Well, thanks for humoring me. You've ruled out a DC power supply problem, at least to those critical circuits.

Did you get a chance to run the AC ripple test under the same conditions? (Sorry, I'm an electronics tech so ALL problems are electrical in nature... )

 

My Jag is back in the Service Department at the Jaguar Dealership. This time, I refused to allow them to write on the service order "dead battery" which is how they summarized my issue the last time, before charging me $150 to tell me they found nothing wrong.

I wrote out a thorough description (much like this post) of exactly what has been happening, including link to the video, and a list of everything we have tried and the results. I watched as they stapled it to the service order. This was a good start!

They believe the issue is with a relay, or more than one relay. They are replacing some. We are fortunate right now to be having unseasonably hot weather, so hopefully we will be able to truly test this, and see if finally my issue can be resolved.

I will report back.