It's not impossible but would be VERY unusual to have a failure on the running light ciruit on the key-switch, especially if the headlights are working normally...
I'm not back-tracking here - I still think it is quite unlikely that there is a problem in the key-switch affecting ONLY the Park/Running Lights; however I will add that is is not impossible.
And if you can replicate the action your mechanic claims - moving the key affects the operation - then fair enough
But please also do these tests:
..Here's something you can check to see if it is the whole running light circuit (front and rear) or just the rear one (where you clearly already had problems):
Pull Fuse #9 (will turn off the main headlights) and see if the small running light bulbs are on; if they are then it is just a rear light wiring issue
You should also check Fuses #'s 8 & 10
And finally turn key all the way to the 'park' position (fully anti-clockwise past the lock position) - does either front or rear come on?
Now here's the deal:
There are actually TWO different (and completely isolated) poles in the key-switch which affect the running lights operation
1. The first pole connects power in through the White wire and out through the brown wire - this output from the Brown Wire will affect the Headlights, the ability for starter to operate, the background illumination on the instruments and also the running lights
2. The second pole connect the Blue Wire to the Red wire - the output from the Red wire indeed feeds the Running (front & rear) & plate lights.
So the important questions are -
Are your headlight s being affected by any manipulation of the switch or is it ONLY the running lights?
Is it ONLY the rear (Running & plate) that is being affected by manipulation of the switch - or are front and rear being affected simultaneously (again, you may need to pull fuse 9 to see what the front running lights are doing)
Here's the good news:
IF (
and only IF) it does indeed turn out that the Second Pole IS the only problem (i.e. ONLY your running lights both front & rear) are being affected by manipulation of the switch, then the fix is fairly simple & almost free:
On the Key-Switch side of the connector, cut the Red Wire and the Blue wire 2-3 inches from the connector plug; then join them together (use a barrel crimp splice or solder and insulate - do not simply twist them together and tape!).
^That will bypass that second pole and your running lights will still
only come on when the Key is turned on.
What will no longer work is that they will not operate when you turn the key all the way anti-clock-wise to the Park Position (but do you ever use that anyway? Unlikely)