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I've made a mistake somewhere


Neil Clark

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Spitfire 4 Mk1.  Last weekend I fitted the new headlamp looms and they worked immediately.  Today I finished connecting the indicators and side lamps and they worked immediately.  I then switched on the headlamps as well but now they didn't light up.  So I switched on the ignition and heard a dull click - still no headlights.  However the dipped beam lamp on the dash comes on when the headlamp switch is on but no headlamps.  The fuses are both OK and the battery is healthy, the starter will engage willingly.  As far as my voltmeter tells me there is now no voltage at the headlight circuit where the loom joins the two headlamp looms behind the grille.  I had not fully insulated all the connections behind the grille so even though all the bullet connectors were firm, it's quite possible that something touched but what can have been blown or tripped please?  I've now checked again that they are made good but still no power where the headlight looms connect.

I can read the wiring diagram for colours etc but can't interpret all the symbols on the drawing.  Could I have tripped something?  What are the square black boxes etc on the wiring diagram between the headlights and the switch?  Thanks

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Firstly have you checked the fuse - always a good start. (although if it's the same circuit as the sidelights then that tells you already!) I think those only have two fuses? If both fuses are good and you didn't see smoke or smell burning it's unlikely that anything has melted.

If the sidelights work and I'll assume they're on the same circuit / same master switch as the headlamps then it's possibly the steering column selector switch that's failed, maybe just the bullet connectors aren't connecting properly or the terminals require cleaning. It's a fairly simple circuit so just work along it checking the components as you go. 

 

 

 

 

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The ignition does not affect the lights and I don't think that the headlights are fused only the sides. The blue main beam warning light is on the same circuit as the headlamps so if that is working the switches are working. does the pull toward you to flash the main beams work? as this does not go through the main light switch (but oddly has an inline fuse). The first click on the main switch should give just dash lights the second sides/dipped/main (lots of terminals to mix up on this switch). My suspicion would be a bad connection somewhere, if a headlamp wire had shorted there would be a lot of smoke (got that badge)

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37 minutes ago, DanMi said:

The first click on the main switch should give just dash lights the second sides/dipped/main (lots of terminals to mix up on this switch).

Actually that's the wrong way round. First click should give exterior lights, second adds the dashboard lights. I have seen cars with the wiring wrong on that but the original wiring is main lights first.

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The 3 position left hand column stalk positions on mine give dipped, main and headlight flash and judging by the blue light on the speedo that switch circuit is working.  The push pull knob on the dash gives sides and dash lights then second pull gives headlights.  

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9 hours ago, NonMember said:

Actually that's the wrong way round. First click should give exterior lights, second adds the dashboard lights. I have seen cars with the wiring wrong on that but the original wiring is main lights first.

you are indeed correct (brain failure). first pull should be exterior lights (side/dipped/main being controlled by the column) and then second dash lights as well

You seem to have the main switch wired incorrectly, though I can't talk as I have mine wired as a MK4 ie first click gives sidelights and second headlights with a later 2 position column switch but that did require adapting the wiring (I hated coming into a corner thinking I was on dipped pushing the stalk up only for the lights to go out as I was on main and switched to sides)

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3 hours ago, Neil Clark said:

he 3 position left hand column stalk positions on mine give dipped, main and headlight flash

That sounds odd. Unless your definition of "three position" isn't the normal one. I've come across people who think the later 2-position stalk has three positions because they include the pull-to-flash. On a Mk2 you should have three distinct resting positions in a vertical plane - bottom is dip, middle is main, top is sidelights only (a.k.a. nothing connected through the column switch). In addition, you can pull towards you for main beam flash, but this is a "momentary" contact and it will return once released.

As DanMi says, if you've got the later 2-position column switch (and don't want to change it) then you will need to re-arrange the master switch contacts to get side-and-dash on first pull, adding the column switch feed on the second.

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15 hours ago, Neil Clark said:

What are the square black boxes etc on the wiring diagram between the headlights and the switch?

Little black boxes on the wiring diag. are bullet connectors. A 'fat' recentangle is double connector (two in, two out all common) and skinny recentangle is a single bullet connector. BCs are, of course, very common failure point.

Having the correct interconnections between master light switch and column has been mentioned above. But perhaps worth highlighting that the column switch recieves +ve power in twofold manner: once via the master switch and once via a fused connection commoned off the back of the ignition switch unfused live (brown).

Maybe worth checking the condition of the column switch. Can become quite corroded internally and not infrequently the soldered connections on the back are either broken or hanging on by a gnats, giving variable behaviour.

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I've spent today identifying and undoing the PO's wiring shambles. There is an isolator wired in, an electronic fuel cut off device with a hidden switch, a DAB radio with more wires and speakers than a decent rock concert etc etc.  I think there is as much extraneous wire as the standard loom.   I have found that one of the 35 Amp fuses blew when I switched on the headlights the other day.  I've replaced the fuse and it doesn't blow now but still no headlights.  The column stalk seems to be doing the right things.  So I've loosened off the dashboard and ordered a new lighting push / pull switch.  The challenge now is to get the bakelite knob off the switch so that I can get the switch out.  The press tab can be pressed in but the knob won't move so I've sprayed some WD40 into the hole and will leave it and see what happens tomorrow.

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Well, I've changed for new both the main lightswitch and the headlight / horn relay and everything except the headlights works as with the old switch and relay.  Since the headlights worked before I connected the sidelights and then switched on the headlights, when immediately the 35A fuse on the bulkhead expired, I'm leaning to an earth problem caused by me removing the jungle of sound system wires the PO had installed.  The headlight blue main / flash light in the speedo has its own earth which may explain why that little light still works but the dipped, main nor flash headlights don't work.  It's one of those days when rebuilding cars in the drive has its own challenges as we are swinging from glorious sunshine to thunderstorms every 45 minutes.  I think it's my putting on my overalls that is prompting the rain to restart.

Because the PO's soundsytem and electric fuel supply isolator needed their own non-standard loom to be created and spliced into what looks like a pretty new standard loom, the wire colours in the wiring drawing no longer seem to apply!  And the connectors that were used are very cheap Halfords and plenty of metal shows in each.  They are all behind the main dash panel, pulled tight in places, join to other colours and if I separate them you know what, I won't know any of their purposes.  If I'm not careful I bet I would need a new front loom.

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2 minutes ago, Neil Clark said:

If I'm not careful I bet I would need a new front loom

That might be the easiest (and neatest) solution, but clearly not a cheap one.

I think you need to get the voltmeter out and see whether any power is getting to the headlights (using the chassis as the reference). If you've got them all fitted up and can't easily access the bulb connectors, you could check at the bullet connectors where the loom joins the bonnet.

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If it's possible (depending on whatever mods have been done to the car that you're intending to keep) then get a good wiring diagram, start at the beginning, identify and eliminate the original wiring - the original setup is very basic so easy to follow.

Anything left over from the factory fittings will then be the add-ons which you can keep / discard as required. Anything missing from the original connections, any adaptions or modified wiring colours should then be easy to spot. It's really not difficult, I can do it! It's just the same as when you buy a new loom; lay it out against the components and there should be two green wires here, and one brown here, and so on. That may help you identify the poor connection or the short that's blowing the fuses.

 

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Thank you both. The headlight circuit is dead at the front (ie at the bonnet) where it emerges and joins the bullet connectors for the individual headlight looms.   I'm wondering about running wires from the switch to those bullet connectors just to eliminate another variable.  If it's dry tomorrow I"ll get under the dash with flashlight and my voltmeter and see if I can find anything odd.

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something is not right if when you switch the headlamps on the fuse blows as the headlights are not fused, a short in the headlights normally releases the famous Lucas Loom Smoke I would check for power to the blue/white (main beam) and blue/red (dipped) from the column switch and check for power in the brown/red from the  main light switch which connects into the column switch(why?). Pay particular attention to the connections on the main light switch as there are many ways this can be wired, with some connectors unused. scan of wiring diag attached IMG_20220531_0001.pdfin case you don't have

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1 hour ago, Neil Clark said:

The headlight circuit is dead at the front (ie at the bonnet) where it emerges and joins the bullet connectors for the individual headlight looms.   I'm wondering about running wires from the switch to those bullet connectors just to eliminate another variable.

The original loom is pretty minimal in this part - there are those bullets at the bonnet, and the ones half way down the steering column that connect the switch. Between them is just a wire. Did you say the main beam work on flash, or was that someone else?

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The blue flash indicator light works but not the headlights themselves.  The push / pull switch connects to the column via a relay now.  The column switch seems to be working OK in that the blue main beam and flash light comes on and goes off correctly.

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11 minutes ago, Neil Clark said:

The push / pull switch connects to the column via a relay now.  

OK, that's completely pointless and I recommend you change it back. It's not where you want the relay if it's to be of any benefit (although you're not the first person I've seen do it). Let's get them working before thinking about how to do the relay right, though.

12 minutes ago, Neil Clark said:

The column switch seems to be working OK in that the blue main beam and flash light comes on and goes off correctly.

Yes, so that suggests the circuit up to that point is OK. Double check the bullet connectors on the column - where the column switch connects - and in particular the double one that forks the tell-tale in the speedo off from the main circuit. There should be four (according to the WSM) blue/white wires connected to it - three fairly fat and one thin. Two of the fat ones go up to the switch (although I'm not convinced about that - there may only be one on that side) while the last fat one and the thin one go into the loom. The thin one is the tell-tale, the last fat one is the one you want to test. It may just be loose or not fully home. Failing that, pull it out and connect it to battery +ve - if the lights don't come on then you have a loom problem, if they do it's got to be that bullet connector.

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A relay is an electronic switch. So it will have an input and ground for the ‘switch’ circuit, and an input and output for the load circuit. Provided things are sensibly wired, your physical switch on the column/dash will operate the ‘switch’ circuit of the relay. Eliminating the relay means connecting the dash switch directly to the output wire of the relay, and removing the other two connections. 

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Josef does that simply mean cutting it out and running a wire from the light switch to the column switch wire?  Doesn't it have any useful function?  I wonder therefore if it was there for the fuel pipe cut off system (which I have removed) which had a switch on the column.

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