wondering if I'm on track or way off.

thanks, ron

Edited:

Found it, I'm pretty sure. It's a blue connector that is farther down than you'd think it should be. It has a red and green wire. I'm going to remove the green wire and connect my green wire from the new harness in it's place. I post a photo tommorrow so others can find it easily.

thanks, ron

Gilly · #7 04-05-2004, 10:58 PM

Yes, you're getting warmer!
It's a blue-colored connector, and I believe it'll be roughly located on this underside of the fusebox UNDER fuse 44.

Gilly

Ron in SC · #8 04-05-2004, 11:13 PM

Gilly,

I just edited my last post went you were responding to it, so it looks like I'm on target.

Ron in SC · #9 04-05-2004, 11:23 PM

Last question, I hope.

So I do I remove the green wire with the female connector from the blue connector (or whatever it's called) without tearing the bule connector up?

ron

Edited:

Well I got it out no problem by depressing from the top , with a very small screwdriver the part that is a little expanded as the connector is pushed in. Put fusbox back together and works fine.

Photo tommorrow

Ron in SC · #10 04-06-2004, 07:51 AM

This first photo show the fusebox circuit board looking at it from the drivers side of the vehcile. The red arrow points to the first multi-pole connector away from the third which is ML/B, which is the one you want. To get to the third you head toward the passenger side of the vehicle from the first connector. To me the third connector, ML/B seemed somewhat past the point where fuse #44 is viewed from above.

Second photo shows the fusebox board from the bottom. The arrow points to the place where the third connector was removed, that is ML/B. As you can see the first connector is brown, and the second is green.

The third photo circled in red shows ML/B connector with the new green wire from the harness connected. The green wire circled in green is the old wire that was connected to ML/B. I put electrical tape over the end and just put it back in the box. It may appear from this photo that the new green wire and the old are connected. They are not. The new green wire was just under the old connector with the tape on it when I took the photo.

To get good access to the bottom of the fusebox board I disconnected the power and ground leads that went to the box. I also disconnected the battery as a safety precaution when doing this job.

To do this job I removed the driver's side headlight, windshield washer fluid tank, (mine needed to be replaced anyway it was leaking, suprise, suprise).

I just attached the new harness to the old with zip ties and electical tape.

Huge thank you to Gilly for helping me.

Gilly · #11 04-06-2004, 09:19 AM

Once the old wire is disconnected from the fusebox, it's a "dead" wire, so you wouldn't really need to tape off the end. Be sure that the new harness follows the route of the old harness all the way out to the fan. Tape or wiretie it to the original harness. Tape off the opposite end, out by the aux fan, to the new harnes (or vice-versa, depending on how you look at it, as long as everything is secured).

Always happy to help out.

Gilly

Ron in SC · #12 04-06-2004, 09:41 AM

Quote:

Always happy to help out.

Very happy to be on the recieving end of much needed help too.

Thanks again, Ron

slowdriver · #13 04-23-2004, 12:29 PM

I had a problem with the AC on my 2000 ML320 not cooling down the vehicle last week when the outside temp was around 85 degrees. I had remembered reading this forum thread and checked my #44 fuse which turned out to be blown (fuse socket stamped as "AC blower"). I took the truck to the local MB dealer and mentioned the fuse #44 issue. They replaced the wire harness and upgraded to the 40amp fuse saying that was the reason the AC was not cooling. I am pleased to have gotten the upgrade but is that a logical fix for the AC problem? It's only 70 degrees outside this week so I can't realy test the AC to tell if it works any better now.

Gilly · #14 04-23-2004, 05:56 PM

Depending on driving conditions, it may have been the problem. The fuse affects the cooling (Aux) fan, which you need to run under certain circumstances, the main circumstance would be slow driving, like in a traffic jam, or even at lower in-town speeds (25 mph or lower). Once you get much above that speed, the fans running are of little or no benefit, so they are just "extra weight" and that point, the wind rush is greater than what the fan provides.
If you were driving under these types of conditions when the AC wasn't working well, it may well have been the problem.
You can just let the car sit in the sun (I am in Wisconsin so I know what the weather is like there near Chicago) and let it warm up due to solar heating, and then start it up and crank the AC all the way down and see if it seems to be blowing cold air or not.

Gilly

#15 04-26-2004, 09:31 PM

Last week my wife’s ML320 had a service done at the dealership where they change the wiring harness for the auxiliary cooling fans. Their claim was the fuse blown for the aux. fans. She had never had a problem with the fans before that. However I remember those fans starting up for a few seconds after starting the engine with or without the A/C. After this replacement they start only and only when the A/C is on. I check them with the engine hot (92-93 Celsius measured at the thermostat housing) and they do not start unless you put the A/C on. Is this normal? At what engine temperature they should start?