Ok just got done checking and replacing another bad glow plug it was the worst one to get at the 5th one closest to the fire wall. It lasted 8.5 months since I last replaced it they are bosch part# 80006 made in France bought at A.Z. for $12/ plug. I figure if I hook them up manually and only use when I have to I might not have to replace one every 2 months. So If I understand you correctly 911 I could take the smaller of the 2 purple wires off the junction box put it on a push button switch run 12 volts to other side of switch and I would be good to go and everthing would be stock except I would be operating off the button instead of the key and only activate when I want to? What do I do with the other heavier purple wire that is on junction box on same place where the thinner one and white wire were what do I do with that wire? This seems like this would maybe be the best way to go this way I would not have to get a solinoid or worry about extra fuses. Does this sound right?

Something is not making a whole lot of sense to me glow plugs should be lasting a good 6 years or more. Have you connected a test light to a glow plug to see how long your relay provides power to the plugs. Maybe an idea to wire in a light and leave it visible somewhere by the windshield wiper for a few days to get an idea of what's happening. Not sure about your car but if I go directly from ignition off to start engine I skip the preglow cycle all together.

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92 e300d2.5t
01 e320
05 cdi
85 chev c10