switch off short

[redtr4]

Have my 65 Superhawk almost completed .. but then put battery in sat for few hrs with switch off and noticed battery felt warm and wouldn't spin starter.. got out voltmeter and there is a 12 volt drain with switch off... tho very low amperage as when i touch ground lead to battery there is no spark. Am going thru process of disconnected a lead and retesting for to see if short goes away...so far no luck. Thought Id ask if there is a common issue that could cause this to narrow my search. any help greatly appreciated. thanks Kurt

[G-Man]

What kind of rectifier have you got?

G

[redtr4]

Well Im not an expert on the 305 but it is orange and large square fins with 3 leads going to it. pretty sure its new as this bike came with lots of extra parts including new points and this rectifier.. pretty sure hooked up correctly as the terminals are color coded to the wire color. Any way to test if its the issue and if so what is remedy? thanks Kurt

[G-Man]

You should be OK with that. Modern silicon regulator-rectifiers seem to draw current when the ignition is off.

Just disconnect things in turn until the fault goes away. Then you'll know where the problem is.

G

[jleewebb]

Here's this from my archives courtesy e3steve...

Testing a rectifier

First disconnect the red (red/wht on C72/77), brown & yellow from the rectifier, as it's not possible to successfully test components whilst in circuit.
With a multimeter, self-powered test lamp or self-powered piezo buzzer, carry out the following tests:

Ready? phasers on stun...sorry multimeter on diode test (or 'beep')
1: probe AC1 (brn) with neg lead and + with pos lead, result should be a short beep
2: reversing probes should result in silence
3: probe AC2 (yel) with neg lead and + with pos lead, result should be a short beep
4: reversing probes should result in silence
5: probe - (gnd) with neg lead and AC1 with pos lead, result should be a short beep
6: reversing probes should result in silence
7: probe - (gnd) with neg lead and AC2 with pos lead, result should be a short beep
8: reversing probes should result in silence

All a diode really is is an electrical non-return valve; positive flow is from anode to cathode (as with all DC circuits), or in the direction of the 'arrow' - this is known as forward current; conversely, negative can be understood to 'flow' in the opposite direction - this is known as reverse current. So think of your multimeter probes (meter on beep) as pos (r) & neg (bk). A good diode will allow forward current (hence the short beep), but will block DC in reverse. A duff diode will either block in both directions or allow flow in both directions. It only takes one diode in a rectifier to mess up the flow sufficiently to reduce the charge dramatically or negate it completely.

I'm open to Qs.

Steve Edwards


And here's a thorough step by step, I think from the same source:

NOTE: always disconnect & re-connect the negative cable at the chassis, not the battery post; think of the chassis grounding bolt as a switch. Sparks at the battery post could cause any stray hydrogen gas (given off by the cells during charging & discharging) to explode. At best that's a new battery, at worst you could lose your sight if you're close!

Take the problem stage-by-stage:
1. are you connecting the batt in the correct polarity (ie: neg to chassis)?
2. is the ignition switch in the off position?
If 'yes' to both, it sounds like
a) a short-circuit to ground within the ignition switch
b) a short-circuit to ground within the harness or a device connected to same
c) a short-circuit to ground within the starter solenoid or circuit

3. is the starter trying to engage?
If 'yes', then the starter solenoid is stuck in the 'closed' or 'start' position

Leave off the heavy wire from the pos batt terminal, that takes the starter circuit out of the equation for now.

Put the 15A fuse in place.

Use a working 12V lamp of at least 60 Watts (the hi-beam filament a car headlamp bulb is good for this), and make up a test lamp with about 2ft of cable (14AWG or larger) with a couple of croc-clips on the ends; connect this 'test-lamp' in place of the negative cable (ie: 1 clip to chassis, the other to battery neg post - remember: connect to the chassis LAST). If there's a short in the wiring somewhere, then the lamp will burn full-brightness. Leave the lamp in place and work around the wiring, disconnecting items until the lamp goes out (or dim).

Ignition switch wiring & terminals should be as follows:
Term BA, battery, red
Term HL, headlamp switch, green
Term TL, parking lights, white
Term IG, (ignition system) & key-on circuit, (unspecified) & light green/red
Term CH, charging from rectifier (celenium diode pack) white/red

4. start at the ignition switch, disconnecting the 15A fused feed first - just take out the fuse

Lamp still bright? Put the fuse back in and disconnect the wires from the ignition switch terminals one at a time; if the test-lamp goes out on one of them, that's the problem circuit.

Email me with your findings. Next stages will follow....

Incidentally, what the lamp is doing is acting as a self-resetting fuse, absorbing the current in place of the short circuit. If the lamp glows full brightness, then your problem is of a high-current, low-resistance nature (starter motor / relay [solenoid] or a dead-short); if it glows dimly, then it's something on the bike that's consuming some current.

It's a good idea to have another lamp of lower wattage (a car winker lamp, 21Watt) with cables and croc clips to hand as well, for smaller wiring conductor size traces.

Also, start off with a fully charged battery.

Rgds

--Lee Webb

[redtr4]

WOW jleewebb... thanks for the very complete and comprehensive response... I did much of what you suggested prob in different order.. but think i found problem... ignition switch. when I would hold in one position ..short.. wiggle a little and no short.. now the bad problem.. in my efforts i think the switch has gone totally bad. Key wont turn any more and tried to disassemble and you can guess how that went.. are there any aftermarket ignition switches out there (for less that $100) or is there way to use two wire switch and some toggle switches in place of?? please advise as bout ready to give up on possibly my most difficult resto in about 40 bikes... Kurt

[redtr4]

by the way ... here is pic of bike.. not a prize winner for sure but should have seen what i started with... my friends thought i was crazy for even attempting.. buy you know how us resto guys like a challenge... well forget that wont let me attach file for some reason.. but glad to share via eamil if anyone want to see.... woops guess it did post .. twice .. im a newbee...