Author Topic: V65 Headlamp Circuit Drain  (Read 110 times)

Offline danomar

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V65 Headlamp Circuit Drain
« on: June 17, 2021, 07:08:33 PM »
On my V65 Lario, when the main headlamp is switched on, the voltage gauge dips far to the left—low voltage.

With headlamps switched off, the voltage gauge remains in the middle or high range; with the parking lamp turned on, the voltage meter still is well within the appropriate green area.

This is where things get odd: With the motor off and the headlamp disconnected, switching the main headlamp circuit on makes the voltage meter dip low (to the left) more than when the parking lamp is switched on. The circuit itself is sucking additional power somehow.

The bulb is a 55/65w H4, but the same thing happens with an older 45/55w bulb.

The headlamp (left side) switch assembly is a new one I got nearly one year ago from MG Cycle.

The fuses are all good and connections clean.

I cleaned intermediate connectors and even re-wired a few things in the past but did not mess with the headlamp circuit.

I added an extra ground strap long ago.

The battery is the correct size and is less than one year old; the charging system works properly.

I thought the voltage gauge might be the problem, but after a 1.5 hour ride this morning with the main headlamp on, the battery did not have quite enough juice to turn the starter without a friendly tap. Normally, the starter spins easily. Empirically, it suggests that the headlamp sucked a bit more juice than it should.

Has anyone experienced similar headlamp circuit strangeness with small-blocks?

Offline John A

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Re: V65 Headlamp Circuit Drain
« Reply #1 on: June 17, 2021, 07:43:44 PM »
The fuse block could be a little melted . I clean the fuse ends periodically  they get fuzzy on the ends. Sounds like there may be a wire rubbing, not enough to blow a fuse.
John
MGNOC L-471
It is easier to fool people than it is to convince them that they have been fooled-Mark Twain

Offline danomar

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Re: V65 Headlamp Circuit Drain
« Reply #2 on: June 17, 2021, 08:43:37 PM »
The fuse block could be a little melted.

I replaced the fuse box and cleaned its connections long ago, and I checked it again this evening. It is not the problem, unfortunately. That would be a relatively easy fix.  :thumb:

Offline pat80flh

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Re: V65 Headlamp Circuit Drain
« Reply #3 on: June 18, 2021, 05:25:48 AM »
Your test, observing the volt meter with headlamp disconnected, isn't really telling you anything. Put an amp meter in line between the battery positive post and the main battery cable, this will tell you if you really have a parasitic draw
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Re: V65 Headlamp Circuit Drain
« Reply #3 on: June 18, 2021, 05:25:48 AM »

Online Kiwi_Roy

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Re: V65 Headlamp Circuit Drain
« Reply #4 on: June 18, 2021, 07:21:24 AM »
I had a Lario for a while, one day it just died completely then a short while later it would run again.
https://www.thisoldtractor.com/guzzi007/schematics/1976_V65.gif
I found under the tank mid-way there is a Molex connector (17) both the red wire up to the switch 13 and the brown wire back 14 were sizzling away.
This connector is just where two sub looms join, I tried replacing the pins but eventually just by-passed the connector with crimp links, there is no reason to ever unplug.
I'm not sure this is what's wrong with yours but a high resistance in either the Red or Brown wire would effect the voltmeter.
Note: I don't see the Voltmeter on this schematic but it must be on one of the switched fuses. The legend is off a little way.
« Last Edit: June 18, 2021, 07:36:43 AM by Kiwi_Roy »
72 Eldorado
17 V7iii Special
76 Convert

Moto Guzzi - making electricians out of riders since March 15 1921

Offline Chuck in Indiana

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Re: V65 Headlamp Circuit Drain
« Reply #5 on: June 18, 2021, 08:09:34 AM »
^^^^^ I had this same problem.
Chuck in (Elwood) Indiana/sometimes SoCal

02 Scura RC
87 AeroLario
79 G5
95 Skorpion tour
 
I think senility is going to be a fairly smooth transition for me..

 


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