Maybe someone could help me with this. I want to know how the headlamp raising/lowering works with the vacuum system. As my car has not run for ten years I have not seen it work.
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On a car as old as the Murena it is quite normal that the lights can be turned on without the ignition key being turned.
As Klumzer wrote, the lights can be raised manually. There should be a wire under the dashboard towards the left side (if it has not broken off) Pulling it will raise the lights. However, it requires the assisting spring(s) on the lift bar to be in place. Otherwise they are too heavy to lift manually. The spring can be easily seen below the lamps. On mine there was only a spring on the left side. But there is also mounting points on the right for an additional spring.
You should start by checking that the vacuum selenoid switch in the front compartment operates when you turn on the lights.
If it does, check the entire vacuum system from the vacuum bottle on the righthand back side of the engine compartment and forward. Mine was ok, but the hose dried and cracked, thus no vacuum. All the vacuum hoses in the engine compartment had to be replaced.
With the engine running, check if there is vacuum to the solenoid switch. If so and the switch works it could be the vacuum motor has a cracked diaphragm. But the most likely cause is cracked vacuum hoses somewhere.