14 replies to this topic

[lewisdw]

Help! I am trying to troubleshoot this on the side of the road. All of a sudden my headlights, parking lights, dash lights are not working. No fuse is blown (4 fuses). This is a lhd 1989 mini. I do NOT have power to the back of the light switch (3 wires, red, brown and unknown third color). Which fuse is for the lights? How does power get to the light switch? Is a relay involved/where?

[lewisdw]

I am assuming the fourth (bottom) fuse is the light fuse. It is not blown, but there is NO power on either side of the fuse. Does power come through the key switch? Any help is appreciated!

[lewisdw]

Where is the headlight (dim/dip) relay? I took out the instrument cluster and there is no relay behind it.

[AVV IT]

If you lift the air filter box off there should also be four or five in line fuses behind/above the carb. One of the 15 amp fuses protects the side, tail light and instrument pack illumination circuit, so check this.

EDIT: Depending on the age of the car it is often the fuse/circuit with the red/white wire. If the fuse is OK then check the connections on the fuse holder too, as those in line fuse holders are notorious for corroding and for the wires breaking away.

Edited by AVV IT, 13 November 2011 - 04:35 PM.

[lewisdw]

No inline fuses at all (that I can find). Still can not locate the headlight relay. It should definitely have one.

[AVV IT]

No inline fuses at all (that I can find).

Well they really should be there, unless a previous owner has re-located them somewhere else of course.

[lewisdw]

No inline fuses at all (that I can find).

Well they really should be there, unless a previous owner has re-located them somewhere else of course.

I agree, looking at the wiring diagram in the haynes.

Please help me understand the wiring diagram. I should have a lighting relay behind the instrument cluster (which I don't). I've looked everywhere for this relay. Also, there should be a resistor somewhere according to the wiring diagram. What is the purpose of the resistor? Is this to reduce the voltage for the low beams? Where would the resistor normally be located?

I have tried directly applying 12V to the red wire on the light switch. The instrument lights and park lights come on, but not the headlights, and turning the switch on/off doesn't matter.

If I trace the blue wire from the dim/dip control on the steering column, should that wire lead to the relay? If I can find the relay, I'm pretty sure I'll find the source of my problem.

Under the bonnet I have a relay that appears to go to the starter (has 4 wires, if I unplug the relay, the engine doesn't turn over), and the horn relay behind the grill. I have a small round metal relay under the dash with two wires, I believe this is the turn signal flasher. Finally, I have another round metal relay under the bonnet on the firewall with two wires, and I don't know the purpose of this one.

[KeithMiniThirty]

In my 89 the dim dip relay was located above the acelerator mounted to the bottom of the dash panel

[lewisdw]

Found the problem. First, I was looking at the wrong wiring diagram in the Haynes manual. I have a 1989 and was looking at the 88 diagram but my car is wired like a 84. I have no light relays. My light switch was melted inside and the brown wire was loose at the fuse panel. This is the second light switch I have had to replace. I am thinking of getting some generic relays and wire those in to take the load of the light switch and the dim/dip switch. Anyone done this?

[NZDraughty]

Just done this to my '75 Clubman while converting to H4 headlights, as you say generic relays are fine, I used two 30A SPST relays, one for high beam & one for low beam/dip mounted in the engine bay & spliced into the wiring loom BEFORE it splits off to each headlight. Power to the relay provided from a new feed from the solenoid with an inline fuse.

[lewisdw]

NZDraughty - I did mine last night, same way as you. I purchased 3 spst 30A relays, one each for the low beam, high beam, and the third I used for the dash/driving lights. The light switch used to get warm to the touch, it stays cold now, and my lights, especially the dash lights, are much brighter.

[L400RAS]

This is the second light switch I have had to replace. I am thinking of getting some generic relays and wire those in to take the load of the light switch and the dim/dip switch. Anyone done this?

Are you using halogen replacement headlights, or sealed beam? The halogens take a lot more current, and "max out " the headlight switch... Fitting relays like you suggest fixes this issue.

[Spherix]

Sorry to dig up an old topic, but I'm having the exact same problem, but the solution mentioned doesn't add up for me as the TS said there is no power to the back of the light switch, but then still mentioning the switch itself as the cause of this. At least one of the bare wires should then still have current on them, correct?

As for my situation, I have the loom/engine of an SPI Cooper, and I am not getting power to any of the wires on the back of the switch, nor any power on the "second" fuse (brown / purple) or the lowest fuse (red - red/green).

I do have headlamps when I pull the stalk towards me, as do I have indicators, hazards and brake lights. Just no sidelights / headlights and/or instrument lights. I just installed the loom, so have gone over all the wiring, replaced any faulty bits and upgraded the fusebox to a blade fuse type, so all is basically brand new.

Edit: I do have power on the aux cooling fan, according to the wiring diagrams, this should come from the same brown feed from the starter... So I'm puzzeled.

I've split up some of the fuses, so for me the main fusebox looks like:
1. White - Green (only has power in key position 2)
2. Brown - Purple (Never has power)
3. Brown - Purple (Always has power)
4. Green-white - 2x Green-orange (Power in 1 and 2)
5. Red - Red-Green (Never has power)

I'd be tempted to 'hotwire' 2&3 back together as it was, but technically each brown should have it's own live on it, hence I fused it separately as the gauge was quite hefty. Not being familiar with the SPi, do I have any relays that might be preventing any power being delivered to the switch and/or fusebox?

Edited by Spherix, 22 June 2021 - 09:16 PM.

[GraemeC]

He also said he found the brown wire loose at the fusebox, hence the lack of power.

 

Join the browns of 2 and 3 together - the terminal on the fusebox (was) acting as a junction for those two wires, one was providing power in and the other was taking it off as an unfused supply to the light switch.

 

How have you calculated the correct fuse sizes for your altered fusebox? Blade fuses are rated differently to glass fuses and then when splitting circuits how do you know what size each new circuit should be? I’d be cautious making the mods you have if you don’t fully understand the wiring as it could lead to (more) problems that will be difficult to understand and trace.

Edited by GraemeC, 23 June 2021 - 06:16 AM.

[Spherix]

So I then guess the confusion comes from the wiring diagrams for me. If you follow the green/red tracers I've added to this picture below, you can see that the brown at the back of the switch should have a permanent unfused live on it, with a splice/join earlier in the loom, not in a fusebox.

 

I've just unraveled half my loom again (sob..) and indeed noticed that it seems that the brown live on the light switch can only come from being joined together at the fuse box terminal. It seems really odd to me that they would've made that choice rather than splicing it as the wiring diagram shows though...

 

As for blade fuses, I usually go for half the amperage rating of what the glass ones were as I am aware of their different properties, a 35 amp glass fuse catering 2 circuits would get 2 10 amp blade fuses by my standard, and up it to 15 in case that blows quickly.

 

I think I'll either have to splice in the brown in to the loom to keep the circuits fused separately, or crimp the browns in the same terminal, for which the wires are a little too heavy gauge if you ask me. Manually /temporarily joining the two browns together on the back of the fusebox at least does give me full headlamps back!