Talk Morgan Forums Community The Malvern Arms roadster brake lights

i have lost my brake lights due to a fuse blowing. Replacement fuse has also blown.
Bulbs look OK.
Clearly a short somewhere.
Is the switch at the brake end of things susceptible to failure?
How do i test it?

Do you still have the in line pressure switch? There are two terminals...12v in and the other is out to the brake lights. The fault could be internal to the switch.

I'd first test that the 12v to the switch is Ok......using a test bulb. If the bulb lights....fine. If that blows the fuse, then the fault is upstream, but I doubt it will.

Then put the test bulb on the out terminal, with the brake lamp wire out of the way. If the bulb lights as a brake light, the fault is downstream towards the lights. If the test bulb blows the fuse, it's the switch.

If that checks out, I'd remove both brake light bulbs, and test the circuit. If it still blows then it could be either side and it gets harder to pin down unless you can trace where the brake lamp wires split to each side.

Just to add to DaveW's suggestions, the feed cable into brake light switch is green, the feed out following convention is green/purple. Disconnecting the latter and operating brakes with igntion on and fresh fuse will identify if switch is the culprit if it blows. If it doesn't there is a short downsteam of switch.

Holding fuse to light usually reveals blown one.

The inline switch is the usual culprit. If not then I would look at each light cluster

You could fit a relay to take the load off the switch:

http://www.gomog.com/allmorgan/brakelightswitch.html

Now so far we do not know if it really is the switch that is the problem, but if it is there is no need to fit a relay. One can simply solve the problem by fitting LEDs in all three stop lights. They draw so little current that there is not really any impact on the switch. There are LED bulbs that combine stop light/driving light and of course also stop light bulbs only. Just remeber to get red ones, not white. A white bulb behind a red glass renders a pink light. I have done this a few years ago, no more switch failures.

Definitely a better solution than adding the extra complexity of a relay on such an important safety feature.

Usually sold in pairs. So the combined ones go into the driving/stop light socket, the non-combined one into the cobra - the other into the rear fog light.

The in line switch is notorious for failing. The pedal switch is nuch more reliable and came in from about 2006.

I fitted a microswitch under my brake pedal ten years ago plus a relay and it's been reliable.

Thankyou chaps, i will have a play.