Last weekend I had the strangest this happen - Both batteries in my 54j became reverse charged by .5v
The original batteries in the unit were dead so I grabbed the two from the tool box. I knew the batteries were low because I checked them with a voltmeter and the unit was blinking low batt when I installed them.
I was in a rush so I was hopping to get one run out of them.
It didn't work. As the car came out of the burnout the display went blank. When I removed the batteries and checked them again with the voltmeter. Both were about -.5v
The Tach seems to go through batteries more often then it used to. I used to get almost an entire season out of one set, now I get about 1 month wether we use the car or not.
Any clues? Has anyone else seen this.

I recommend sending the unit back to Digatron for us to look at. Our address is:
Digatron
120 N. Wall St.
Suite 300
Spokane WA 99201

It sounds like there is a short somewhere, which should be easy for us to fix. There is a repair form on our website, digatronusa.com and we do our repairs quickly.

You might be able to temporarily help the situation by backing off on the battery door screw. You can also call and talk to one of our techs at 866-DIGATRON (344-2876).

Jen
Digatron