left turn signal doesn't work

[Rob]

Left turn signal on my 1971 CB750 stopped working. Right still works. Bulbs work. I keep reading that it could be a bad ground or to check ground. I don't really know how to do that. I took apart the switch, when I jumper the two contacts in the switch for the right, they work; do the same for left, don't work, so I think its not the switch. Not knowing how to "check the ground" I looked for continuity between the middle of those three contact pads in the switch and the engine and found them connected. Did the same for the other contact for the right side signal and also found continuity to the engine, which doesn't make sense to me. Tested the left side contact in the switch and also found a weak electrical connection to the engine.

Everyone else seems to know exactly what is meant by "checking for grounding issues" but I don't. Can you give me some advice how to start?

[Piute]

                              front or rear ? , are they stk. lights ? info others will need.

           my rear(winker only) have a 2 wire set up but front(running N winker) has 3

[Rob]

Stock setup. Neither front nor rear work.

[Piute]

                         I take it you have this BUT.........................(K2 right)


    YA see all those dang Grn. ground(from winkers) wires,there's 3way plugs in yo head light bucket (like mine)check them all.

[TOOLS1]

It means to check the ground connections. Make sure they are connected, and clean. Sometimes the unit like the turn signal housing will be the ground.
TOOLS

[shinyribs]

Everything that runs off 12 volts has to have a ground to work. It is what makes a complete circuit for the voltage to come from the positive side of your battery,thru the device( in this case,your turn signal) and then back to ground. The negative side of your battery is ground. The negative cable off your battery is attached directly to your frame and engine,so they are grounds also.

It does sound like it would be a grounding issue,but it seems unlikely that you would lose both the front and the rear together,at the same time,due to a ground issue. Tools is right,the housing of the turn signal itself could be what grounds the light.If so,then clean the mounting surface/attaching fasteners of the light and a proper ground would be restored.

  To know if the housing of the signal is the ground or not , look and see how many wires are going into the signal. If there are two wires going into each signal one of those should be your ground. If the wiring is all stock it most likely will be a green wire. If there is only one wire going into the signal then the housing is your ground.
 
  But since your front and rear stopped working at the same time you could very well have a loose or cut wire on the positive or hot side of the wire.
 
 Your right side works so you know that you have voltage at the switch,so that part is good. Would have need to find which wire coming out of the switch feeds the left turn signals and check it for voltage. Chances are if it is a loose/cut wire you will be able to just see that and repair it without needing a meter to check for voltage.

 But check your bulbs. I have blown two bulbs on one circuit many times before. It seems highly unlikely,but it can happen and it is easy to check and fix. Start with the simplest things and work your way out from there.
Good luck!

[Rob]

Thanks for the advice. This is the first time I've gotten a recommendation that I actually understood with some specific things to check. I plan to give this a go tonight and will let you know how it works out.

[shinyribs]

Keep us posted,we're here to help!

[Rob]

Only one wire going to each of the turn signals. I was told this was a 1971, but when i check, the wiring diagram looks more like a 1970, does that sound right? (also only one fuse that I can find)

Ground connections at turn signal bulb/housing is good. The other thing I tried doesn't make sense to me either. I assumed that if I jumpered the two contacts for left turn in the switch, and ran a jumper directly from what i think is the ground contact in the switch to frame ground, then if the problem was a bad ground this should bypass that and cause the turn signal to work ( I hope that made some sense). What I got instead was the flasher relay started clicking, but still no lights. I'm still scratching my head about what could be going on. I'm hoping I'm right about the circuit diagram though, the older one has fewer lines and is easier for me to understand.

[shinyribs]

The wires in the switch are all hot wires,or have voltage present. There are no grounds in your switch housing. The housing of the turn signal itself will be your ground. I might have been unclear about that. Sorry! When you grounded the wires in the switch and it made the flasher start clicking,what probably happened is it completed the circuit for that side and allowed the flasher to work/click.

Were you able to tell if the signal housings were clean and making good contact? A good test would be to run a jumper wire from your negative battery terminal to the signal housing and see if that works. You could try whatever fastener the signal is mounted with first or touch it to the housing itself as long as it is some sort of conductive material,of course. I know some of the signals are chrome plated plastic.

I just had an even better idea. Remove the lens and attach your negative jumper wire directly to the bulb holder itself. Or maybe even to the brass base of the bulb. That way you know for a fact the bulb is grounded. Sometimes the bulb holder itself will corrode and cause you to lose ground. That would be a better test for a ground issue. If you do that and the bulb lights up you know for sure it is a ground issue.

[Rob]

Victory is in sight! I tried all of the suggestions about verifying the grounds, and everything checked out. So I started with the other wire going to the front turn signal lamp and started working backward looking for voltage. The first connector I came to, the wire practically fell out by itself, almost no friction. I held that connector in a way I thought would make the connection stronger and then the turn signal started working (yea!). I still have to reassemble everything, but I'm wondering what I should do to improve that connector? I considered crimping either the female side to make the I.D. smaller, or deforming the male side so part of it is larger, but am nervous about causing damage that could make it worse, so I'm looking for suggestions. I hope I don't have to replace those connectors, I'm not sure where I could find those parts.

Thanks again for all the coaching to help me diagnose this problem.

[shinyribs]

NAPA can get those connectors you need. Some locations stock them,some dont,but they can get them for you. You can spread those connectors back open,though.They are brass and very soft. Occasionally one might break when you are working with it,but usually they will do just fine.  Glad you got it sorted out!

[LukeM]

Sometimes, those brass connectors have a little tang on them that helps them stay in the plastic housing.  It's possible that tang may have dislodged or gotten bent.  Depending on how bad it is, you may be able to just reposition the brass part so it's secure.  The alternative is to get some solderless connectors from your hardware or auto parts store, and replace it.  If you go the crimp route, please buy a good crimping tool.  Vise-Grip (tm) or regular pliers won't do as good a job.

How about posting a picture of the connector and the wire?  

Luke M