New kid on the block,puzzled 14

gort55 · Post by **gort55** » Thu Sep 27, 2012 11:35 pm

Help,i'm a 59yo newbie to the forum and AJS and hope you guys can advise me on a simple wiring problem i don't understand or i'm a bit of a div.What is the purpose of the RESISTOR WIRE attached to the two White/green wires,and where do they connect to?,other than that i'm quite happy.Thanks for any advice offered.

cbranni · Post by **cbranni** » Fri Sep 28, 2012 12:12 am

Hi there Roscoe and welcome .............now the dreaded translucent coloured resistor wire hidden away in the lightweight wiring loom, whats it for? well my interpretation is (did I spell that right?) that with engine running and no lights on this wire stops the battery getting over charged in simple terms.
It runs from the earth point of the battery to the light switch with a link going to headlamp shell as an earth.
I have two lightweights and have replaced the rectifier and the resistor wire with an electronic gizzmo that works great, much better control of charging the battery.
If you need more info just ask, there are more learned people on here so they may be able to give you a more detailed answer

Colin

gort55 · Post by **gort55** » Fri Sep 28, 2012 12:30 am

Hello Colin,that sounds good to me,i will check it out tomorrow and let you know what occurs,more info on your GIZMO would be handy(yes you spelt it correctly)Thanks for now,Roscoe.

Janet · Post by **Janet** » Fri Sep 28, 2012 6:57 am

Colin Farrington makes wiring looms so he may be able to add to cbranni's answer.

Definitely being a div, I had no idea what the wire was for but it was in the loom, so in the loom it stayed. I did change the rectifier for a regulator/rectifier and added a fuse to the system.

I wouldn't have bothered if I hadn't melted my electrics but, since by then it was broke, I thought I might as well fix it.

CR · Post by CR » Fri Sep 28, 2012 10:16 am

The resistor wire was indeed designed to prevent the battery from overcharging when daylight running with an alternator.

Early alternator charging control was a bit iffy until zener diodes were employed - these simply converted excess power to heat. The resistor wire did the same thing but often caught fire in the process!

Modern control units employ thyristors which actually chop the electrical sine wave and prevent excess power entering the systsm. This is the way to go both for safety and for the protection (and longevity) of the battery.

Talk to Colin Farrington (hopefully he'll read this and contact you - if not PM me and I'll give you his number). He can custom build you a new harness for your lightweight which will allow you to fit a modern voltage control unit (assuming you may not be able to do this yourself).

Rob Harknett · Post by **Rob Harknett** » Fri Sep 28, 2012 11:00 am

I am no electronic expert, but I notice Chris mentions thyristors. In the 1970's I have replaced many of these in discotheque lighting equipment controlers. Thyristors were forever blowing. I beleive thyristors are still used in the home dimmer switches. I wonder why Triacts are not used, which will take an inductive load, and a part I have never had to replace.

CR · Post by CR » Fri Sep 28, 2012 11:20 am

Not wishing to cause deviation on this thread, but a thyristor is simply a switch that can operate at vastly greater speeds than anything mechanical. A Triac is simply a bidirectional thyristor, i.e it can conduct electricity in either direction.

gort55 · Post by **gort55** » Fri Sep 28, 2012 2:59 pm

WOW & CRIKEY,did not expect such a good response,thanks everyone.This is the situation at present,the resitor wire to batt earth,positive(white with green tracer)disconnected,The 2 G/W wires in H/Lamp shell had been fastened to earth along with a White wire which bells out to the H/Light switch.So with these 3 wires disconnected and left safe for testing everything appears to work ok and with a good charge rate etc,this might sound daft but in this day and age of BLIND car drivers could one not just ride with H/Lamp turned on.(oo er,don't leave bruises)

Ian5913 · Post by **Ian5913** » Fri Sep 28, 2012 6:02 pm

Yes ride with your lights on, the resistor wire is for when your bulb blows.

Best wishes

Ian

CR · Post by CR » Fri Sep 28, 2012 6:12 pm

quote: in this day and age of BLIND car drivers could one not just ride with H/Lamp turned on

You most certainly could and it would probably balance the power and preserve the battery. However, if you get into heavy traffic and start crawling along (and start using your 18 or 21w brake light) you'll find that the battery possibly goes into deficit quite quickly. Then you'll turn the lights off when you see the ammeter hard over in the minus, and then the traffic will clear and you'll forget that you turned the lights off, and then...

But lightweights had an emergency start facility when standard, which poured all the power through the coil and most often actually worked quite well (turn it back to IGN after a minute or so and don't try to ride on EMG).

If you do just use it as it is, at least fit a fuse from the battery supply to the harness (not the earth). Calculate the fuse size by adding up all the watts that you use (lights, coil, etc) and then divide it by 6, and then double that figure. You'll probably find that a 20 ot 25A fuse will do the job. This way, if your system springs a short circuit, you'll probably not burn.