How To Find A Bad Earth?

[Guest b3nny]

I have no main beam at the moment but every time I with turn main beam on or use the flasher it blows the fuse, I have changed the stalk to rule the switch out, so I'm either no guess It could be a bad earth or a dodgey wire somewhere.

 

Is there any tips to go finding a bad earth? I have a multimeter.

[Jez Morton]

Or a bad bulb, or a bad light fitting, or a short circuit? Blowing the fuse would mean the earths probably not the issue, dip is more than likely on same earth. Keep it simple take the bulbs out try that, disconnect the lights try that, look for shorts in the most likely places panel joints and holes the wire passes through.

[Guest b3nny]

Cheers, so basically disconnect one thing at a time and try it to see if the fuse goes? Could it be something as simple as a dodgey bulb?

[Dave R]

yes a dodgy bulb could.... as said before, most lilkely a damaged wire somewhere.....

has it ever worked?

[Guest b3nny]

I'll run a one by one check tomorrow, I have only owned the car for a week but and never worked, I found a disconnected cable from the relay it makes me think it may have been done on purpose.

Edited June 6, 2014 by b3nny

[sj-bradley]

I would take all bulbs out to begin with and test with the switch.

 

Also take out the fuse that blows and test which side goes +ve AND then test resistance on the other side of the fuse.

If you have low resistance to ground with the bulbs out, then that circuit has a short somewhere between fuse and bulb.

 

Probably the quickest way to find which circuit is doing it.

 

Simon.

[fry61]

Put a high wattage lamp (bulb ) in place of the fuse -- then try all possible combinations of switch position ( with all lamps / bulbs in correct places ) Try waggle-ing the wiring around on its way to the head-lamps. The test lamp ( in place of the fuse) will glow if circuit is found - then take out head lamps/bulbs ( & all side lights) & if test lamp continues to glow that indicates a fault.

Will save a lot of blown fuses.

[Guest b3nny]

Right I have a test lamp, would the test lamp not continuously glow anyway once either flashed or main beam turned on as there is power going through?

[fry61]

No, a route to earth is required; either by way of the lamps/bulbs then to earth or via a fault in the wiring where the current will pass direct to earth & make the test lamp/bulb glow at full brilliance. ( Higher resistance paths -- through correct lamps/motor/ignition coil -- will cause the test lamp to glow less bright.)