Electrical failure

[Mark Reeves]

Hello All,
I was out on my GT 250 A on sunday and as I approached a roundabout I had total power failure. I managed to pull over onto the pavement and find neutral. There was no neutral light and no electrics where working, not a single thing. I checked the fuse which was ok and the battery had full power. I had to be recovered and taken home.
When I got home I was hoping to find a loose wire behind the headlight, but everything looks good.
Electrics are not my strong point so can anyone walk me thru what to look for. I have a multi-meter.
To me it would appear the ignition switch has failed, but that is just a guess.
Any help would be appreciated.
Cheers

[karl pa]

First I would check power on fuse, sometimes the plug between battery and harness looses contact, then check power at plug where fuse plugs into harness, I had fuse holders loose contact, then check power on red wire going to ignition switch, if you have power there then check orange wire coming from ignition switch, if the switch is bad the orange wire will be dead. And everything runs on the orange wire

[Mark Reeves]

Thanks Karl, that gives me a starting point.

[Mark Reeves]

Hello Karl,
I tried all that you suggested and I think the ignition switch is knackered. I left the block connector together and removed some insulation from the orange wire. I then placed my meter on the exposed core and the other end to earth. The meter read nothing with the switch off and on.
I think this points to a knackered switch.
I will let you know when I buy and fit a new switch.
Cheers

[jabcb]

Check the red wire to see that power is getting to the switch.

[Mark Reeves]

There is power going to the switch from the red wire.

[karl pa]

I never lost an ignition switch suddenly while riding, most switches that went bad for me gave intermittent loss of connection, but it can happen.
Another test you could do is, unplug ignition switch and install a jumper wire between the red and orange wire in the block, and see if lights come alive.

[Mark Reeves]

Hi Karl,
I only bought the bike late last year so when it failed it was only the second time I had ridden it. I do recall that when I first got the bike the ignition sometimes worked (ie the neutral light came on )and sometimes you had to waggle the key for it to work. !!!!.
I could not get a bridge across the the red and orange, but what I did do was connect the ignition switch via the block connector. I then put my meter on the back of the switch on the red and orange solder points with the switch in the off position and the meter reading was 12.7 volts.
I did the same thing with the switch on and the reading on the meter was zero.
I can buy a new switch for £15-£20 quid which will eliminate that.

[Mark Reeves]

A New ignition arrived today and I rushed to fit it and solve all of my problems, but to no avail. It made no difference. Bugger.
I am taking both ignitions (old and new ) to be checked for resistance tomorrow.
If they are both ok at least I will be able to cut the block connector of one and try and bridge some of the wires.
Any other suggestions are welcome.
Thanks

[karl pa]

I would hold off on cutting wires for now.
What is the battery voltage when ignition is turned off?
What is battery voltage when ignition is turned on?

I then put my meter on the back of the switch on the red and orange solder points with the switch in the off position and the meter reading was 12.7 volts.
I did the same thing with the switch on and the reading on the meter was zero.

This is telling me the ignition switch may be working, I am wondering if your battery has good voltage but no amps, when you put a load on battery the voltage drops.
What type battery are you using? and is the charging system stock? If you are using a modern battery type like AGM, with stock charging system, the battery will cook dry and have no amps. stock charging can put out 16-17 volts which is way to high, AGM need to stay below 14.2

[Mark Reeves]

I had the ignition switches tested for resistance and the original switch is intermittent when turned on and off and the new one is constant so that sort of solves one problem , but not the main one.
The reading on the battery is 12.8V when the ignition is on or off.
I am using a new motobatt battery which i believe is an AGM type although I do still have the original battery.
I am going to repair some of the suspect wiring today if I have time and then start looking for the issue again.

[karl pa]

Using an AGM or new type battery, you should upgrade the charging system to new style regulator/rectifier to limit volts going in battery, if volts go over 14.2 the battery will cook dry and ruin battery.

[Mark Reeves]

Thanks Karl,
Do you know where I can get a new style reg/rec.
I still have to solve my original problem yet.
Cheers

[jabcb]

This is how I installed a Tympanium rectifier/regulator on a GT250. Available from eBay & lots of retailers. Was around $50 the last time I bought one.
GT250-1976_Tympanium by jabcb, on Flickr

[karl pa]

I still have to solve my original problem yet

I agree, you should fix original issue first.
I also used Tympanium as jabcb.
Rexs speed shop lists one for GT250 and other models, It looks like it may plug into harness without modifications, (part number RR12V-16), I don't know if it does or not, or how good it works.