i have a 2000 v70 which I bought in 2008. Presently there are a little over 165,000 miles. Recently my odometer and speedometer will occasionally stop working and suddenly reappear. Also I will get sporadic warning lights for Brake, traction control, ABS, and once Battery light. Usually everything is normal. Recently my transmission arrow started blinking and will not stop even with battery disconnect. I have to manually shift to first gear as the tranny defaults to second in auto mode. Could an old battery do this. I like to assume the cheaper way out first. Maybe wishful thinking? If you read this far have a good day and thanks!!

I would start with some basic measurements of alternator output. Measure at the positive post on the back of the alternator, and at the battery posts. Both measurements should be between 13.7-14.1 VDC (load and temperature dependent). If there is a significant difference between the measurements (voltage drop), suspect the cables. See if the positive cable gets hot to the touch with the car running. Measure the voltage drop on the B+ cable too-- it runs from on top of the positive cable to the underhood fuse box.

Report back with your results. The advice on rowing the shifter is good for the flashing arrow and tranny problem.

Here are 2 "cheaper way out" things to do first.

I'd start with cleaning the battery terminals and cables thoroughly as well as the ends.

Regarding the transmission, try cleaning the contacts of the PNP switch. Do this with the engine OFF. Row the gearshift from Park to 1 about 20 times. I've heard this works.