Article description: by devilsadvocate
Date added: Aug 11 2008, 07:07 PM
Article starter: Joshua
Through necessity I have designed and fitted my own hazard warning system to three UC Toranas that are owned by members of my family.
I believe my design is roadworthy and non conflicting in operation with other electrical systems of the vehicle and should be of interest to any one who wants to update the safety of their pre 1980 vehicle(for the benefit of themselves and to those who may otherwise run into it!) The electronics are minimal – just the logistics of the switching is the main feature.
As you may be aware, hazard warning systems were only fitted, by law, to Australian cars after 1980. My own inspections have revealed that all cars with factory fitted systems carry independent reversing lamps(which incidentally don’t operate on trailers), unlike the combined rev/indicator lamps fitted to most Australian cars(and all trailers) pre 1980. Consequently a simple switch transfer is not possible from a post 1980 vehicle into a pre 1980 vehicle. I’m not sure whether there was a criterion that the reverse lamps still had to become separate at this stage, but think it was probably the case as I think GM would have tried to stay with only two rear lamps(cheaper) if they could have!
The main problems to overcome were:
- Front turn indicators should not function when reverse is engaged
- Rear indicator lamps should flash in hazard mode whether reverse is engaged or not.
- Use single/existing flasher unit
- Hazard mode not affected by position of turn indicator switch
- Hazard mode independent of position of ignition switch
- Instrument panel indicators should both flash when in hazard mode
- Minimal use of diodes
- Minimal breaks and reconnections of wiring.
- Allow hazard mode to operate on trailer
- Allow for increased current draw(x2) on flasher unit-the wiring in the Holden was only 7A here.
- No ‘feedback’ to ign or accessories circuits when in hazard mode
- No 12 V relays to be used
- Minimal amount of extra wiring
The only devices needed are:
The diodes would not be needed if a 20A five pole or greater switch was commercially available(this would cut down installation time significantly.
- 20A four pole double throw switch
- 2 x 6A diodes(protected in 3AG plastic fuse holders) +
- Connecting materials - 15 A wire, 7A wire - terminals, solder, heatshrink etc)
- Higher current flasher if existing flasher can not cope. Standard Holden flasher will work with four lamps but could struggle with more, ie if a trailer is connected.
The four pole switch proved quite difficult to track down(Jesec Switches – ST425 NF), and obtain in a 20A rating, cost $18 – the switch is a standard chrome lever toggle type which takes up minimal space on a dashboard, however, it is quite chunky at the connection end and at least 4x4x4cm of space is needed behind the mounting surface. It has male spade type connections .
P1, P2...P4 represent the centre terminals of the the double throw 4 pole switch.(4PDT is how it would be listed in an electronics part catalogue) There are 12 terminals in all on the switch, not all used as can be seen from the diagram. I drew the diagram using software that didnt have this switch as an option, so I used 2 x 2pole switches for the sake of the diagram. There is only one switch, but it changes 4 sets of contacts at once, hope that makes sense. I have also represented the flasher cone with a capacitor, ignore the rating in Farads, just used it as most cones these days rely on capacitor operation(I appreciate that the original gm/hella flasher is a completely electromechanical device)
The circuit is attached above – the wiring colours should be the same for all old Holdens – I haven’t checked out other makes.
Depending on the car(ease of getting to flasher connections etc) installation takes ~ 2 hours for someone that has done electrical work on their car before, but can be done in half the time once you’ve done it once!. Rather than trying to get into wiring looms under the dash it is quicker to identify the wires near their operating features , ie make connections to front indicators under bonnet and wires leading to and from rev selector. You only want to do this job once, so soldering all connections is recommended.
It has been pointed out that the earlier commodores shared the same indicator mechanism as the torries and all that was done to activate the hazards was to bridge the wires at this point, hence a button on the steering column was used. this is possibly an easy mod, but doesnt overcome the reversing lamp prob. I havent followed this aspect up 1st hand but it sounds believable.
Hazard Flasher Circuit, Diagram + Instructions