Ouch.

It could be worse...on the older Ford diesels, they used 6 volt glow plugs and apply 12 volts to them. If they stay on for longer than 8 seconds, they will swell up and will likely break...and if you lose the tip into the cylinder, the only way to get it out is to pull the heads. And not getting that tip out can lead to disasterous results. This is coupled to an old bimetallic controller that activates the glow plugs based on coolant temperature...and is prone to failing and leaving the glow plugs ON. This is why many of them have moved over to a push-button control.