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MG MGB Technical - Earth lead issues
As I didn't have the benefit of stripping down my mgb I am finding it difficult to determine where the black earth leads should be connected. I am using the wiring diagram but could do with some help with the following
1. My new wiring harness has 3 black wires grouped together and two other individual black wires in the cockpit (behind the dashboard) area. Can someone please explain where these should be fitted?
2. I also have 1 or 2 black wires in the engine bay (near the fuses). Do I just attach these to a nearby bolt (which is screwed into the body itself)?
3. I have opted for a single 12v battery and could do with knowing where on the body to attach the negative connection to. A photo would be most helpful
|Alex - The earth leads can go to any convenient screw hole in the body, but you do need to get all the paint and/or corrosion cleaned from around the hole clear down to bright metal, then coat it with a good corrosion preventative, electrical grease. See article, Electrical Connection Preparation in the Other Tech Articles section of my web site at: http://homepages.donobi.net/sufuelpumps/ Cheers - Dave|
|Helps to say what year/spec the car is.|
The group behind the dash goes on one of the three wing fixing bolts along the top edge - center one I think. On US cars this is immediately above the wiper motor.
The ones in the engine compartment go on a 10-32 screw in the area, usually the same one that retains a loom clip below the fuse box or near the coil. Some cars use more than one of these locations; doesn't matter so long as they reach.
Front lamp earths go to one of the wing fixing bolts forward of rad diaphragm.
|Thanks the car is a 1971 roadster. |
I will look for this wing fixing bolt for the cluster of three earth wires.
Do you know where the negative terminal for a single 12v battery should go?
|UK behind dash earthing point is behind the wiper motor on the bulkhead below the screen from what I've seen, not on a wing fixing bolt. Engine compartment is near the starter relay/fusebox. Both have a threaded boss going through the panel, so if not used for relay or fusebox should be obvious. They have a crinkled surface, possibly to cut through paint to get the the wire tag.|
While early headlamps were earthed at a forward point later ones came back to the starter relay point. Chrome bumper parking/indicator lights never had an earth wire but earthed through their physical fixings, same as all rear light clusters.
Single 12v in a chrome bumper car was never a factory option so there isn't a 'proper' place for the earth strap to connect to the body when the battery is on the right-hand side. The most obvious place would be a hole drilled in a similar position to where the hole for the left-hand battery is.
|I found all sorts of earth problems after a restoration involving a new paint job inside and out (2 pack). The paint was proving to be a pretty good insulator. For the rear and front light assemblies I fitted unique earth wires just to be sure each globe was well earthed rather than relying on connection through the light fitting base and mounting screws. |
This thread was discussed between 14/01/2012 and 19/01/2012
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