my left speaker seems to be cutting out and in.
is it blown or shorted
Normally speakers open, but it could be a wire to the speaker shorted, the amplifier driving the speaker bad, or anything in the channel driving the speaker bad. Short or open, who cares? Bad is bad.
The easiest way to find it is substitution. Substitue another speaker temporarily by swapping speakers with a good channel, or a speaker that you have laying around. If you change ONLY the speaker and the problem goes away, you know it was the speaker.
You can swap the speaker leads at the amplifier too. If you swap the Left and Right amplifier speaker leads at the amplifier (or radio) and the problem moves to the other side, it is the amplifier (or radio).
Anyone who knows electronics that can help you should be able to tell without guessing in a few minutes.