It's hard to say if "it's worth it or not", until you open it up to look.
I'd look for rust, dust (from worn brushes) or worn mechanical parts for starters.... I'm guessing brushes or brush dust causing "grounding/short circuit" type issues.
After disassembly, I'd...
1) Clean it out, by blow it out with compressed air hose and/or electric contact cleaner
2) Re-lube anything that should be lubed (bushings, gear teeth, ect), with a light coat with dielectric grease as at 5 years old it may gave dried out.
3) Re-assemble and test!!
Note: Should you find any rusty components, clean them up with steel wool.
2012 SPORTSMAN 800 EFI (INDY RED) Sept. 2015 ATV Of The Month
Mods: SuperWinch 3000 Winch - MotoAlliance Line Stopper - Glacier3 60" Plow - Polaris Rack Extenders - Polaris Bumpers - LowPro Shield - Polaris Hand Guards - Warning Debadge - 3Way Head Light (Relay) - Cabelas Mirrors - Wes Ind. Std Seat/Box - Kolpin Fuel Pack Jr - 26" Kenda BearClaw HTR Tires - HighLifter HD Springs - MotoAlliance Sirius 6" Pro LED Light Bar
2005 SPORTSMAN 400 (SONIC BLUE)
Mods: Warn 2500 Winch - MotoAlliance Line Stopper - Polaris Mid Shield - Wes Ind. Seat/Box - Shift Interlock Delete - Coleman Mirrors - Polaris Bumpers - 25" Kenda K590 Tires - PVC Spring Spacers
2014 RZR 570 EFI EPS LE TRAIL (WHITE LIGHTENING)
Mods: HarborFreight Badland 3500 Winch - MotoAlliance Winch Mount - MotoAlliance Line Stopper - Polaris Sport Roof - 1/2 Windshield - Warning Debadge - Rear View Mirror - Seat Adjuster - 26" Maxxis Tires - MotoAlliance Sirius 10" Pro LED Light Bar