Testing for a short...

[felix42o]

I know I'm overthinking this, so I'll submit this problem for ideas from you all. My bike has either a very slight, or a very intermittant short which drops the voltage down low enough to prevent starting if left to sit for more than, say, three days. I've checked most of the connectors, grounds, etc. but it could be anywhere. Any ideas on troubleshooting a short down to a circuit? I know there's a way to do this, but I'm drawing a blank.

[gstallons]

We need more information. what other symptoms, how long has this been going on, battery condition,etc.?

[Guest ratchethack]

Coupla things, Felix

 

First off, the salt air will be unkind to your Guzzi electrics, so I hope it's well out of the famous Coronado "ambience" whenever it's put away.

 

If you have a DMM, it's easy to check for a current draw between the battery and ground with everything off. If you read anything at all, you can pull fuses and relays one at a time until it disappears, at which point you'll have identified the circuit with the short. From that point forward, it's a methodical process of elimination of everything on that circuit, starting with disconnecting the easiest to test and most "suspicious" items first, one at a time. You should have no prob. finding just about anything that might be going on -- unless it's INTERMITTENT. Forum member Carl Allison has a very complete library of the most reliable V11 electrical schematics I know of, and you can find yours with a search.

 

Good luck.

 

EDIT: Thanks for the reminder, Emry. I sloppily said "DVM" above when I meant DMM. Correction made. Had a DVM for decades, got good and used to it, then got a good DMM. The ability to measure current is a great big PLUS with a Guzzi.

[emry]

Just to clearify a "short" is a direct path to ground before the load in a circuit, this will almost always blow a fuse. A "grounded circuit" is a ground that is after the load but before a switching device, thus the circuit stays active. A "drain" is a small draw on the battery that if left for a period of time can drain the battery. Normally corrosion of a switch, it allows a small current to flow even when the switch is in the off position. An ammeter is normally used to measure the drain as "likely" suspects are removed from the system. Removing the fuses will one by one will normally narrow the drain to a specific circuit where more detailed tests will be performed.

[felix42o]

Well, that should get me going in the right direction anyway. It's exacerbated by moisture, so my thoughts were targeted at handlebar switchery or the ignition itself, but inspection turned up nothing unusual. I think, as Ratchet offered, that the new coastal environment, while scenic, is going to expose a new round of gremlins that the Nevada desert covered up.

 

Gstallons, the battery is new (

 

Thanks all for the help. Fortunately it's no real issue day to day 'cause it stays on a tender, but it's a new issue that's been working it's way up the priority list.

[gstallons]

Sorry for not getting back in the post quick enough. The BEST tool you can use to find a draw or drain is a bulb or test light. Remove one of the battery cables and put the test light in series with the battery cable and battery terminals. If there is a current draw the test light will be illuminated. If so remove fuses until the light is extinguished. If and when this happens check a wiring diagram to see what the circuit controls.Reinstall the fuse and start disconnecting components until the light goes out again. Be deliberate and methodical about this and you will not make any mistakes. Electronics stores sell cleaners,solvents,lubricants,etc. to help to salvage any switches that might be in poor shape.

Good luck and keep us informed!

p.s. the term "short" is the most misused word in electronics.

[gavo]

I had a similar problem, park bike battery flat after a week, disconnect battery then reconnect after a month bike would start; I assumed there was a drain somewhere but when I eventually had to buy a new battery the problem went away

[moscowphil]

gstallons is right that a 12v bulb in series is the best way of telling whether current is flowing. It will need to be a low wattage bulb (say 5w, but the lower the better) to ensure it will light up sufficiently brightly if the current flow is small. And it is best to connect it in series with the earth strap, as there is more than one wire connected to the positive side of the battery. With a bit of imagination you can trace most electrical faults with a bulb and length of wire. Incidentally, I recently had a battery drain problem on my VW camper, which turned out to be down to a faulty output diode in the alternator. The alternator output on the VW isn't fused (and I assume isn't on a v11 either), so if the test bulb is still lit after you have taken out all the fuses, try disconnecting the alternator output.