Here's how the circuit works... Power enters the flasher unit and comes out as pulsing power. This "pulsing power" then goes to the turn signal switch on the handlebars. The switch merely selects Left, Right or OFF.

Turn Signal Circuit

So if the bulbs flash on at least one side, then the flasher unit is operating perfectly. By deduction then, your issue then is in the switch, wiring, or bulbs to the opposite side.

With a "test light" clipped to either an unpainted cylinder fin or a Brown wire ("return") terminal, one can compare the Left and Right sides of the turn signal circuit, which should be doing the exact same thing at the exact same point in reference to the presence or absence of electrical power. In other words, inside the headlamp shell on the multi-color circuit board, if your test lamp sees power come out of the handlebar switch on both Left and Right sides, then you can rule out the handlebar switch.

Your issue is most likely corroded (oxidized) connectors simply not allowing an electrical connection. This is a very common fault on 40 year old motorcycles which I have discussed ad-nauseum. If you have corrosion on one connector, then you have corrosion on ALL connectors. Just becasue you don't see the weaker headlamp, flickering tail lamp, lower battery charge rate, or lower volume horn doesn't mean for an instant that it's not there. I highly suggest you unplug and add a dab of No-Ox-Id to each and every connection pair on the bike. This will take maybe a week to do the entire motorcycle, but it is well worth your time and effort.

Photo 7ml tube of No-Ox-Id available on Amazon

The very smallest 7ml tube is enough to complete 10 motorcycles. It just takes a dab to dissolve the corrosion and keep it from ever returning.

Hope this helps.

I'm having a very similar issue with my 71 /5. I took it out for a test run yesterday. I noticed that the signals weren't working, but the generator light would blink as if it were the blinker.

I took the headlamp off and one of the fuses had blown. (I added two fuses about 5 years ago when I put the new harness in). I replaced the fuse and tried the turn signal. Left was fine. Right blew the fuse.

That's as much time as I had to investigate so far.

Yours sounds like a short,mine they flash all around left and right but not the left on the panel,so if i forget to turn it off it flashes continuously

I'm having a very similar issue with my 71 /5. I took it out for a test run yesterday. I noticed that the signals weren't working, but the generator light would blink as if it were the blinker. I took the headlamp off and one of the fuses had blown. I replaced the fuse and tried the turn signal. Left was fine. Right blew the fuse.

/5 had the globe-shaped turn signal switch, which is inside a metal hosing. As the wiring ages, the insulation will erode and back away from the terminals making it very easy for the wire to short to the round housing.

At the auto parts store you can get a miniature circuit breaker to plug into an automotive fuse panel. If you take one of those and add wire leads and alligator clips it makes a great test tool. Instead of blowing $50 worth of fuses, you'd clip this in place of the fuse and do your testing. When you solve the problem, then remove the circuit breaker and add the fuse.

Hello again,

I did a bit more troubleshooting and made a video of my findings. https://photos.app.goo.gl/9TbJdjqoTQpPHfBQ2
This is a 71, but I rebuilt it and put a whole new wiring harness in about 5 years ago, adding the two fuses that would have been in a 72.

Again, referencing the schematic I made up....

Flasher Schematic for Reference

Thanks for the video. From it we can see...

• Both flasher pods work correctly. Therefore the issue is NOT in either RH flasher pod OR the harness wiring leading to them.
• The LH flashers work normally. Therefore the issue is NOT in the fuse or the flasher module.
• The LH flashers work normally. Therefore the issue is NOT in GRN/YELL wire taking power into the turn signal switch.
• The LH flashers work normally. Therefore the issue is NOT in BLU/RED wire bring LH TS power out of the turn signal switch.

By deduction, there are only two places remaining:
1) The turn signal switch in the RH position only, OR
2) The BLU/BLK wire bring RH TS power out of the turn signal switch, but only between the handlebar switch and the headlamp shell.

DO THIS
Take out the 2 tiny cheese head screws from the top and bottom of the Turn Signal Switch on the handlebars. Pull the switch clear of the metal globe on the handlebars about 1-2 inches so that it is now in mid air and no longer touching the housing or handlebars. Turn the key ON and operate the TS switch normally....

► If the RH flashers work properly, then the switch or wiring is shorting to the interior of the metal globe. (Maybe the big screw in the interior of the globe is backing out and now touching the rear of the TS switch contacts? Maybe the cheese head screws are NOT the correct length and thread far enough into the globe to touch the wiring or contacts?)

► If the RH flashers continue to blow fuses, then the short is in the one single BLU/BLK wire between the switch and the headlamp shell. It might be a worn place in the insulation where the wire is tied to the handlebars, or it could be cut by the sheet metal where the wire enters the headlamp shell.

It has to be one of those 2 places.

Wobbly,

Thanks for the write up instructions. I did try a systematic troubleshooting routine. I just couldn't make sense of it as at times it seemed to be the front turn signal on one side, then it was the rear turn signal on the other.
I ended up squirting some electronics cleaner in the turn signal switch, even though I'm waiting for the new one I bought from MaxBMW, that "fixed" the issue. Seems it was just the WD-40 I'd squirted in the switch in the Fall.
I put everything back together and took a 50 mile ride. It's great weather in Portland, OR now, and so far so good.

Once again, thanks to all that helped me with this.

I ended up squirting some electronics cleaner in the turn signal switch, even though I'm waiting for the new one I bought from MaxBMW, that "fixed" the issue. Seems it was just the WD-40 I'd squirted in the switch in the Fall.

In order to blow fuses you'd need a good, hard short circuit. In other words, if your flasher fuse was rated at 10A, then the 'short' would need to be substantial enough to be capable of carrying in excess of 10A. So I really doubt that any residue remaining from any type of switch cleaner caused your problem. WD-40 is not conductive, and neither is its residue.

The /5 grip switches are not well sealed to weather or wash water, and that means you'll continue to need an array of "helpers" to treat those switches. Therefore, don't be too quick to completely write off the benefits of WD-40 as a water repellent, occasionally useful in the maintenance of these controls. All we can conclude is that it wasn't successful in this particular instance. Other useful tools in this array might include your contact cleaner, compressed air, and maybe a heat gun. All to be tried in various orders and combinations until the missing electrical function returns.

But the main things for now is you've had success, and that you and your Airhead are back on the road !

Congrats !