I have issues with cold starting on my Boxer at the moment which is clearly a glow plug problem. The light in the cab indicating operation started to go intermittently, and now doesn't come on at all. When it worked the van started fine. My instincts tell me this is more likely to be a relay issue rather than the plugs themselves, but what does anyone think? Do all the plugs pack up at once, or would this be unusual? And would the light come on even if the plugs were faulty?