Modern Vespa

So I went to upgrade my signal lights to LEDs on my 2006 Typhoon and used the directions from Pedparts:
https://www.pedparts.co.uk/blog/piaggio-gilera-led-indicator-flasher-relay-upgrade

I have done a flasher upgrade on other motorcycles with no problems before so this was a new one.

When I signal all 4 lights go on, with the side selected full brightness and the opposite side dimmer. Note that the dash indicator doesn't light up. When I select the other side with the switch the opposite occurs. They do blink at the proper rate so doesn't seem that the flasher is the issue.

I tested continuity between the positive signal leads out of the switch and they have continuity which makes sense because they both feed to a single dash indicator light.

I reinstalled incandescent lights and it works fine with the dash light blinking.

It seems the LEDs are such a light load that it is sending power through the instrument cluster to the opposite side light. I tried flipping the polarity of the LEDs with no change.

Would installing a load resistor help. It's really bizarre behavior.

Also since I have a parts bike I tried swapping signal switches and instrument clusters with no effect. Even tried 2 different brands of LEDs.

Probably need to switch the turn signal relay to something for LEDs. The old mechanical ones probably need more resistance in the circuit to work right.

Pretty sure this is a solid state one already.

The problem is that unlike a normal filament lamp, the LEDs have a polarity; if the circuit is designed with a "round trip" system with the indicator light as part of the circuit, a part of it that uses the LEDs prevents the necessary completion of the indicator light.
I don't know if I've made myself clear ... and I don't know if my hypothesis (it's a possible explanation) is the correct one.

Ok so I tried with LEDs in the fronts and incandescent in the back and that works fine. Normal blink rate and the instrument cluster indicator lights up.

If I replace one of the rears with a LED that side works. If I try the side with the incandescent than I get the same problem. So it definitely seems like it's a load issue.

Question is should I try another flasher relay first or just add in the load resistors on each side? (thinking 25 watt 6 ohm).

Try the relay.

Got some parts. Let's see what happens.

So the new flasher relay didn't fix it. The load resistors did however. So that means all the work I did splicing that relay in was for not as it's not required on the typhoon. Just the load resistors themselves. Oh well good to know and hopefully helps the next person out.