wondering if someone has run into this:

all lights on my sons ranger ext cab work fine EXCEPT when the headlights are on. if headlights are on, turn signals blink faster than normal (like what i remember in the old days as a bulb out or going out) and the tail lights/brake lights dim in and out. this only happens when the headlights are on.

we did have an issue about a year ago with brakelights not working at all and i found and repaired a loose connection in the turn signal assembly on the steering column.

wondering if anyone has any ideas on this - alternator possibly or a short (i hope it isnt a short)-

thanks for your time

M Tedford