Shifting Issues

2001 Mazda Protege LX
I just bought an ‘03 Protege5 about a week ago and am having some strange issues. When I have the AC on, and am accelerating hard to get on the freeway and such, it will randomly downshift from 4th to 3rd once I’m at speed (65-70) and rev up to 4K and get stuck in 3rd, battery light comes on, subwoofer shuts off, and air blows hard. Only way to get out of that gear and back into 4th or any gear for that matter, would be to let off the gas, shift to neutral and back into drive. This will happen many times in my drive. I don’t have this problem when the ac is off. Any help would be amazing!
2001 Mazda SP20 323
Hmmmm, could be the AC pump playing up under load? That'd cause the engine to drop power and shift down a gear, but probably wouldn't cause it to stick in gear.

Any squealing or noises when it happens?

Might pay to see an AC specialist and get their opinion


The Diagram Dude
2002 MP5
I'm just guessing here but here's my thoughts.

Our alternator only puts out 77 amps.
If you're running your AC on full and your sub cranked you could easily max out your alternator and start pulling huge amps out of your battery.

I say take your car for a spin with the AC on full but the sub and all unnecessary electrical loads off and see what happens.

Your alternator may be maxed and turning on the battery light and your voltage takes a dump and preventing the sub and transmission from working properly.

You may have a bad alternator.

Here's a link to a thread about the battery light.