Based on your testing, sounds like bad relays. I similarly built my own kit with relays I purchased at O'Reilly Auto Parts. One was dead out of the box, but once I replaced it's been working flawlessly since.
jim
jim
Head Light Relay
To make my headlights brighter, (on my 68 Camaro) I've added a homemade relay kit with parts I ordered from the internet. After installation the headlights are brighter, but keep flickering and shutting off while driving. They work in the garage with no apparent issues. These are 4 pin relays that come from China. I've tried several other relays of the same brand and found the same problem. After bypassing the relays I found the lights worked normally while driving. I'm wondering if there's a certain type or size of relay that I should be using.
