I had the blinking light experience with the expansion tank water level sensor.  Someone suggested to clean the contacts at the battery and at the instrument cluster, suggesting not enough current went through, even though the voltage tested OK.   That solved my problem.   
Perhaps this may help in your case.  (maybe put back your old sensor, the new one may be faulty)  
Alfred
85 Westy

Sent from Mail for Windows 10

From: Dan N
Sent: December 7, 2020 10:20 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Blinking oil pressure light

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