No sound coming out of speakers

Several possible reasons.

I suggest you remove the radio and disconnect the speakers wires. Test each speaker with a multimeter or even better by connecting each pair of speaker wires to a 9 volt battery when clicks, rustling or other noise will emerge from each speaker proving the wiring is good and the speaker working. If all tests are good the fault is likely to be in the radio audio stages.

posted 6 times.
run new wires from new radio to speakers
or bench test your radio (easy) with your speakers.
if still low the speakers are bad or just dirt cheap , car speakers.
try new speakers, if weak now the wires are bad, try new wires
id still weak the radio is bad. (or just a cheap radio)
and define weak, to me most radios are way too load.
but to others, all are weak until 1000watt amp is added.
weak is a relative term. as is hardly any.
do not quote persons guessing, its just a wild guess. they can see car either, do the tests your self and find TRUTH.

to bench test, (modern way)
1: 12vdc 1amp power pack, or battery 12v. and ground.
2: connect up USB mem,. with some mp3s. on stick.
3: connect one good speaker (KNOWN GOOD)
to one of 4 speaker lines. (2 wires)
4: push play, does it sound good, yes, move to next speaker port.
ok , the radio is good. so
try it in the car, is it now low volumn
yes, then move that test speaker to the car speaker that is low.
still low, yes, then the wiring is bad.

easy huh?,,, takes only , a test speaker.

if no usb use, cassette, if no that , use CDDA disk( store bought real)
if none of that us the radio to test. connect a test antenna.
tune in Am or fm. bam.

If you got the stereo used the speaker wires might not work. I stereo only puts out sound thru the RCA output using an amplifier.

To troubleshoot the problem start with the bit that is working - the left speaker.

1. Unplug the input leads on the back of the left speaker and swap them round.
2. If sound now comes out of right speaker and not the left the problem is with your sound source (computer, IPOD or whatever) or the connecting cable is faulty.
3. If there is still no sound from the right speaker try turning the volume control knob up and down quickly several times - does this produce any sound from the right speaker? Sometimes the electrical contacts get dirty and this can help clean them.
4. Turn the speakers off using the volume control knob. Disconnect the speaker wire for the right speaker from the OUTPUT on the left speaker (push the red and black tabs downwards and gently pull the wires out. Find a small 1.5 volt battery (an AA or AAA size will do nicely) and touch the bare ends of the speaker wire briefly on the battery terminals. If you hear a slight crackling sound the wire and the speaker are okay and the problem is in the amplifier, which will need repair or replacement - not a job for an amateur.
5. If you don't get any sound from the battery test find another piece of speaker wire (any piece of 2 core cable with bare ends will do for testing) and repeat the battery test. If you get sound then replace the speaker wire. If not remove the speaker wire again and go to next step.
6. Lay the speaker face downwards and carefully unscrew the back panel (don't do this if it is still under manufacturers warranty - take it back for repair or replacement). Lift the back panel off carefully and slowly taking care not to pull the connecting wires inside the cabinet, which will probably be quite short. You may have to settle for just rotating the back panel slightly so that you can see inside if the wires are too short to do otherwise.
7. Use sticky tape to tightly attach the bare ends of the speaker wires to the terminals of the battery. Touch the loose ends of the speaker wires on the two metal terminals where the internal wires are joined onto the back of the big loudspeaker cone. If this produces a crackling sound it is the internal wiring in the cabinet that needs re-soldering. Otherwise the loudspeaker unit has failed and will need replacement.

It sounds like you have some wiring issues, moreso issues with your speaker wiring, or your speakers. I would first test the speakers, 1 by 1 using a double A, or AA 1.5v battery. Each speaker wire pair should be tested by attaching 1 wire to the negative side of the batter, and momentarily making contact with the other wire to the positive side of the battery. A low popping/scratching sound should be heard from each speaker. If not, replace each defective unit. Also, double check your wires to ensure they are not damaged.

I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

Try testing the car speakers and the wires connecting the speakers.

Wiring speakers with reverse polarity doesnt have adverse effects. It cant give distorted sound. Seems like the wiring from the head unit to the speaker might be at fault. For testing purposes, connect the speaker directly to the head unit, bypassing, the car wiring. If the sound comes out alright, you have to replace the car wiring. If it is still distorted, speaker might be at fault. Try with a different speaker.

Check in speaker setup menu that your rear surround channels are enabled.

1st make sure your amp is coming on. Use another speaker that you have heard play to test it.
Next test the woofer with a 9 to 15 volt battery. Touch the battery leads quickly across the + and - on one side at a time. The speaker should move and make a pop on both voice coils.
If the amp plays and speakers play, then you need to know the power rating and impedence stability of both amp and speakers. That will determine how they are wired up.

On many cars there is an exterior amp that the sound goes through before it is sent to the speakers. If the remote turn on wire isnt connected after you take your previous cd player out then the amp wont know when to turn on and therefore no sound will come from your speakers although your cd player is doing its job.