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Re: [Mgs] alternator wiring quick question

To: "dave willner" <davewillner@pa.net>, <mgs@autox.team.net>
Subject: Re: [Mgs] alternator wiring quick question
From: PaulHunt73 via Mgs <mgs@autox.team.net>
Date: Thu, 13 Aug 2015 15:45:33 +0100
Delivered-to: mharc@autox.team.net
Delivered-to: mgs@autox.team.net
References: <16EDE44434A64DBB921D5E98DF7D98DE@DavePC> <20E3A2B5BE41496985465A4F176BC7E8@paul> <3AEA2FB25EE24A828003065EA0B01AC3@DavePC>
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Is your alt like this?  =
http://www.paulhunt73.webspace.virginmedia.com/mgb-stuff/images/alt16acr.=
jpg

That is the 4 wire system with two plugs.  The upper one is pos (thick =
brown) and neg, although there may not be an earth wire on the neg if it =
makes that connection through the mounting ears as on all the other =
types.

In the second plug B+ should have another brown going back to the =
solenoid battery terminal with the brown from the first plug.

A brown/yellow should go to the IND terminal in this second plug, then =
loop back into the harness and out again to a 3rd terminal alongside it =
in the same plug.  I think this is to protect the electronics in case =
that plug becomes detached.

Is your clear plug like this?  =
http://www.paulhunt73.webspace.virginmedia.com/mgb-stuff/images/altbee3.j=
pg

If so then it sounds like your harness has the plug for the later 2 and =
3 pin alts, but you still have the 2-plug, 4-wire alt.

This shows the three types, how they were wired, and how to convert =
between them =
http://www.paulhunt73.webspace.virginmedia.com/mgb-stuff/images/altconv.j=
pg

If yours aren't like the first two images then without pictures of your =
alt and plugs it's a bit difficult to work out what is what.

Coming on dimly as the revs drop is actually what happens with a dynamo. =
 On an alt the light should switch out as the revs go above about =
1000rpm, and switch back on again if they drop below about 600 rpm, with =
little changes in brightness.  In practice the idle should never drop =
that low with an alt, as that stops it charging, and one of the benefits =
of the alt is that it should be charging at idle, unlike a dynamo.  If =
yours isn't coming on with the ignition but does come on dimly as you =
describe, then it is not wired correctly.

Paul.
  ----- Original Message -----=20
  Thanks Paul. It is a 16ACR, I had it rebuilt about 5 years ago. The =
only connection that fits it is the old clear 3 prong plug with the =
heavy brown lead and 3 brown/yellow leads. The plugs are not like your =
photos though, its 2 side by side and one below on the right side?=20

  Also the large brown =E2=80=9Cmystery=E2=80=9D lead on the other 2 =
prong plus is not live, and I=E2=80=99m not sure if it hasn=E2=80=99t =
been hanging off for years or not...Also my red ignition warning light =
doesn=E2=80=99t come on either when the key is turned and I believe it =
never has since I=E2=80=99ve owned the car, I did see it come on dimly =
last night when the revs dropped low, which I know is typical?

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=EF=BB=BF<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META content=3D"text/html; charset=3Dutf-8" http-equiv=3DContent-Type>
<META name=3DGENERATOR content=3D"MSHTML 8.00.6001.23588">
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<BODY dir=3Dltr bgColor=3D#ffffff>
<DIV><FONT size=3D2>Is your alt like this?&nbsp; <A=20
href=3D"http://www.paulhunt73.webspace.virginmedia.com/mgb-stuff/images/a=
lt16acr.jpg">http://www.paulhunt73.webspace.virginmedia.com/mgb-stuff/ima=
ges/alt16acr.jpg</A></FONT></DIV>
<DIV><FONT size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2>That is the 4 wire system with two plugs.&nbsp; The =
upper one=20
is pos (thick brown) and neg, although there may not&nbsp;be an earth =
wire on=20
the neg if it makes that connection through the mounting ears as on all =
the=20
other types.</FONT></DIV>
<DIV><FONT size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2>In the second plug B+ should have another brown =
going back to=20
the solenoid battery terminal with the brown from the first =
plug.</FONT></DIV>
<DIV><FONT size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2>A brown/yellow should go to the&nbsp;IND terminal =
in&nbsp;this=20
second&nbsp;plug, then loop back into the harness and out again to a 3rd =

terminal alongside it in the same plug.&nbsp; I think this is to protect =
the=20
electronics in case that plug becomes detached.</FONT></DIV>
<DIV><FONT size=3D2></FONT>&nbsp;</DIV>
<DIV>
<DIV><FONT size=3D2>Is your clear plug like this?&nbsp; <A=20
href=3D"http://www.paulhunt73.webspace.virginmedia.com/mgb-stuff/images/a=
ltbee3.jpg">http://www.paulhunt73.webspace.virginmedia.com/mgb-stuff/imag=
es/altbee3.jpg</A></FONT></DIV>
<DIV><FONT size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2>If so then it sounds like your harness has the plug =
for the=20
later 2 and 3 pin alts, but you still have the 2-plug, 4-wire =
alt.</FONT></DIV>
<DIV><FONT size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2>This shows the three types, how they were wired, and =
how to=20
convert between them <A=20
href=3D"http://www.paulhunt73.webspace.virginmedia.com/mgb-stuff/images/a=
ltconv.jpg">http://www.paulhunt73.webspace.virginmedia.com/mgb-stuff/imag=
es/altconv.jpg</A></FONT></DIV>
<DIV><FONT size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2>If yours aren't like the first two images&nbsp;then =
without=20
pictures of your alt and plugs it's a bit difficult to work out what is=20
what.</FONT></DIV>
<DIV><FONT size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2>Coming on dimly as the revs drop is actually what =
happens with=20
a dynamo.&nbsp; On an alt the light should switch out as the revs go =
above about=20
1000rpm, and switch back on again if they drop below about 600 rpm, with =
little=20
changes in brightness.&nbsp; In practice the idle should never drop that =
low=20
with an alt, as that stops it charging, and one of the benefits of the =
alt is=20
that it should be charging at idle, unlike a dynamo.&nbsp; If yours =
isn't coming=20
on with the ignition but does come on dimly as you describe, then it is =
not=20
wired correctly.</FONT></DIV>
<DIV><FONT size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2>Paul.</FONT></DIV></DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; =
PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px"=20
dir=3Dltr>
  <DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
  <DIV dir=3Dltr>
  <DIV style=3D"FONT-FAMILY: 'Calibri'; COLOR: #000000; FONT-SIZE: =
12pt">
  <DIV>Thanks Paul. It is a 16ACR, I had it rebuilt about 5 years ago. =
The only=20
  connection that fits it is the old clear 3 prong plug with the heavy =
brown=20
  lead and 3 brown/yellow leads. The plugs are not like your photos =
though, its=20
  2 side by side and one below on the right side? </DIV>
  <DIV><FONT size=3D2 face=3DArial></FONT>&nbsp;</DIV>
  <DIV>Also the large brown =E2=80=9Cmystery=E2=80=9D lead on the other =
2 prong plus is not=20
  live, and I=E2=80=99m not sure if it hasn=E2=80=99t been hanging off =
for years or not...Also=20
  my red ignition warning light doesn=E2=80=99t come on either when the =
key is turned=20
  and I believe it never has since I=E2=80=99ve owned the car, I did see =
it come on=20
  dimly last night when the revs dropped low, which I know is =
typical?</DIV>
  <DIV>
  <DIV=20
  style=3D"FONT-STYLE: normal; DISPLAY: inline; FONT-FAMILY: 'Calibri'; =
COLOR: #000000; FONT-SIZE: small; FONT-WEIGHT: normal; TEXT-DECORATION: =
none"><FONT=20
  size=3D2 =
face=3DArial></FONT></DIV></DIV></DIV></DIV></BLOCKQUOTE></BODY></HTML>

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