Relay For Headlights And Dash Lights Failed

[jrjackso]

Driving my defender (1986 2.5 NA Diesel) last night and smoke pours out of the dash and headlights and dash lights go out. Everything else works, just headlights and dashlights out. Get home, pull the panel off where the hazard switch, rear window defrost switch, and overhead light switch are. There is a relay behind here. It looks like someone wired this up, definitely not factory. The power wire going to relay had melted all the insulation off and burned in two. Possibly the relay had gone bad and shorted it. Apparently this relay serves the purpose of only allowing the headlights and dashlights to be on if the ignition is on. My real question is if this vehicle came with a relay for this purpose or not. It doesn't appear to me like it should based on the wiring diagrams I have. Wondering if someone added it afterwards and if I should just remove it or try to replace it.

[Maverik]

Hello, My 90 is an 86 with original loom still installed. Certainly for UK spec'd vehicles of this era, neither the main beam, side lights or high beam had any relays full stop. all the lights where switched directly through the column light switches, not particularly safe. I have since relayed all my lights bar the side light circuit.

I had a loom "smoking" incident earlier this year, I'll pull out the thread in a minute. You'll find that the circuit you've spoken about has a severe weakness in that certain supply wiring specifically to the binnacle instrument lights does not have a fuse.... so if any of the elements gets a short it just burns up the whole section of loom...

Try this, there's a copy of the Haynes circuit diagram in there too... http://forums.lr4x4.com/index.php?showtopic=86895

[jrjackso]

Maverik,

Thanks for the input. That's what I thought looking around at the wiring job and also at the circuit diagram; i.e. there was no original relay. I was found it unsettling that the wire providing main power didn't have any protection on it at all. When I repair I will probably at the very least put a fuse link or something on it. I haven't pulled out the relay yet, but will give it a test. I figure it went bad and shorted the wire as it burned until it burned in two. Since I would like to know what cause the problem. It looks like I may have gotten lucky and only that wire really got affected since it ran by itself for a distance before going back into a bundle/harness. But a full inspection seems in order. A quick glance and all other wiring in the vincity seems ok. All other electrical functions as well.

Just to be clear when you say you have relayed all your lights I assume you mean that full power runs directly to the lights via a relay and the only power running thru the switch is used to energize the relay ? In my case someone had just put a relay in line of the power line going to the headlight switch and used an ignition-hot wire to energize the relay. So all they accomplished was to make sure lights couldn't be on unless the ignition was on, but full power still went thru the switch.

thanks

jeff

[Maverik]

Hi Jeff,

Yes I actually totally re-wired my front main/high beam light system power circuit I only use the original wiring/switches to provide the relay switch signal.

I took a fresh new battery source and wired it straight to a multi fuse box then wired the relays from that. I then tapped into the light switches at the column. I did it all so you can still use all standard LR switches etc in the genuine set-up. So the fuses for the original light circuit in the centre fusebox are now removed and redundant.

When I did the re-build I also converted my fusebox to blades fuses.

I had my truck totally stripped down and the original loom removed, which made life rather easy for me, but having said that with a bit of time and some planning, you could do it with it all together too.

I like to plan all my electrical mods properly, so I have a book of lots of drawings of the circuits, so I can properly plan them, get the correct materials, measure up, make the looms then install.