I just ordered the upgraded aux fan wire harness upgrade for my 1998 ML 320 from my local dealer. After looking under the hood last night I have a few questions. My dealer has not been much help.

Will the replacement harness contain all of the wires and conections that are presently in the harness (front light, windshield washer pumps, etc) or will it just be a replacement of the wires and plug that run to the aux fans?

Besides unhooking the battery are there any other precautions I should take before I get into the fuse box?


Thanks for your help

I think I can get an answer for you, check back in a day or so.

Gilly

The more I think about it, I believe it is just the fan wiring itself, you connect this new part where the old one plugged in, and the old one they don't even tell you to remove, it just hangs there. I'll try to get a more solid answer for you though.

Gilly

Thanks Gilly for your help. I will wait for your response.

It's just the harness for the fan. You're installing a larger diameter wire for the fans, and after doing this you can install a 40 amp fuse into position f44. the thicker wire can handle the 40 amps after installing the new aux harness. Sounds like you need to remove a plug in on the bootm of the fuse panel, open up the connector, and install a wire in the new harness into the present connector.
Sounds a little involved.

Gilly

Gilly, How many hours or estimates will it cost to have the harness updated?

The wiring mod is just a replacement wiring for the fan only. The aux fan wiring plug is just disconnected and cable tied out of the way and the new wiring routed to the fuse box.

Im the only one in my workshop who orders the wiring harness, everyone else just installs the 40A fuse.

The tricky part is knowing which single wire to disconnect from the underside of the fusebox as they all look the same. The earth point is just below and infront of the washer bottle.

The plug that you need to remove the existing wire and retrofit the new harness is in the middle of the fusebox (underneith), from memory is blue and has just 2 wires in it. Unfortunately I can't remember the plug number. Disconnect the wire from the aux fan plug next to the fans and check for continutity between the 2 ends of the wire to check you have the right one (make sure the battery is disconnected when you have the fuse box open!!!!).
Insulate the old wire even though it's not connected to anything as well.

Give yourself 30-45mins to do it, dont rush anything and don't be afraid to ask lots of questions.

__________________
Alex.

MB Tech
Sydney, Australia
Volvo 122S
W201 190D 2.5 manual
W202 C240
W203 C32

I just got a quote for $330 from my dealer to replace the wiring harness and install a 40amp fuse (existing one had blown). Service tech described the process as "involved".

Read thread in link.
Aux fans blowing Fuse 44 (ML series)

If i remember correctly, as per the DTB, it only pays 1.5 hrs for the job. If you do it yourself, be very carefull about the ground behind the headlamp. It can seperate from the sheet metal very easily. good luck.

My Aux Fan Does Not Come On When It Should, What Should I Check Besides The Fuse?