Why doesn't my radio operate in the "PA" mode?

There is a separate speaker socket for the PA function on the back of most radios, to save you swapping the lead.....

hi dude

nothing,thats what its supposed to do. Don't try transmitting on pa though you will blow that speaker. the type you would need is a bull horn speaker.

because when you switch to PA it is because you are on the outside of your vehicle.When another party calls you ,you can hear them and then go to your vehicle flip it to cb and talk to your party.

it is possible that the PA speaker output is intended for a normal (unpowered, unamplified) speaker. Perhaps in your case the audio you hear from the PA speaker is only signal leakage from the PA Speaker connection.
To know.. connect a regular speaker to the PA speaker connector (any speaker, home audio, old car 6x9....). If the PA works and drives the temporary speaker OK, and you hear no CB receive, then the PA output is for a normal speaker, with leakage of CB audio.
It is just a guess, but easy to try.

no,its supposed to work that way so you can monitor it while you are outside your vehicle.

Are you following the user manual that came with the radio?
NB-ANL/CB/PA SWITCH: When the switch is in the NB/ANL position, the Noise Blanker (NB) and Automatic Noise Limiter (ANL) circuits are activated.
The Noise Blanker is very effective in eliminating repetitive impulse noise such as ignition interference. In the CB position, the PA function is disabled and the radio will transmit and receive on the speaker that is connected. In the PA position,
the radio acts as public address amplifier. Your voice will come out of the speaker that is plugged into the PA. SP. jack on the rear panel. The radio does not operate when you are in the PA mode.

When you plug a speaker into the ext. jack does it kill the radios internal speaker? It should until you unplug it; if not and you are following the about you may have a wiring issue with the jacks.

Turn the radio on.Now make sure its in cb not pa mode.Nowturn the squelch all the way to the left.Now turn RF gain and RF power all the way to the right.Hook an external speaker to the radio and see if it helps.By now the radio should be operating. If not then you have an internal problem..

look into buying a new radio. If you had researched further you would have found out that unless you are on cb your radio will not operate . If you are on PA the you can only transmit through the PA system not the cb. If you changed the audio IC then you probably did a cold solder on it. You need an external speaker to operate the pa mode and an external speaker to operate the CB mode .If you decide to fix it more it will cost you more then buying a new radio.

There are some different things you could be facing like:
the speaker sound being cut-out by the mic switch, but my first guess is the switch in the external spkr. jack being faulty. Here is a schematic for you.

http://xbones_antennas.tripod.com/id21.html