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Hey there, I was hoping someone could lend me a hand. The glow plug and airbag lights don't always turn on when you press the key in my MK4 Mondeo TDCI during startup. 2. When they do, the glow plugs still function properly, and the engine starts up without a hitch. Then there are instances when the oil and handbrake lights are the only ones on, and the automobile has trouble starting.

Based on the sporadic nature of the problem, it seems like you might be experiencing CAN-BUS communications troubles.
Could you please tell me the circumstances under which this is taking place? When I say "weather," I mean temperature and precipitation in particular.
An odd electrical gremlin would pop up every once in a while on my old Mondy, a 2010 Factlift 1.8 TDCi. Occasionally, the radio wouldn't turn on and other issues like that would sometimes go away after the ignition was cycled.

You mentioned that the glow plug and airbag lights aren't always turning on, which is completely normal; in fact, the airbag light problem is a failure of the motor test (MoT). This leads me to believe that you may have a corroded terminal someplace.
Another thing you may do is connect Forscan to the vehicle and look for codes related to the airbag and glow plug systems. If you find any, you can fix them.
Additionally, it's possible that the glow plug fuse (60A if my memory serves me well) has blown, although I doubt that this would affect the dashboard light. The dashboard light was still on when I found out my car's glow plug fuse had blown.
Obviously, blown bulbs in the cluster are another potential explanation. If you want to know, you'll have to take it apart and look at the parts, but that's not too difficult.

Include the test's outcomes and the methods used to obtain them (e.g., meter connected to the battery, meter inserted into an internal socket, OBDII tool, dashboard diagnostics, etc.).

The recommendations you made are greatly appreciated. I read that the actual ignition switch or barrel could be the problem; it's strange that it works sometimes and not others. When I use my car every day for work or when it sits for a week

As part of a procedure known as "Failure mode analysis," I offered some recommendations concerning certain circumstances.
For 39 years, Mr. Dad was an integral part of Ford Motor Company's quality vehicle engineering team. He oversaw investigations into mysterious breakdowns and their causes on multiple occasions. When I was an IT support team manager, I often found myself involved in investigations that started with a result and then traced back to its source.
It is critical to determine the precise circumstances under which intermittent problems arise because they are the most difficult to manage.

Information collecting is the crux of fault diagnosis.

This is really unusual, however I have noticed that the radio sometimes takes a bit to turn on. It does not work under any specific circumstances.