10 replies to this topic

[mayfair1988]

Hi everyone

First post so please bear with me if I have inadvertently got something wrong!

Having an issue with the sidelights and headlights on my 1988 mayfair. I can usually disgnose and fix electrical faults pretty competently but this one has me stumped (it's the first electrical gremlin on the car that I haven't managed to fix!)

The wiring loom is the four fusebox plus three inline fuse (under the scuttle) type, so main fusebox position four covers the sidelights, and one of the inline fuses covers the dim-dip system. Wiring is pretty much standard, no odd modifications to confuse things.

To run through the normal checklist items:

Sidelights: not working (on any ignition position)
Tail lights, number plate lights, dash illumination: not working (on any ignition position)
Headlights (dim-dip / dipped beam): not working (on any ignition position)
Headlights (main beam): not working (on any ignition position)
Rear fog light: not working (on any ignition position or headlight switch position)
Headlight flasher: working fine (dash light plus both headlamps)
All other electrics working fine (except hazards which are temporarily out of action thanks to a dead flasher unit, soon to be replaced with the newer electronic type)

So basically I can't get my sidelights ( + other associated lights on the same circuit), dipped beam or main beam lights to come on (except that the headlight flasher works fine). All lights had been working fine until very recently, then I had a couple of flickers on the lights whilst driving, now nothing.

I have had a good trawl of all the existing forums I can find and been through just about all the suggested fixes - see below with my comments:

Main fusebox: replaced recently so should be fine
Line fuses under scuttle: all removed recently and wired into new blade fusebox so no dodgy old line fuse carriers to mess things up
Headlamp bullets behind front grille: all replaced recently with brand new 4 way bullet connectors, and existing bullets all cleaned up.
Headlight switch (in dashboard): just replaced with brand new switch after the lights stopped working, the old switch had seen better days anyway.

I get a +12v reading on the supply wire into the lightswitch so that appears fine.
The earth from the headlamp units appears fine, as I understand the main beam flasher uses the same earth as everything else in the headlamps, and this is working ok
I have seen suggestions that this could be a faulty dim-dip relay, but if I understand the principle correctly, this doesn't even come into play except when using sidelights on ignition position two.

Does anybody have any pearls of wisdom for me? Many thanks in advance.

James.

[lrostoke]

Looking at the wiring diagram the dim/dip relay shouldn't affect the rear lights. Sounds like the switch

Brown wire in should be perminant 12v feed

red wire out is sidelights / number plate light this originally went to a fuse and changed to red/green for the rear lights / number plate light / sidelights...the red wire side also spurs off to the dim/dip relay.

Blue wire out of switch goes to dim/dip relay

[The Principal]

Mini wiring is usually dead simple but to help sometimes a little background to the issue helps - has this just happened out of the blue or has some work taken place on the car or has it always been like it since you purchased the car etc?

Of what you suggest it relates to perm batt feed and ignition supply so would help to have a bit more info

[mayfair1988]

Thanks for the quick responses guys.

Like I say, I get a +12v reading from the brown wire going into the light switch in the dash so that appears ok. And the switch itself should also be ok as it is brand new. I actually tried my old switch again, and another old one I had lying around, just to check the new switch wasn't bad. No joy. Have to admit I haven't yet tried just bridging the switch wires in the connector, but it seemed unlikely that I would have three completely dead switches including one brand new one.

The car had been off the road since the middle of 2001 until very recently. Just got MOT'd after a fairly extensive list of mechanical and bodywork issues were sorted. I had been working through all the minor electrical niggles before the MOT, all of which I had managed to trace and fix. All the front lights had been very intermittent but replacing all the bullet connectors behind the grille sorted that (these were replaced a few months ago).

So she has only been on the road for a couple of weeks post MOT, lights were all working fine until a few days ago when I got the flickering and then no headlights. Must have covered 500 miles or so after the MOT before this happened.

Hope this might shed some light! (no pun intended)

Edited by mayfair1988, 13 September 2012 - 01:33 PM.

[lrostoke]

Ok got power to the brown this should be live with ignition in any position including off.

Now check the red wire coming out of the switch, does it go live when the switch is on (both positions)

Trace that to the fuses find the red/greens are these live with switch on.

Check the brown wire stays live when you turn the switch on, sometimes bad connections can break down under load, and it maybe losing the feed

Edited by lrostoke, 13 September 2012 - 01:52 PM.

[Udo]

Id follow the wiring from where you know its right ie before the switch, check after the switch to make sure switch is working then work your way along the loom. ie if the switch works try the wires before the dim dip relay then after etc etc

[mayfair1988]

OK, here's tonight's update. Checked the voltage on the switch brown wire whilst turning the switch on, sure enough the voltage dropped right off with the switch set to either the sidelight or dipped beam position. So it seems the issue is somewhere in the switch feed. Time to start checking those connections on the circuit into the switch.

I don't think this is likely to be the connection at the starter motor itself, as I think the same feed goes to the hazards amongst other things, which are definitely still working (checked with another flasher unit, hazards working fine). And I reckon the load with all the hazards lit is probably more or less the same the the load with sidelights, tail lights etc, so I would expect the voltage dropoff to cause similar issues with the hazards.

Suggests something in the brown wire feed to the lightswitch, after the point at which the brown feed splits off to feed other circuits - or possibly the issue could be at the point where the split occurs?

I will update as and when I find the actual problem. Thanks again for the help guys.

[tiger99]

Check that the wires have not corroded or broken right at or even inside the crimped on lug at the solenoid end, and the spade at the switch end. It is a known problem on cars in general. The wires rarely break anywhere else.

It could be, of course, that someone in the past has used a cheap, nasty crimp tool, and you are now experiencing the inevitable result.

[mayfair1988]

Hi All

Well it's taken a while but I've managed to do some more diagnosis on the headlight problem. I had a good look at the wiring loom serving the headlight switch (on the basis that the issue seems to be related to the headlight switch feed wire) and I think I have tracked down the potential cause.

My loom has two brown wires connected to the started solenoid, one slightly heavier than the other. As fas as I can tell, the thicker one feeds into the ignition switch and on tol all 'position 1' / 'position 2' switched equipment, and the thinner one feeds all the permanent supply equipment.

What I found is that a former owner (I hesitate to add this was definitely not me!) has scotchlocked a new wire straight onto the thinner brown wire within about a foot of the connection from the solenoid, using a standard blue scotchlock (designed for a far smaller cable size). This seems to have made a real mess of the wire, with half the wire strands looking like they were captured by the scotchlock, and the other half pushed the the side, splitting the insulation in the process. Now I can't say 100% that this is the cause of the headlight issue, but it seems logical. And of course I need to fix this mess anyway.

It seems that with the connection being in the engine bay, and not sealed in any way, the wire conductor has started to fail.

So the question is, how should I go about fixing the wire? I guess I need to cut and rejoin the wire somehow.

I can solder and heatshrink small wire connections pretty well, but I know I don't have the equipment or the expertise to solder a wire of this size. Also as I understand it, soldered connections can be vulnerable where subjected to high levels of vibration, and of course this wire is directly connected to a big vibrating lump of metal!

I can crimp small connections too, and I have a proper ratchet action die crimper, but I'm pretty sure it won't crimp anything for this size of cable.

So any suggestions for fixing the wire would be very gratefully received!

Thanks

James.

[tiger99]

It seems that you will have to run in a new wire, but that is definitely not what is causing your headlight problems. It would take a complete break to do that, or more likely corrosion at a connection.

[mayfair1988]

So!  It may have taken a while to solve this one, during which time my lights have been working only when they felt like it!  They would occasionally work, but before too long would stop working again.

 

I repaired the main wire from the alternator, not quite as good a repair as I would have liked, but good enough to eliminate this as the source of the problem.

 

But here was the cause of my problem:

 

Checking over the fusebox the other day, I noticed one of the connections looked a little dodgy.  It was the 'rear' conection into terminal 3 (i.e supply terminal to the second fuse down from the top, the one for items operating indenpendently of the ignition switch); on the four fuse type boxes there are of course two connections at both ends of each fuse.  With this one being hidden behind the 'front' connection, it may have been dodgy for a while without being as noticeable as the front connection.

 

The black sheath around the terminal had melted and deformed; this initially got me worried about a short circuit somewhere, but looking at the actual connector, it had got quite badly corroded and part of it had broken off, so I suspect had just ended up overheating due to the reduced contact area with the spade terminal on the fusebox.

 

Anyway at first I didn't think this would have been linked to the issue with the lights, but it turned out the Haynes wiring diagram was sending me off course slightly.

 

The diagram shows a brown wire coming into this fuse, which splits off before the fuse to serve the line fuses for the fog light and dim-dip lighting, as well as the main feed into the lighting switch.

 

Clearly this is not the case, and the rear terminal is actually taking the supply back out from the fusebox and feeding the lighting switch (with the 'front' terminal being the actual feed into that fuse).  Obviously the terminals may not be the same way round on other cars.

 

For the record, the supply into that fuse was working fine, as circuits fed from it (such as the brake failure test switch) were working fine.

 

I had been thinking about whether there might have been some wire insulation rubbing on a sharp edge somewhere and shorting out the lighting supply wire, but in the end it came down down to that old troublemaker the corroded connection (just as tiger99 says above).  Just not a connection I initially thought was anything to do with the circuit in question.

 

Anyway hopfully that makes sense, and gives other confused Mini owners another area to check when their lights stop working!