The radio in my 1975 cutlass will turn on ,but I have to turn the volume all the way up to barely hear anything . Any info on the cause and possible repair would
be appreciated.

 

It could be as simple as a speaker or it could be the amplifier.

 

Is it AM or AM/FM? If the radio was changed in the car it needs to be trimmed or adjusted to the existing antenna. It's possible the antenna is not plugged into the radio well, it's possible there is a bad connection where the windshield plug goes onto the antenna lead. Those are easy things you should check first.

 

The radio is am fm and original to car. Does not appear
to ever have been tampered with. I did check antenna connection
and seems fine . Thanks for possible problems. Is there a way to check
Amplifier?

 

You need to hook up a known good speaker.

 

As oldcutlass has said, hook up the radio to a know good speaker. If it is still bad, it is most likely a bad output transistor. It is the single largest cause of radio failures. If the resistance from the speaker to the radio is reduced from the 8-10 ohm norm it causes the output transistor to burn out. Running a today's standard 4 ohm, will kill these old radios in days.

 

can you just put a 4-ohm resistor in line with a 4 ohm speaker for an 8 ohm radio or is it not that simple??

 

I hooked up a good speaker and instantly played , so I am assuming the speaker is bad ? What would be the reason for a speaker to go bad ? Does not appear to have any damage . Thanks for all the help.

 

Old age

 

Sort of. It's impedance vs resistance. I know you can run two 4 ohms in series to get 8 ohms impedance. But, yes, I think you can do that, it will just sound quiet.