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Discussion Starter #1
Just installed NPD's sequential LED's in my '67 taillight housings. They work beautifully when the headlights are off, but with the headlights on, there are two problems.

The first is that one of the boards has a rectangle of LEDs that is brighter than the other two and will not sequence properly. This occurs whether that board is installed on the left or on the right.

The second issue is that with the headlights on, using the turn signals causes both taillights to sequentially and simultaneously blink.

My harness is NOS and my incandescent lights work perfectly, so I don't think this is a wiring issue. I've swapped in the digital flasher for the flasher mounted on the back of the cluster. The package was obviously re-sealed when I received it. I suspect that this was a return that they shipped back out--or at the very least that somebody at NPD had messed with.

Does anybody have any suggestions before I disassemble this and ship it back?
 

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Make sure you have a good ground at the tail lights. Sounds like they be grounding through the headlights when they are off.
If your ground is good I would ship them back.
Good luck
 

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Discussion Starter #3
Please elaborate.

As I understand it, the digital flasher needs to be grounded, and each taillight socket is grounded via a dedicated ground wire.

I checked the flasher ground--it is ok. I pulled the ground wires on each taillight socket with the lights on, and the LCD boards totally shut down--so if there was a bad ground, I don't think they'd work at all.

Does this sound correct?
 

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um try pulling the headlight plugs in the front of the car, and turn the switch on, see if the same problem occurs with the headlights disconnected, maybe its a bad switch?
 

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What kind of shape is your alternator/voltage reg in? If you're not getting much chage it could mostly be taken up by the HLs. First, the other ideas would be good to check. Bad grounding will emulate poor charging..
 

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Discussion Starter #7
Thanks for all the input, guys. I will try pulling the headlights out of the circuit just for kicks, but if no change, they're going back in the box and back to NPD. Maybe this time around they'll send them back to the manufacturer and not out to a third or fourth customer.

In their defense, the guy at NPD just said to send them back and they'd send out another set. Didn't give me any problems at all (of course, last time I did that they claimed they didn't receive my part and I wound up eating the cost of the part plus the shipping). This time I guess I'll insure it.
 
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