Although mine were working when I did my rear cross member I found the wire harness that runs inside the right frame rail totally rotted and had shorted to the frame and melted together. I was surprised the lights still worked. Under the hood on the right side close to the firewall is a bunch of about 6 quick connectors, from here they go into the dash and this splits front and rear so you can check for power here and isolate front and rear.
1971 series 2a 88, series 3 trans, Fairey OD, owned since 1978.