Blinkers one side works fast the other side stays lit

Hello All.
Thank you for excepting me to the group.
I am currently working on a one owner 73 Norton 850. I am the second person to ever place a wrench on the bike. It has not been on the road since 1990.
I have it running tip top shape now and have only two items left on my to do list for the owner. Those items are.
1) New Petcocks / Fuel stops. one OEM busted the handle while turning the plastic gave way. I can still turn with plyers. I've seen some nice OEM units and some cheap imports.
1Q) Is there a quality all brass unit that looks OEM?
2) Right side blinker / winker works however a bit fast for my liking. The left side does not change state (no blinking). All bulbs will illuminate just fine but left side stays on solid. The output brightness seems the same. I have cleaned the bullets and used DeOxit D5 on the connections
2Q) I'm thinking some sort of corrosion at the handle bar switch. Any other ideas?

Thank you for any help you can give.

Tony aka 44Dwarf

For indicators

Check that the correct bulbs are installed. If the bulb current is too high, the relay will flash fast. If too low, it won't blink at all.

bad ground makes for low current flow,
same as wrong high resistance bulb
therefore only on one side is slow

Mass? you should join NENO!

DynoDave. I got a T-shirt! A few years back I attended the brit show in Lancaster Mass.
If I end up buying this 850 which is a want but somewhat out of reach with out selling off some race bikes I would join for sure.
BTW: You dyno looks alot like my Patraco water brake unit circa 1970. I need to upgrade to modern electronics but mostly use just as a load cell so i can check O2, high HP number is not as important as clean running.

The indicator stalks are chromed plastic and serve as the positive feed for each indicator lamp.
...this is the only weakness in an otherwise very well wired bike, and should be the first thing you look at.


Dirty contacts in the switch is another factor as you rightly say:

• Using a piece of wire and jumpering the GW (green/white) with the LG/N (light green/brown) from the flasher unit will bypass the switch for testing the right side.
• Then you can do the same and jumper the GR (green/red) with the LG/N (light green/brown) from the flasher unit which will bypass the switch for testing the left side.

This would be the preference over taking your handlebar switch apart!


The flasher unit itself ‘only’ lasts about 40 years before it starts to get tired, but the symptoms you would see if this was the issue would affect both left and right turn signals in the same way.

The stock Lucas flasher relay needs the current from 2 bulbs to flash. If one bulb burns out, the other will be on steady. A poor ground or connection to one might lower the current below the flasher's threshold but you'd notice it as being dim. The blinker switch is a definite possibility for a bad connection to one side. One bulb plus one LED would also likely not flash.

I put a trailer hitch on my family car a while back and with the trailer blinkers on the flash rate was really fast. Needed an electronic flasher to cure that.

What I find odd is all the bulbs seem to be same output Brightness. I have not opened the front one but did open one rear for non working and found the plastic plated chrome busted up. The owner had new units but the stalk length was slightly different so both rears got changed. A simple solid state flasher would easily fix this but he want to retain 100% factory as the bike is as he bought it. This is the 1st trouble he's had with the electrics. I will open the fronts as see if the bulbs are correct and see if I can sneak a second wire for the ground connection up the stalk and ring lug to the metal bulb holder. I was shocked to see they used chromed plastic as the ground connection.

Sounds like your flasher has died on you.

jsnorton said:

Sounds like your flasher has died on you.

Click to expand...

But it works on a right turn, just a bit fast. As there is only one flasher unit it have to be good.

I was a mechanic for 45 years and changed a lot of flashers that were doing the very same thing yours is doing. If you have a spare flasher give it a try.

44dwarf said:

But it works on a right turn, just a bit fast. As there is only one flasher unit it have to be good.

Click to expand...

I’d try directly running ground wires, grounding all turn signals back to the chassis.

These kinds of problems are just a little difficult to diagnose so be systematic in trouble shooting it. The blinker works on one side and not the other, while the other side blinks fast—perhaps meaning you have two different problems on each side. Just logically follow the flow of electricity and you’ll find the problem. Older English bikes can experience a fair amount of voltage drop in the switches, Lucas connectors, and grounds, and the idea someone posted here of jumping to isolate the problem is a very good one, as is making sure all the light bulbs are good.

I had very similar problems on a Triumph and it turned out to be a bad ground in the front signals. To fix it, I hard wired the ground side of all the turn signals back to the chassis (actually, back to a ground wire in the headlight bucket that connected to a ground circuit I wired directly to the battery) and the problem was solved.

Flasher units are cheap so that's an easy/inexpensive thing to change. If the lights are illuminating, I can't see how there could be a wiring/ground issue. If it was a connection/ground issue, they wouldn't illuminate at all.

As far as the OEM wiring is concerned, there shouldn't be any need to add ground wires EXCEPT (on pre MK IIIs) a direct ground to the engine (rather than to the head steady). The issue is that some connection(s) have become corroded, etc over the years. Cleaning the appropriate connectors will solve the problem. Of course, that is assuming there are no broken wires or wires that are shorted due to missing insulation...

@MexicoMike if it was the flasher unit, the behaviour would be identical switching left or right hence my assumption that it’s not the OP’s issue.

Because the turn signals get their positive feed through the chromed plastic stalks, it is possible (and very common) that a connection can be poor.
Higher resistance/intermittent connectivity on one rear turn signal will make it‘s front counterpart blink irregularly.

Our forum friend @marshg246 has an excellent picture of the way he wires additional red wires into each turn signal.
I like this idea.

A "1973 850", however, would normally have a Lucas 917 tail lamp assembly which has no earth/ground connection to the plate, only the rubber-mounted bulb holder so perhaps a simpler alternative as the 917 lamp doesn't make use of the plate bolt (therefore, is an unnecessary additional connection) would be to replace the single bullet connector with a double common into which all four earths/grounds can be connected.

Although the best way is to add a gorund wire directly to the sockets inside the turn signals as I did in the writeup Grant posted above, for a 917 with new signals, I do it differently which is documented here: https://www.gregmarsh.com/MC/Norton/Norton_1974_Wiring.aspx.

In either case, the point is to get good ground to the turn signal sockets and since I powder coat the taillight metal parts the standard grounding definitely does not work for either taillight type without scraping power coat. There is still a possibility of a bad connection between the stalk and housing but I've never had one.

Even on Triumps, BSAs, and Nortons before Commandos where the frame and therefore the rear fender are decent grounds, I do the same. Tracking down ground problems is sometimes difficult so I prefer to prevent them.