JimAttrill Posted December 23, 2013 Share Posted December 23, 2013 My headlights - dipped and main - occasionally would not switch on at all. I did the normal thing and changed the switch. All seemed fine for a couple of weeks (mainly driving during daylight) until last night when the lights would not come on again. I don't think it can be a fuse as the lights are separately fused (4 fuses). Any ideas where the fault lies? BTW the sidelights work with the switch ok. Quote Link to comment Share on other sites More sharing options...
Tanuki Posted December 23, 2013 Share Posted December 23, 2013 Which switch have you replaced? Both the off-side-headlamp and the main/dip switches are marginal for the currents they are expected to carry and do tend to fail. The usual one to go is the off-side-headlamp switch: the spring-loaded brass "saddle" that the lever moves makes poor contact with the three contact-studs, gets hot, melts the plastic... also the three contact-studs are riveted to metal tags that take the three wires - these rivet-to-tag connections make poor contact so get hot... and the stud then sinks into the plastic to a point where the moving 'saddle' will not make contact. The answer I've adopted is a normal 30A relay used to take the load off the 'headlamp' part of this switch. It can easily be concealed in the plastic shroud round the switchgear. The other possible failure mode ios with the main/dip switch. Again, the contacts melt. Third consideration is that - on a UK-spec TD5 at least - there's an ignition-controlled relay in the headlamp circuit which only allows power to the headlamps when the ignition is on and you're not actually cranking the engine. If this relay fails you get no headlamps. Fourthly - the "headlamp flash" circuit on the stalk is powered separately - you can at least check that your headlamps are OK [fuses/bulbs intact, earth connections good] by trying to flash the headlamps since this provides headlamp-power independent of the relay and the off-side-headlamp switch circuit. Quote Link to comment Share on other sites More sharing options...
JimAttrill Posted December 23, 2013 Author Share Posted December 23, 2013 I know about the contacts melting as I changed many burnt-out switches on other people's Defenders. I have fitted relays to the dip beam to avoid this. It was done quite a few years ago. I think the answer is the ignition-switch controlled relay. Is it one of those yellow things in the fusebox? It could be the main/dip switch. The headlamp flashers do not work either - is this a good clue? Quote Link to comment Share on other sites More sharing options...
pete3000 Posted December 23, 2013 Share Posted December 23, 2013 sounds like the stalk switch common has failed, i.e not sending the flash to the high beam or sending the same to the relay in the other position for prolonged operation. Could you link it out to prove it? i.e push 12v at the main beam relay Quote Link to comment Share on other sites More sharing options...
Tanuki Posted December 23, 2013 Share Posted December 23, 2013 I think the answer is the ignition-switch controlled relay. Is it one of those yellow things in the fusebox? Yes the relays are in the central fuse-box. [There were 4 on my TD5 until I removed the "electric windows" one and replaced it with a jumper so the E/W are now usable even without the ignition being on] There should be a decal on the inside of the big plastic cover that tells you which one is the headlamp relay. You can swap the yellow relays round to 'test by substitution'. When you pull the relays out, look at the contact pins for any signs of melting or "blueing" that might hint at nasty things going on inside. Quote Link to comment Share on other sites More sharing options...
JimAttrill Posted December 23, 2013 Author Share Posted December 23, 2013 There is no decal, but the two yellow relays are identical - at least the numbers for the connections are the same. Tried swapping them around to no effect. No signs of burning. BTW when I switch on the headlamps the indicator green light comes on. When I flash the headlights or go onto main beam the blue light comes on and I can hear a relay clicking. Quote Link to comment Share on other sites More sharing options...
Tanuki Posted December 23, 2013 Share Posted December 23, 2013 There is no decal, but the two yellow relays are identical - at least the numbers for the connections are the same. Tried swapping them around to no effect. No signs of burning. BTW when I switch on the headlamps the indicator green light comes on. When I flash the headlights or go onto main beam the blue light comes on and I can hear a relay clicking. That sounds more like you have an earthing problem - or something horribly melted/shorting in the main/dip/indicator-switch area! Quote Link to comment Share on other sites More sharing options...
Plukje Posted May 23, 2020 Share Posted May 23, 2020 Dear Jim I have the same problem at the moment. Did you find the problem? Or a solution? Kind regards, Ward Quote Link to comment Share on other sites More sharing options...
Snagger Posted May 24, 2020 Share Posted May 24, 2020 Jim, you said you fitted a relay to the dip circuit, but did you also add one for main beam? If so, check the outputs of the trigger wires to the relay control pin, which I presume is the original wiring that used to run all the way to the lamps. If the relay is getting the signal to operate as you make the switch selections, then you know it’s not the switch gear or relays in the vehicle fuse box. Check the relays you added are getting power from the battery - it could be a bad connection or blown fuse(s). If the relays have power and are being triggered correctly, check their output terminal voltages as you operate the switches to verify the relays are working. Then check the voltages on the connections of the H4 bulb socket; if you have good voltages there, then an earthing fault between those connector blocks and the vehicle body are the likely cause. Be aware that checking voltage with a multimeter to find where the circuit breaks can be misleading. A bad contact, because of corrosion, dirt or a broken wire with just a few strands remaining, can allow the voltage to look normal because their is no current, but the current demanded by the appliance can outstrip that available in a faulty circuit and drop the voltage. I had that happen chasing a failed horn - the colts looked good everywhere when I had the horn disconnected from its wire, all the way to the end of that wire, and when I ran a tempest wire directly to the horn it sounded, but when I reconnected the original wire, it still didn’t work and the voltage dropped off - it transpired to be that grey corrosion of the contacts in the fuse box. Quote Link to comment Share on other sites More sharing options...
rusty_wingnut Posted January 7, 2022 Share Posted January 7, 2022 (edited) Seems I am suffering this problem at the moment. It all started with a buzzing on the pink dip/dim relay, and no lights apart from side lamps and high beam. So I replaced the pink relay thinking it was at fault, but the new unit buzzes once the lights are switched on. I replaced the small light switch back in the summer, and the new unit was a genuine unit. I have pulled the cover off and contacts look fine on this swithc, no burning or sunken connectors. When I remove the pink relay and jump the connectors to remove the dip/dim function the lights work. Before I order a new indicator stalk is there a basic check I can do to confirm the stalk is at fault? Edited January 7, 2022 by rusty_wingnut Quote Link to comment Share on other sites More sharing options...
Arjan Posted January 7, 2022 Share Posted January 7, 2022 Check your earth. 1 Quote Link to comment Share on other sites More sharing options...
Snagger Posted January 7, 2022 Share Posted January 7, 2022 Yep, sounds like the relay Earth. Quote Link to comment Share on other sites More sharing options...
rusty_wingnut Posted January 7, 2022 Share Posted January 7, 2022 Checked earth by running wire from earth terminal to a good earth. The pink relay only buzzes when taking the headlight switch from side to headlights. Quote Link to comment Share on other sites More sharing options...
Snagger Posted January 9, 2022 Share Posted January 9, 2022 Have you checked the voltage on the relay control circuit input with the lights on? You may be getting a voltage drop from faulty wiring or a bad switch somewhere, so the relay control side isn’t getting enough energy to stay open. Quote Link to comment Share on other sites More sharing options...
western Posted January 9, 2022 Share Posted January 9, 2022 Remove the dim dip relay & in its socket join the 2 blue/red trace wires with a jumprr lead that should restore normal operation. Quote Link to comment Share on other sites More sharing options...
rusty_wingnut Posted January 12, 2022 Share Posted January 12, 2022 New stalk didn't improve matters either, so rather bemused I started to remove wiring and circuit test. I tested the bulkhead side earth (even though I had bridged this already) Shamefully I'll admit that in all the wobbling, and checking of the pink relay the buzzing stopped! Possibly a dirty connector down stream, or a broken wire. But for now it is working again. I will investigate further as and when. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted January 12, 2022 Share Posted January 12, 2022 54 minutes ago, rusty_wingnut said: will investigate further as and when. When at the side of the road, dark, cold, sleeting, and you are 200 miles from home? Sounds like a plan 👍 Quote Link to comment Share on other sites More sharing options...
rusty_wingnut Posted January 12, 2022 Share Posted January 12, 2022 When it stops raining 1 Quote Link to comment Share on other sites More sharing options...
Mo Murphy Posted January 12, 2022 Share Posted January 12, 2022 3 hours ago, Bowie69 said: When at the side of the road, dark, cold, sleeting, and you are 200 miles from home? Sounds like a plan 👍 No, that's usually me 🤣 Mo 1 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.