So is the Centech harness been installed? If so, I would contact the tech line; check for good grounds; re-check for good ground wires. If you have the 30 yr old wiring, I would start with checking everything from the fuses back to your lights. Ensure everything is getting power at the panel. My stock '73 wiring went through the firewall; down and under the driver side along the frame. There is a ground connected to the frame next to the fuel tank. The wires continued back to the driver side tail light with another ground inside the fender behind the light assembly itself. From there, the wires go to the passenger side tail light, and you guessed it; another ground inside-behind the light assembly. My compete rebuild is in-process, and I have a Painless harness that I'm almost ready to tackle. Centech vs. Painless... Both have good points to consider. I went with the Painless simply because later in life I plan EFI, and the folks at Painless offer a harness that is plug-n-play for EFI . Good luck! B)
PS May I also suggest checking out braided sleeving to protect your new or old wires. Do a search on Ebay for "braided sleeving". My dad and I have purchased from:
http://stores.ebay.com/FURRYLETTERS. No discount for recommending, but he was easy to deal with. There is fire resistant; many colors; sizes; etc. to choose from. FYI
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