Help with electrics

[Paultan]

My truck was trucking along nice, but now the dimmer switch fuse keeps blowing. Just happened out of the blue while I was driving.

I have recently added a compressor, which works fine, 12v power sockets, again working fine, and a cb radio, this is hooked up directly to the battery.

Am a novice when it comes to electrics so any help, direction would be gratefully acceptd.

Paul.

[Phil B]

Paul,

AFAIK the dimmer fuse only looks after the dimmer switch.
That means it can only be the dimmer switch itself shorting to earth (they are know to be unreliable after time)
To check for a short connect a 12v bulb in place of the fuse. If it lights then there is a short to earth in the switch
Phil.

[Paultan]

Paul,

AFAIK the dimmer fuse only looks after the dimmer switch.
That means it can only be the dimmer switch itself shorting to earth (they are know to be unreliable after time)
To check for a short connect a 12v bulb in place of the fuse. If it lights then there is a short to earth in the switch
Phil.

Thanks Phil. Looks like it's the switch. Next problem where can I get my hands on one, in NZ.

[Dervish]

The fault could be anywhere from the fuse to the instrument bulbs, it could be worn through insulation on the cables, a bullet plug that hasn't been pushed all the way in and so has some conductor showing, a bulb holder that has been deformed so the positive hits the negative - a thousand things really. It really pays to learn how to use a multimeter.

If you want to check it's not the dimmer switch, just pull the two cables out of the back of it and attach them together. The circuit will work just fine without it in there, you just won't be able to dim the lights (they'll be full brightness). The dimmer switches at ~25 years old are really more trouble than they're worth.

[BadCo.]

Bring it over if you want and we can have a crack at it, do your fuses at the same time, and figure out why my tail lights don't work when my headlights are on.

[Dervish]

Bring it over if you want and we can have a crack at it, do your fuses at the same time, and figure out why my tail lights don't work when my headlights are on.

Is it just your tail lights, or are the side lights at the front going out too? Uncommon to lose one without the other. If so, it's the little brass plate in the switch not balancing properly.

[BadCo.]

Is it just your tail lights, or are the side lights at the front going out too? Uncommon to lose one without the other. If so, it's the little brass plate in the switch not balancing properly.

Oh its also the side lights at the front, hadn't noticed. Aaaand the dash light goes out too when going from park lights to headlights.

So you reckon its this brass plate thing? Might have to take it apart and give it a clean out then, cheers for that Dervish!

[Dervish]

Oh its also the side lights at the front, hadn't noticed. Aaaand the dash light goes out too when going from park lights to headlights.

So you reckon its this brass plate thing? Might have to take it apart and give it a clean out then, cheers for that Dervish!

Yep, the dash light is on that same contact.

Ok, so inside the switch is a plastic plate with 6 copper studs through it. Power flows from two of the three studs at the rear to the studs at the front. At the headlights on position, the copper contact that connects the rear studs with the front has to balance on four studs and make contact with (at least) the right three of the four. A bad design, but so far so good. What happens though is that the bad contact with the studs makes them heat up so that the plastic plate melts and the contact recedes into it, making balancing on that contact and the other - non-melted or not as melted - contact impossible.

Have a look, you'll see what I mean. I fixed mine a few times by either bending the sprung loaded switch contact to match the stud profile or filing the studs so they were level.

Here's a photo from when I gave up and replaced mine with something else. Note the melted plastic plate with the copper studs sinking in.

https://www.aulro.com/afvb/

[BadCo.]

What did you replace yours with? If mine is buggered would I be better of incorporating the switches into a raptor dash pod or something similar?

[Dervish]

What did you replace yours with? If mine is buggered would I be better of incorporating the switches into a raptor dash pod or something similar?

https://www.aulro.com/afvb/

https://www.aulro.com/afvb/

https://www.aulro.com/afvb/

http://i940.photobucket.com/albums/ad246/OreganoM1/IMG_8303copy_zpsebf98ec0.jpg

https://www.aulro.com/afvb/

It's a Narva part no. 63216BL. The Land Rover switch is let down by a few things, mainly the fact that each switch position isn't sprung to latch into place quickly and reliably. The original switch can be left in a "half on" position -> high contact resistance -> heat -> melting -> dead switch. The crucial point though is that no matter what switch you use, it's lifetime will be shortened switching the full headlight current; the headlights need to be switched with relays. There are many threads on that subject in the Defender forum.

[BadCo.]

That looks pretty good, definitely will look at incorporating this when I install my headlight upgrade kit.

Thanks again Dervish