Morris Minor Owners Club

I've just bought another minor equipped with an amp meter. Every time I brake it sucks all the power from the battery and the amp meter reads -50 out of -60 when it should be just under 0. To make matters worse, I can't brake and indicate at the same time and if I use my full beam and brake, the next morning the battery is flat. Somewhere there must be a bad earth but I'm not sure exactly where it is, has anyone had a similar problem or does anyone know how to fix it? (Another negative point, the previous owner re-wired the car and has used different coloured wires rather than the standard ones i.e. some earths are purple)

Cheers

Obviously there is a dead short when you brake ! The mystery is - why does that not blow the fuse to the brake lights... Or - is the brake pedal perhaps rubbing on some wiring ?? You need to look into this urgently..... Do the brake lights actually come ON when you press the brake pedal?

Thanks for replying. I have just replaced the brake light switch terminal and the brake lights do come on but when they are on my indicator does absolutely nothing and and it really drains the power. If the brakes are rubbing on the wires, how would I go about sorting that out?

Did you replace the terminal because of the problem or did the problem appear after you renewed the terminal?

The brakes were originally working but were sucking power as they are now, they then stopped working as the terminal was on it's way out, I replaced the terminal thinking it'd solve everything and now I'm pretty much back to square one.

Try disconnecting the wires from the switch and try the brakes, does the ammeter drop as before? if no then there is a fault on that circuit. If the ammeter does drop then the problem is elsewhere (obviously) so a good search will be needed using a multi-meter to identify the offending wire. First have a god look round for any wires that might be rubbing against the body.

Cheers man. I'll try it tomorrow morning and see how it goes.

As BMC suggested check the obvious and make sure nothing is being trapped by the brake pedal as well.

Does it 'really' drain the power? Put the headlights on - engine not running - what does the ammeter read? Now try the brake lights - do the headlights go really dim - what does the ammeter read now ?

Just disconnected the wires from the terminal and when the brakes are applied the lights don't come on but the amp meter doesn't move. When the engine is off with the headlights on it reads -5, when the brakes are applied too it reads -50.

And the headlights do dim.

Ok - so there IS a bad 'short' somewhere down line from the brake switch....but I still don't understand why the fuse doesn't blow...are there any 'fuses' in the fuseholder - or have 'nails' been fitted??? You need to find the short - most likely a feed wire has been connected to earth by mistake - but it could be a wire chaffing on metal where it passes unprotected through a hole in the bodywork. There is no shortcut - you will need to follow the wiring all the way between switch and lights to find the fault.

Excellent, the most labour intensive scenario. There are fuses and one blew previously but the one in at the moment seems to be going alright.

Firstly if you're getting a short and the fuse isn't blown is the fuse of the correct value and secondly is the fuse box wired correctly? Take both fuses out and see if the fault is still there. Replace one fuse at a time and try to understand what works and what doesn't. If all looks as it should under the bonnet then go into the boot and disconnect the wiring from the rear light - where it joins the main chassis loom. Is the fault still there? If it is the the fault is in the chassis loom somewhere. If not then the fault is in the rear light wiring. Still doesn't explain the fuse not blowing though!

I'd be surprised if the brake pedal had caused the fault by rubbing a wire as there isn't any wires near it in the chassis leg. Does your clutch pedal move at all when you press the brake? The wiring to the rear of the car isn't ideally routed around the clutch linkage/pedal so you could have some 'chafing' there.

If the wiring has been "messed up", you might as well fit a new loom. In future years you will be glad you did

Very true. Wiring and its insulation has a finite life. Modern insulation can also be better with a longer lifespan.