Turn Signals + Horn Don't Work Without High Beam Flashers On

[kymaera]

Hi all,

New Airhead owner here. I've got a 1983 R65 I've been cleaning up and putting back together. It runs pretty well (throttle response sucks, but that's not what we are here for today). Unfortunately after a few hundred miles it has developed a problem where the turns signals and horn wont work unless the high beam switch is in the all the way down high-beam-flash position. Just having the switch all the way up (high beams on) doesn't work to make the turn signals and horn work.

I took it apart and there are no obvious bad connections. I went ahead and replaced the left hand unit containing the switches. Again unfortunately the new switches suffered from exactly the same problem.

So, the problem is somewhere downstream of the switches.

This doesn't make any sense to me. I don't understand why the particular position of the high beam switch would effect the turn signals and horn. Does anyone have any thoughts or suggestions? Any help would be greatly appreciated.

Thanks!

[robert]

Bad ground.

[SteveD]

Bad ground.

Welcome kymaera.

Unusual electrical behaviour in these bikes will often be traced back to a bad ground.

It's a wise thing to go over a new, old airhead and disconnect and clean and insulate as many connections as you can see and find, including the relays, headlight, flasher, starter.

[Rob Frankham]

OK, I think I've got an explanation as to what is going on,,, or at least one that fits the known facts which is a start...

Power feed to the horn and the indicator relay comes from one of the fuses and they are on the same wire . This power feed also goes to the Lighting switch to feed the headlamp flasher. It also, incidentally, goes to the front brake lamp switch.

The headlamp flasher switch simply connects the main beam circuit to the feed we've just mentioned.

The theory assumes that you have a US spec machine where the headlamp is permanently connected.

If there is a break in the circuit between the fuse and the indicator relay AND a wiring fault that makes the main beam circuit live, the horn and indicators will not work except when they are connected to 12 volts via the flasher switch.

So... how do you prove the theory:

1. Check whether the brake lamp is working from the switch on the front lever (the rear switch uses a different power feed). If the theory is correct, it'll show the same symptoms as the horn and indicators.
2. Check the fuses... this may just be a blown fuse although I'd expect other circuits not to work if that were the case.
3. Check for 12 volts at the green/black wire on the connector for the left handlebar switch when the headlamp flasher button is pressed and when it isn't. If the theory is right, you will only have 12 volts when the button is pushed.
4. Check for 12 volts at the white (main beam) wire on the connector for the left handlebar switch. If the theory is right you'll have a constant 12 volts at that point.

If all of these points check out, you have two faults. The first is a break in the live circuit (green/black wire) between the fuse and the indicator relay. The second is a fault that makes the main beam circuit live all the time.

Hope that helps.. if your still having problems, let me know the results and any other info you discover.

Good luck

Rob

[kymaera]

Thanks very much for the awesome feedback.

Here is what I found.

1) I was able to confirm the brake light issue.

2) I did find a blown fuse. Honestly I hadn't been able to find the fuse box previously. I was looking for modern fuses and what I found is very much an older style fuse. It was the top fuse of the 2 in the box just under the tool tray.

3) There is no green/black on that set of switches, but there is a blue black and a green yellow going to the turn signal. Unfortunately neither is exposed enough to get a tester to.

4) There is only 12v on the white wire when the flasher is on.

So, I'll replace the fuse first. Do you think that will fix the problem? Any suggestions on where I can get these old style fuses? Looks like it has an '8' on it. I'm assuming that's the fuse rating. I'm very tempted to replace the old style fuses with a modern box. Seems like it should be easy enough to do. And, is there really only 2 fuses for the whole bike (?!) or are there other fuses somewhere on the bike?

Once I replace the fuse I'll let ya'll know where I'm at.

Thanks again for the help! Mybad for not finding that fuse box earlier. I really did try!

[Airbear]

G'day Kymaera. Those fuses are used on old VWs and Mercedes cars (and probably lots of other european vehicles). But rather than bothering to find some, I suggest you get a couple of modern blade type fuses and make up some short spade type connector wires. You might need some 'double adapter' clips if there aren't enough male terminals on your connector board. Welcome aboard, by the way.

And kudos to Rob Frankham for some excellent detective work and a thoughtful post.

[bluesman]

I have seen the old style fuse's at the local Advance auto stores.

[Rob Frankham]

My advice would be to get the circuits working with the old type fuses before making any mods. That way you'll know whether any problems are the rsult of the current faults or what you've done.

If, ultimately, you decide to replace the fuses, and I can see the advantages of not having to delve into the headlamp bucket, make sure you use good thick wire or you'll incur a voltage drop.

Rob

[kymaera]

My advice would be to get the circuits working with the old type fuses before making any mods. That way you'll know whether any problems are the rsult of the current faults or what you've done.

If, ultimately, you decide to replace the fuses, and I can see the advantages of not having to delve into the headlamp bucket, make sure you use good thick wire or you'll incur a voltage drop.

Rob

Definitely planning on making sure the issue is resolved before I fiddle with upgrading anything. Just need to find one of those fuses today.

[Major Softie]

For testing only one thing at a time, you don't HAVE to have the correct fuse, you can use a lower rated one if that's all you can find. Probably won't work for riding, but it will work for careful testing.