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[Solved] How to test 1982 R100RT headlight relay and left combination headlight switch

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Richard Whatley
(@wobbly)
Posts: 2499
Member
 

The fuses and fuse holders you show are "after market" owner add-ons. As I previously said, this was a standard "upgrade" for cross country riders back in the 1980's. And was suggested in the BMWOA newsletter back in the day.

The problem with them is NOT with the location, type of fuse, or amperage of the fuse, but rather the reliability of the whole installation. Those fuse holders work great... on your stereo amplifier... which never gets wet. But motorcycles get rained on and washed. Water then causes contact corrosion... the LARGEST contributor to electrical system failure on 40 year old motorcycles. And we should also consider the reliability of the installation. Are the connections soldered? Are the connections covered in heat shrink? 

That was a great setup back in 1980, but WAKE UP !! That was 40 years ago. Time has marched on. My suggestion is merely that you consider adding some 21st century reliability where you can. And since all the cars in the world switched over to 'flat pack' fuses decades ago for the purpose of reliability, maybe you should at least consider doing the same. 

Anyway, here's an article on the subject...

https://www.airheads.org/community/wrenching/home-mechanic-more-reliable-fuses/

 

Hope this helps. 

[color=blue]Don't hide 'em, Ride 'em !!
#15150[/color]

 
Posted : 11/20/2023 09:01
Steven Rankin
(@14724)
Posts: 145
Estimable Member
 

I have the wiring schematic in front of me.  Gray wire from ignition switch to LEFT side of fuse, pin 15u.  Gray wire from 15u LEFT side of fuse to headlight relay.  The ONLY two gray wires for the headlight system are on the SAME side of the fuse.  I am thinking current flows from the ignition switch to the board then from the board to the relay, but IS NOT passing through the fuse unless the schematic is lying?

At pin 15, on the right side of the fuse, gray/black wire (the fused circuit) goes to running lights or clock. This circuit is obviously fused as again it really looks like current is flowing from pin 15u through the fuse to energize pin 15.

So again I say the headlight is NOT fused.  IF it were fused and the fuse blew then tell me how the bulb lit when the passing switch was depressed? This falls in line with my as you say limited experience in that I have never blown either of  the two fuses and lost headlight function.  

St.

 

This post was modified 3 months ago by Steven Rankin

Beware! I do not suffer fools gladly! St.

 
Posted : 11/20/2023 09:52
Steven Rankin
(@14724)
Posts: 145
Estimable Member
 

By the way, if you really want to get into the 21st century, go circuit breakers.  St.

Beware! I do not suffer fools gladly! St.

 
Posted : 11/20/2023 15:29
Steven Rankin
(@14724)
Posts: 145
Estimable Member
 

Okay, made a mistake in pin locations I cited in my reply to the headlight not being fused.  I am getting old, and can't see like I used to.

I wrote pins 15u and 15 top fuse.   Those are for the turn signals, different circuit

The correct pins are on the bottom fuse, 58u and 58

Maybe time to get a change of prescription,  St.

Beware! I do not suffer fools gladly! St.

 
Posted : 11/21/2023 10:31
Lee Nyboer
 5499
(@5499)
Posts: 20
Eminent Member
Topic starter
 

I had done a fairing rebuild about 6 years ago and remember improving the fuse connectors so it would be easier to reassemble. Double action crimpers and spade connectors was what I came up with. I looked at the connection board again and do not see anything spaces for the bullet nose fuses on the board…. Patently waiting for my relay to arrive.

 
Posted : 11/21/2023 13:01
Steven Rankin
(@14724)
Posts: 145
Estimable Member
 

Let me clarify my position.  Whatley suggests changing fuse system.  I do not agree for the reason I listed I will stand by my reasons.

That aside, you have already changed the fuse assembly.  So that is kind of a dead issue.  

I will NOT criticize your work in doing this because I don't know you, LOL, the picture shows an acceptable job.    IF it works, great, it is in fact easier to access the fuses where you have them on the dash.  

So to try to answer your question regarding the stock fuse spots, I will attempt to attach a picture showing where they are located.  LOL, the picture doesn't show the bundle of snakes attached so it I far easier to see the fuse placement. St.

Beware! I do not suffer fools gladly! St.

 
Posted : 11/21/2023 13:24
Lee Nyboer
 5499
(@5499)
Posts: 20
Eminent Member
Topic starter
 

OK! I received my used light relay yesterday from Dave Alquist of "Quality Cycle Service". I did a quick swap expecting all my problems to go away... and they did!!! Hooray!!! The low beam works w/ my three position off,parking Lt and Lights on switch, the low beam stay on in the lights on position and the Hi beam works and passing flasher still works so the problem solved. Faulty relay.

Your thoughts got me thinking how I could isolate the handlebar wiring switches with my OHM meter and that lead me to know the switches were OK. The only possibility left was the relay that was in between the lamp and the switch.

Steven, thanks to your image of the board, I did finally see where the fuses use to be. I was looking for something open/unused on the board and in fact, there were female spade connectors attached to the old fuse spring male spades and those wires ran directly to the dash fuse upgrade receptacles. There is no sigh of corrosion in the fuse upgrade in the 30+ years of service and the convenience of getting at them so easily convinces me to leave well enough alone for now. As I said, I carry enough replacement fuses to get me out of trouble and glass AG fuses are still available.

Thank you all for your help

 

 
Posted : 11/26/2023 11:04
Steven Rankin
(@14724)
Posts: 145
Estimable Member
 

I am happy things worked out well, I am sorry for any confusion trying to troubleshoot via forum.  Yeah the wiring in the headlight shell is a tight space to work in and if you have big hands, and poor eyesight it doesn't help.  

You should see the way my friend in his shop "neatens up" the area after previous owners or guys do after sometimes working there. I swear he worked at the BMW factory and did thousands of assemblies.  Neat and precise.  Me, I do OK, LOL. St.

Beware! I do not suffer fools gladly! St.

 
Posted : 11/28/2023 09:34
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