I recently purchased a 98 blazer and the check engine light is on. I had the car hooked up to the diagnostic computer and there were four codes (P1860, P0758, P0753, P0740) that came up as needing repair. To me this seems to be an electrical issue, but I'm not a mechanic and need some input. Also, the instument cluster is not working all the time. Sometimes it will come on for a few seconds to a few minutes. I figured this was an alternator or battery issue, but as I have been reading up, it seems that all the problems might be fixed by changing the ignition switch. Does anyone know if changing the ignition switch could fix all of these issues? Or what the problems could be? How long does it take to change the ignition switch? Thanks!!

 

Those are transmission related codes. You can research them on this page in the Diagnostic Trouble Codes section.

 

More specifically:
P0740 - Torque Converter Clutch Circuit
P0753 - Shift Solenoid A Electrical
P0758 - Shift Solenoid B Electrical
P1860 - TCC PWM Solenoid Circuit

I would look for something in common between all of these codes. Inspect the electrical connection to the transmission for corrosion or damage to the wiring harness close to the exhaust or any moving parts.