Hi Bernie, welcome to the wonderful world of MB electrical gremlins. One thing that may be obvious but I haven't mentioned yet is the battery. Check the posts on top to make sure they're clean (between the post and terminal) as well as the battery ground attachment. I cured a bunch of glitches by removing the ground cable bolt and cleaning under the cable terminal where it attaches to the body. I sprayed the connection with fluid-film to stop any further corrosion. This suggestion may seem a little archaic but try turning on the key and then tap on the relay, sometimes the contacts in the preglow relay just need a good smack
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