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Any electrical boffins want to set me straight?

bigtex

bigtex

Cruisin' Guzzisti
GT Contributor
Joined
Oct 27, 2008
Messages
223
Location
Northern Colorado, USA
So, after a soggy day commuting to a customer about 120 miles south, I got within 4 miles of home and the Stelvio shuts off. One moment, 70 mph, cruising, and the next nothing. No lights, no dash, no motor. I was barely able to dash across the right lane and on to the side of the road. Bike was completely dead, the only things running are the Ipod and the GPS, both battery powered.

It was raining and rush hour traffic was way too near, but I decided to try a fix. The way it quit catastrophically, I decided it had to be a fuse. I pulled the seats and sure enough, one of the two main fuses (the 30 amp) is blown. Don't know why, but as MG has been kind enough to include a spare, I swapped them out and thought about what I could shut off. The only option was the fog lights, so I shut them off and she restarted. I made it home, and just as I pulled in to my driveway, I got curious and switched the fogs back on, and everything went dead again. Problem isolated.

(On a side note, I have installed a GPS, radar detector, heated grips, power outlet for trickle charging and running a heated jacket, and HID headlights. Everything but the headlights are on separate circuits with their own fuses. The headlights pull much less amperage than the stock bulbs, so that shouldn't be the problem unless of course they are faulty.)

Today in the garage I pulled the panels off the top and pulled out my wiring for the fog lights. I used the factory fog wires, cutting off the factory plugs and inserting my own, running wires from those connectors to the fog lights. I use the stock fog switch and relay.

I disconnected both lights, put in a new fuse, bike runs fine. I reconnected only the right light, bike runs fine. I disconnected the right light, reconnected only the left light, fuse blows. Getting closer.

I looked over as much of the wiring I could see and didn't see a crimp/break/etc. Just for a test, I ran some jumper wires from the disconnect directly to the battery, though with an inline fuse wire (10 amp) I happened to have lying around. With the direct wire, the left light works perfectly. No sparks, no blown fuses. WTF?

Am I missing something here, or does that mean something in the factory left side fog light wiring is amiss?
 
If you can, run a jumper from the wire for the left fog light, to the connector you have for the right. If the fuse blows, the problem is in the lead to the light. If the fuse doesn't blow, the problem is in the factory harness. Just keep trying to eliminate possibilities until you find the culprit. This thread may help https://www.guzzitech.com/forum/160/3001.html This thread mainly hunts for an open circuit, but the same technique is also used to find a short.
 
Don't know if this will help or not..........

When I have issues I attempt to isolated the circuit, power it with a 12v source (battery charger), then install a 12 light bulb (1056) with a known good socket in line on the suspect circuit between the 12v source and the wiring circuit (+ wire). Normally the bulb will light up (cause theres a short), then I start the wiggling process, checking connectors, etc. When your light bulb goes out, you have found the short, then inspect and repair.

It has always worked for me whether it be chasing a short on a bike or car or finding a short in a house (substitute 120V for 12V).
 
The other two suggestions are good.

Just in case, though this is not highly likely:
Is there a chance that you reversed the polarity when you wired the light direct?
What I am wonder is, could you have for example had the hot wire on the reflector side of the light. Then some how it finally made a ground and popped the fuse. If when you wired it directly you actually wired ground on the reflector, all would be fine. (or maybe one of the wires grounded out.)

Simply disconnect the light and measure resistance to ground. It should be infinite.
 
Good suggestions all. I probably should have also mentioned these fog lights have been installed in their current state for about 4000 miles.
 
bigtex said:
Good suggestions all. I probably should have also mentioned these fog lights have been installed in their current state for about 4000 miles.
Click to expand...

Driving in the rain = lots of driven water (more so than giving the bike a bath) = blown fuse :S

Sounds like the left hand light is the problem child, could be the light has filled with water and you can't see it........this happened to my wife's Cadillac, left rear turn/stop light assembly. Hair line crack in the lens, lots of rain water and snow this fall / winter and the car kept blowing tail light bulbs, 1/4" drill, two holes to drain the water was cheaper than $400+ for a new part from the Cadillac dealer.

Chasing electrical gremlins are so much fun :silly: :side: :S :pinch:
 
Okay, I'm ready to call this one diagnosed and fixed, and everybody's ideas (including mine) were wrong.

I replaced all of my wiring and the lights - still blew the fuse.

I chased as much of the factory fog light wiring as I could get to - no chafing found.

Finally I had some mild brain activity and considered the relay. It is a factory job I purchased new from the dealer, but who knows. I went and bought another $30 relay from the dealer while passing through town on the way to camping. Somewhere during the camping trip, the little bag with the relay fell out the truck. Rats.

Rather than spend yet another $30 bucks, I took the forum advice and ordered the generic relays from "Pyro Dan", 4 relays for $11 postage paid. :lol: I pulled the old relay and it didn't fall apart or look blackened or anything, but it was definitely not as nice as the cheapo jobs.

About 250 miles so far, no blown fuses. Going to join the local BMW boys for a 500 mile mountain ride this Saturday, and I'm feeling pretty confident. Though I do plan to keep a whole bunch of extra fuses on hand, just in case.
 
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