There are various ways of making the existing flasher unit operate all four indicators with the use of a relay(s) but with the use of a correct switch there is no need for additional relays.
This is my solution.
The original flasher unit operation relied on a bi-metal strip heating up and breaking/making a connection, the speed of this depended on the battery state, wiring connections, good earths, bulb condition, etc. Adding an additional two indicators and a warning lamp will change the speed again. The solution is to replace the old flasher unit with an electronic three pin flasher unit which will flash at a constant speed in all conditions.
Original 74MY switches are not readily available, I was lucky to find one for sale in Holland at ICCCR2016, it matches the existing dash switches and has four arrows on it depicting all four indicators. Other switches are available; the seven pin 2CV switch doesn’t look out of place and are available from ECAS or Burton, other ‘period’ switches also look good. Therefore I will be describing two options; the astonishingly simple DS option (4 pin) and the 2CV option (7pin)
The parts you will need;
• Hazard switch
• 3 pin electronic flasher unit
• Coloured wires (yellow, brown, green, red and black)
• Dash warning lamp and holder
• Spade connectors and insulators
First and foremost DISCONECT THE BATTERY you don’t want any sparks, burnt fingers or melted wiring. Don’t say I didn’t warn you.
You will need access to the flasher unit and indicator switch by removing the dash binnacle. Replace the flasher unit as per wiring diagram and using a black wire add an additional earth to pin 31.
Next you will need to fit your hazard switch, where you fit this is up to you. The original one fitted in the metal part of the dash next to the choke cable (carb.model), if you don’t fancy cutting the metal part of the dash use the plastic facia panel that houses the other switches; I think that’s close enough. The aperture required is 30mm. x 20mm.
How the switch works. (DS option) This has one feed in from the flasher unit and three feeds out to LH indicator, RH indicator and warning lamp. Told you it was simple.
(2CV option) The switch is basically two sets of contacts joined by the action of the push button. Set 1, this redirects the ignition live to a permanent live so you can use the hazards without the ignition being switched on. Set 2, this has one feed in from the flasher unit and three feeds out to LH indicator, RH indicator and warning lamp as per the DS option. The good thing about this layout is (a) your hazard lights will operate with the ignition off and (b) you won’t leave your indicators flashing all night by mistake.
Wiring the hazard switch depends on your switch, unless you have the switch diagram you will have to use a meter to establish which contact does what. If you only have a six pin switch you will have to use a four pin flasher unit for the warning lamp (I will come back to this later)
Either way the principle is the same,
2CV option; (Set 1) the original yellow wire from F3 goes to the normally closed (NC) contact and the common contact now goes to pin 49 of the new flasher unit. This will allow normal operation of the direction indicators with the ignition on and a new permanent feed from F5 which supplies the normally open (NO) feed for the hazard lights, you can alternatively us a feed from the +ve accessory post. Next (Set 2) supply the common (NO) contacts with a red wire which connects to either the red wire on the indicator switch or pin 49a on the new flasher unit whichever is the easiest, this will feed all four indicators and the dash warning lamp when activated. The (NO) contacts feed the indicators via a new green and yellow wire which are spliced into the existing wiring from the indicator switch. Finally the last feed is for the dash warning lamp.
DS option; as per Set2 on the 2CV option.
On the white plug that connects onto the dash binnacle there is a spare connection in the middle row this supplies the feed to the hazard warning lamp, connect a black wire to this from the switch and fit a new lamp holder at the very lower blank space in the binnacle (Hold it up to the light and you will see a red lens with the four arrows on it) The earth for the warning lamp is already in place. Reconnect the battery, rebuild your dash binnacle and test your new hazard lights.
If you only have a six pin switch you will have to use a four pin flasher unit for the warning lamp, the last feed for the warning lamp comes from the fourth pin on the flasher unit (marked C)
Last thing, you will be drawing extra load on the indicator circuit with the hazards lights switched on, so if you find yourself blowing a fuse just up the rating by 4 Amps for the additional 2x21W and 4W bulbs.
Wiring diagrams can be found here, feel free to download.
|Front of original DS hazard switch|
|Rear of switch|
|Rear of switch showing colour coding for wiring|
(courtesy of Burton)
(courtesy of ECAS)
|3 pin electronic flasher relay|
(courtesy of vehicle wiring products)
|4 pin electronic flasher relay showing pin C for warning lamp|
(courtesy of vehicle wiring products)
|This is the section of the metal part of the dashboard where the hazard switch should fit|
|Here we have an alternative position with the easier to cut plastic facia panel|
|At the rear of the warning lamp lens cluster showing the hazard lamp position|
(courtesy of aussiefrogs)