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Re: grounding MGB

Subject: Re: grounding MGB
Date: Sun, 19 Dec 1999 02:40:20 EST
Remember that when it comes to electrics, there are two very distinctly 
different cars.. Metal dash (generator, positive ground) and plastic 
dash.(alternator, negative ground, different instrument sizes) Other than the 
general perversities, some of the details are very different, and answers 
appropriate to plastic dash cars are often not even close to helpful for 
early cars. Always make sure you are using the appropriate wiring diagrams 
and other details, it does matter a lot. (as you can see reading the "Haynes 
manual" posts..)

To answer the question, on the steel dash car the small lugs on the harness 
ground to Each Instrument. Every one of your gauges is mounted to the dash 
via 2 metal clips that slide  down threaded studs protruding from the rear of 
the instrument and are fastened by knurled nuts and washers. Grounding takes 
place via slipping a ground lug under the the knurled nut and washer before 
installing, one per instrument. (use which ever side of the instrument that 
works best for the wiring harness) This causes the instrument and harness 
both to ground to the dash at that point. The dash then grounds into the 
shell via the numerous 1/4 in . mounting bolts that hold it in place. There 
are several places on the firewall where there are holes for mounting the 
clips that hold the harness physically in place to keep things tidy.  Do make 
sure the rear side of the dash isn't corroded around the instument mounting 
holes before you put it all together, or you will later curse both the day 
you and joseph lucas were born...
While you're in there, be aware that you can choose to use either the 3 
position toggle switch for your lights, or use the 3 position pull switch as 
found on the late 66 and all 67 cars. 
Also, if you have a late enough 65 to have an electric tach, be careful with 
the white wires going to the tach pick-up loop and ignition switch, as they 
go directly to the points. The wire from the tach  to the points doesn't 
really re-enter the harness, and I one had a B where the wire was trapped 
betwixt the metal choke cable housing and a loosely installed -dpo-bmc radio. 
The chaffing eventually brought about a sudden halt and the smell of burnt 
wires... late at night, only a mile from home but in 30mph winds and 35' 
temps.. Now that wire gets extra protection on my cars via layers of heat 
shrink tubing, careful routing, and overlay of duct tape. (Fool me once, .etc)

Date: Thu, 16 Dec 1999 11:19:35 EST
Subject: Fwd: Grounding locations on 65 MGB

I am installing a new harness in a 65 MGB shell. I have no pictures of 
previous wiring so I have no clear idea of where ground wires go. There are 
three  wires to be grounded on the drivers side and two wires to be grounded 
on the passengerside. Are these wires to be grounded to instruments or to 
various points on the body. By the size of the fittings (small round 
fittings) on the ground wires it appears they would fit on instruments. Some 
of the reading I have doing suggests that the instruments are grounded when 
they come in contact with the dash which makes me wonder if the wire belong 
on the body. Any help would be appreciated.


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