Headlight wiring on early (1968/70) Toyota Corolla cars

Submitted: Friday, May 15, 2009 at 20:53
ThreadID: 68872 Views:1845 Replies:2 FollowUps:1
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This was only relevent back in the 70's .
I was asked to connect driving lights to a station wagon, normal way via relays etc.etc.
I was having problems and after double checking found that the Toyota headlight switch was conncted to the earth side of the headlight !
Can anyone tell me why this circuit was used?
Thanks Ian
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Reply By: Eric Experience - Friday, May 15, 2009 at 21:09

Friday, May 15, 2009 at 21:09
Ian.
About that time vehicle designers were asked to make vehicles less likely to catch fire after an accident. One of the accidents in evolution of vehicle design was to not fuse the head lights in case the fuse blue at speed and left you in the dark. [Remember Lucas fuses?] As a result of this design if you switched the positive for the head lights on the steering column you had a heavy unfused wire impaled in the chest of the drive in an accident, so it was better to switch the negative so the lights would limit the current to the switch. Better ways of doing it like using relays are used on less crude vehicles. Eric
AnswerID: 365107

Follow Up By: Member - Ian F (WA) - Friday, May 15, 2009 at 21:24

Friday, May 15, 2009 at 21:24
Thanks Eric you just jogged my memory now as I recall the headlight switch did seem very light and not very robust.
Ian
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Reply By: Lex M (Brisbane) - Friday, May 15, 2009 at 21:27

Friday, May 15, 2009 at 21:27
Toyota haven't changed much. They usually have 12volt switched to the headlights common (via a relay and separate fuses left and right) and high/low beam switched on the earth side.
AnswerID: 365114

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