No front sidelights with engine off

My car is a 1992 VW Passat estate, 1.6 diesel.

This recently started happening;

The front sidelights, and headlights too, go off when the engine stops. The rear lights stay on.

With the engine running , it all works ok.

Anyone know what's going on?

The headlights should turn off when the key is turned off, the park lights shoud stay on as long as the switch is on.

Yes, I know that.

With the ignition off and the light switch on, only the rear lights are on.

With the ignition on, all lights are functional.

Thanks for the reply though.

Oops! Turned out it was the bulbs! Silly me.

I was fooled because they both went at the same time , and also they appeared to be on with the ignition switch on. In fact it was the headlights in dim mode.