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Headlamp Switch - Relay Mod

No More Melted Column Switches

This little collection are just a few of the switches that have graced Bert's steering column in the last year.

A couple of them were brand new, a couple more were sourced from breakers.

Fact that the ones from broken Rangies also displayed signs of having melted kind of gives me the idea that this is a generic problem and not something to do with Bert's electrics alone.

It seems that the early Rangy switches are a bit weak, and it would seem that use of 60/55w halogen headlamps are enough to put them well into the stress zone.

So, this piece is a quick fix for that problem.

If you are suffering intermittent dip beam, or intermittent main beam or a loss of dip beam - chances are its one of the two head lamp switches stressing out on you.

Check the obvious like fuses, bulbs and earth's first though. But having eliminated them, read on.


So, starting point is that relaying the lamps is a way of reducing the current draw through the switches.

Normally you would only need to do this if you were upgrading the lighting arrangement quite markedly, but in the Rangies case, just 20W seems to be enough.

The basic principles of relays and relaying a lighting circuit are covered in the 'Workshop - General' section as:- Circuit Relay. So, in this section I am going to concentrate on what I did with Bert, rather than the alternative ways that it could be done. And the starting point is this:

Schematic on the right is a simplified version of the wiring diagram, we have to start with.

Power comes from the battery, through the two-position light switch, then through the dip-switch

This means that the light-switch sees all the power drawn by the side-lights, tail-lights and headlamps.

The dip-switch sees only the power drawn by the head-lamps, but that is the biggest current draw, and effectively double's on 'flash'

This is the circuit we are going to make.

Power for the side & tail lamps still goes through the two-position light switch, but we've cut the wires from the dip-switch and taken them to a pair of relay's, instead of the head-lamps.

Power to the head-lamps, we have taken from the original 'feed', but provided it to the relays, by-passing, the light switch and dip switch.

Four 15w side or tail lamps, will draw about 5A. A pair of 65w headlamps will draw about 10A, but on 'flash' they'll probably take over 20A.

A relay will draw probably less than  1/10A, so by using the relays to switch the power going to the head-lamps, we should see the 'peak' load on the column switched reduced by about 80%, and 'normal' load reduced by about 65%

That kind of reduction should mean that there is no where near enough power going to be going through them to cause the wires contacts or cases to get hot or arc or do anything else particularly nasty.

BUT, they way I have done it, I have placed the relays under the dash board and coupled them into the original wiring close to the switches. This means that all the power for the lamps is still coming from the one feed wire into the bottom light switch, and all of the power to the lamps is going out through the original wiring to the lamps themselves.

Right, so this mod can drastically reduce the current through the switches, which is the primary reason for doing the job this way. But, the current is still being passed through the stock wiring. In this case, the lights haven't been upgraded, and are running pretty well standard 60/55W bulbs, so the wiring shouldn't really be in question - it does seem to be that the switches were the weak link.

But, if higher wattage bulbs or additional accessory lamps are envisages, it might be better to think about relaying the circuits at the headlamp end of the wiring, so that the original lighting wires are only carrying the relay current, the power for the headlamps and any accessory lamps passing through new high current wires straight from the battery.

Advantage of relaying close to the switches are that it keeps it simple and obvious what has been done, and keeps the relays tucked up out of harms way under the dash board. Out in the elements, unsealed or shielded relays can suffer quite badly from corrosion and dirt, and cease to function after as little as eighteen months. Less still given a few off road excursions.

If you intend to locate relays under the bonnet, and or indulge in a bit of off-roading, I strongly recommend getting metal bodied relays rather than the cheaper plastic bodied ones most widely available from accessory shops, and I also recommend weather proofing them in a balloon or condom.

This may get explained in a later feature, on the various practices involved in preparing your Landy for wading and the like, but for now, basically get a kids party balloon or one of English Rubber's finest prophylactics. Connect up your relay, and smear the contacts in Vaseline, after you have attached the spade connectors. Do it liberally, so that the whole bottom plate of the relay is covered, and give the body a good smear too, just to act as a moisture barrier.

Now, take your kids party balloon, and carefully roll the end down the neck, then like a sock roll it back over the relay. Once you have worked the neck over the head of the relay, and the connectors, you should just have the wires poking out of the bit you normally blow into. Plug the end of the balloon with some more Vaseline, to get a seal and then use a cable tie to grip the neck against the wires and get a good seal. Your relay is now 'weather proofed' and should resist the worst effects of wind rain and water to destroy its workings. Right, so lets get on with it.

Step 1 - Removing the trim.

There are three covers that need to be removed, all are secures with self tapping screws. The first one to be removed is the lower column cowl under the steering wheel.

There are four screws holding it to the upper cowl, basically one at each corner. The screws are quite heavily recessed and screw up into the upper cowl. Its probably easiest to undo them if you push the seat right back and sit on the floor with your legs out of the door, so that you can see from underneath.

Once the screws have been removed, the cowl may 'drop' a little, but it wont easily come away from the column, as it is clipped around the ignition switch barrel and the bottom switches, the light switch and rear wind screen wiper control are both attached to a plate riveted to it. So just let it rest, while you take the other cowls off.

Top cowl is held to the steering column with a single self tapper centrally over the top. Remove that, and it should lift away. Note that this should be removed AFTER undoing the lower cowling. If you remove this one first, the upper and lower cowlings will wobble all over the place as a unit.

Next, you need to drop the lower panel from under the dash that covers the bottom of the steering column. There are about three or four self tappers in the lip of the dash, holding the upper edge up, either side of the steering column. You need the upper and lower cowls removed to get at a couple of these. Take note of the corner piece, where the cover is attached to the dash at the far edge, there is a small plastic insert and a long screw through the three pieces.

If you want to remove the cover completely, then you will need to undo the three large self tapping screws at the bottom edge by the pedal box, and disconnect the dash back light dimmer, but this is not absolutely necessary, you can leave the panel to just fold down. Right, with that lot off you should be able to see the switches

Step 2 - Examining What you Got

This shows the view through the steering wheel of the upper compound indicator, horn, dip and flash switch.

It isn't a particularly easy thing to get a decent 'photo of in situ, but you get the idea, there is a bunch of wires coming off it, and you can see the contacts.

Following pictures are of the switch as removed, but you should be able to see a lot of the features I'm going to point out without taking it off.

You may need to be a bit of a contortionist to do so, but I don't know, for all its only four screws to put it back on, it can be a bit of a pain.

So.... Pictures below of the detail. On the left is the top face of a 'good switch. On the right, and with the damage highlighted in the red circle, is the duff one.


I say good, because the contacts aren't melted or anything, and its in reasonable and useable shape. What is missing though is the self cancelling pawl that you can see on the duff one. The tang of plastic coming off the boss where the plastic has melted around the contact pin, highlighted in the red circle.

This is the 'problem', and what has happened is that the current going through the pin has been high enough that it has got a bit warm; hot enough in fact to melt the plastic around it.

This consequently gave an intermittent contact and eventually no contact on the dipped beam circuit, as the wire attached to the pin is held in place by the pressure of the pin against the plastic. Eventually, that wire, because it was loose and unsupported eventually broke away from the contact, rendering the switch inoperative.

Attempts to repair the switch were ultimately self defeating. The wire was soldered back onto the contact, only for the high current load to further melt the plastic and leave it loose again.

Switch shown right, is another switch, again with the same fault, but this time removed before the wire broke off. It is the blue wire with the red stripe that we are looking at, and the compound joint made with three thin copper plates all clamped by that contact through the plastic, highlighted in the red circle.

From the switches I have looked at, this seems to be the most common failure, though looking carefully I have seen signs of current stress on other similar contacts, though none often as bad. I imagine this is because this is the man contact for the dip beam lighting circuit, and is the one which carries most current, most often.

Moving down, the other switch that concerns us is the two-position switch for side lights and headlights. This is actually attached to a plate riveted to the lower steering column cowl, but is secured to that bracket with a single thin nut, and can be removed easily, as it has for this picture. Note that there are three wires off this switch.

The brown wire is the one subject to the highest current loading, and is usually the one that will fail. Mode of failure is that the PVC insulation around the wire will get warm and relax. This will result in the wire not being particularly well supported, as the mechanical connection for the terminal is made by crimping the copper contact around the insulation of the wire.

When the PVC relaxes then, all that is supporting the wire is the soldering of the electrical connection between the wires and the contact, and that is not that strong, and will eventually fail. Indication of a failure on this switch will tend to be that you will get no lights or intermittent lights on all circuits, ie: side lights, dipped beam and main.

Step 3 - Preparing the Compound Switch

Right, well having decided that the best way to stop the switches melting is to relay them, the first problem is that the reason for deciding to relay them is that they are already melted!

Now, the best starting place is to accept that you needed new switches to start with, get them, relay them and that's an end of it, replacements shouldn't melt.

But, chances are you'd probably prefer to try and salvage the old switches if you can, and given that you are seriously reducing the load they are going to be under, any degradation is probably NOT going to be all that significant.

Any way, switch you see in these pictures has been subject to quite a lot of salvage work to make it serviceable.

The switch body was cracked right the way through one of the indicator terminal pins. No longer married, I don't need to be diplomatic about it and offer other possible causes! Reason this switch, and numerous others, got cracked, was the wife's tendency to pull herself into the drivers seat by the steering wheel.... with a crook lock on it!

Any way, repair was effected by clamping the two fractured halves together and then welding the plastic with a soldering iron.

The plastic was then dressed and a piece of aluminium wrapped round and screwed to the switch body, before being shaped to fit the steering column.

The back of the switch was then filled with epoxy resin to build up the switch body between the strengthening webs and impart some strength back into the part.

The dip beam contact, was as other switches quite relaxed, and the plastic tangs that press the contacts to actuate the 'flash' circuits had melted quite badly.

To bring the whole thing back to a functional standard, plastic had to be removed, and shaped, and contacts cleaned and set, and the flash actuating tangs had to be cut off and rebuilt.

End result was a functional switch. Techniques I used will probably be covered in one of the Work-Shop Basics features when I get round to writing them.

So, having got a functional switch, the next job is to identify where the relays are to be cut into it. On the compound switch, we need to cut two wires. Blue with a white stripe, and blue with a red stripe.

Blue with red stripe is the dipped circuit, Blue with white is the Main Beam circuit.

Either way, it doesn't really matter - all you need to be sure of is that when you connect them to relay, you connect both halves of the same wire to the same relay.

For now though, identify the two wires in question, and make a cut in each, about half way between the switch and the connector block, maybe a bit closer towards the connector block than the switch.

Next the four ends can be stripped of insulation and terminated with a female spade connector. Personally I prefer soldered terminations, but crimp on ones will do.

Step 4 - Preparing the Two Way Switch

Next job is to prepare the Two Way Switch.

Brown wire is the main feed for the other circuits, so we need to splice into that before the switch to by pass current for the headlights through the relays.

Probably the easiest way of doing this is to use a couple of 'scotch-locks' - but don't even dream of it, they aren't reliable enough.

Cut the wire, and make a four way joint, with two other wires. Make sure that they have a high enough current rating though.

If you can, splicing and soldering is the best way to do this, but if you have to a screw clamp 'lego brick' connector would suffice.

Either way, remember to insulate the joint afterwards, & the free ends of the two wires need to have female spade connectors, just like the compound switch.


Step 5 - Making an Earth Lead

Small job, new wire, to make the earth termination on the switching side of the relays. How long and what type of termination you use really depends on where you find a decent earth point.

I found one up on the top right hand corner of the area under the dash, it was holding the cover on an electrical equipment box, I don't know what it is, probably the wind screen wiper delay, but it was already being used to earth part of the loom via a ring terminal - so seemed reasonable enough for my purposes. A note while we're looking at this picture, you can see the relay panel already there for the original equipment relays.

There are actually a couple of clips there to mount extra relays on, and depending on the model and year of your own, there may even be a couple of spare sockets in the relay panel you could use. This would make the job a lot tidier, but mean extending the wiring from the splices, and possibly introducing some connector blocks to allow the switches to be removed. Personally, I don't think its worth the effort, and leaving it 'loose' provided it is tidy keeps it simple and its clear to see what has been done.

So, find your earth point, and splice together a couple of wires to a suitable termination at that end and a pair of female spades at the other, long enough to stretch from the bond point to where the relays are going to sit, with a bit to spare.

Step 6 - Connect Relays to Compound Switch wires

To start with we need to identify the terminals on the relay, and decide which wires are going to be attached to which. Schematic, left, shows the 'pin out' for the relay. The 'switched' side is between pins 30 & 87. The switching side is between pins 85 & 86.

OK, so going to the switch, we have two wires that we have cut. One is blue and white. The other is blue and red. We need to connect the same colour coded wires to the same relay. This is the important bit. Right, let's get on with it.

Normally, the power would come in through the switch and out through these wires to the lamps.

So, the connector end goes to the lamps, the switch end comes from the switch.

So, if we take the blue and white wire first;

Connect the switch side wire to pin 86, the switching side of the relay.

Connect the connector side wire to pin 87, the switched side of the relay.

Likewise, with the other, blue and red wire.

Connect the switch side wire to pin 86, the switching side of the second relay.

Connect the connector side wire to pin 87, the switched side of the second relay.  

Step 7 - Connecting Power Feed & Earth

OK, well, we have used pins 86 & 87, which leaves pins 30 & 85.

30 is on the switched side of the relay, so you need to connect one of the brown wires spliced off the two position switch to pin 30 of each relay.

That leaves just pin 85 for you to connect the earth strap wires to.

Then the end of the earth strap to attach to the earth bonding point. And that should just about do it. Except it might be useful to give each spade connector a wrap of insulation tape to help prevent short circuits.

Step 8 - Putting all in and back together.

OK, well that should do it. All that's left is to put it back in the car. Should be the reverse of removal, but it can be a bit awkward. One tip is to start with the lower cowl and the lower switches.

If you can get these into position before you put the compound switch and wiper switch back on, it gives a bit more fiddle space getting the cowl over the ignition cowl.

The relays should lie reasonably comfortably in the wiring and on the lower cowl when you fit it back up.

If you want to be sure that they wont rattle or limit any damage from them being 'loose', it may be worth putting a wrap of foam held in place with insulation tape around them, but I didn't bother.

With a bit of luck, that should see an end to melted switches, and allow scope for maybe a headlamp wattage increase.


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