1975 Mk3 Commando indicator problem

Hi again everyone back again with yet another problem, I took it out today to blow the cobwebs off and out of it and found I have a problem with my indicators and have a feeling it is a bad earth problem, when I use them left or right the indicator warning light glows and the ignition light comes on, this is the first bike I have ever had with them so as you can probably imagine they are not overworked but also I have not got a clue where to start looking so any and all advice gratefully received thanks Chris

chrisf1 said:

...when I use them left or right the indicator warning light glows and the ignition light comes on...

Click to expand...

Is that with the lights (headlamp, etc.) on or off or is it the same for both?
Better, worse or no difference with the engine stopped or running?

Hi again LAB my saviour it seems to make no difference what else is going on the result is the same

Sounds more like a low-voltage (low stator output?) problem for the ignition/charge warning lamp to glow so does it have an original 3-pin (silver can) assimilator, 5-pin (black plastic) assimilator or some type of voltage monitor?

Perhaps a short to ground when the indicator switch is on? Need to check with a Voltmeter and or a test lamp as to what voltage does with/without indicators on.
On my MKII I found a wire perilously close to shorting inside the switch cluster. It was pinched between the circuit board and lower side cover shell. Insulation very squashed flat.

Battle will commence tomorrow afternoon and I will start with the switchgear thanks LAB

Hi again battle has commenced and more revelations engine not running ignition on front flasher lights but does not flash, rear does nothing not even come on the same for both sides when riding I followed the bike and the rear lights dimly and does not flash, I understand from other info I have received that because the stems and a lot of the kit is plastic this often causes an earth problem can someone enlighten me where and how to go about improving this situation do I need to do it for each indicator or is one sufficient (ELECTRICKERY I HATE IT)

chrisf1 said:

I understand from other info I have received that because the stems and a lot of the kit is plastic this often causes an earth problem can someone enlighten me where and how to go about improving this situation do I need to do it for each indicator or is one sufficient

Click to expand...

The basic problem with the rear indicators is they have to rely on the number plate bracket, mudguard, fasteners and frame before eventually reaching a red earth/ground wire which results in the rear indicators having poor earth (unlike the front indicators that have a connection to harness red in the headlamp shell).
One thing you can do is connect an earth wire (or wires) into the tail lamp earth connection (under the lamp fairing) by replacing the single red wire bullet with a double common connector and use that as the rear indicator earth/ground (either a single wire connected to the indicator bracket or one from each bulb holder etc.).
A simple check to identify a bad indicator earth is to run a jumper wire from a known good earth point or battery positive terminal and touch the other end of the jumper wire to the bulb holder, housing or stem.

I had some weird indicator effects shortly after re-painting my tail light bracket. The joining place between the actual lamp section and the bracket from the mudguard needed some paint removal, especially around the through bolt holes. Perhaps if your hasn't been painted there is rust accumulation in that area?

One of my past bikes, Triumph?, had a ground problem in the blinkers. I was able to fish a small Teflon coated telephone wire thru with the feed. The phone wire won't handle much amp draw but works fine for ground.

chrisf1 said:

Hi again battle has commenced and more revelations engine not running ignition on front flasher lights but does not flash, rear does nothing not even come on the same for both sides when riding I followed the bike and the rear lights dimly and does not flash, I understand from other info I have received that because the stems and a lot of the kit is plastic this often causes an earth problem can someone enlighten me where and how to go about improving this situation do I need to do it for each indicator or is one sufficient (ELECTRICKERY I HATE IT)

Click to expand...

Make sure you have a good earth on the rear indicators , some of those brackets don't earth well , you can try adding a jumper lead for quick check . Cheers.

All sorted now thanks everyone it was bad earth to rear attached fresh earth wire to bulb holder all hunky dory