Headlight relay...

[planedick]

I can't seem to locate the headlight relay. Does anyone know where it's mounted on a '78 E? The light doesn't come on when the engine starts and I wanted to troubleshoot the problem, but I can't locate the relay. Is it possaible it's inside (part of) the reserve lighting unit?

[Kurt]

I had the same problem with my xs750. I never found the fix for it. I just wired a three-way switch to the batt and used it that way.

I do have a complete wiring diagram for the 11 at home. I can take a look and get back to you.

[planedick]

Wiring diagram

I have two versions of the wiring diagram and I'm sure I can fix the problem if I can just locate the headlight relay. So far it looks like it's in the reserve lighting unit. I just need to check the input from the alternator to see if it's gettin' juice.

[Kurt]

yep

[XMRGWX]

The headlight realy should be under the tank just behind the neck forward of the 1st cross brace.

-Mike

[Goin Commando]

The headlight relay should be under the tank just behind the neck forward of the 1st cross brace.

Yeah, what he said ^ Right in front of the fall-over switch.

[planedick]

Found it...

OK, I found it and according to the print the yellow wire comes from the alternator. I found only 6 - 7 volts there when I start the motor but the relay is marked 12v. Does this mean I have a problem with the alternator?

[John]

Dick, according to Randy Rago, the voltage on the yellow wire should be around 7VAC. That is the signal that controls the relay. The contacts are what's rated at 12VDC.

[XMRGWX]

Don't forget the obvious, make sure you have voltage on both sides of the headlight fuse. If it was me, I would put a jumper across the headlight relay to eliminate it from the equation. Jump the brown & blue/black wires and see if the headlight comes on.

-Mike

[planedick]

Relay diagnostics...

Yes, I have already done the obvious and the light works just fine. Some of you with a '78 E know that there is a light switch on the right handlebar just above the starter button. However when left in the off position it should still come on when the engine is started. I found the relay and tested it and it is NG. I opened it up and it is just a simple SPST relay which, according to the label is 12V Although I applied 7 and 12 volts both AC and DC to the coil it would not actuate. Ohm meter said there was 19 ohms resistance to the coil which led me to believe it was OK, but applied power and no actuation is a definate no good. Now I need a light relay.

[John]

Dick

Can you find one that is controlled with the 7VAC that is supplied? I guess you could control a relay using 12VDC, and routing it through an oil pressure switch. That way the light would only come on when the engine is running, and go off when the engine is turned off.

[planedick]

Relay options...

I would seem to me that I could find one somewhere, but if not I could always rewind the coil on the one I have or subistute some other type. McMaster Carr will probably have several I could adapt. Probably oughta PM andreaswiess, huh?

[HobbyMan]

Yo should probalby contact andreas. You might be able to find a comercially available relay and just attach a resistor to two of the leads that would keep the relay closed and it would function the same. There are plenty of automotvie relays out there, just got to find the right one.