Switch replacement

[yourpalcal]

Hope I’m not wearing out my welcome on this message board but this build keeps offering new and challenging projects. I noticed a crack in my left horn/dimmer switch on my 72 r75/5. Closer inspection shows the inner spring is coming out and when I removed it from the bars the thumb portion basically broke in half probably due to age. Therefore, I went ahead and ordered a new replacement switch. I just opened my headlight assembly and must admit feeling a little overwhelmed. I can see where the switch cable routes in from the back but it looks like it splits with some wires going up to the speedo and others to a small connector.

Any advice on simplifying this replacement. Should I just cut the old wires, solder and use butt connectors?

 

[Friedle]

Hope I’m not wearing out my welcome on this message board but this build keeps offering new and challenging projects. I noticed a crack in my left horn/dimmer switch on my 72 r75/5. Closer inspection shows the inner spring is coming out and when I removed it from the bars the thumb portion basically broke in half probably due to age. Therefore, I went ahead and ordered a new replacement switch. I just opened my headlight assembly and must admit feeling a little overwhelmed. I can see where the switch cable routes in from the back but it looks like it splits with some wires going up to the speedo and others to a small connector.

Any advice on simplifying this replacement. Should I just cut the old wires, solder and use butt connectors?

Your new switch, unless NOS, is probably a /6 switch which while similar looking has different connections on the wire ends from the /5 switch (and possibly some mismatching wire colors). You might be able to figure it out with a good understanding of wiring diagrams and understanding what you see and what presently exists.

Have you joined the Airheads Beemer Club yet (wwwairheads.org) to get some hands on help. If you screw the project up, get back to us and I can direct you where to obtain a new wiring harness. You do realize the /5 bikes don't have fuses in the wiring as standard equipment?

Friedle
NY AM
ABC BoD

 

[jagarra]

My 74 R90/6 has the same switch assembly as the 75/5. I ordered new ones for each side, when they arrived the wire ends were not terminated, one will have to put connectors on the them. The originals were a 1/4 push on 90 degree style, not easily found.

Amazon has some that would work https://www.amazon.com/INSULATED-TE...t=101&pf_rd_i=306724011&pf_rd_m=ATVPDKIKX0DER

 

[m_stock10506]

The 1974 /6 bikes were a unique year. Many parts on the '74s were one year only. The handle bar switches for the 1974 are NLA. Although they look like the /5 switches there are differences besides just the wire end terminations. I think you are more likely to acquire /5 switches than you are 1974 /6 switches. The later /6 switches are much different visually.

 

[lmo1131]

No butt crimp-on connectors... please. More people screw up their machines by doing this.

If you ordered " /5 " switches the ends should be pre-tinned. If you don't have a wiring diagram, get one. Sorting through the headlight nacelle can be daunting, but it's actually well thought out (once you know your way around). The tinned ends are easy to work with and have the added benefit of not needing any other component to secure a connection.

MAXBMW Parts diagram #61-0216

 

[yourpalcal]

No butt crimp-on connectors... please. More people screw up their machines by doing this.

If you ordered " /5 " switches the ends should be pre-tinned. If you don't have a wiring diagram, get one. Sorting through the headlight nacelle can be daunting, but it's actually well thought out (once you know your way around). The tinned ends are easy to work with and have the added benefit of not needing any other component to secure a connection.

The switch is NOS for my model year and the ends are pre-tinned. Is any soldering required to connect or do they plug in?

 

[lmo1131]

No soldering required. Just insert them into the terminal block and tighten down the set screws.

It can be intimidating, but just go slow; it isn't a race. The up side is ... if you ever encounter electrical problems when you're on the road you'll know your way around your electrical system. That's why I suggest leaving everything stock.

 

[jbarneshb]

One thing I learned working on mine is take pictures. Especially before you unhook anything. And if you can do one wire at a time that's even better. Label writes too. They make tape with numbers for just that.

Sent from my SM-G900V using Tapatalk

 

[yourpalcal]

The new switch arrived and after careful inspection it doesn't look too complicated. Two wires go to the headlight for the dimmer and three wires (assuming the horn) attach to the switch board on top of the headlight assembly. I reviewed the Clymer manual but not much there on this board. How do you remove it? It looks like it snaps in but don't want to break anything.

 

[brook.reams]

The new switch arrived and after careful inspection it doesn't look too complicated. Two wires go to the headlight for the dimmer and three wires (assuming the horn) attach to the switch board on top of the headlight assembly. I reviewed the Clymer manual but not much there on this board. How do you remove it? It looks like it snaps in but don't want to break anything.

Here is a link to Duane Ausherman's description of how to do this work.

http://w6rec.com/duane/bmw/ignkeys/index.htm

And a link to one on the internet bmw riders site.

https://ibmwr.org/index.php/2018/07/14/bmw-5-ignition-switch-removal-repair/

IIRC, the metal tabs securing the board are fragile, so GREAT CARE should be taken when bending them open and closed again.

I hope that helps.

Best.
Brook Reams.

 

[20774]

Be absolutely sure you need to remove the board. As Brook alludes to, you don't get many chances to do it. The four prongs that hold the board in are quite fragile...they work harden and break quite easily. Bending them needs to be done only so much as to get able to get the board out. In order to save things, you likely will need to anneal the tabs which makes them flexible again. This is usually done with a very fine heat source like a miniature propane/butane torch. The issue is that in doing so, you will likely ruin the paint on the headlight shell. Possibly using a wet towel in the region can keep the area beyond the tab location cool enough so as to not ruin the paint.

 

[beemeruss]

Speaking of paint, look at Lew's picture of inside the headlight nacelle in post #7. You will see that it has been painted white to add contrast to the wires to more easily see inside the cave. I am not advocating the gutting of the unit of wires and switches just to paint in there but if you have to anyway, that would be a good time.
Cheers, Russ

 

[lmo1131]

+3 on you DO NOT want to remove the main switch if you can absolutely avoid it. Those tabs are weak at best. I only removed mine when I stripped the nacelle for painting; I also took the opportunity to anneal the tabs with a propane torch. Re-crimping them is a real PITA, and not a little phobic...

There is nothing on the back (top) that you need access to. Take a deep breath and work from the front side. This will sound a bit scary, and counter productive... but think about disconnecting ALL of the wires to the terminal block to gain working clearance. It will be a good learning experience and will ensure all the connections are tight (after you reassemble it). You DO have a wiring diagram to work from. Say yes.

Bottom side (that you see)

Top Side (that you can't)

EDIT... DISCONNECT the battery before plunging into this.

 

[yourpalcal]

Ok, so now I’m a little worried of the fragile nature of removing the board. I mean it’s been in there for over 40 years. I think I will take Lew’s advice and try to replace the wires without removal. Gentlemen, if I haven’t said already, thank you so much for all your advice so far. I can’t say enough how much your expertise has helped me along. I have two kids in college and one in diapers so my time is very limited and certainly my financial resources. Your guidance has certainly helped me to avoid any costly mistakes.

 

[brook.reams]

SNIP ...

Top Side (that you can't)

EDIT... DISCONNECT the battery before plunging into this.

Hi Lou,

What I love about those pictures is they show the necessary labor and skill required to assemble the boards. Now, compare that to the /6 solution for wiring inside the headlight shell.

Clearly, reducing labor cost and skill became important to BMW by the 1970's, in part, due to the Japanese invasion of the US and European motorcycle markets. I find it interesting to see the evolution of these machines that reflect the affect of market forces on BMW design.

Best.
Brook Reams.