Odd Electrical Problem

[Andy64]

Hi,

It's literally been winter in Yorkshire in the UK since last July, only just now getting around to getting my 64 3TA ready for the summer riding season.

When checking things over since the bike went in to hibernation last October I've came across this odd electrical problem that wasn't there when I put it away.

When I press on the the rear brake pedal the headlight comes on, not full, slightly dim but on, remove the tail light, head lamp stays off.

When I turn on the lights properly the lights are full & bright front & rear, so wouldn't be able to tell if the problem is there when pressing the rear brake pedal, full beam is working good also.

Can anyone help please ?

TIA,

Andy.

 

[atomsplitter]

Wow, let me express my admiration for Lucas (Prince of Darkeness) going to the light side!! Can't help you, but just amazing to read....

 

[rodsridin]

Does this occur no matter what position your dimmer (high or low beam) switch is in? Because the head light comes on dimly suggests it isn't fully connected (lots of resistance) in the positive ground connection. That connection is broken when the tail/brake light is removed from the equation. I don't have a schematic nor am I an electrician, but I would start with what's common to both systems and check for corrosion that may have formed over the winter shut down.
Sorry I can't be more help.

 

[Rudie]

When I press on the the rear brake pedal the headlight comes on, not full, slightly dim but on, remove the tail light, head lamp stays off.

When I turn on the lights properly the lights are full & bright front & rear, so wouldn't be able to tell if the problem is there when pressing the rear brake pedal, full beam is working good also.

As @rodsridin suggests, first place I would look is the rear light earth - your post suggests the brake light filament is earthing through the rear light filament and then the headlight, common problem. Lucas did not fit a proper rear light earth wire until 1971, standard 3TA rear light relies on the bulb holder contacting the housing, the housing contacting the numberplate mounting, that mounting contacting the mudguard, the mudguard contacting the frame ... all of which are painted ...

Initially, I suggest testing with a length of wire connected between the rear bulb holder and the battery positive terminal. If that fixes the problem:-

. I advise against simply scraping paint off components to make/improve the earth, the bare steel will rust and rust also does not conduct electricity ...

. Run a/the new (Red ideally) wire alongside the existing (Brown/Green and plain Brown?) wires from the rear bulb holder at least to an existing Red wires snap connector under the seat, otherwise to the battery positive terminal itself:-

.. When Lucas added the Red wire from 71, a sleeve for a bullet terminal was formed on the outside of the bulb holder. If it is possible to thread the new wire into the rear light without compromising any waterproofing, bare the end and solder that to the outside of the bulb holder?

.. Otoh, if it is not possible to thread the new wire into the rear light, the pattern one I have makes a good all metal connection between the bulb holder and the mounting studs on the outside; terminate the new wire with a ring terminal, secure the ring under one of the mounting nuts?

 

[Andy64]

Thank you for taking the time to reply, I appreciate it.

Yes, the headlight does come on with the switch in low & high beam position when the rear brake pedal is pressed down.

I will certainly take a look at the earthing & try your suggestion.

Regards,

Andy.

 

[Andy64]

Hello.

Things are going from bad to worse.

I have posted on here a few times about the problems I've been having with the clutch for quite sometime.

I'm not going to go in to that issue just to say I have spent most of last week & all this weekend working on that as well as other stuff.

The light problem. Checked the earth on the rear light, no problems there, so I detached the earth to see what would happen.

Rear light didn't come on when I pressed the brake pedal but the front one still did.

Any ideas what's going on there ?

Next thing, yesterday the charging system was working perfectly, volt meter going up as the engine was revved, today it isn't working.

I plugged the alternator wires in to my multi-meter started the engine, reading was zero.

Is this the correct thing to do to check the out put of the alternator ?

TIA,

Andy.

 

[Andy64]

I think I had the multi meter set incorrectly, set it to DC volts, should I have it set to ohms or AC volts to check the alternator?

 

[atomsplitter]

Set it to DC volts and check at the battery terminals. If the regulator/rectifier/zener diode whatever is working the voltage should be higher than 13.3 (assuming 12 volt battery) and peak around 14.2 when you give it gas.

 

[Rudie]

Set it to DC volts and check at the battery terminals.

+1.

If the regulator/rectifier/zener diode whatever is working the voltage should be higher than 13.3 (assuming 12 volt battery)

(Nominal) "12V" battery fully charged, engine not running, calibrated meter should read between 12.6V and 12.9V (12.6V is more likely on a flooded battery, AGM or gel battery can be the higher reading). If your meter reads higher, the calibration of the display is poor.

Diagnosing charging problems, or not, requires accurate knowledge of rpm because, engine running:-

. raising rpm slowly should show a similar increase in Volts, until about 3,500~4,000 rpm, when Volts should stop rising even if rpm is increased further, Volts should remain steady until rpm is reduced;

. Zener diode fitted, DC can reach 15V;

. reg/rec fitted, peak DC might be a little lower, but should not be less than 14.5V; less and I would suspect a problem.

Standard 3TA, accurate knowledge of rpm can be a problem - modern timing lights often have a rev. counter function; or cheap electronic tachometer that connects to an HT lead? However, accurate knowledge of rpm then depends if timing light or tachometer can be set for a spark every two crank revs (points) or a one every rev (electronic ignition) or you can extrapolate correct rpm from a 4-cylinder setting ...

Also, reg/rec fitted, fully charged battery, DC output will correctly not rise to maximum possible charging Volts; if you think the battery is fully charged and you do see maximum charging Volts, something is not right, more testing required.

plugged the alternator wires in to my multi-meter started the engine, reading was zero.

Not only should any connected multi-meter be set to AC Volts, a 1 Ohm resistor is also required (as detailed in any Triumph workshop manual) - neither the original Lucas company nor Wassell publish/ed 'no-load' Volts values for comparison when testing.

Checked the earth on the rear light, no problems there

Does your bike have a standard Lucas 564 rear lamp, as shown in the parts book? If yes, please explain this "earth".

 

[atomsplitter]

Sorry Rudie, I'm too used to modern large scale machinery (see below pic).

Lead/acid batteries typically are assumed to be 2.2 volts per cell, so by multiplying that value times 6 cells yields 13.2 volts. So fully charged the voltage should be closer to 13 than 12 volts. To obtain battery 'charging' the charging system voltage must exceed total cell voltage.

Industrial battery chargers have two settings, float and equalize. Usually the battery charger is selected to float for normal operation with a voltage output higher than battery rating. The usual float voltage on a 125VDC (57 cell) battery is 133 volts, the equalize voltage to force all cells to maximum on the same battery is 145 VDC. Standard automotive chargers are typically float type chargers with a voltage above battery voltage and as the battery cells get charged the amp loading drops off until the amp draw is minimal and the battery is fully charged. There isn't an equalize option on most home battery chargers. Battery tenders are also float chargers.

Depending on what the charging system is (generator (DC) or alternator (AC)) the system has to get charging voltage above battery cell combined voltage to 'charge' the battery. So if you check the battery terminals before engine start, that value is going to be lower than when the engine and charging system are operating at the same terminals. Since the battery is DC and the charging system output is DC regardless of type it's easiest to check at the battery terminals.

If the charging voltage goes too high the battery can be literally cooked, meaning the regulator in the system isn't functioning properly and is boiling the battery dry. Again can be checked at the battery terminals with the engine running.

This is a substation battery (and it's pretty small compared to large battery banks).

 

[Rudie]

Lead/acid batteries typically are assumed to be 2.2 volts per cell

Ime of motorcycle batteries, I expect 2.1V~2.15V per cell = 12.6V~12.9V.

Depending on what the charging system is (generator (DC) or alternator (AC)) the system has to get charging voltage above battery cell combined voltage to 'charge' the battery. So if you check the battery terminals before engine start, that value is going to be lower than when the engine and charging system are operating at the same terminals.

Not standard Lucas alternators on these old bikes, they do not charge the battery at low rpm; all lights on, can be 3,000~4,000 rpm before a standard alternator's generating enough to run the ignition, power all lights then charge the battery.

Standard battery checks on these bikes are:-

. Volts measured across the battery when everything is switched off;

. Volts with just the ignition on;

. Volts with ignition and all lights on;

... standard 12V 9Ah battery (or even a 7 Ah), the meter reading should change very little; -0.1V change between the stages usually indicates a battery on its way out; greater drop between stages indicates a dead battery.

If the charging voltage goes too high the battery can be literally cooked

Workshop manual Zener diode check permits up to 15V. Components like electronic ignition for these bikes, tolerance up to 16V is standard.

 

[atomsplitter]

Ime of motorcycle batteries, I expect 2.1V~2.15V per cell = 12.6V~12.9V.

I can live with that.

 

[Andy64]

As you can see from my avatar my bike is a bobber, there is very little that is still original.

I have the tail light earthed via the casing to a good earth point on the frame.

I am going to plug my multi-meter in to the two alternator wires, set it to the AC fire the engine up, see what happens & swap out the regulator rectifier & see what happens.

I have had sat on my workbench a solid State R & R for a couple of year's just waiting for me to install it. There's only four wires & fitting this will get rid of the current four post R & R, the zenner & a whole lot of wires that are in the battery box. Apparently these all in one R & R's are supposed to be a big improvement to the old set up.

Once I have sorted the charging system problem I'll be back on to my original problem of the front light coming on, then wait for the next problem to rear it's head

 

[Andy64]

Got lucky with the charging system, it was only a wire going to the regulator, it had came loose, result..

I've taken a look at the wiring in the headlamp shell, I have two wires going to the
on / off switch, one being the power supply the other is the rear lamp wire.

This rear lamp wire is the one that's turning the headlight on when the rear brake pedal is pressed. So I have got to figure out how to wire that in so when I flick the switch the headlight & the tail light come on & when the switch is in the off position the headlight doesn't come on when the pedal is pressed, just the tail light.

Electrics is not my forte so unsure how to solve this problem.

Andy.

 

[atomsplitter]

Got lucky with the charging system, it was only a wire going to the regulator, it had came loose, result..

I've taken a look at the wiring in the headlamp shell, I have two wires going to the
on / off switch, one being the power supply the other is the rear lamp wire.

This rear lamp wire is the one that's turning the headlight on when the rear brake pedal is pressed. So I have got to figure out how to wire that in so when I flick the switch the headlight & the tail light come on & when the switch is in the off position the headlight doesn't come on when the pedal is pressed, just the tail light.

Electrics is not my forte so unsure how to solve this problem.

Andy.

Where's Rudie when you need him?? I recall that pre '74 bikes had a switch to turn the headlight off and on, and post that date the laws changed requiring the headlight be on whenever the ignition system was on. So most of the manufacturers went with a relay that dropped the headlight power out when the starter motor was engaged. Hopefully someone will chime in with a solution.

 

[Rudie]

Where's Rudie when you need him?

Reading and posting ...

The problems are:-

wiring in the headlamp shell, I have two wires going to the
on / off switch, one being the power supply the other is the rear lamp wire.

. @Andy64's post does not make a lot of sense; how is the headlight powered?

my bike is a bobber, there is very little that is still original.

. What does the switch look like? One or two photos might be a start ...

recall that pre '74 bikes had a switch to turn the headlight off and on, and post that date the laws changed requiring the headlight be on whenever the ignition system was on.

My understanding of US federal motorcycle lighting regulations is it was the 1978 FMVSS that required lights on with ignition on motorcycles built after 31/12/77. Triumph initially produced the 1978 US-only T140E, lights-on with ignition was achieved by fitting a light switch previously used pre 75 but wiring it slightly differently. Then 79 on T140E were fitted with handlebar switches based on those fitted to the 75 electric start Norton Commando, the wiring harness was designed so a simple different connection either included or bypassed the headlight on/off switch on the right handlebar.

So most of the manufacturers went with a relay that dropped the headlight power out when the starter motor was engaged.

78 T140E, the rider could switch the headlight on/off but pilot and tail lights were always on with ignition. 79 on T140E were fitted with 3-phase alternators that produced a little more at low rpm, all lights were on with ignition.

 

[atomsplitter]

Thanks for the clarification Rudie. It would be helpful if Andy64 gave a photo or two because with heavy mods usually comes bizarre wiring, dubious engineering, and fickleness in biblical proportions.

 

[Andy64]

Hello.

it just a simple toggle switch, on & off, that's it, two wires to the off side one wire going to the bulb.

We don't have headlamp on laws in the UK, don't even need lights if you only use the bike in daylight hour's.

Thanks,

Andy.

 

[Andy64]

Hello again.

Taken a couple of photos. Won't upload, no idea how to make them fit, this site says they are to big.

Why is it always in pain the f ing arse just to put photos on forums ?

 

[atomsplitter]

If you have WORD you can insert it into a doc as a jpeg and then copy paste it on the forum. Usually if I take pics with the phone I email it to myself as a "medium" pic to get the file size down. Then copy paste from the email. Just some options.