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1987 VN750 turn signal issues

3K views 17 replies 3 participants last post by  RoadHopper 
#1 ·
Hi all:

Have an '87 750. Turn signals were working fine at one point, but then I decided to switch to flush mount turn signals and now i'm having some issues.

Bought new incandescent blinkers (3-wire for the front, 2-wire for the back), should work fine. Pretty much the same blinkers except flushmount. Unplugged all the turn signals, can't get the new ones to work.

The '87 750's have integrated running lights and blinkers. The running lights turn on, but they don't blink. I kind of suspect a flasher relay problem, but I don't even know how to test that. But I played around with the connections to see if I could figure anything out.

So, I have a 3-connector flasher relay. It has a b/y (black/yellow) wire going to it (ground), and an orange wire, and an o/g (orange/green) wire going to it.

When I unplug the flasher relay, I'm left with a connector coming out of the wiring harness with those 3 wires on it—b/y, o, o/g. I am not entirely sure how flasher relays work, and my multimeter literally just crapped out yesterday (buying a new one today), but I still wanted to see which wires had power and when so I figured I could take one of my rear turn signals, which are 2-wire, and use it like a test light.

So I grounded the ground terminal of the turn signal on the b/y wire on the flasher relay connector. Then, when I plug the hot terminal of the turn signal into the o/g wire on the connector, the turn signal lights up. But then when I plug the hot terminal into the orange wire on the connector, the light doesn't light up. Doesn't matter what position the turn signal or hazard switches are in, it doesn't light up. So, somewhere along the line, I don't have any power whatsoever going to my orange wire.

Is this normal? Which wires at the relay are supposed to have power (orange and o/g? or just o/g?). I also tried jumping the o/g wire to the orange wire to see if I could get the turn signals to light up (although they wouldn't blink with the relay not connected), and it seems that even when I jump those two connections i don't get my turn signals to light.

Any help would be very appreciated.
thanks!!
 
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#2 ·
Try plugging in the old ones at the stock location to confirm there is nothing wrong with the electrical system. Then temporarily mount the new ones the same way.if they work in the stock location you may have a grounding issue. If I remember correct the blinkers ground through the assembly to the forks on the front and the backrest mount on the rear,but I might be thinking of another bike.I've played with a few too many in the past few years and lately the gray stuff between my ears has been acting more like mud than a brain so someone with more knowledge should probably chime in.I know I'm probably not old enough to suffer from CRS but I can't remember how old I am (just know I'm not ;)).
 
#3 ·
Then again incandescent bulbs might need a new blinker relay if they don't draw as much current as the stock bulbs do.the system might be acting like it has a dead bulb
 
#7 ·
Just information for you...

I have an 87 too. It's a California model ( emissions, etc ). Front turn signal lamps have black/yellow, a blue, and a gray on mine.

Also, tell me where you want a voltage reading and if i get time tonight i will measure them for you. I only have an El Cheapo brand MM though, and it's analog.

One other thing... on my bike, the right turn signal goes fast, and the left goes slow. But i only have one hooked up on the left while waiting for a replacement to arrive.
 

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#8 ·
Ah, thank you! yeah, mine has the grey/blue/black-yellow at the actual signal as well.

What would be really helpful would be if you would't mind taking a reading at the flasher. On mine, it's really easy to get to. Just pop the seat off, and right behind the battery (towards the rear wheel) should be a little black box just kind of hanging off the back of the battery cage. There will be a 3-wire connector going to it, which should just pull out.

The connector should have b/y, orange, and o/g wires going to it. Mine has power going between the b/y and o/g (b/y is the ground). I wonder if you have power between the b/y and the orange? It might only get power by turning the turn signal switch or the hazards on, but maybe there's power all the time. Or maybe there's no power, ever.

If this isn't too much trouble, it would be very appreciated!

Thanks!!
 
#13 · (Edited)
Ok, sorry the delay, something came up on this end, but got the measurements and some photos.

I flipped it upside down, the colors were both orange, hard to see it in the picture maybe, but one of the orange had a stripe on it, the plain one was what i will call the center one since the striped orange was on the opposite side of ground. Key off, all dead ( thankfully ).. Key turned into on position with engine off. I had the ground wire screwed under the battery ground. Got a good solid B+ reading ( 12 to 14 volts ) on both orange wires, and of course, the ground was 0. Turned on the blinker. The striped orange wire ( opposite of ground on the "square" ) just stayed at B+. Every time the blinker would blink, though, the plain orange center wire would bounce my meter about 2 volts or so. Did the same on both left and right, as it should.
 

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#15 · (Edited)
Actually...
I wonder if I might be able to trouble you for one more piece of information.

When you tested the leads, did you test them with the flasher relay plugged in, or unplugged?

I wonder if the relay transmits power somehow (actually, I think it must). I get no power at the orange wire with my flasher relay unplugged... Do you have power when your relay is unplugged?


I have been doing a lot of tracing on the wiring diagram, and I can not for the life of me figure out how that orange wire would have power. Where does the power come from?

thanks!
 
#16 ·
As shown in the photos, plugged in. And yes, right after i read my reply i was thinking . . . DOH! LOL

Dark here now, i can check it out again tomorrow but my unit is seriously rusty on its leads. This bike had a battery overflow big time from its previous owner ( among other things ) and still picking up for his lack of care. When i say rusty, i mean to say rusted solid. Before even trying, odds are, if i try and unhook it, it will more than likely bust one or more of the connector ends ( a little "if it aint broke don't fix it" experience there. I am trying to get the bike up to State Inspection level, but after she's inspected, i'll be ripping things left and right. Until then, though, i am sort of trying to leave her as stock as possible, and right now at this moment, my blinkers are blinking, no what i mean? :D
 
#18 · (Edited)
Just a guess, and based on how my signals are acting... On the left side, it blinks about twice as fast as the right, but there is only one bulb hooked up on the left side.

I am thinking the unit is a simple tank circuit, and sure, possibly a relay too, but one wouldn't be necessary if they are using a transistor. All a tank circuit is/does is fill up a capacitor until it "fires" and that in turn empties the capacitor to a state of needing to be refilled again. When the capacitor fires, it turns on a transistor which acts like a switch to pass current through its main leg. It could also be a tank circuit with low power enough to just turn on the primary of a relay ( avoiding a high power transistor and big heat sink ). The reason why i say this is because of one of my circuits going faster than the other. The load is actually changing the frequency of the firing. Make sense? In any case, for a tank circuit to work, both of those wires would need power, but since the whole thing is enclosed, that power could be coming from a resistor inside the housing anyways.

Long story short, disconnect yours, then between the two orange wire tabs, check the resistance. Tomorrow at first light i will be working on my bike and see if i can get the rusty tabs off without breaking them. A replacement part would cost about 8 bucks, but what bothers me about a regular auto-zone replacement is how the existing unit hangs on that rubber holder.
 
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