Electrical Diag Quests?

[jjwaller]

Hi Folks:

I am an Industrial Instrument and control Technician so I know just a little bit about schematics and electrical components.
Have a 78 E and trying to sort out the last fine points of the Elect. system.
Question: Headlight Relay? Can't Physically find it or in Yamaha parts diagrams. Possibly known as dimmer Relay (In Clymers) I don't have one. Second, I have a right hand control that has Light on/off switch that doesn't do anything.
Traced out the cable from the RHC to the plug under the tank and found that the blue and white wires are switched by the RHC light switch. The blue wire does not leave the downstream plug. Anybody have a clue? Do I have a europeon replacement part or was this standard in 78? Does the XS11 CD ROM available have all the real schematics
for all the early bikes?
Last, I do have a Windjammer on the front. So naturally the headlight goes through the fairing. There is no relay behind the fairing.

Thanks
John

[randy]

John,

The headlight realy should be under the tank, between the frame rails directly behind the steering stem. If you don't have one, and you headlight works, maybe the PO rigged it somehow? You should find a 4-pin plug there. If the plug is there, contact Andreas here he may have a relay for you.

As for the RHC that does sound like a European part, the US models did not come with a light switch. There is a remote chance that you have a European model, but the serial number on them would begin with 2H9, check the tag on the steering stem for your serial #.

[mro]

RHC

Could have been an after market part too.
MikesXS sells em. Found one on a 79F I picked up awhile ago.


mro

[newc4]

My 78E has the light switch on the RHC, it is standard equipment. It allows you to turn off the headlight when the engine isn't running. For instance, if you have a weak battery, you can turn off the headlight while starting. For a while I could turn off the headlight while my bike was running but after some poking around under the gas tank to replace my regulator it operates as advertised.

I believe the relay senses current from the alternator activating the circuit.

Darrell

[D. P. Larmee]

The yamaha shop manual shows the 78 wiring diagram as having a "lights" switch that when on links Blue, Red/Yellow, Black/Blue. It also shows the relay. It sort of looks like the switch could be used to turn the headlight on while the bike was not running, but did not turn it off if the relay was tripped.

[CarolynS]

Windjammer

If you go onto the Vetter site, they have the wiring diagram for the Windjammer. Don't know if that helps.....

[planedick]

Switch

I have a 78E and it has the switch on the right which allows me to turn the headlight on when the engine isn't running. The relay is set (turned on) by current from one leg of the alternator so if the engine is running the headlight is on. There is also another relay in the circute which will turn on the other element of the headlight if on burns out, and lights a light on the panel to let you know what happened. It's called a auxilary relay I think.

[jjwaller]

Originally posted by randy
John,

The headlight realy should be under the tank, between the frame rails directly behind the steering stem. If you don't have one, and you headlight works, maybe the PO rigged it somehow? You should find a 4-pin plug there. If the plug is there, contact Andreas here he may have a relay for you.

As for the RHC that does sound like a European part, the US models did not come with a light switch. There is a remote chance that you have a European model, but the serial number on them would begin with 2H9, check the tag on the steering stem for your serial #.

Thanks Randy, found it finally after looking closer. Now I have someplace to start tracing from.

[jjwaller]

Originally posted by D. P. Larmee
The yamaha shop manual shows the 78 wiring diagram as having a "lights" switch that when on links Blue, Red/Yellow, Black/Blue. It also shows the relay.

Thanks DP:
Guess I'm finally going to have to spring for the shop manual.
John