| Author | Message | ||
     Digby Squires Unregistered guest Posted From: host217-44-237-221.range217-44.btcentralplus.com |
I have a 1973 T1 (Ch No. SBH 15865) in very good condition, well maintained and, for what it is worth, relatively low mileage. However, it is presenting me with a rather wierd electrical problem. The front and rear sidelights and the brakelights have both stopped working. The side marker lights all light up OK, as do all other lights. I have tried using the parking light switch to illuminate the near- and offside sidelights and, using this switch, they do light up, so the bulbs have not blown. I have checked the fuses in the main fuse panel and they are fine. The only unusual thing I did on the night they went, a really filthy night with unbelievable rain, was to put on the rear window demister, but this could be a complete red herring. So, I was driving with no tail lights, no brake lights and no front side lights until some kind soul started to flash me, because there was no warning light illuminated for the brake lights. I am deeply ignorant about electrics so I am really making stabs in the dark, here. Could it be relays, Could the demister have done something? The brake lights went once before and a relay was changed by someone who used to look after the car (and who is not an electrician) but surely this should not affect the sidelights? There was no warning light that time either. Any advice will be very gratefully received! Digby Squires (Message approved by david_gore) | ||
| bob uk Unregistered guest Posted From: brig-cache-4.server.ntli.net |
Bulbs need a postive and negative to work and a switch to control them which is about as simple as an electrical circuit can get. Electricity follows logical rules which are not disimilar to maths. The battery is earthed via the negative terminal to the car body to save on negative wires. Black wires are earth wires. ( Lucas System ) The side lights are wired through the parking switch and a fault here could put them out. So using the wiring diagram in the technical section of this forum and a test light check the switch. Because the lights work when on park the wiring from the switch must be OK. The red wires are for side lights. Green/white tracer -indicators Green/red tracer -other side indicator. Green -stop lamps. White - ignition on live Brown -live all the time (Lucas system ) In the rat trap under the floor under the drivers seat is the stop lamp switch with the ignition turned on, one side of the switch should be live (+) and when the pedal is depressed both sides of the switch should be live. If the two wires are connected together the brake lights should alight. Your car having a manual master will also have a limit switch on the master cylinder which has nothing to do with the stop lamps. This switch is to the rear of car and the stop lamp switch is forward of the limit switch and works directly off the brake pedal and is adjust via a small cam. My friends T1 stop lamp switch actually fell of and was dangling in the rat trap on the wires needless to say the brake lamps were not working.Refitting of the switch fixed the stop lamps. The nuts and bolts were also lying in the rat trap. The stop switch should be adjusted so that the contacts close ( stop lamps on ) before the brakes work ------ cruise control best to be able drop the cruise control out on the brake pedal with out actually applying the brakes. If you have cruise control when the brake pedal is depressed the cruise control should disconnect and the car slow down under engine braking. If the car does this then the brake light switch must be working. This switch does live under the car and the rat trap is not entirely water proof. The switch is easy to strip down and clean and repair --- mine went about 10 years ago since repair it has given no more trouble. In the boot on the bulkhead is a relay which senses the amperage going through the brake light circuit if the amperage is less than it should be --- bulb(s) blown--- the relay alights a light on the dash. I think that there is another relay in the circuit because on my car when I use the brakes I hear a click. But that relay may be cruise control related. using the diagram in the technical section trace the two wires that come from the rear brake lights and the one wire that comes from the brake light switch ( the others work the the dash light and the relay ) join these three wires together ( a paper clip suitable bent will brigde the socket connectors ) and then depress the brake pedal and the brake lights should work. There is no relays for the side lights and they are direct to the main lighting switch. BUT do refer to the wiring diagram in case I am wrong. The rear demister is not connected to the brake or side lamps. However it does get its power from an ignition on source as does the brake lights. To hold the brake pedal down an old broom cutdown and jammed against the rim of the steering wheel saves your wife or mate from doing a very tedious and boring job. When working on live car electrics and always make sure that there is quick access to the battery ( I have a 500 amp isolator switch fited to my car.) It is worth disconnecting the battery and pushing the terminal back on and leaving it loose because a burn up in car wiring is expensive to repair and can actually write the car off. Another safety method is to disconnect the battery and reconnect using a short lenght of fuse wire-- in the advent of a mistake the fuse wire blows and protects the car wiring. ---15 to 30 amps should be enough to check these circuits. Engaging the starter motor will pop the wire. To make a test light solder wires to a 12 volt 5 watt side light bulb. There should be 2 in the tool kit on top of the battery. Also it is not uncommon after working on car electrics to find that the battery has loss its edge and have not got enough power to start the engine so have a battery charger handy. Also the ignition may be for and extended period which means the ignition coil if the points are closed will be sucking power from the battery --either disconnect one side of the coil or open the points and slip a piece of paper between them. It is possible to fry the ballast resistor other wise. (Message approved by david_gore) |
