No sound from left speakers

So as I recently posted, I swapped out the front 4x6 delco door speakers for pioneers because the ONLY the driver's front was NOT playing, and I saw a pair of 4x6 on clearance at a local store.  

Car is a 95 caprice wagon, 70k miles, base AM/FM/CASSETTE radio.  I loaned my 95 FSM to someone, so I am looking in the 94 FSM for a wiring diagram of the radio but have had no luck.  The 94 FSM specs the front speakers as 4x6 10 ohms, but the delcos I removed were 4x6`, marked 4 Ohms.

When I had installed only the front driver's side pioneer and tested the radio, I tested the radio to make sure I didn't have to pull the door panel back off.  I noticed that all speakers were playing at very low volume.  I made a 0recent thread about it.  After installing the passenger front pioneer speaker, I tested the speakers and they all worked at normal volume.  I buttoned up the passenger door panel.  when I tried the speaker and switches afterward, the REAR left speaker was only half working (I suspect the woofer was not working).  Today, after installing a new battery and gary's headlight harness, I drove the car into town.  Now BOTH driver's side speakers (rear Delco, front pioneer) are not working.

It doesn't matter if the radio is on FM, AM or cassette.  There is zero sound from the left side.

Before taking the door panel off again, should I be suspecting the head unit vs the speakers ? Is there any wire that, if damaged, could cause this ?

I'm wondering if I should pull both Delco speakers out of the garbage and test them with an amp ?

I have had issues with speakers not working on both of my cars. The opposite sides no less. I installed an aftermarket head unit, and now both work correctly.

The use of higher or lower ohm rated speakers will affect volume. If the speaker is a lower ohm rating, and you turn the volume up, it can burn out the output transistors. If the ohm rating is higher, the speaker will produce less volume at a give setting.

I would test all of the speakers, and test the wiring for continuity. If the continuity is good, and the speakers test good, it is your head unit, or an incompatibility issue.

Im with Fred...Quick test of the speakers,with a known to work head unit/power source will clear things up. IMO is sounds like your head unit is loosing a channel. Not real uncommon considering the age.

Thanks.

If you can, run jumper wires from the good side to the bad side. If they come back on,, then it's either a connection issue, or they amp for that side is blown. Does your head unit have fuses within it, like maybe one for each side?

My car hasn't had had a stock unit in it for over twenty years so I don't know for sure..