1.Do you have an aftermarket (Non Mercedes) alarm?
2.Replace Fuses "A" and "C"
(Notice I said Replace,Not Check...You don't need any more grief.)
3.Ain't No WHITE wire showing in the ETM portion of the FSM for the '90 or '91
300CE.[What's commonly called the "Wiring Diagram"].
There is However a RED wire with a white stripe.
There is also a YELLOW Vacuum Hard Plastic line.
There is a BROWN wire.
There is a BLUE wire.(This is the one that would go to the "Comfort Control")

4.Testing Accomplished with a Multimeter and Wiring Diagram[Spelled FSM]
And an understanding of German Electrons
(They're more "Fussy" [Correct]than American Electrons)
[I know, I know you have an American Battery...How can the Electrons be German?
Apparently Electron's nationality is determined by the Wiring.]

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'84 300SD sold
124.128