Parking lights and turn signals

Regarding Ford F-150, 1977 model year. What causes the right front parking light to be dim. I cleaned both the contacts on the bulb and the receptacle. Even tried a new bulb. Also, when the parking lights are turned on the right turn signal does not work.

there is a high resistance, (voltage drop) in the parking light circuit somewhere, most likely the ground.

Thank you. I removed the ground wire terminal for the lamp and cleaned both the terminal and frame to which it is attached. Do you have suggestions on where specifically I should check the circuit?

I would put an ohm meter between the power conn. point on the socket, and the other end at the input side of the signal sw. that is the most likely place for this problem to be occuring. If it has a multi-function sw, check for a high resistance short somewhere in the sw. possibly corrosion at the contact points in the sw.

Thank you. I’ll try that. Appreciate your help.