1984 720 headlight and parking lights problem

1984 720 truck, Z motor, 2WD with 260K miles.

I have two problems:

first - Parking lights will not turn immediately on with switch. Delay varies with outside temperature. Anywhere from 5 seconds when warm to 10 minutes when winter. Brake lights will light up and blinkers will work immediately however.

second- Headlights low beams will now only work with high beams switched on.

I have been checking the end sockets for corrosion but have found very little (cleaned and electrolyte pasted). I believe either have a short/break somewhere or maybe a failing combi switch.

(Combi switch I believe is the one on steering column if I got the name right). Any ideas to shorten the search? Much appreciated.