Bad Earth
Author
Discussion

paul.davies

Original Poster:

86 posts

293 months

Monday 9th June 2003
quotequote all
Do we have any sparkies on the forum?
Whenever the reverse light contact on my gearstick is triggered it causes the fuse to blow. I've taken the bulb out and then triggered it but it still blows, so I guess I've got a bad earth.
What's the best way of tracking this down?
Thanks

nubbin

6,809 posts

306 months

Monday 9th June 2003
quotequote all
Naughty moon! ....oh, sorry I thought this was the word association thread.....

I'm off back under me rock now.

taylormj4

1,635 posts

294 months

Monday 9th June 2003
quotequote all
Hi Paul, I'm an elec. engineer but that's close enough!
Actually it sounds as if you've got a very good earth but sadly in the wrong place. If you have taken the bulb out and still blown the fuse, this shows that the positive lead has a short-to-earth somewhere between the fuse carrier and the bulb. Maybe the wire has been chaffed or burnt through by touching something hot. It'll need replacing anyhow. Shouldn't be too difficult. You should be able to pull the new wire through with the old one.
Alternatively, the gearbox switch itself could have earthed out internally through damage.
You could check the resistance to earth from the bulb end of the circuit and then from the fuse carrier, with the gearbox in and out of reverse, this would show up the problem area....if you have a multimeter. If you're near South Wales I may be able to assist?
Matt

paul.davies

Original Poster:

86 posts

293 months

Tuesday 10th June 2003
quotequote all
Thanks Matt, that's just what I was after.
I'll pop out and get a multimeter today.
Should be a bit of fun.

paul.davies

Original Poster:

86 posts

293 months

Thursday 12th June 2003
quotequote all
Hi again,
I've been checking the electrics with a multimeter.
The bulb end of the system seems fine, so I took the reverse switch out of the gearbox and holding it in my hand helpd one probe against a terminal and the other agains the casing and the ohmmeter showed 1, swapped terminals and it showed one again. So I checked for continuity by putting a probe on each terminal and pushed the switch, the ohmmeter changed from 1 to 0. I put the a new fuse in and tried the switch in my hand and the fuse did not blow. I attached the swich back to the gearbox and switched it with the gear lever and the fuse blew again.
To me, this seems to point to a dodgy switch????
Although I don't know why it passed the earth test with the multimeter.
Any advice please?
Thanks
Paul