Trailer Hitch Set UP???

[MLMaiden]

Help! I'm trying to hook up my 2001 ML 430 and I'm having issues with the electrical set up. What is the deal with the brakes?
Someone looked at it today adjusted all of the other wiring to the plug, but said there's a full 12 volts on the wire.
If it is controlled by a module, then why is it not recognizing it has a trailer?
What is wrong with it and how can I fix it?
Thanks.

[Gilly]

Possibly a MISSING fuse for the module, I think it's 45, see if you have a fuse 45 installed (and check the fuse list to make sure I am giving you the right number)
Gilly

[MLMaiden]

Thank you so much!! I am supposed to take it to the shop today. I tried it yesterday and the trailer brakes lock up when I hit the brake in the car.
I'll try it and let you know! Thank you so much.
I am so happy you responded.

[ML320]

Some info about installing a brake controller is on this page:

http://www.whnet.com/4x4/towing.html

[Gilly]

I thought you were referring to the brake lights, not the trailer brakes, but check for the trailer fuse anyways, may have something to do with it. I assume you mean electric trailer brakes, you sure the trailer doesn't have surge brakes?
Gilly

[MLMaiden]

Well, we looked in the fuse box this morning and the ESP fuse is in the car and looks to be intact. I don't think the trailer has surge brakes. I'm pretty sure that they're electric. I was told that the ESP module may need to be reset. Is this right and can my local repair shop do this?
Thanks for any and all help.

[Gilly]

OK, there would be, I believe, a seperate electrical connector for electric brakes. A surge brake setup it totally independent, the weight shift of the trailer forward when the truck stops is what applies the brakes. I don't know much about trailer brakes though, that's about the extent of it. I think electric brakes requires some type of controller for the driver to use, so you'd know if you had those. Check the link the user "ML320" posted.
I would recheck the fuse thing. Under the fuse box lid is a list of fuses, I think #45 should say "trailer" or something, if that's not what #45 is, then just look down the list and look for one that says "trailer" and check whatever fuse number that is and make sure one is there, it's supposed to be installed when the hitch is installed. If you have elctric brakes, someone is going to have to install that contrller for you, it's NOT part of the normal hitch installation job, I don't think MB even sells the kit for that.
Gilly
PS, NO I don't think that a change needs to be made to the ESP module, but getting a bit out of my range of knowledge, check the link I mentioned or let me know if you want me to look at the link for you. If a change IS required it will more than likely require a dealer or very good independent shop with the proper computer to make a change.

[MLMaiden]

Hi, I read up on the information about the brake box. I need it! It mentioned if I'm hauling over 1655 lbs. then I need a brake box.
I'll do that this week. Problem hopefully solved.

Can I ask another question regarding the same vehicle?
When it rains or it gets wet in the right place the "circle with the dashes around" orange light and the red Brake! light flash at the same time and beep as though the E-brake is on while I'm driving. When it dries out it stops. At one point, my husband adjusted the connector on the brake fluid cap and it worked for a while. My shop said it would take hours of labor to diagnose the problem because the computer is not dropping down a code on this. You are obviously knowledgable... What could it be???
You guys rock by the way!

[Gilly]

What makes the most sense to me is that you have worn out brake pads, that's what the orange with dashes light means. I don't recall this being used in combination with the red light and the beeping noise though, but could be. The rain part makes sense for it to be a pad sensor. Make sure the brake fluid isn't low as well, but this wouldn't explain the orange symbol, just the red Brake! light and I believe the beeping noise.
The brake controller I am thinking depends more on what type of brakes the trailer actually has. I understand what you are saying about the weight of the trailer, but really you have to know for sure what the type of brakes are before doing anything. I've seen some pretty big trailers with surge brakes.
Gilly

[MLMaiden]

You are in the right area, but I have gone through all of those already. Now are you stumped? I had new brakes, rotors, and sensors installed regardless of the beeping. I needed them anyway. Also had an oil change at that time. It did three days after an oil change in the rain.

As far as the trailer goes, I'm certain it has electric brakes, based on remembering past experiences with my old Pick-up. So I hope this works and just finally solves the problem. It's been several months that I have been trying to finish this hook up. It's getting old with me.

I love my car but it seems to be a quite complex machine!

[Swizzles]

I had the same problem with my hitch/plug setup. Whenever I put on the brakes the trailer would go to full lockup. I had my hitch installed at the dealer and it appears that the factory setting wires the brake lights share the same wire that the trailer electric brakes use…or something. I printed out the install instructions from Mr. Wolfgang’s site and took them to a hitch specialty shop. They installed a brake controller no problem and it worked fantastically after that. I had some other strange towing issues…..

When towing up hill (hard) for a period of time the low oil indicator would go on. Then after a while it would turn off. I even had it show low oil show -2 oil warning in the odometer section then 5 minutes later it showed oil hi!!! When I checked it that night it was 2 ticks off of full. The temp gage would also start acting funny jumping from 80 to max back and forth very loosely. When it did this my AC would shut down. Even with these strange occurrences it towed solid with good power 4200LB trailer with a 98 ML320 245,000KM on the OD.

Have fun hope this helps.