LED conversion and hazard flasher

[David C]

I was sufficiently impressed with the new LEDs from Classic Car LEDs that I fitted to the 406 that I decided to do the 410 as well.

Changing the indicator bulbs to LED requires a new design of electronic flasher unit as the LEDs don't draw enough current to operate the old mechanical flasher. This is a straightforward swap just requiring the modern replacement to be earthed.

Less straightforward, however, is the hazard flasher. It has an unswitched power supply and works by switching the load. If replaced directly by an electronic unit this would permanently be switching. The answer is a current sensing circuit absent from any flasher unit I can find. I have, however, found what looks to be the solution. The RLHM module from Retronics. Not particularly cheap at about £50 but the simplest fix I could find.

[David C]

Update: I bought an RLHM module from Retronics for about £55. When fitted the Hazard lights worked well but the tell light was on permanently. Also, when I tried the indicators all lights came on together. When I finally heard back from Retronics they suggested I fit diodes to both outputs and move the tell light to one of the outputs before the diode.

Suitably unimpressed, I fitted a 12VFL flasher unit (about £12) identical to the one I have used for the indicators and fitted a pair of diodes in parallel to the output. All now working beautifully.

It's not completely plug and play. A few wires have to be moved around but it's not difficult. Anyone thinking of following suit is welcome to copy my homework.

[David C]

Further update - Retronics just got back to me and tell me that they have had an issue with recent PCBs which have now been sorted. They have also offered a full refund.

A bit of bench testing suggests that the Classic Car LEDs 12VFL module is cleverer than I thought and is current sensing. This means that my re-wiring may well have been unnecessary. It looks as though I could simply have swapped out the flasher unit and grounded the flying earth lead on the replacement. Live and learn...

[Sam410]

Thanks David, I may try this. I was very impressed with the LED stop/tail lamps I fitted last year but have put off doing the indicators so far as I was not ready to faff about with the flasher units too.

I was once told that if you leave incandescent bulbs in the small side indicator repeaters they should draw enough current to work with the old mechanical flashers, but I am unconvinced this is true.

My bigger worry is that if I have wipers, fans, lights, etc all on at once my indicators run very slowly indeed. Would an electronic flasher fix this, or would the voltage drop simply mean the LEDs don't work at all?

[David C]

I don't think the repeater lamps would draw enough current to work properly. Speed of flash will be dependent on current draw with the original units.

Changing the flasher units is very straightforward. The most difficult challenge is bending up a thin bit of metal to mount them.

I would suggest you start with the Hazard module and check my assumption is correct. If all well then replace indicator flasher. Once everything is working happily with new flasher units you can replace the bulbs.

The electronic flasher units should have the same interval regardless and I would fully expect them to fix your issue.

[David C]

A voltage drop sufficient to slow your indicators significantly is a little concerning and may point to high resistance in the ignition switch.
I suggest you switch on blower, wipers (wet screen), run engine so fuel pump is working and turn on radio. Then measure voltages of battery and switched ignition feed.

Current should be roughly 10 to 15 Amps.
Measure battery voltage and then voltage on either end of the upper fuse that has white wires one side and green the other. This is fed from the ignition switch.

Then work out power loss in wiring / switch.

If battery voltage is 13.5 and switched supply 12.5V, difference = 1V
For current of 15A, resistance is 1/15 = 0.06 Ohms.
Power is current squared times resistance. 225 x .06 = 13.5 Watts. Roughly the power of a small soldering iron. Although a voltage drop of a Volt doesn't sound much it can have a serious heating effect.

Any significant power loss would suggest you consider fitting a relay or contactor in the switched ignition feed. It can be simply done by removing the wire that feeds the switched fusebox and using that to operate the relay. The main contacts of the relay are then supplied direct rom the battery and fed back to the fuse box. Suitable relay Sterling Power R12120.