BJ8 Phase II conversion to LED turn signals

I ordered 4 superbright amber LED's and the flasher unit FL-3 for my turn signals. I tested first with just the flasher unit installed and kept the incandescent bulbs in place. It worked perfectly.

I replaced the 2 front turn lights with LED's, everything worked correctly. Each side flashed and interior indicators worked correctly.

Then I added the 2 rear LED's. All four exterior turn signals flashed at the same time and the indicator lights on the dash did not blink. I removed the rear LED's (no bulbs) and front's worked okay.

I now have FL-3 flasher unit with LED's in front and incandescent bulbs in the rear. That works as it is supposed to work.

Has anyone else seen this problem or do I need to start tracing out the wiring. I have not added load resistors as I thought I did not need them with the FL-3 flasher. I am wondering how I am getting enough voltage to the opposite side lamps of the car when I have all 4 LED's and it only works correctly with a mixture of the two types. I have not tried all possible combinations. I will give that a go next.

I realize there is a lot less current with the LED"s but thought the flasher unit would handle that. The wiring diagram for these cars is about as bad as it gets. I had major restoration done about 12 years ago and electricals have worked okay to date so I am not sure there is a wiring error. Although that is always possible. It is the original wiring harness. Modifications to negative ground and alternator added at restoration.

Goldie said:

... The wiring diagram for these cars is about as bad as it gets. I had major restoration done about 12 years ago and electricals have worked okay to date so I am not sure there is a wiring error. Although that is always possible. It is the original wiring harness. Modifications to negative ground and alternator added at restoration.

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What seems to be the problem? I have installed new harnesses in a BN2 and BJ8 and found the wiring diagrams in the shop manuals to be 100% accurate and easy to read (except for being too small for my old eyes). The only problem I had was with a harness wire that was incorrectly color-coded.

I don't know what an FL-3 flasher is, but the original flashers require a specific current draw in order to function properly (that's why the blinking is faster if one of the bulbs is burnt out). I would think the only way add-on resistors would help is if they were shunted to ground--and not inline--as your problem sounds like too little current draw instead of not enough.

Yes some LED's allow a small bit of feedback and cause this. I have had to solder inline a diode to prevent the feedback. I did this on a Chevelle we converted to all LED's. The problem was in the front bulbs, which were a 1157 equivalent, not with the rear lights which actually had a Chevelle specific circuit board light assembly, which I assume had diodes installed to prevent this as well.

Also the FL-3 flasher is rated for LED's so that is not your problem.

The circuit schematic is accurate but difficult to follow. The flasher unit is specifically for LED's and will also work with incandescents. I am trying to figure out how I am getting enough voltage feedback through the other side of the turn signal circuits so that all of them flash

I I wonder if the LED bulb is not 100% compatible with the socket in the brake light. Possibly the bulb is not completely seating where the two contacts of the bulb are contacting both contacts of the socket at the same time. That could give you that hazard light effect.

Goldie, it is likely that the crossover between left and right is occurring at the dash indicators. They are joined together through the wire that runs to the "P" terminal of the flasher. The very low current necessary to operate the LED bulbs can pass through without causing the bulbs to light up. To test, either remove the indicator bulbs or disconnect the appropriate wires that feed those bulbs.
Did you install the ballasts that Moss states are required in all big Healeys?

I had same problem with my 67 BJ8. Install one RL-650 load resister to each side of the tail lights and problem will be solved. Itms from Superbright and was $4.95 ea at the time.

my LED at the rear work fine but the dash lights both blink when the turn signals are on. That works for me since they are just reminders that one is on. I also used an electronic flasher unit. Seems to work but occasionally, the rear brake lights blink. Still, brighter than before.

To stop both dash indicators from flashing at the same time, disconnect the Light Green/Purple wire from the flasher P terminal and connect it to ground.
This will work for the original bulbs, but I don't know if it works with LEDs. I think it should. The turn signals work normally, except that the indicators do not flash together.

I will add the resistors. I have been looking at the schematics and noticed that the flasher lamps have a common connection but I do not know the actual circuit inside the flasher unit. The original used a bimetalic strip which is heat sensitive and needed heat effect to open and close. . The superbright flasher uses electronic components but not sure what is going on inside for the P circuit relative to the L circuit. Anyone know the resistor value and wattage rating.

I have ordered and received the resistors but yet to be installed. That should do it. I have studied the schematic and the method used to send the pulses to the dash lamps is a bit confounding. If the P terminal is an input or lower voltage output than at L terminal, then a couple of diodes would isolate each side. That would be a simple and more elegant solution than those big resistors. However, now that I am retired and no longer have access to an o'scope, I don't really know whether P terminal is sinking or sourcing current. Guess it will have to be resistors.