R75/6 LED turn signals. Dash light won’t flash

[Jmix1981]

Hello. I am a new member and new to BMW bikes. I have owned several english bikes and restored a few old Triumphs so motorcycles are not new to me and I have some mechanical skills.

I am in the process of converting this 1976 R75/6 over to LED bulbs and i have run into an issue which i have not been able to resolve by searching online.

I have installed 4 new LED turn signal bulbs from Euro Moto Electrics along with the new LED compatible relay. With the new LED bulbs and relay, the turn signals flash fine but the turn signal dash/dummy light is constantly illuminated. Prior to switching out my incandescent bulbs for LEDs I did not have this issue. What may be more telling is that if I put incandescent bulbs back in with the new LED relay, the turn signals flash as indented as does the dash/dummy light.

Right now I have an incandescent dash light in but I do have LED which I have tried and it does not make a difference…. The dash light for turn signals is always illuminated.

If I take the black wire with a white stripe and piggyback it off the green wire with yellow stripe, the turn signals flash as intended as does the dash light but when I switch the turn signals off, the dash light continues to flash.

I don’t believe it’s the relay as I have now tried two, 4 pronged LED relays with the same results.

I have also tried only having bulbs in the left side and then only the right side and then only in the rear position and the only in the front position…. No of these scenarios change the issue that the turn signals flash dash/dummy light will not flash with the relay hooked up correctly.

Brown = ground
Green with yellow stripe =49A on old relay to49A of the turn signal switch
Green with black stripe = 49 on the old relay to 15 on the circuit board. I believe this is the positive lead
Black with white stripe = KBL to the dash turn signal warning light.

On the new 4 pronged relay (EP29 model) I put the brown wire to the ground terminal, green with black stripe to the positive terminal, green with yellow stripe to the lamp terminal and the black with white stripe to the sense terminal.

Any help or suggestions would be massively appreciated.

Thank you,

Jordan

[Jmix1981]

Relay and wiring diagram

[Jmix1981]

More wiring diagram

[Jmix1981]

Last part of wiring diagram

[Rob Frankham]

Was the relay specifcally sold as suitable for a BMW Rxx/6 model? The flasher circuit is unusual and different to that on most contemporary vehicles including late (post 80) models of the airhead.

I'm wondering (based on the packaging) whether this relay is intended for use on a vehicle with a trailer indicator repeater, in which case it is unlikely to work in the airhead application. Might be worth talking to the seller or the manufacturer.

Looking at the symptoms you describe, it looks as though the bike circuits are working so there's a good probability that the relay is incompatible.

Rob

[gspd]

Do you want a cheap and easy fix to circumvent the problem?
Power the dash indicator bulb directly from the flasher hot leads. You’ll need two 1W diodes so the left side doesn’t power the right side and vice-versa. This minor surgery can easily be done from inside the headlight. You can get the diodes at any electronics store for a few cents each.
WARNING: This is not BMW (or anybody else) approved but will work perfectly and permanently.

What say you Rob F ?

[Jmix1981]

Thank you both for the reply. Rob, i think you are right, the relay is for LEDs and has a 4 prong set up but the 4th prong is labeled “sense” which I thought was for the dash warning light but it appears to be a “bulb out” sensing feature.

GSPD - I like this solution. In experimenting last night, I used jumpers from the hot leads of the front turn signals to the wire for the dash light. With only the left or right jumper hooked up, the turn signals and dash light flashed correctly but with both jumpers hooked up, I had hazards, not turn signals.

I will order some 1W diodes today. Does it matter what voltage I get? I see there are a lot of options.

[gspd]

Thank you both for the reply. Rob, i think you are right, the relay is for LEDs and has a 4 prong set up but the 4th prong is labeled “sense” which I thought was for the dash warning light but it appears to be a “bulb out” sensing feature.

I haven't seen a conversion to LED turn signal bulbs that allows the 'flash too fast' function to warn of a burnt bulb.
Most factory LED systems still have that feature.

... but with both jumpers hooked up, I had hazards, not turn signals.

Another cheap and easy hack. A small toggle switch between the left and right will give you hazard (4-way) lights when activating either turn signal.

I will order some 1W diodes today. Does it matter what voltage I get? I see there are a lot of options.

I think they sell them by wattage ? It's only powering a led indicator so 1w is OK.
Maybe Rob F can suggest more precise specifications.

[Rob Frankham]

Rectifier Diodes are rated are rated by voltage and current. The voltage is the reverse voltage that the diode will take before it fails i.e. the blocking voltage), the current is the maximum current the diode will carry in the forward direction. They aren't rated in watts and you can't infer a wattage by multiplying amps by volts since the two ratings refer to different conditions.

The 'diode' solution is perfectly viable and has been done many times both with LEDs and incandescent bulbs. In this case, the fourth terminal on the relay is redundant and should be left disconnected (but insulated).

The diodes are polarity conscious and must be included into the circuit in the right direction. The simplest solution is to place the diodes together with the white bands facing in the same direction and connect the wires from the banded ends together. Connect wires, to each of the non-banded ends a third to the connected wires from the banded ends. Insulate the resultant circuit making sure that none of the wires can short to each other. Connect the 'non- banded wires, one each of the left and right indicaor circuits and the third to the repeater. All of these connections can be made at the connection board in the headlamp shell. The diode 'assembly' is small enough and light enough to be tucked in among the wiring there.

I would recommend a diode with a forward current of 1 amp and a reverse voltage of 100 volts. The voltage may seem excessive but it's a safety factor to allow for voltage pulses on the 12 volt line. It's no bigger or more expenxive so there isn't a downside. The industry standard is probably a 1N4002. Google will recognise this numberand give you any number of suppliers... you'll probably find yourself buying ten for less than a single one. I'm seing prices for around 30 pence (say 50 cents) for ten... you can probably get cheaper than that if you look.

Rob