TURN SIGNALS PART II

[jamman18]

This is a continuation of my turn signal saga....1977 cb750f, got after market turn signals, hooked up rear and they work fine. Hooked up front LED in the mirror type to the wiring in the rear and they blew my 15amp main fuse I'm guessing because too long of wiring for the system. Changed the wiring to hook up to blue and orange wires coming right off the turn switch. Right blue wire signal works great.  The left one though, when activated, makes the headlight flash fast and then blows the main fuse again!  Confusing and would love some advice.  Thanks!

[sgtslag]

Well, I can't speak directly to the colored wires to use, but I can give you some generalizations, which should point you in the correct direction...

Dig out a schematic for your specific bike, and look for the signal light wires, and make sure you splice into the correct wires.  They can be tricky, with the different color schemes employed by Honda.  If you splice into the wrong wire, you can, and likely will, short something out, and blow fuses.

LED's draw less than 0.3 Amps!  A regular, 7W, incandescent bulb in a running light, will draw 0.6 Amps, and a 23W turn signal will draw 1.9 Amps.  If you are blowing 15 Amp fuses, then you have wired things incorrectly, and you need to reverse what you have done, and start over, with the schematic in hand.


If the headlight is flashing when you turn on your signal light, then you have cross connected the turn signal (23W circuit/1.9 Amp), and the headlight (55W/60W, 4.6 Amp/5 Amp circuit!).  If you reverse the polarity, it can get even worse...


Get the schematic, and follow it carefully.  Cheers!

[shinyribs]

I have yet to find a wiring diagram that matched the wire colors used on my bike.Test light did the trick though

[TOOLS1]

I could understand crossing the blue wire with the blue high beam wire, but that is not the case. I think there is an internal short in the left turn signal, or it is grounding through the head light.
TOOLS

[jamman18]

Yeah, I was going by the wiring diagram, original in the manual and the right blue wire worked fine.  I do have a multimeter so maybe I should try that.

[jamman18]

Lots of great info!  Back to the drawing board!

[jamman18]

Yeah, I will look for a short too.  Thanks!

[sgtslag]

I spent 3-1/2 years as a component level analysis Electronic Technician, reverse engineering, troubleshooting/replacing diodes, resistors, transistors, etc., on computer parts, and accessories.  We rarely had schematics to go by, so we used crude, but effective techniques, to find the failed components.

If there is a schematic, I will always steer folks to them. Clymer books have decent schematics in them, so if in doubt, check for a Clymer manual on your bike.  If the wire coloring codes don't match up to the schematic, then you are screwed...  Using a test light can work, but it is far less direct, and usually more difficult, than reading a schematic.  I prefer the direct approach of looking for the correct, color-coded wire node, rather than the 'hunt and hope' methods -- did that professionally, don't need the stress!


If you have a schematic, it is safest to verify the wire is correct with either a voltmeter (best), or a test light.  Grounding the wrong wire, or applying 12 Volts to the wrong lead, can be...  Troublesome.
  Cheers!

[LukeM]

This is, of course, assuming the bike has the factory wiring harness. If not, then it's schematic out the window, and test light time.

I also started in component level troubleshooting back in the 70s.  A good VOM, a good oscilloscope, and good schematics was all you needed to make stuff work. Now it's module level troubleshooting, or just junk it and buy a new one.  May God help us if all the systems in the world go belly up, and there's no one around but me and the Sarge to fix stuff. :-)

Luke M

[jamman18]

I checked the diagram again and the light blue lead off the turn switch is right signal which works fine.  The plain orange is for left turn.  Tried each wire independently to see if it made a difference but still no left signal and flashing headlight.  Took multimeter to both and the right gives me a pulse when on but the left goes up to about 8v and does not pulse.  Besides no left flash in front I also get no left flash in rear until I disconnect the front, then rear left works fine again.

[TOOLS1]

Trace that orange wire back. It must be crossed with the headlight wire somewhere.
TOOLS

[sgtslag]

Tools is correct:  the front turn signal bulb's wire is crossed somewhere.  The front and rear turn signals are normally wired in parallel to each other, which gives both bulbs a full 12 Volts.  If you are reading only 8 Volts, then it is wired wrong.  The fact that the headlight is flashing when you activate the left signal light, indicates the two are connected in some way.  By disconnecting the front light, and seeing that the rear light works, you have located the fault:  the wiring on the front left turn signal, and the headlight circuits.  Excellent trouble-shooting, Tex!  Now you only need trace those wires, in the organized mess that is your wiring harness.  Unfortunately, this is going to be a taxing job.  Still, you know which wires to look for, and it is a relatively short trail to follow.

Look up the color code for the headlight Hi/Lo wires:  try to determine which circuit on the headlight is cross-connected, by switching between Hi/Lo modes.  If it flashes in both modes of the headlight, then it is most likely the ground side is cross-connected -- not gospel, but most likely.  If it only flashes in Hi, or Lo mode, then follow the wires for that circuit, only (check the schematic, as they will be different color-coded wires).  Good luck!  Let us know what you find.  Cheers!

[jamman18]

The headlight flashes in both hi and low beams!  On to finding the ground.......which will have to wait until Thursday when I'm off work again.  Ran out of time for this day.....

[sgtslag]

All of the ground wires, in every circuit, are color coded the same...  You will need to physically trace the ground wire from the headlight, and the left, front signal light, to see if they are crossed/connected to a non-ground wire -- they should only connect to the bike's chassis:  ground wires are often just routed to a point on the bike's chassis, and screwed to it, as the chassis is the common ground point (the battery's negative terminal is usually connected to the bike's chassis by a heavy, black cable, and a large screw into the chassis tube).

Remember, the ground wires might be the problem...  It may be something else, but this is the first circuit/wires to trace out, physically.  Good luck.  Cheers!

[jamman18]

Thanks!  Just to be clear, the mirror/turn signals are grounded to where they mount to the handlebars and only have one wire that connects to the right light blue and left orange, respectively.

[sgtslag]

Is there a light failure circuit shown on the schematic?  My Voyager has a 'black box' that controls the headlight filaments:  if one filament burns open, the other takes over, regardless of the switch position, with the Hi beam filament running at a lower amperage, to mimic the function of the failed Lo beam; there is a dash light to show a headlamp failure -- when the Hi beam burns open, it just runs on Lo beam, no matter what.  Anyway, if there is such a box, or failure circuit shown on the schematic, then things get a bit more complicated.  Any such failure circuit is doubtful on a '77, but it's possible.  If there is such a 'black box' device, it will be shown, and labeled, on the schematic.

Another potential gotcha', is the dreaded "floating ground", where the circuit is not properly grounded.  This creates very strange symptoms.  It is easy to test, though:  put your digital Ohmmeter (not recommended for analog/needle deflecting meters...) leads between the ground lead on the left turn signal, and the negative battery terminal, and see what the resistance reading is.  It should be <2 Ohms.  Do the same with the headlight:  measure the resistance between the ground plug on the bulb, and the negative terminal on the battery, it should be <2 Ohms.  By the way, testing for good ground connections, is much easier than tracing wires through the harness, so I recommend these tests first.

If you do not have any electrical terminal/contact grease, get some from your local auto parts store.  Apply this to all contacts, and connectors.  It will prevent them from corroding, ensuring good electrical connections, preventing weird problems down the road.  With older bikes, corrosion on contacts, and connectors, can be a major source of headaches.  The best practice is to clean the contacts, first, with a brass brush, then apply the grease.  If they're already corroded (white, or green, fuzzy stuff on the metal contacts), the grease *might* improve the connections, but brushing them with a brass brush to remove any corrosion on the metal surfaces, is the best.  Cheers!

[jamman18]

Thanks to all for your help!  The signal is fixed!  Found out that the left signal wire was not hitting the headlight wiring at all.... it was actually grounding itself out!  On these aftermarket signals the base is grounded but has a small hole that the 12v wire connects to the left orange from the bike.  When I originally attached it, I was not careful and as a result wound up pinching and cutting the sheathing down to the wire, so when the power came on the 12v would ground itself to the handlebar.  Once I fixed that with a little insulation it works fine...only cost me 2 more fuses and a bit of frustration!