Hans, here is a "basic" overview of the MG wiring system. This covers the
basic 4 colors, there are
over 50 colors in an MG, but all the rest of the colors are branches of one of
the following:
1) Brown wires. These are the primary power distribution wires from the
battery/alternator. They are hot at all times, and are NOT fused.
2) Purple wires. These are hot at all times, and are fused. They are fed from
the Brown wires. These are typically for courtesy lamps, trunck lamps, etc.
3) White wires. The are hot only when the ignition key is on, and they are NOT
fused. These are primarily the ignition circuits, and other components
required to run the engine, such as the fuel pump.
4) Green wires. These are hot only when the ignition key is on, and they are
fused. They are fed from the White wires. These are for accessories that only
operate when the car is running, such as WS wipers, Turn Signal, etc.
Larry Hoy
>-----Original Message-----
>From: owner-mgs@autox.team.net [mailto:owner-mgs@autox.team.net]On
>Behalf Of Duinhoven_Hans@emc.com
>Sent: Wednesday, October 25, 2000 12:01 AM
>To: barneymg@ntsource.com; Gonaj@aol.com
>Cc: mgs@autox.team.net
>Subject: RE: adding an ammeter to a RBI
>
>
>Really Barney,
>
>You've put a lot of effort in this.
>I only was quoting the advises I got from the list earlier.
>
>You don't like to have unfused wires carrying heavy current in the dash.
>Well let me tell you a story with the standard MGB wiring I got:
>While I just started with the first attempts to fix the MG electrics, almost
>nothing worked in the GT. So I thought: "why not getting some voltage from
>the fusebox (red wire = lights) and have a wire temporarely run to the
>ventilator motor and see if it starts.
>
>Well it started, but lots of smoke came from the dash immediately as well.
>My eldest son warned me.
>What happened?
>Pure bad luck and ignorance.
>A day before I had made the heater valve cable lose on the dash side.
>The cable slipped away and I did not take care of that (stupid!).
>The cable with a metal outer cableframe so being ground in this way touched
>the rheostat.
>So when voltage was applied to the fusebox, the voltage at the rheostat was
>grounded.
>BEWARE THIS IS UNFUSED WHATSOEVER! I cursed the MG electrical designers!
>Fusing in this circuit only is done to the main lamps and the sidelamps and
>rearlamps including license plate lamps. The dashlights are not fused at
>all.
>
>I had to repair the wiring loom - had to take out all the gauges (except the
>oil pressure one) to get the job done. It has cost me hours of work.
>The damage luckily was limited to one burnt wire only. The switch was
>slightly damaged, so I have built in a relay to protect the switch contacts,
>also because I use H4 duplo lamps instead of the sealed beams. H4's use some
>more current.
>
>So Barney standard electrics on MG's are not really safe!
>I've studied for electrical engineer, and I have seen quite some violantions
>against the basic rules how to fuse electrical systmes on cars including
>MG's.
>
>Cheers,
>
>Hans
>
>
>>>>>>>>>>>>
>I personally do not like the analog type amp meter, simply becasue I don't
>like having unfused heavy gauge high current wires routed up behind the
>dash in the passenger compartment. If there should ever be a short in
>these wires, and a meltdown and/or fire to ensue, I would much prefer to
>keep the problem out of the passenger compartment. This is why I voted
>$.10 for the volt meter and only $.05 for the amp meter.
>
>Incidentally, I do like the idea of a digital volt meter pluged into the
>cigarette lighter, except I can see possible problems maintaining a good
>electrical connection if the lighter is actually used and the socket gets
>cooked and dirty. As a matter of reliability I would still rather have a
>digital volt meter hard wired.
>
>$.02,
>
>Barney Gaylord
>1958 MGA with an attitude
> http://www.ntsource.com/~barneymg
>>>>>>>>>>>>>>>>>>>>>>
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