The New And Improved Unofficial R65 Forum V2

Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Breezerider on February 10, 2010, 01:09:37 PM

Title: Headlight Relay
Post by: Breezerider on February 10, 2010, 01:09:37 PM

My 1979 R65 has a headlight relay in the circuit.  Is this meant to turn the headlight off when starting the bike?  My headlight does not turn off while cranking the engine, yet this relay is in the circuit and I can only assume it isn't working if it is meant to turn the light off to add more juice to the starter motor.

Title: Re: Headlight Relay
Post by: Bob_Roller on February 10, 2010, 01:14:02 PM

That's pretty much it's function .

Don't have a wiring diagram in front of me, I'm at work right now .

But from memory, there is a small diameter black wire that goes between the starter relay, and the headlight relay, if that wire has been removed, the headlight relay won't cut out when the starter is used .

Title: Re: Headlight Relay
Post by: Rob Valdez 79 R65 on February 10, 2010, 02:04:53 PM

Here is a link to the '79 wiring diagram.

Please feel free to save it to your hard drive.

http://www.pbase.com/tomfarr/image/121670650/original

Title: Re: Headlight Relay
Post by: Bob_Roller on February 10, 2010, 02:29:51 PM

Thanks Rob !!!!

The relay could be bad, this is an unusual relay, most relays make contacts on a circuit close to provide a path for electrical power .

This relay, in it's relaxed state, has the contacts together, then, when activated, the relay opens the contacts to interrupt electrical power to the circuit .

You can test the relay out of the bike, you need to apply 12 volts to the holding coil circuit pins, then have an ohmmeter attached the the two other pins on the bottom of the relay case, if the relay activates, you will have an open circuit, or infinite resistance in this circuit .

There are numbers on the bottom of the relay case, I can get those for you if you like, the diagram Rob provided, doesn't have the numbers on it .

Title: Re: Headlight Relay
Post by: Rob Valdez 79 R65 on February 10, 2010, 04:39:41 PM

The schematic in the owners manual has the relay terminal numbers.
Unfortunately, my scan of that is so poor, the numbers are invisible. :(

Title: Re: Headlight Relay
Post by: Bob_Roller on February 10, 2010, 06:28:44 PM

I blew up the wiring diagram to 11x17 inches, and all of the numbers at the relays are 'washed out' .

If you want to test the relay out of the bike,you need to put 12 volts to pins 85 and 86 .

Place the ohmmeter on pins 87 and 30, and check for continuity when the relay is not operated, with voltage applied to the holding coil, you should get and open circuit, or infinite resistance .

Title: Re: Headlight Relay
Post by: Breezerider on February 12, 2010, 10:11:29 PM

Thanks, guys, I'll put your data to use.

Breeze