Jazzy chair 600 3 red lights 4 yellow 1 green no power both batteries read 12.5

SOURCE: My Jazzy won't move.

If your batteries are truly charge they should read around 24.5 VDC. And if the freewheel lever is engaged and you still have no movement your probably need to get into a service tech. Also check the circuit breaker on the chair.

SOURCE: lights on hand control flash off and on and chair will not operat

There is a series of diagnostic flash codes associated with the controller. The diagnosis depends on which color and how many lights are flashing. If you post the combination, I can help you. Or you can download the Basic Operation Instructions of the Pilot Controller from the Pride website. The codes are listed on page two on the troubleshooting instructions.

SOURCE: Motor Wiring

Two white wires are for the electric brake.  When the wheelchair is turned off while on an incline, the motors automatically lock up, preventing the wheelchair from rolling backwards.  The white wires disengage the electric brake when power is applied.

SOURCE: Replacing battteries in Jazzy 1103 power chair

Here's a quick link to the owners manual for the 1103 that will show you how to replace the batteries on your chair.
http://www.pridemobility.com/pdf/Owners_Manuals/US_Jazzy/US_1103_Ultra_om.pdf

SOURCE: chair no longer charges, no flashing or blinking, lights,

The number of lights that are blinking indicate what the problem is. Visit this site to locate the type on controller on your power chair and you will be able to see that the blinking lights mean:
http://www.pgdt.com/scenter/diagnostics/diagvsi.html
Try to reset your manual brake release as this is a common problem.
If you continue to have a problem, contact your manufacturer or dealer for service. If your insurance purchased they power chair for you, they may also cover the cost of repairs.
Good luck!