I have a 2004 Mazda 3. Lately, it will not start or turn with heavy humidity. This doesn’t happen all the time. Light turn on and the radio works, I don’t think it’s a battery issue. It’s a coil on plug igition system. Any ideas?
Will not turn implies a problem getting juice to the starter motor so I would focus on that area if it was my problem. Clean cable connections at battery, chassis and all starter motor connections. As a test you could try a spray bottle of water on those 3 areas and find which one reproduces the problem. I would guess the starter solenoid is incorporated into the starter motor but do not know for sure. My best guess would be the connection that operates the starter motor solenoid, or a solenoid that is susceptible to moisture. If that does not work start tracing your way back from the solenoid checking connectors and looking for wires that have worn off insulation.
I have had problems with the clutch switch in humidity. I haven’t replaced it yet, because it always works when i repress the clutch pedal, but it may be a place to look.