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Electrical question

4K views 24 replies 3 participants last post by  bonneydude 
#1 ·
1965 t120R. Original 6 volt system w/points. I completely replaced all the wiring ( awg 14). New ignition and lighting switch and battery. When I turn the key on, voltage drops to about 4.5 volts going to the coils. Checked the terminal from the ign. socket, same voltage. Is this normal to get a voltage drop from light switch to ignition switch? I find no bare wire touching metal anywhere. Would the heavier gauge wire be a problem? Happens even when battery is still attached to charger and tested.There are no lights hooked up yet to draw power.
 
#2 ·
Hi Buzz,
1965 t120R. Original 6 volt system w/points.
New
battery. When I turn the key on, voltage drops to about 4.5 volts going to the coils.
First thing to check is the battery, "New" doesn't always mean "good". :( Difficulty here is having another 6V 'known good' battery to jump from? How far is your nearest proper auto-electrician with the necessary kit to load-test the battery?

Checked the terminal from the ign. socket, same voltage.
If the battery is dud, it'll be the "same voltage".

Is this normal to get a voltage drop from light switch to ignition switch? I find no bare wire touching metal anywhere.
Mmmm ... but you keep assuming "New ... battery" = "good battery". ;)

Try moving the Brown/Blue wire from the Ammeter off Lighting Switch terminal #2 and on to Ignition Switch terminal #12A:-

. if you get the same Volts drop switching on the ignition, you'll know the Lighting Switch isn't the problem;

. otoh, if you don't get the same Volts drop switching on the ignition, you'll know the Lighting Switch, or the link wire between the switches, is the problem. (y)

Would the heavier gauge wire be a problem?
No.

Happens even when battery is still attached to charger and tested.
Coils draw 3~4 Amps; if the battery charger can supply that, it's wa-aa-ay too big for the battery. Charger for the battery should supply about 0.75A.

Hth.

Regards,
 
#3 ·
I'll need to search for auto-electrician for load test. Rare as chicken's teeth around here. Something I can DIY? I should have said battery tender instead of charger. It is low amp slow charge. Will try your advice tomorrow and post results. Any opinions on reliable battery? As usual thanx much.
 
#4 · (Edited)
Hi Buzz,
The brake lamp should have about the same current draw as the coils, if you disconnect the coil feed wire , then check for volt drop with the brake light on and brake light off. This is not a comprehensive test but just a quick check.
Brake light off coil disconnected - voltage will show if there is a discharge anywhere else-(charging system etc.)
Brake light on coil disconnected - voltage will show if battery is holding up under similar load to good coils. If voltage drops it is more likely that there is a battery fault. If it stays good then it is more likely that there is a high current draw from coils, or a high resistance in the coil feed.
This is only a quick indicitive test not a comprehensive check and we are assuming the wiring is connected correctly.

regards
Peg.
 
#5 ·
Thanx Rancidpegwoman. I was wondering if something similar would work. Just didn't know what to use for a load. The coils are new (hard to find 48 mm), so I really hope they aren't a problem. I have checked the wiring according to the workshop diagram at least six times. Probably check at least another six. Just curious, would a short show up on a meter set to millivolts? Again, thanx much.
 
#6 ·
Hi Buzz,
The coils are new
For them to draw 3~4 Amps, the resistance between the LT terminals should be 1.5~2 Ohms - easy check with the meter.

coils are
hard to find 48 mm
Unless you must have the physical size, you can use later 40 mm. '6V' coils, just pack between each coil and clamp - strip of rubber form an old inner tube? If you have to go this route, current Wassell Lucas coils can have a problem with high (5 Ohms! :eek:) LT resistance, PVL seem to be more reliable and consistent.

would a short show up on a meter set to millivolts?
Millivolts are just thousandths of a Volt, Volts are just a measure of difference between two points - 6V = 6000 mV.

You're thinking of (milli)Amps? A short-circuit is high Amps because there isn't any resistance (=Ohms) between battery -ve and battery +ve. Blows the fuse (I know standard 6V electrics didn't have a fuse but you have fitted one anyway, in the single wire actually attached to the battery +ve terminal?).

A "parasitic drain" would measure mA. But the original problem you posted - 6V dropping to 4.5V when you switch on - is neither a "parasitic drain" nor a "short".

Hth.

Regards,
 
#7 ·
I can't remember offhand where I purchased the coils. Maybe from the Bonnevilleshop. They were advertised as Lucas made in India. I'll check the resistance just to be sure they are within specs.
I bypassed the light switch #2 terminal and still got a voltage drop from 6.09 to 5.60 when switched on. Out of curiosity I unhooked the coil + and - and the voltage didn't drop when switched on. Could this mean a bad coil? The battery came with two wires going to the + terminal. One is direct, the other has a fuse holder but no fuse. Would be the correct fuse be a 10 amp?
 
#8 ·
Hi Buzz,
bypassed the light switch #2 terminal and still got a voltage drop from 6.09 to 5.60 when switched on.
Depends on your meter's calibration. If the calibration is good, 6.09V just across the battery with nothing switched on is poor, I'd want to see ~6.3V.

In what way did you "bypass the light switch #2 terminal"? By connecting the wire from the Ammeter/battery to Ignition Switch terminal #12A as I suggested in post #2? If so, that suggests there's Volts drop across the Lighting switch and something else. :(

unhooked the coil + and - and the voltage didn't drop when switched on. Could this mean a bad coil?
What is their primary resistance, as I asked in my previous post?

As I've posted already, the coils draw 3~4 Amps; meter connected across the battery, this should show as a slight Volts drop. If you disconnect the coils, they can't draw any power, so the Volts won't drop ... ;)

One thing that has occurred to me is, before you started the thread, when you switched on and saw a large Volts drop, both sets of points could've been closed; then both coils wold be drawing 3~4 Amps; I should've suggested turning the engine so that one set of points was open, only one set closed. 😔

The battery came with two wires going to the + terminal. One is direct, the other has a fuse holder
Don't connect the one without a fuse holder; if you use 'em both, if there's a short-circuit, the one without a fuse/holder bypasses the fuse ...

Would be the correct fuse be a 10 amp?
Too low:- :(

. As I say, each coil could draw up to 4A, and there are points cam positions where both set are closed, = <8A.

. Headlamp bulb is 30/24 listed in the parts book? If so, main (30) is 5A.

. Rear bulb is 6/18 listed in the parts book? If so, brake (18) is 1.5A.

. Pilot bulb is 3W listed in the parts book? If so, 0.5A.

. Horn is the 8H listed in the parts book? If so, Lucas advised it draws 6.5A when set correctly.

Total 21.5A so, if all the bulb Watts are correct, a 25A fuse. :(

Hth.

Regards,
 
#9 ·
Thanx Stuart. I did bypass as you recommended. Did the ohms test on the coils LT, got 1.9 ohms. The lights aren't installed yet, so no problems there (wires are protected from contact with any metal). Meter is pretty accurate, not a cheap model. One thing confusing me is this. Referencing the wire diagram, I see green/white from alternator to rectifier, also to #4 on the light switch. According to 88SA switch positions, the only time this terminal (#4) is in contact is with #5 when in the off position. My question is why does the wire connect to #4 when it apparently breaks contact with all other terminals when switched to on positions?
 
#10 ·
Hi Buzz,
Did the ohms test on the coils LT, got 1.9 ohms.
(y) So they're probably good.

did bypass as you recommended.
But still have the battery load-tested.

When I turn the key on, voltage drops to about 4.5 volts going to the coils.
bypassed the light switch #2 terminal and still got a voltage drop from 6.09 to 5.60 when switched on.
It's possible you have some Volts drop across both switches. :(

Reconnect the coils and the end of the wire from the Ammeter back to Lighting switch terminal #2.

Trickle-charge the battery for a long period (say overnight?). After you reconnect the battery to the bike's electrics, turn the ignition switch key on for a few seconds then turn it off again - this will dissipate any 'surface charge' which could give a misleadingly-high meter reading.

1. Everything turned off, connect the meter across the battery; note the meter reading.

2. Turn on the ignition, note the meter reading (4.5V?).

3. Leaving the meter lead end connected to battery +ve, move the other meter lead end from battery -ve to the nearest Ammeter terminal, note the meter reading; if it isn't the same as at 1., there's a problem between the battery -ve terminal and the Ammeter.

4. Move the meter lead end from the tested Ammeter terminal to the other Ammeter terminal, note the meter reading; if it isn't the same as at 1., there's a problem in the Ammeter.

5. Move the meter lead end from the Ammeter terminal to Lighting Switch terminal #2, note the meter reading; if it isn't the same as at 1., there's a problem between the Ammeter and terminal #2.

... and then to Lighting Switch terminal #10, and then to Ignition Switch terminal #12A, and then to Ignition Switch terminal #13 and finally to the coil -ve terminals; each time noting the meter reading; any time it isn't the same as the previous reading, there's a problem in the component between the two tests.

Referencing the wire diagram, I see green/white from alternator to rectifier, also to #4 on the light switch. According to 88SA switch positions, the only time this terminal (#4) is in contact is with #5 when in the off position. My question is why does the wire connect to #4 when it apparently breaks contact with all other terminals when switched to on positions?
Mmmm ... 'scuse me while I :ROFLMAO: ... this is part of what Lucas called 'charge control' before the Zener diode ...

Electricity and magnetism are interconnected. Lucas (most) motorcycle alternator rotors are permanently-magnetised (others are electro-magnets). Put a magnet near a coil of wire, the magnetism induces electron movement within the wire, electron movement is the basis of electricity.

Upside of permanent-magnet alternators is they're simple, downside is they generate electricity anytime the rotor's ... errr ... rotating ... and the faster the rotor rotates, the more electricity it generates. Which is great when you speed up at night leaving town - headlamp's on, battery needs charging, etc. ... but not so great when you're riding along in sunshine, battery fully-charged, all lights off ...

To cope with these varying electrical conditions, Lucas had the Ignition and Lighting Switches also connect some of the alternator stator coils differently. The system is pretty-good 'in theory'; in practice, it couldn't cope with the realities of crap assembly, no maintenance and unforeseens like blown bulbs. You and the bike'd be way, way, wa-aa-ay better off with a discreet 6V reg./rec. and dispensing with all the standard junk; "the past being a foreign country", standard Lucas pre-Zener charge control is the bits of the world where humans still eat each other. :)

green/white from alternator
#4 on the light switch.
The alternator stator has six coils, connected together in three 'series pairs'; i.e. a given coil is connected at one end to another coil and at the other end to one of the three wires out of the stator:-

. One coils pair is connected to the Green/Black wire at one end and the Green/White wire at the other end; these are the (stator) 'ignition' coils, in that they power the ignition and charge the battery.

. The other two coils pairs are connected to the Green/Yellow wire at one end of each pair and the Green/White wire at the other end of each pair; these are the 'lighting' coils, in that they're only 'switched in' when you turn the Lighting Switch to "H".

However, as I posted above, electron movement (generating electricity) is being induced in all stator coils any time a permanently-magnetised rotor is rotating. When lamps are switched off, to turn the unused electrical energy in the lighting coils into heat that could be radiated, the Ignition and Lighting switches connect the stator lighting coils' Green/White and Green/Yellow wires together (this is sometimes described as 'shorting' the coils but, in reality, there isn't any other power source and all stator coils have some resistance).

"connect the stator lighting coils' Green/White and Green/Yellow wires together" is done by:-

. you've seen "green/white from alternator to ... #4 on the light switch" already;

. "the only time ... terminal (#4) is in contact is with #5 when in the [lights] off position";

. terminal #5 is connected to Ignition Switch terminal #18 by a Blue wire;

. terminal #18 is connected to terminal #17 when the Ignition Switch is in the "IGN"(?) position (the engine is normally running, the alternator is generating);

. terminals #17 and #16 are connected internally;

. Green/Yellow is connected between terminal #16 and the alternator stator. (y)

why does the wire connect to #4 when it apparently breaks contact with all other terminals when switched to on positions?
Engine running, Lighting Switch "OFF", the stator ignition coils' output is depressed by the magnetic effect of the current flowing in the 'shorted' stator lighting coils.

Lighting Switch turned to "L", greater output from the stator ignition coils is desirable, the switch position disconnects terminal #4 from terminal #5 to break the connection between the lighting coils' Green/Yellow wire and the Green/White wire.

Lighting Switch turned to "H", the stator lighting coils are 'switched in' - connected to the rectifier:-

. as above, stator Green/Yellow is connected to Ignition Switch #16, #16 and #17 are connected internally, switch in the "IGN" position connects #17 to #18, Blue wire connects #18 to Lighting Switch terminal #5 ...

. Lighting Switch #5 and #6 are connected internally, Lighting Switch in the "H" position connects #6 to #7, #7 is connected by a Green/Black wire to the same rectifier AC terminal as the stator Green/Black wire (i.e. the opposite rectifier AC terminal from the Green/White wire).

However, as I've written above, the problem with this charge control system is it looks good in theory, in practice you find out about a failure with a boiled and/or dead battery; e.g. Lighting Switch in the "H" position, headlamp bulb blows and you don't know about it (say riding in daylight), first thing you know is acid boiled out of the battery over the bike or, if it's a sealed battery, it's 'blown'. :(

Otoh, a 6V reg./rec., you connect stator Green/Yellow and Green/Black together to one reg./rec. AC (Yellow?) wire, stator Green/White wire to the other reg./rec. AC wire, reg./rec. Red to battery +ve, reg./rec. Black to battery -ve, the reg./rec. automatically and quietly handles all the different electrical supplies and demands, you simplify the bike's wiring by junking all the 'charge control' wiring. (y) :)

Hth.

Regards,
 
#11 ·
Thanx Stuart. I really appreciate your patience and knowledge. I believe I did test from steps #1 thru #5 last summer (also 2 days ago), except I went directly from terminal 10 or 12 to the coils. Will check #13 tomorrow. For now the ammeter not hooked in, but I connected the wires together to complete the circuit. The headlight shell is basically empty but for wires ready for components. I checked the points and they are both open. reg./rec.= regulator/rectifier? Know of a supplier? I'll check my sources.
 
#12 ·
Hi Buzz,
reg./rec.= regulator/rectifier?
(y)

The only 6V reg./rec. I know of is the "A Reg 6" and the two retailers I know of are both in GB - Al Osborn and Paul Goff - fwiw, I checked a BritBike forum thread from about 6/7 years ago where the OP in the US wanted to keep 6V electrics on a '64 BSA Lightning Rocket; he used an A Reg 6 from Paul Goff so there might not be a US retailer?

test from steps #1 thru #5 last summer (also 2 days ago), except I went directly from terminal 10 or 12 to the coils.
Did the meter show any Volts drops across the switches or connecting wires?

Btw, looking at the BSA wiring diagram showed a difference from the diagram in the Triumph 650 workshop manual, that you might consider copying? The BSA had a Brown/White wire from the Ammeter terminal directly to the equivalent of Ignition Switch terminal #12A - this would mean ignition power wouldn't rely on good contact between Lighting Switch terminals #2 and #10. (y)

In case you're wondering, the reason Triumph connected the battery output to the Lighting Switch is GB had (and still has) a legal requirement that anything left on an unlit road at night must be lit; connecting battery directly to Lighting Switch allowed the latter to be set to, say, "L" and pilot and tail lamps would be on even though the Ignition Switch was off.

The BSA still had the wire from Ammeter to Lighting Switch terminal #2 but, as I say, also had a wire from Ammeter direct to Ignition Switch.

Hth.

Regards,
 
#13 ·
OK. So I did all the tests. I get no voltage drop anywhere until I turn the switch on with the coils connected. The points are open so.....? Three tests showed 6.63>5.36v. 6.15>5.56v. 6.14>5.47v.
The battery seems to recover to about 6.30V. when disconnected for a short while, so I take that as a good sign. In hindsight I think this would have been a lot easier to make sure every thing functioned to specs. if I had done all this on a bench
instead of in situ. I switched the wires so the wire from the ammeter feeds the light switch and the ignition switch directly before testing. On the diagram, red is bypassed and blue is the new wire.
733103
 
#14 ·
Hi Buzz,
did all the tests. I get no voltage drop anywhere until I turn the switch on with the coils connected.
If you disconnect the coils, they can't draw any power, so the Volts won't drop ...
... for testing with a Voltmeter to be of any use at all, the circuit being tested must be complete from battery -ve to battery +ve;

... for a circuit to be complete, all switches in the circuit must be on and there must not be any other disconnection;

... the points are switches. So one set needs to be closed so one coil is connected, then you have a "complete" circuit to test.

Three tests showed 6.63>5.36v. 6.15>5.56v. 6.14>5.47v.
The battery seems to recover to about 6.30V. when disconnected for a short while, so I take that as a good sign.
Errr ... no ...

:confused: You haven't posted what these "Three tests" are? Between battery +ve and somewhere in the ignition circuit? If so, where in the ignition circuit?

If the ignition circuit was complete when you took these readings, there is substantial Volts drop between the test points and battery +ve, compared to between battery -ve and battery +ve.

A 'good' battery doesn't need to "recover". You really, really need to have the battery load-tested; without a 'good' battery, only very limited conclusions can be drawn from the results of any tests you make.

if I had done all this on a bench
Uh-uh. You'd have to disconnect everything to fit it on the bike; if it then didn't work, you'd have to test it again. :(

switched the wires so the wire from the ammeter feeds the light switch and the ignition switch directly before testing. On the diagram, red is bypassed and blue is the new wire.
Mmmm ... :unsure: the wire from the Ammeter that was connected to Lighting Switch #2 is now connected to Ignition Switch #12A?

Hth.

Regards,
 
#20 ·
Hi Buzz,

Risking telling you things you know already, Wassell Lucas offers complete sockets/terminals kits for both the Lighting and Ignition Switches, enter "lucas 54930007" or "lucas 54930008" respectively into your preferred internet search engine and it should return links. As you posted earlier that your bike has new switches, I'm guessing these are Wassell Lucas too, in which case there shouldn't be any fitting problems? Or the terminals would be useful on their own?

Or LUCAS 54930008 NOS OE Socket adaptor c/w wires+terminals (Ignition) PDH AP9 | eBay appears to be a more-original complete built-up IgnitionSwitch socket? About twice the price of the Wassell but, if it's any help, I've known the seller for a long time as a Triumph parts dealer. (y)

Hth.

Regards,
 
#21 ·
I ordered an analog ammeter for testing since my multimeter doesn't measure amps. First I watched this video to understand the process () Did more re-testing and came up with these results. One coil connected 2.5 amp draw. Two coils 5 amp draw. Measured voltage with key on. #1 coil (connected to switch) 5.12 v. on white, 5.12 v. on black/white. #2 coil 5.12 on white, .48 v. on black/yellow. According to my understanding of the video, I should have the same voltage at the blk/ylw terminal, also at the stationary points contacts. I have tested these (brand new) coils across HT and LT and they are within specs. I really don't know where to proceed from here. I have followed all instructions posted here and still no luck. Could I have gotten a bad coil? I would assume that if the LT test was OK I should get 5.12 v. at the black/yellow terminal.
 
#22 ·
Hi Buzz,
One coil connected 2.5 amp draw. Two coils 5 amp draw. Measured voltage with key on. #1 coil (connected to switch) 5.12 v. on white, 5.12 v. on black/white. #2 coil 5.12 on white, .48 v. on black/yellow. According to my understanding of the video, I should have the same voltage at the blk/ylw terminal, also at the stationary points contacts.
'Fraid the video is a crap explanation ... :(

. The video sort-of echoes some of what I've posted before, although the ignition switch on your bike is supplied (through the Ammeter) from battery -ve.

. However, what the video fails completely to explain is the crucial role of the ignition coil:-

.. Any electrical circuit must have a resistance in it (y) or its a short-circuit - blown fuse or smoking and melting wire insulation. (n)

.. The ignition circuit on your bike is from battery -ve (through the Ammeter, ignition switch and wires in between) to coil -ve, then from coil +ve through the points, the engine and (hopefully) a Red wire from an engine component through the harness to battery +ve.

.. However, on your bike, it's important to understand each coil is the resistance in its own circuit - i.e. each coil -ve has its own supply from battery -ve and its own return from coil +ve (through its points) to battery +ve.

. When you "Measured voltage with key on. #1 coil (connected to switch) 5.12 v. on white, ... #2 coil 5.12 on white", you had one meter lead connected to the battery +ve terminal and the other meter lead connected to each coil's -ve terminal.

. However, when you measured ".48 v. on black/yellow", while you still had one meter lead connected to battery +ve, you had the other meter lead connected to the coil +ve terminal.

. Volts are the units of 'potential difference' between two points, there actually should be zero Volts p.d. between coil +ve and battery +ve; ~0.5V difference on a 6V system is another fault. :(

. Otoh, the reason you "Measured ... #1 coil ... 5.12 v. on white, 5.12 v. on black/white" is its points were open, no circuit through that coil ... ;)

I have followed all instructions posted here
Firstly, have you had the bike's battery properly load-tested? If still not, you really, really are wasting your time ...

If you have had the battery load-tested and pronounced OK, each of my post #10 instructions #1 to #4 and post #16 instructions #5 to #7 says ,"note the the meter reading"; these meter reading are ...? Because:-

. If 5.12V is what you see on the meter connected just across the battery when the ignition switch is turned on, the battery has not been properly load-tested, it's donald(-ducked, that's rhyming slang).

. Otoh, if you see greater than 6V on the meter connected just across the battery when the ignition switch is turned on, there is Volt drop somewhere between battery -ve and coil -ve; you need to post the meter readings following my post #10 instructions #1 to #4 and post #16 instruction #5 to #7, so we can see the component(s) with the Volt drop; to be clear, your bike can't have Volt drop between battery -ve and coil -ve unless something's wrong, that needs fixing.

Risking labouring the points when testing: the ignition circuit must be and remain complete from battery -ve to battery +ve, including at least on set of points closed, don't disconnect any connections and don't switch off and switch on between meter lead moves.

One coil connected 2.5 amp draw. Two coils 5 amp draw. Measured voltage with key on. #1 coil (connected to switch) 5.12 v. on white,
#2 coil 5.12 on white,
The figures look about right albeit, as I say, they're crap. :(

The basic relationship between Volts, Amps and Ohms is known as Ohm's Law - Volts = Amps x Ohms.

You've previously posted you measured 1.9 Ohms between each coil's LT terminals, so ~2.5 Amps multiplied by ~2 Ohms = ~5V. Resistance essentially remains constant so, when the coils get the proper 6V, they'll each draw the desirable 3A.

have tested these (brand new) coils across HT and LT and they are within specs. I really don't know where to proceed from here.
Could I have gotten a bad coil?
Nothing you've posted shows a bad coil. You've a dud battery (as I've told you from the beginning) and/or other dud components in the ignition circuit. As I've advised, post #10 instructions #1 to #4 plus post #16 instructions #5 to #7 and posting all seven meter readings should reveal the culprit(s).

Hth.

Regards,
 
#24 ·
Hi Buzz,

Apologies for the delay replying. 😔

should I try to find one with higher amp hour rating? This one is rated 6AH. I have seen them as high as 10 AH.
Higher Ah usually equals physically-larger; would a 10Ah fit in the battery carrier?

I like a smaller batteries for their fewer fitting problems, lower weight and cost, but then I use 12V electrics powered by 3-phase high-output alternators. :) Absent changing other parts of your bike's electrics, and particularly the standard alternator, a bigger battery could be useful, it should better-handle any problems from the standard 'regulation' ...

Hth.

Regards,
 
#25 ·
No apologies necessary. I don't log in every day. Well, I had the battery load tested and it failed, so I ended up buying a new one. Same as the other 6ah. I managed to find another that would fit, but was only 7ah, and decided not worth the 1 extra ah. I also found one rated for 10 ah which is big for the battery carrier, but I could easily modify that to fit the battery. For now I will connect new battery and do all the tests again and post results (hopefully all good).
 
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