Headlight Relay

Fergie · Posted: September 1, 2008, 4:46 pm Post subject: Headlight Relay

OK, so I think I cried victory too soon on this problem.

I've been having problems with my headlight where it only works some of the time (more not working than working). I have been combing through the wiring for the better part of a month trying to figure this one out, but every time I think I've figured it out, I put every thing back together and the headlight won't work. As my dog can attest, there is a lot of swearing going on.

Things I have done:
1) Checked and cleaned all ground connections, and soldered some connections that were loose
2) Disconnected the Reserve Lighting Unit and permanently soldered the blue/black and blue/yellow wires together.
3) Took apart the turn signal switch. Cleaned all connections (that needed it), and re-soldered a few connections that had come loose
4) Measured voltage at all "hot" connections

After all of that, I measured the voltage at the headlight relay, and with the ignition on I get 12.8v to one of the red/white wires, and after I start the bike I get 12.8v to both red/white wires, but I'm only getting 0.4v to both the yellow and blue/black wires, and my tach and speedo aren't lit up and the headlight isn't either.

I have installed a jumper wire from the blue/black and the red/white wires at the headlight relay, effectively bypassing the relay all together. When I do this I get 12v at the headlight socket, and my gage lights are all light up. Does this mean my headlight relay is toast? If so, are these relays easy to come by? Can I leave the jumper in there permanently and not mess anything up?

Fergie · Posted: September 1, 2008, 8:08 pm Post subject: Re: Headlight Relay

I've pin pointed the part number of the relay (21317-001), and bikerbandit.com says it's $111, but they don't have any.

Retiredgentleman · Posted: September 2, 2008, 2:04 am Post subject: Re: Headlight Relay

What you call the headlight relay is the safety relay. The safety relay is not operating because you only have 0.4 volts on the yellow wire. The real problem here is not the safety relay, it's the alternator not putting out voltage on the yellow wire. If the alternator is working correctly you should measure about 13 or 14 volts AC on the yellow wire.
I suspect your alternator is faulty,which is common on these old bikes. If you measure voltage across the battery terminals you should have 13.5 volts DC @ idle and 14.5 volts DC @ 2500 RPM. I doubt that you have that.
There is a 6 pin connector in front of the battery box that has the 3 output wires from the alternator ( white wires). Start the engine and run at idle. Select AC volts, carefully insert the 2 probes into the connector, and read the voltage across any 2 of the white wires, 3 combinations to take readings. Readings should be 12.5 to 13 volts AC. The DC and AC readings should tell us what's happening.

Fergie · Posted: September 2, 2008, 11:14 am Post subject: Re: Headlight Relay

Now that I read this, it makes sense. In the owner's manual, it calls it the headlight relay, but it also has the alternator going through it. I didn't really know the full understanding of how it works. When I started the bike last night, I did put my hand on the relay and it did "click", but once the bike was running it "clicked" again, but the lights didn't come on. I suppose this could be a broken wire internally in the engine.

The first signs of the headlight failure was on a long trip I took with some buddies from work last month (150 miles round trip). The first half of the trip was fine; bike sounded good, the light worked, and the bike started like a champ. On the last half of the trip my instrument lights would go in and out, and the guy infront of me said my headlight was going on and off. When we stopped for the final rest on the trip, I was unable to get the bike restarted with the electric starter, and had to pop start it, which tells me the battery wasn't getting charged. Maybe with all the constant vibration, the wire from the alternator finally went kaput.

I'll check the things you mentioned when I get home from work today. Thanks.

Fergie · Posted: September 2, 2008, 10:04 pm Post subject: Re: Headlight Relay

OK, the answers are not good for me. I measured each of the white wires coming from the 3x2 connector out of the alternator. I used the ground from the 4x2 connector coming out of the regulator, but when I touch the probe to the frame, I get the same results. This rules out a bad ground.

With the engine running at idle ~1200rpm
Battery Terminals = 12.4vdc
First set white wires = 4.8vac
Second set white wires = 6.7vac
Third set white wires = 5.9vac
Yellow wire = 6.2vac

With engine rev'ed to ~3500rpm
Battery Terminals = 12.3vdc

Does this mean I get to go alternator hunting?

dps-rider · Full Member Joined: Aug 25, 2007 Posts: 100

Did you check the alternator brushes?

Retiredgentleman · Posted: September 2, 2008, 10:59 pm Post subject: Re: Headlight Relay

The voltage at 3500 RPM means you have no charging at all. Sounds like you measured from each white wire to ground.............you should have measured with the probes on 2 white wires, but lets move on.
As dps-rider is saying, first thing is to remove the brushes and check for minimum length ( 7.0 mm or 0.276 in). While brushes are out measure the resistance between the 2 slip rings on the alt rotor, should be approx 5 to 6 ohms.. Also measure resistance from one slip ring to the rotor frame, should be infinity.

Fergie · Posted: September 2, 2008, 11:44 pm Post subject: Re: Headlight Relay

Breaking News! I took the brushes and stator off. I cleaned the face of the rotor, and I also cleaned the brushes. Measured the resistance and it was about 5.5 ohms. Brush length was short, but still better than the minimum.

After I reassembled the alternator, I started the bike and got 13.4vdc to the battery at idle, and the yellow wire going to the safety relay was also measuring 13.2vac.

I went back and measured each of the white wires (this time white to white), and they were only reading 11.1vac.

I also still have no head light unless I put the jumper in.

Retiredgentleman · Posted: September 3, 2008, 12:24 am Post subject: Re: Headlight Relay

OK, things are looking much better. You have a good rotor and the voltage on the yellow wire is operating the safety relay. If I understand you correctly, when you start the bike the headlight and panel lights now come on ( because you have the jumper replacing the reserve relay). I'd say just leave the reserve lighting relay in your tool box and go with the permanent jumper.................the relay has no value that I can see. Is the charging system working fully? At 2500 RPM, do you get 14.5 V across the battery?

Fergie · Posted: September 3, 2008, 12:45 am Post subject: Re: Headlight Relay

Well, I have the Reserve Light Relay jumped (blue/black to blue/yellow), but to get the instrument panel and head light to come on, I have to jump the safety relay from the red/white to blue/black.

With the bike off, but the ignition switch on, I get the following at the 3x2 safety relay connector:

red/white(1) = 12.8vdc
red/white(2) = 12.8vdc
red/yellow = 12.8vdc
black = 0vdc (ground)
yellow = 0vac
blue/black = 0vdc

With the bike idling, I get the following at the 3x2 safety relay connector:

red/white(1) = 0vdc
red/white(2) = 12.8vdc
red/yellow = 12.8vdc
black = 0vdc (ground)
yellow = 13.4vac
blue/black = 0.7vdc

The first red/white wire goes from 12.8vdc to 0vdc in about 1.5 sec. while cranking the engine. I feel the relay clicking during cranking, and then clicking after the engine is running, but I still get no voltage to the blue/black wire.

Retiredgentleman · Posted: September 3, 2008, 1:29 am Post subject: Re: Headlight Relay

So, the safety relay is still not working correctly, and the jumper has the headlight on when you are cranking the engine...........thats not good. By the way, the jumper should not be from red/white to blue/black, it should be from red/yellow to blue/black ( power comes from headlight fuse). On my 78SE the safety relay can be opened up and inspected/cleaned. The contacts can be cleaned up if they appear oxidized. On the 82 that may not be possible.Check that the black wire goes to a good solid clean ground. If you can't get the relay to operate reliably, it will have to be replaced.

Fergie · Posted: September 3, 2008, 12:10 pm Post subject: Re: Headlight Relay

The relay can be opened up, but the back is sealed in a good amount of epoxy, so I'll have to chip it away. I noticed that the epoxy is cracking and showing its age, so it's possible some dust has gotten in. I'll check tonight after class.

Thanks for your help.

pumps · Posted: September 3, 2008, 4:39 pm Post subject: Re: Headlight Relay

I'd like to see a picture of it if you can, after you get it opened up. Be careful...if it were me I would see bandages in my future...

jpowell · Posted: September 3, 2008, 9:49 pm Post subject: Re: Headlight Relay

I would be careful before chipping away at the epoxy. In my exeriance every time I've tried that all I have done is ruined whats inside I was after. By all means if you're sure the relay is bad, go for it, but I'd leave that as the last option, eliminating EVERYTHING else before, knowing for sure that it is bad before chancing destroying a $111 part.

Retiredgentleman · Posted: September 4, 2008, 2:17 am Post subject: Re: Headlight Relay

You could try searching e-bay for a safety relay, but it might be worn out as well.
If you want to do this on the cheap, you could replace the safety relay with a manual switch, so in effect you become the human safety relay. You would need to purchase a 2 position switch with 4 contacts. In 1 position the starter push button would be enabled but the headlights would be off. Start the engine, then throw the switch to the other position which would disable the starter push button and turn on the lights. Connect the Red/Yellow and the Blue/Black to one set of contacts, and connect the 2 Red/White wires to the other set of contacts. The Yellow and Black wires not required. Some switches have a small light (led) on them as well. The switch needs to be capable of 5 amps (high beam), so better to buy with 7 amps rating.

Fergie · Posted: September 6, 2008, 10:18 pm Post subject: Re: Headlight Relay

OK, I hit a home run tonight. I took the safety relay apart (forgot to take pictures), and hooked it up to the bike and started it. The relay function is working just fine, just wasn't getting voltage to the appropriate places. I noticed that when I was measuring the voltage to the red/yellow wire, I would get 12.8v across the connector, but when I measured it at the relay, I only got 0.4v. I moved the red/yell wire around while the bike was running, and the head light came on. After closer investigation, the wire was broken inside the insulation, so I didn't catch it before. I spliced in a new wire, and the headlight works like a champ.

I am now confident that the headlight problem is 100% fixed. I still need to replace the headlight since the low beam burnt out, but I'll just ride around with the high beam for a while.

Thanks to all that helped out.

Retiredgentleman · Posted: September 6, 2008, 11:34 pm Post subject: Re: Headlight Relay

Glad you found that broken wire..............all it took was a little detective work. I replaced my old headlight with a H6024 Halogen 60/40 watts from Wal-mart for $16.77. It gives a much better and whiter light.

jojoaruba · Posted: September 16, 2008, 12:41 pm Post subject: Re: Headlight Relay

Retiredgentleman is the MAN!

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