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MG MGB Technical - hazerd warning trouble

Hi

I was installing a hazard warning switch and flasher to my 68 gt over the weekend.

I connected the green/white, green/red and brown wires from under the steering wheel to the new switch (brown with a new inline fuse) but the darn thing didn't work.

I then ran the brown from the new inline switch to the brown direct from the fusebox and it worked (well sort of see below). Can anyone explain why running from the fusebox works but running from the brown under dash doesn't.

I say it sort of worked because only the drivers side indicators were flashing. passengers dead. (The passenger indicator works although i would say it is slightly slower blink than the drivers side - could this be a cause of the problem)

thanks
mike m

The first thing to be aware of is that hazards should be unnaffected by the problems that cause slow flashing of indicators. Basically if there is a lamp there it will flash, or two or three or four. This is because after an accident for eanmple there could be any number of the corners brokewn, and they may have to be left on for some time without the engine running.

Does your hazard switch interrupt the green 12v suppy to the indicator flasher unit when the hazards are on? It should. If it doesn't then it is possible to have the ignition and fuel pump powered even when the ignition is turned off, which after an accident could be very dangerous.

Do the hazards have an in-line fuse in the 12v supply to them? They should. If not it is again a safety hazard as if a corner has been damaged in an accident the wire could be shorted out and use of the hazards could cause a fire.

If the brown behind the dash didn't make the hazards work but the one on the fusebox did then either the brown behind the dash isn't a brown but some other colour, is a brown but is dead for some reason, or you didn't make a good connection. Likewise if the indicators work both sides, even if one is a bit slower than the other, but the hazards only flashed one side then either you didn't make a good connection to the green/white or green/red that side or the flasher unit is faulty. Use of a voltmeter will give you the answer to both these problems.

Finally be very careful working with the brown when the battery is connected, it is always live and unfused, shorting it to ground will damage the wiring, possibly set fire to the car. Before working on live circuits always disconnect the battery ground strap (not the 12v connection) first.
Paul Hunt

thanks paul

yes i have an inline fuse on the brown wire to the hazards.

i'm unsure of what you mean regarding interrupting the 12v green supply to the indicator flasher. I don't think it does. I have just connected it up to the green/white and green/red and brown wires behind the steering wheel.

how would i go about interupting the 12v supply to the indicators?
They don't work when the ignition is off but the hazard does.

mike m

If the hazard switch doesn't have a normally closed contact specifically for the 12v supply to the indicators (to break it when the hazards are on) then the only way to achieve it would be to use a relay, with a normally made or a changeover contact, operated by the hazard switch to do that job. The problem is that when the hazards are off, if the indicator switch should happen to be on for any reason, then power from the hazards will feed back through the indicator flasher on to the ignition circuits hence powering them, even though the ignition switch itself is off.

What hazard unit are you using? Any name or model numbers? You really should contact the manufacturers and ask them about this, it is very definitely a safety hazard. Strictly speaking if the powered ignition and fuel pump caused a fire, and could be proved to be due to the non-standard hazard system you fitted, your insurance company could deny liability, both for the damage to your own car as well as any other. That may be a small risk in practice, but personally I wouldn't take it.
Paul Hunt

its not a standard mgb switch. i bought the kit from a guy advertising in the MGOC magazine. The company is something solutions. They sell all sorts of aftermarket kits eg delayed windscreen wiper kits, anti theft devices etc

i looked at the wiring diagram in the haynes manual last night and it is wired differently to the switch i have.

My switch only has 4 connectors. one each for the green/white, green/red wires. the brown goes to one of the other two remaining connectors which are themselves connected together by a wire.

can't recall how the flasher unit is connected but i'm pretty sure the green wire doesn't come into it at all.
Think i'll have to pop to leacy mg and buy one of the pukka switches just to be safe!
mike m

Your Haynes should show and the car should have a green (12v fused ignition) on one side of the indicator flasher unit and a light-green/brown wire on the other going to the indicator switch. Interrupt the green at the indicator flasher. The switch is probably the most expensive bit. If you are buying that you could have bought the hazard flasher unit as well. I'd send the kit back and get your money back.
Paul Hunt

i have the same problem all my indicaters work but when you switch on the hazards only the passeneger sides flash is this switch or unit problem ?
Richard H

Switch, or possibly a wire (green/red if LHS doesn't work) fallen off the back. Flick it on and off a few times, might help. Generally they are used so infrequently the grease inside hardens and acts as an insulator instead of just a lubricant. BTDT, I dismantled mine in a poly bag (to catch all the bits) cleaned, regreased, and reassembled and it has been OK since.
Paul Hunt

what kind of connectors connect the wires to the back of a pukka hazard switch?
I bought a new one from leacy but when i got home the connectors are not spades but llok like bullets. I rang them up but they said they do not sell the connctors - they came already on the loom but as my car is a 68 there are no such connectors.

ps when you say interupt the green at the flasher will using a piggyback spade connector suffice for this job bearing in mind the fire hazerd etc mentioned. how best would you do this?

thanks
mike m

This thread was discussed between 17/01/2005 and 28/01/2005

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