Burning out our Multiplex in Honda Element

[JucenBrudi]

Greetings,

We tow a Honda Element with our Winnebago Adventurer. We have burned out our Element multiplex unit twice in 3 months. Replacement is about $500 each incident. The Honda people don't know what is causing it but say it probably is something wrong with the RV electrical system or the Unified Tow Brake.

Has anyone here had this problem? Any ideas?

Thank you,
Bruce

[Muddypaws]

I have a 2006 Element and a 2008 CRV. The CRV can be towed but the Element states that it cannot be towed 2 down or 4 down.

I thought I knew the Element well, but what is the 'multiplex unit'? Is it the diodes you added to power the Elements tail/brake lights?

When I wired the CRV for towing I chose to add a complete new harness and additional lights and circuits to power & control the EvenBrake. There is no electrical connection between the TV and the toads electrical system.

[JucenBrudi]

Good morning Muddypaws and group,

Thank you for your reply.

Originally Posted by Muddypaws

I have a 2006 Element and a 2008 CRV. The CRV can be towed but the Element states that it cannot be towed 2 down or 4 down.

Ours is a 2004 with automatic transmission. We bought it explicitly to tow and the manual clearly mentions towing and gives instructions on how to prepare it for towing. I am aware that Honda has changed their recommendations. Frankly, the fact that Honda changed their recommendations for the Element but not the CRV is very curious. I am suspicious that it may be that the Element for some reason "fries" the multiplex units when towed.

I thought I knew the Element well, but what is the 'multiplex unit'? Is it the diodes you added to power the Elements tail/brake lights?

It is not the diodes, etc. It is the gray device under the steering column with the fuses in it. I used to call it the fuse box before we burned one out and had to replace it and learned the real name.

When I wired the CRV for towing I chose to add a complete new harness and additional lights and circuits to power & control the EvenBrake. There is no electrical connection between the TV and the toads electrical system.

That might be relevant. Ours was wired some years ago when we had a Roadmaster tow bar installed. At that time we used a Brake Pro which was not wired into the Element. Later, I installed the Unified Tow Brake which is wired into the Element according to instructions. It has worked well for many miles so it seems to me unlikely that it is causing the problem. At this point I'm not aware of any recent changes which are obviously related to this problem.

Bruce

[cb1000rider]

In order to help, we need more info on what the multiplex unit does - it sounds like power distribution, but we'd need to know more.. and need to know what is burning...

[JucenBrudi]

Originally Posted by cb1000rider

In order to help, we need more info on what the multiplex unit does - it sounds like power distribution, but we'd need to know more.. and need to know what is burning...

I wish I knew, myself. I've done some more searching and found that it is called the Multiplex Control Unit. I've seen some talk about it which makes it sound like an "electronic brain" analogous to one of the control modules in our Adventurer. It has a bunch small fuses on it.

As for what is burning, I'm still in the dark. The techs have variously said it is "burnt" or "fried" but nothing about the previous one removed looks burnt in any way. I suspect it is the chip buried inside which has stopped functioning. They talk about it failing after having excessive voltage applied to it over a period of time. I think they are guessing when they say it must be the RV just because they are so vague about it all. They all have said it is rare for one to go out.

Thanks for your help.

Bruce

[Muddypaws]

It's been so long since I had to work on my 'E' that I forgot I bought the shop manual. In the manual I found wiring diagrams, test information, and a good explanation of what the multiplex control unit does.

If you send me your email address in a PM I will scan the pages for you. Since mine is a 2006 there may be some small differences, but maybe not.

[EDALLSAILS]

We tow a 2005 Element. Been using a Blue Ox tow bar. Brake buddy and had problems with electric power. Hard wired a power line from the coach to the battery and it worked fine every since. Try doing a tow with out the brake being hooked up. You might want to put a low value fuse in the line so if you are getting a short it will burn out the fuse before it does the multiplex. I'm in process of dropping my Brake buddy and installing a Ready Brake in its place. no electric hook up needed for that. Of course i'll still be wired to the MH for lights, etc. Honda "claims" the element manual was a mis-print and the Element was never meant to be towed. I went to an independent Honda repair garage and they scanned the manuals comparing the CR-V and element trannies. Appears they are the same. Towed mine now for over 40,000 miles. Only provblem is screwing around with the Berake buddy. That is why I'm switching to the Ready brake.

[YC1]

How long have you had this setup? If it is just now occuring there is a possiblility if you are using diodes to isolate the systems that a voltage is getting fed back via a blown diode. One test might be to hook up, get in the toad, then turn the toad turn signals on. See if any turn signals come on the rear of the motorhome. Then hit the brakes and see if they are lit on the motorhome. My new Ford Edge did not like me hooking up my boat trailer backup lights. It sensed the extra current and actually shut it off. That drove me crazy for awhile. I had the backup light then control a seperate relay to drive the boat trailer backup light.

A picture of the device would be very helpful. If you have the old one smell it. If it smells burnt it is. You might want to hook up as usual and then feel the device that is dead to see if it is getting warm. What is the warranty period for the new part? Might be a year.

[mrv8outboard]

I also have a 2004 Element AWD. We have been towing it since new and three different coaches. That being said I installed the towing system (Blue Ox) and have installed the electrics completely separate from the Element. I only pull the one fuse from the multiplex (fuse panel) as described in the owners manual. All other function are from the coach via the trailer plug.

[JucenBrudi]

Originally Posted by Muddypaws

It's been so long since I had to work on my 'E' that I forgot I bought the shop manual. In the manual I found wiring diagrams, test information, and a good explanation of what the multiplex control unit does.

If you send me your email address in a PM I will scan the pages for you. Since mine is a 2006 there may be some small differences, but maybe not.

Hi Muddypaws and group,

I'd like the pages. I've been trying to figure out how to send a PM; instructions don't seem to match up with what's in front of me. I'll keep trying. Thank you.

Bruce

[JucenBrudi]

Originally Posted by EDALLSAILS

We tow a 2005 Element. Been using a Blue Ox tow bar. Brake buddy and had problems with electric power.

In the beginning we had trouble, too. The Element battery ran down frequently. I finally decided that every time we hit the brakes it would draw power and over a full day's drive it would run the battery down. We eventually changed to the Unified Tow Brake which keeps the Element battery charged from the coach battery.

You might want to put a low value fuse in the line so if you are getting a short it will burn out the fuse before it does the multiplex.

Maybe with the wiring diagrams Muddypaws has offered I'll be able to see where to put a fuse. Thank you.

Honda "claims" the element manual was a mis-print and the Element was never meant to be towed.

I'm real skeptical about that.

Towed mine now for over 40,000 miles. Only provblem is screwing around with the Berake buddy.

I went over my records today and found that we had used the Unified Tow Brake better than 20,000 miles over nearly 3 years when the first multiplex control unit "burned" out. The 2nd "burned" after another 4000.

Not having to mess with the Brake Pro since we installed the Unified Tow Brake has been nice.

Thanks for your input,
Bruce

[JucenBrudi]

Originally Posted by YC1

How long have you had this setup?

3 years and 24,280 miles.

If it is just now occuring there is a possiblility if you are using diodes to isolate the systems that a voltage is getting fed back via a blown diode.

The original tow bar install was done by Camping World and I don't know the details about diodes, etc. I presume I can track that information down.
Thanks for the test procedure, I'll keep the group posted on what I manage to do.

A picture of the device would be very helpful. If you have the old one smell it. If it smells burnt it is. You might want to hook up as usual and then feel the device that is dead to see if it is getting warm. What is the warranty period for the new part? Might be a year.

I have a picture somewhere, I'll find out how to post and post it.
I just smelled the old one; no burned smell. "Burned" may have been an expression like "fried." I don't know about the warranty.They want to say it is not their fault, its the fault of the tow equipment.

Thank you
Bruce

[Muddypaws]

I checked my PM's this morning a couple of times but didn't check this thread!

I spent most of the day under my Bounder

I'll scan them for you tomorrow. There are indeed schematics that may indicate which fuses to pull to turn the crazy thing completely off, and I suspect that may be what you need.

I haven't read the whole section but it looks like the multiplex controls lots of little things like the dome light, the map lights, the 12V outlets, automatic door locks etc.

[Muddypaws]

I tried scanning. The book is over 2" thick and the pages are very thin. I couldn't get a decent scan so I decided to photograph the pages instead.

The PDF I made from the pictures is close to 20MB.
To big to upload here.