Odd Electrical Fix !!

[AZBMWRIDER]

I've got an '87 Guzzi V65 Lario, bought it 5 years ago, got it on the road in April of this year .

The bike was parked in '06 for not being able to pass exhaust emissions testing as part of the annual registration renewal process .

The bike has the same Bosch charging system that the airhead BMW's have .

The charge indicator light has glowed dimly since I started riding the bike .

I went through the charging system, removed the brushes, the length was fine, replaced the brush springs, replaced the regulator and diode board with known good parts off of an airhead .

Checked all of the connections all tight and no corrosion, the bike has been in Arizona it's whole life and garage kept .

Last week I installed a headlight harness from Eastern Beaver, it uses relays, so the bikes original headlight circuit activates the relays and the relays carry the heavy electrical load for the headlight .

I noticed that the charge light is not dimly illuminated any more and the voltmeter on the bike shows 2 volts higher at idle than it did before, at 3500 rpm, the voltage at the battery is 13.7 volts, barely got to 12 volts before .

Disconnected the new harness and reconnected the wiring like it was before, same conditions as before, charge light on and low voltage agin .

The bike has a new AGM battery and is fully charged .

Any ideas why the new harness will cure the problems ??

Make no sense to me at all why it does !!!!!!

[CycleRob]

Symptoms say the stock harness has a break in it or there is a poor connection at a crimp-on wire terminal. Connect a heavy wire jumper to the same 2 terminals as the alternator output to battery wire and see if the regulated voltage improves. Then do the same for the (+) terminal wire to the regulator.

A few years ago I did carburetor cleaning and synch work on a poorly running GS AirHead that after it was running had a similar dim glowing charge light and low voltage readings at every RPM. That was more troubling to me than the gummy carbs were, and was not mentioned by the owner. The wiring diagram in the shop manual the owner provided with the bike showed 2 wires connecting to the alternator were on the wrong terminals!! One of the grounded wires was supposed to go to a (unused) regulator/diode board terminal. Fortunately, no parts were damaged by the wrong hookups and the bike's normal charging was restored. There was no characteristically low voltage dim glow even at an idle on high beam, meaning the stock stator was replaced by a fatter aftermarket high output model and likely when the wires got mixed up.

Given the age of your Guzzi and it's poor charging performance, do not trust the wire harness hook ups. Solder the crimp connectors to the Copper wire brush terminal ends to guarantee a 100% full current carrying connection. Wire brush the fuzzy/oxidized terminal plating on the terminal connection surfaces and lightly grease them to prevent corrosion. To repeat the warnings in the shop manual, if it's like the AirHeads, be very careful installing the Aluminum(?) alternator cover IF the battery terminals are connected, that you do not short out the unprotected diode board terminals to ground.

[AZBMWRIDER]

The diode board on the Guzzi is located on the left side of the bike, about less than a foot farther back than the battery under a side panel cover .

I'll add a 10ga wire from the diode board to the battery .

The alternator output wires are molded into a connector and the same at the diode board, the only wires I could not check the crimps on the terminal ends, that's a good 4 foot run from the alternator back to the diode board .

I'll start looking for some 10ga wire at work to make up a new alternator output harness .

[AZBMWRIDER]

Update, I spent some time today replacing two terminal ends that connect to the battery for the Dyna S ignition system .

While I was in there, I removed the negative lead from the frame to check for corrosion , none found, hit the area on the frame where the cable makes contact with sandpaper, couldn't see it, confined area .

Had to cut a wire bundle ty wrap to get the nuts back on the rear master cylinder, the attach bolts for this, is also the main ground .

In messing with the wire bundle to get the two nuts on, I found a ' stray ' terminal end with four wires, it wasn't under either of the nuts when I took them off .

Installed the terminal end with the rest of the grounds and amazingly, my charge light has finally gone out .

It was intermittently coming on but unless it was dark outside, you could not tell .

At 3000 rpm with the headlight on high beam and all the the lighting on, I get 13.8 volts at the battery and the voltmeter on the dash, shows about the same now .

Looks like the previous owner didn't get this back on, during some maintenance, who knows how long it's been off !!!