Concours Owners GroupTM - COG                                                 
"Sport touring at its fines
t SM"

Concours Through Time

Join for the Bike,

Stay for the PeopleSM

   Forum           Events   

BMW Accessory Plug Installation



Because an accessory plug provides easy access to motorcycle electric power for electric clothing, GPS units, radar detectors, battery chargers, air pumps for tires or mattresses, and a handy way to power a laptop, cell phone, or digital camera on the road. You can even buy 12 volt hot plates in truck stops, if you’d rather not use a camp stove for cooking.


A permanently mounted accessory plug also looks better than a dangling SAE plug, won’t scratch paint, and should last longer as well since the wires in the permanent mount version aren’t being flexed each time you plug / unplug something.

If your motorcycle didn’t come with an accessory plug (and most don’t - BMWs, some Ducatis, and some Triumphs being the exception), it’s fairly simple to add one. All the parts are commonly available, not expensive, and installation isn’t difficult given basic electrical and mechanical skills.

Where to install?
Choose a location on the bike that’s easy to access for the user. That location will vary with the bike and with the user, on my Concours I have installed a pair of plugs in the left-hand fairing liner because that’s handy for me to access and I normally travel solo anyway. I know a Honda ST-1100 rider that has an accessory plug and a switch in the rearward portion of one of the side panels for his wife to access and easily control her own electric gear.

How many accessory sockets, and why?
I installed two totally independent fused accessory sockets for several reasons:

I use my accessory sockets mostly for electric clothing, mostly just a single vest, but sometimes also a vest for a passenger or a vest and gloves for myself. If a single fuse were to blow on a cold solo ride, I could simply use the other socket and replace the fuse when I arrive somewhere safe, rather than alongside the road in the cold dark rain. Trust me on this, you won't have a critical failure on a nice day because on a nice day you won't be using your electric vest. A combination of Murphy's Law and logic ensures that failures happen at terribly inconvenient times. Keep this in mind, and do good work.

I can power two articles of electric clothing, either vest and gloves for me or a pair of vests for myself and a passenger, without having to mess with a Y-shaped harness.

Should the accessory socket be:

a. Switched through the ignition switch and a relay:
The socket is only “hot” when the ignition switch is on. The good news is that this prevents a rider from leaving something plugged in and draining the battery. The bad news is that you must have the ignition switch turned on to access electrical power for accessories, and to minimize voltage drop you should also use a relay and large gauge wire from the battery to the relay to the socket - this is added complexity and cost compared to an “always hot” installation.

b. Switched through a simple on-off switch:
A friend has a rocker switch permanently installed on the rear area of his ST-1100 so that his wife can control her vest using that switch. More complex than an "always hot" installation, due to the added switch, but only slightly more.

c. Switched through an electronic controller:
There are Heat-Trollers designed for in-dash mounting, I use one for controlling my heated grips. Some people like to power their electric clothes and then control them with a Heat-Troller permanently mounted in the dash, it makes for a very clean installation. The downside is that in the case of Heat-Troller failure, it could be very difficult to access power off that circuit from upstream of the Heat-Troller, if the whole affair is buried in bodywork and plastic.

d. Always hot:
This is the method I prefer. The reason is because it gives me more versatility, more redundancy, and more reparability.
Example - if a permanent mounted Heat-Troller were to fail on the road, it would be difficult at best to bypass or replace it on the road if it’s under a bunch of plastic bodywork, and then you’d have no power available to run heated clothes. Depending on the time of year, this could be a serious problem. Partly for that reason, I use “portable” Heat-Trollers Velcro'd to my tank bag for heated gear, rather than controlling the accessory circuit with a permanently installed controller. With the portables; I can swap, replace, or bypass easily - just in case. Also, an “always hot” installation allows easy access to the battery for battery charging using a Battery Tender and a male BMW plug.

An “always hot” installation also allows you to power accessories with the ignition circuit off - such as an air pump for a mattress, a heated vest while pumping fuel, or a laptop. Related - when powering my laptop, I simply feel better not running that power through a Heat-Troller first, and not being forced to have the bike’s ignition circuit turned on to run the computer.

Parts and Supplies




Fused battery harness available from



40” SAE extension cord available from


Female BMW-type accessory socket. Bosch or Hella, various sources as follows

BMW socket by Hella:

BMW or John Deere dealer. See below for more info. 

Heat shrink tubing, solder, and soldering iron. See your local Radio Shack
Spade crimp connectors, yellow, from Radio Shack. May not needed with the Hella BMW-type socket, as it has set-screws for the SAE leads.
Combination crimper / wire cutters from Radio Shack. May not be needed with the Hella BMW-type socket, as it has set-screws for the SAE leads.
Some of the above items may be optional, depending on how you hook the SAE lead to the accessory socket.

I've had good experience with the Warm-n-Safe folks at . The quality of their Hella parts has been extremely good when I've ordered from them.

Given the worldwide nature of the Web, I realize that you may be able to get some or all the above items in your own area. Here are alternate sources for some of the above items:

Bosch male and female BMW accessory plugs are available from BMW dealers. I don’t have the BMW part number nor the exact prices.

A simpler and much cheaper Bosch accessory socket is available from John Deere dealers for about $9. In fact John Deere apparently has two female sockets available, with the AL25073 part being mostly plastic and cheaper , while the MG82002966 part is made with more metal and appears to be more durable. I've used the AL25073, and it's Ok, but just Ok. The Hella female socket (in my experience) grips the male part much more securely than the John Deere / Bosch AL25073 does.

John Deere part numbers:

Female socket: MG82002966
Female socket: AL25073
Male plug: RE11344 
Installation Procedure:
(for an "always-hot" socket, other installations will vary)

Step 1.
Figure out where you’re going to install your accessory socket. This may not be as easy as it sounds, spend some time thinking about where it will be most handy. Choose carefully and double and triple check before cutting or trimming anything so that you don’t put a hole in a dash panel and then say “Uh-oh.... there’s no room here for the wires.....” Measure twice, cut once. Cheaper that way in the long run.

Step 2.
Install the fused battery harness on the battery. Install the negative terminal first, positive terminal last. The positive terminal is marked with a red band, assuming that it's from the Warm-n-Safe company. Other companies may or may not mark their product in a similar way. Use caution!

After connection, check the SAE power plug at the end of the fused battery harness. The female receptacle should be positive, and the male prong negative. Pay absolute attention to polarity!

Reason for caution is because if the connector dangles and the male half of the SAE plug is negative, it won’t create a spark if it touches any part of the bike. Also because it might be possible to damage a controller if you have the polarity backwards.

If the bare male half is positive, you could have a serious problem with big sparks right near the gas tank and / or battery, both of which are highly explosive!!

Never hurts to double-check, especially in this case and considering the consequences.

Step 3.
Install the Bosch / BMW / Hella accessory plug. On my Concours, this involved cutting two holes in the left hand fairing liner using a Dremel tool, and installing the two sockets in the two holes. Carefully, as there isn’t much room and I’d bet that the liner isn’t cheap if you flub it.... Measure twice, cut once.

Step 4.
Now you can run the SAE plug / lead from the new accessory socket to the SAE plug on the end of the fused battery harness. Route it in such a way that wires will not rub through anything / anywhere over time. Keep it away from any moving parts, and once routed properly measure the length needed and cut the end off, leaving about a an inch extra so that the lead isn't going to be stretched tight. If possible, use cable-ties to secure it to an existing wire harness in such a way that it can follow existing wires in toward the battery.

Don’t actually plug the SAE lead from the accessory socket into the SAE lead on the fused battery harness, because you have more work to do.

Step 5.
Connect the SAE lead / extension cord to the newly installed accessory socket. There are several ways to do this:

a. Use yellow spade crimp connectors from Radio Shack on the wire end of the SAE extension cord. Attach the newly attached connectors to the accessory socket, verifying that the center of the socket is positive when you're finished. Or:

b. Set screw(s) on the Hella BMW-type accessory socket. Verify center-positive when done.

c. Solder with heat-shrink tubing over the soldered connections.. Verify center-positive when done.

Step 6.
Connect the two SAE style plugs together. Use your multimeter to verify that the center of the BMW-type accessory socket is positive. If it is, you’re done. Go riding.

If the center of the BMW socket is not positive, you’ve got something hooked up backwards. Return to the start of this document, and methodically search for the reason why. Do not use the accessory socket until the center is positive, or you may burn up an electronic controller. Instead, correct the problem. Then go riding!

Stay warm, stay found, stay out of jail, stay in touch, take only pictures, and don’t go hungry while out and about. How many other mod's can keep you out of trouble and so well connected in so many ways?

Additional Info / Suppliers / Related Reading:
The various plug types can be mixed and matched to a great degree, as there are adaptors on the market to allow a Widder controller to be used with an SAE plug, or a Heat-Troller (which uses SAE connectors) to be used with a Widder vest, etc, etc, etc.

All of the above plugs, fused battery harnesses, and SAE extension cords are commonly available from:

Warm-n-Safe , makers of the Heat-Troller

Other sources for some or all of the above items:
Your local BMW motorcycle dealer
Your local John Deere dealer
Radio Shack

A Method To Prevent Melting Accessory Sockets
By Brian Curry
Hosted on the Internet BMW Riders Tech pages.

NOTE: Link provided here with permission of the Internet BMW Riders admins.
See for more information on the Internet BMW Riders. The IBMWR site also contains other excellent articles on electric clothing repair, and many well-written travel articles as well. A great place to visit even if you don't have a BMW.

Summary (from the first line of the sockets article): "There have been a few reports of melted accessory sockets/plugs, and the resultant cold riders. :(:( I think I know why. I just had a socket come apart when I tried to take the socket wiring connection off..."

The article then goes on to give a detailed analysis of the failure mode of the BMW part, and a possible cure. Presented here for informational purposes only, and not meant as a slam against the BMW plugs. Please realize that any connection with high miles and lots of use can fail - that's one of the reasons I prefer a dual plug arrangement on my own bike.

You are ultimately responsible for determining your ability to install the accessory plug and for the suitability of this modification to your motorcycle. You must know how to use a multi-meter, and the difference between positive and negative in an electrical circuit. The author assumes no responsibility or liabilty for a reader’s lack of mechanical skill, lack of electrical skill, inability to follow directions, or ability to use common sense.

If you have any doubt about your ability to do this work, seek qualified help!!!!

Otherwise, it is possible to damage expensive parts and / or injure yourself.

Article By: Doug Grosjean

 Updated January 2005

Credits Javascript Menu by

   Join Now
   Renew Membership
   Membership Benefits
   Membership FAQs
   Industry Members
   Forum Subscriber Only
   Contact COG
COGMOS Features
   Calendar of Activities

   National Rally
   Common Questions
   COG Links
   COG Member Store
Social & Community
    COG Forum

    Twitter: COGRiders

Join COG
Renew Now
Contact COG

COGMOS Version 1.1 © 1989-2016 Concours Owners Group™, All rights reserved.    Privacy Policy  | Terms of Use  | Contact Us 

Bookmark and Share

Membership Management by Memberize™
© 2001-2020 Hill Country Technologies, LLC. All rights reserved.

Your session is about to expire...
Login Required
Admin Order Form