I have a invacare wheelchair pronto91 wont move 2 red lights flash 3 times

The three light flash indicates a short circuit between the left motor(as you are sitting in the chair)and the battery. Check all the wiring from the control box to the motor and make sure it is not damaged in any way. If it is okay, you have most likely fried the left side motor. A new motor-gearbox assembly for this chair runs in the neighborhood of $1,400.00, or you can take the motor off and take it in for a full rebuild for about $250 or so. Unplug the joystick and remove the seat and cowl. Jack up the left side with both motors in gear. Remove the center nut cover and take off the nut holding on the wheel taking care to retain the key that slides into the groove on the axle. Disconnect the wiring plug to the motor and remove the six bolts holding the motor to the frame. Separate the gearbox from the motor and take the motor to a rewind shop for repairs. Reinstall and it should be good to go.