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6 cyl Bristol cars Type 400 to 406 - restoration, repair, maintenance etc

Wiring blues

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Old 18-08-13, 07:07 PM
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Default Wiring blues

A long story but basically I had the car rewired negative earth with a RB controller. Out of it came two browns, two yellows, two greens, a green/red, a white and black earth.

I have fitted an alternator and distribution fuse box. There is a supply from the battery through fuses to the two browns, two greens and white. I joined the green/red and yellow from the alternator field assuming it is the return from the ignition warning light and isolated the other yellow as I now have a heavy duty supply to the starter relay.

After experiencing a flat battery I have discovered that the ignition runs off the live brown rather than switched white. Is this correct and why didn't the battery die when the dynamo was in place?

Looking for enlightenment!
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Old 18-08-13, 07:17 PM
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Default

I would imagine that one would need to see the suggested wiring diagram before getting too excited about colours and suggestions as to where they may go.
I have several pre-war and post war cars all running nicely with original generators/dynamos. Never had battery or lighting issues.
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Old 18-08-13, 07:41 PM
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Default Switching polarity

Not an issue unless you have accessories like radios and such that are usually negative ground these days. Alternators, at least modern ones, have built-in voltage regulators. On the old systems that used a generator(dynamo), there was an external voltage regulator, and it may have had the means to turn everything off in the charging circuit. The positive wire to the alternator may still be 'hot' when you shut the car off. Easy to check with a volt/ohm meter. This means that it will continue to draw from the battery if it shows 12 volts or more. Just a suggestion. The mossbacks who stand by the 'original' setup will tell you to keep what you have and give up having bright lights and a hot ignition. You may want to hand the car over to a specialist to sort this out. I have two six-volt cars in my stable and will change both over to 12 volts. Yes, they will have alternators.
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Old 18-08-13, 09:27 PM
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The issue for me is that I know the brown wire is permanently live and has the ignition running off it.

The white is switched. What I do not understand is why the ignition doesn't operate through the (ignition) switched wire and why the system didn't discharge when it was fed by the dynamo as it must have had a live battery supply on starting.

Should the ignition switch have operated a relay to energise the ignition circuit from the live brown?

Not sure what the other brown does but there is clearly a switch on it somewhere (think it operates the fog lights).
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Old 19-08-13, 09:04 PM
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Problem solved. The white output was actually a white input to the controller (terminal A3). Tracing it back to the instrument panel it was on the other side of the ignition switch which has a (live) brown feed. It is shown (with a lead to the coil) on the 403 wiring diagram.

With the fused distribution box permanantly linked to the live feed I was sending a live to both sides of the switch. Still don't understand how it worked when the dynamo was in place though.

One step closer to risking it on the roads!
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Old 03-09-13, 09:59 PM
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Problem not solved. The system is still draining about 5 amps through the ammeter when the ignition is turned off. I thought it was not centring properly (a lot of my bike ammeters don't). Wrong. My brand new battery has been drained!

There is so little equipment on the car. Where could it be going?

Another query. Should the wind screen wipers work when the ignition is turned off?
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Old 20-09-13, 01:55 AM
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Default 405 wiring...

I'm in the middle of re-wiring my 405 so just happen to have hte schematic to hand...

The wipers come off the switched supply and are connected to fuse A4 via wire 17.

Can't help much with the charging side as I'm retaining my dynamo setup but with an electronic regulator (from Dynamo Regulators of UK).

One tip is to get a clip on DC ammeter, this really helps with tracing where those electrons are leaking away to.... Worth their weight in Dark Munro...

Rgds. Stuart
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Old 24-09-13, 06:32 PM
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Quote:
Originally Posted by peterg View Post
Problem not solved. The system is still draining about 5 amps through the ammeter when the ignition is turned off. I thought it was not centring properly (a lot of my bike ammeters don't). Wrong. My brand new battery has been drained!

There is so little equipment on the car. Where could it be going?

Another query. Should the wind screen wipers work when the ignition is turned off?
I may have missed which car you refer to, but the 400 and 401 do not have self parking wipers as standard.
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Old 25-09-13, 03:33 PM
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Default There is an obvious drain

Some wire in the wiring harness is touching a ground, and nothing short of examining the entire harness will do. The only alternative is to go through the fuse box one at a time and place a volt-ohmmeter between the positive side of the battery and the battery terminal (after it has been disconnected) You will see the draw on the battery. Now, one at a time, remove a fuse and observe the meter. You may get lucky and find the culprit. Otherwise, you will need to follow each wire to a bare spot that is touching the chassis.
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