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Earthing problems

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Mg_Bizzle

Mg_Bizzle

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My righthand front lights (main light and indicator) as well as my heated rear windscreen have earthing problems. Its hard to trace the earth wire back to its source, obviously somehwere along the line it meets the body...where does it?
 
Under the dash and at the battery.

Think it maybe a chubby brown wire just to the right of the tunnel. Also think it comes through from the engine room, might find it that way.
 
Would have thought they'd be more then 2 places, so the problem probably isnt right at the end of the line otherwise id see more problems with other electrics?

Is a poor earth a common fault?

Think il have to do more detective wire work tomorrow /bcforum/images/%%GRAEMLIN_URL%%/laugh.gif
 
Earth is a common ground, but it isn't always a common fault. However, many like to fault Lucas as the common ground to our electrical faults. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif


Uhhhhhhhh... yeah...

Seriously though, I wouldn't say poor earth is a common fault, as much as I would say that ensuring you have good earth is one of the easiest trouble shooting steps you can take. If the earth connection proves to be good, I'd make sure you're getting power out to the troubled spot.
 
BE AWARE!!! A ~BROWN~ wire is a HOT LEAD on our cars! BLACK is earth.
 
Lighting will be blue with a tracer for headlamps, green with a tracer for the t-signal and red for running lamps.

Headlamps are usually grounded someplace close to the buckets or the grill area.

Which car are we talking here?

EDIT: Checked your profile. MGB-GT. Headlamp grounds have a "gang" Lucar (three-into-one) connector in the center of the grill, the ground point is a chassis ground inside the cab around the wiper motor area. The park/turn indicators get their ground from the physical connection of the lamp housing to the sheet-metal.
 
Where did you find that information? Iv got a 79 BGT. The indicator and front headlight share the same earth, as well as various other things.

Il have a scout about for an earthing point otherwise it looks like im just going to have to make a new earth.
 
I meant the info about the earthing points as mine are different to what you say, theres no earthing point near my grill.

Also do you have any idea where the earth for the heated rear windscreen goes? Surely that doesnt go all the way to the front?
 
The grill has a Lucar gang connector, not the earthing point. Since you're describing a condition affecting only lights on one side, that 4-way Lucar could be the gremlin. The earth point is what is under the facia, near the wiper motor. On yours it may be the motor is on the port side, so I mis-spake. The gang of black wires connected to the bulkhead may be on the starboard side for all RHD and LHD B's.

I've no recollection there was aught for the rear "heater grid" but a trace wire going to a terminal on the hatch metal for an earth. Opposite side of the one for voltage supply. Been years since I've seen a heated rear screen MGB-GT.

Keep us up on what you find.
 
Well, you were right about the earthing point. I could only find one by the wiper motor in the cab.

What iv ended up doing is taking the earth from the headlight lead (break into it not cut it) and made a new earth. Hopefully this will get me through my MOT tomorrow (dunno if you have some similar car test in the U.S?) and then il have to look into it more.

A major part of the problem could be my really old battery.

God I hate wiring /bcforum/images/%%GRAEMLIN_URL%%/crazyeyes.gif
 
well, the US is somewhat complex in the automotive standards area. There are standards that ~NEW~ cars must meet set by the Federal Government. However, the "Feds" seem to allow the individual ~STATES~ to use their own standards ~IF~ the State's standards are higher.

The Feds have no dictation on old cars. So, policing of "safety" and "emissions" is left up to the states to decide on how to handle them.

California, for example, has no safety checks in place to keep a car on the road, as far as I know. They only seem to care whether or not you can make your 1976 and newer car jump through emissions hoops and checks that weren't in place when the cars were initially made, and whether or not you still have the ~stock~ emissions equipment in place.

I've heard of ~other~ states out there that only check to make sure you have safety equipment that's serviceable, and could care less if you have no emissions equipment.

It's a quagmire we must navigate through if we ever decide to move to a different state. Some states are easier to live in than others. Which is why I will move back to Florida when I'm finished with the rat race of living in the "greater Los Angeles metropolitan area".
 
The USA has nothing really as strict as the MOT test. Some states carry out safety checks in addition to emissions tests, but nothing as stringent for roadworthiness.

Wisconsin where I live checks emissions only. Consequently, there are some right sheds on the road here that have no right to be. Main objection to that kind of test is that it discriminates against the low-income residents who can't afford to maintain a car properly. There are cars running around with holes in the wings, and even the sills eaten away with rust.

Good luck with your MOT test, I know what a nail-biter that thing is!
 
Woooo it all passed fine, apart from the king pins need to be replaced for next years one.

Thanks for all your help guys, no doubt il be back for more soon /bcforum/images/%%GRAEMLIN_URL%%/thankyousign.gif
 
Very good news indeed! Ya don't need to just run away now, y'know. This place is a lot more than just LBC Q&A.
 
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