Drifter288

iTrader: (3)

I have a 95 RX7 Non bose sound system stock all around no mods

So the left front side speaker shorted out again after I replaced it with a refurb one, worked for a while but then no more sound an really bad static even with the volume turned down...ONLY the left front speaker went out, every other speaker works fine. Ohmed out a working one before installing and got 4ohms but after the incident my speaker that I replaced it was now at .7 ohms, shorted out.

Did voltage across the left speaker terminals and saw about 7V without a speaker connected but eventually it dropped back down to 2.7V after letting the car sit a while after driving an hour. But will slowly go up after a while when playing music for about 10 minutes topping out at about 4V. So now I'm between condemning the center speaker amplifier that is hooked to the speaker or the head unit per the schematic.

So I dug into the car center console to find the center speaker amp and conducted tests with it connected and without it connected. Again no difference unless the unit is already broken?

But a real tell tale sign is when I use the bottom head unit to balance the bass, when I turn it to the full right w/o the center amp connected the full bass goes to the right which is what it should do. When I turn the bass balance to the left speaker w/o the center amp connected, there's no bass at all just small sound and a dying speaker. Repeated the test with the center amp connected and same results. This was using another 4 ohm working speaker to conduct the test.

I replaced the upper portion of the head unit not too long ago but didn't send in the bottom half, maybe I need to send in the lower unit to get fixed?

Drifter288

iTrader: (3)

So I realized that I could use the wiring harness coming off of the center amp as a breakout box, so I connected up the speakers and did some voltage drops. On the good speaker I was able to pull a nice low .018V compared to the bad side it came out to be around .800V!!! Same results while back probing into the center amp.

In case of any doubt, took the passenger side panel off just remember there's a hidden screw behind the window switch, messed mine up pretty good...and unplugged it and used my test speaker (with the good 4ohm reading) and was able to get good results. Even took off the working one originally on the passenger side and moved it to the driver side, the problem is still isolated to the left front speaker. I'm feeling good to condemn the head unit so I'm sending them out for bench testing. In addition, I'm sending the amp as well since if it piggy backs off the left speaker, there's a chance the amp might be bad too.

Ohmed out the center speaker and has a healthy 4 ohms per specification. Be looking forward to seeing if my diagnosis is correct.

Montego

iTrader: (1)

wow you did way more work than would ever do... I would had just ditched the head unit after the second blown speaker.

I think that most likely the problem is with the head unit. For instance if a short was being caused at the load (a speaker wire touching chassis) causing an over current the occur, it is most likely that the head unit would overload and shut off prior to the speaker coil permanently shorting out.

An easy way to tell is to test both speakers against each other. Measure the resistance of each speaker, measure the voltage across the speakers, and ultimately measure the current being delivered. I'm thinking that on the side where the speaker is blowing out you will find that you have an over current scenario. If you do find a diffence swap the speakers and see if there is any change from your last readings. If the left side still experiencing higher level signals then you know the problem is either your wires or the head unit. So then you swap the speaker wires to determine if it the wires or the head unit. Now if the over signal was swapped with the speakers then you know where the problem is.