96 850r head unit woes

[Mstrshkbrnnn]

I bought this car back in August of 2019. The previous owner installed an aftermarket head unit. It sounded great, but I’ve always hated how they look, especially this particular Sony one contrasted with an 850 interior.

When I first got the car, the sunroof didn’t work and after a while of trying to find the reason, I found a blown fuse. I can’t remember off the top of my head what fuse number it was, but I remember it was shared between the sunroof and the dash illumination lights. I tried replacing the fuse and itd pop immediately. I traced that issue to be a burned out dimmer switch. I replaced that switch, replaced the fuse, and got functionality of my sunroof back. My dash lights still didn’t work. One day spontaneously after work, the dash lights came on. The next day they wouldn’t come on again, and it stayed that way for months.

I was also having boost issues so I bought a cheap, temporary boost gauge from harbor freight, and plumbed it under the dash and into the single din slot under the aftermarket head unit. In the process of doing that, I pulled the radio out, and was greeted by the rats nest of wiring the previous owner left behind. He didn’t solder OR use butt connectors. He simply twisted wires together and put a piece of electrical tape on every connection. I was surprised it still worked so well after who know how many years, but now that the car was mine, I couldn’t live with that.

I took it upon myself to redo the harness, at least with some insulated butt connectors, and heat shrink. I did every connection exactly how it was before, but this time more secure. After all was said and done, I buttoned it up, and the entire right speaker channel was dead. Technically I should say “left” as the right and left channels are flipped for some reason. That was all back in 2020. Shortly after this, the alternator died, and that, mixed with other maintenance the car was behind on, caused the car to sit for the last 4ish years.

I recently did a bunch of work on the car to get it roadworthy and “reliable” again. That work including new upgraded pcv, alternator, timing kit, etc. driving the car again, I’m reminded of the dead right speaker channel. Since it all worked before I touched it, I figured it was my fault, and I must’ve messed up a couple crimps. I took the head unit out, undid the harness loom I wrapped it up in, and tugged a bit at each connection trying to find the bad one. I found 3, which I thought should’ve been at least a positive or negative for the three right side outputs. I redid those connections. Still nothing. I did also notice static coming from my left speakers when touching the harness coming out the back.

My biggest gripe here, is that it looks like the “original” harness that was hacked into to wire in the head unit, is now missing wires that would’ve/should’ve been there when stock. My goal was to return the head unit harness to stock, then buy an adapter to run the aftermarket head unit until I can source a nice stock one ast they sound great and actually match the interior. I cut a harness at the junkyard, and those two connectors have way more wires in them than I have coming out of my loom behind the dash. Apologies for the shitty photos, I’ll get some better ones when the sun rises.


This was a long post, so I’m going to summarize my questions again here at the bottom:
1)my dash lights are currently working with no issue. Is the issue of them intermittently working in the past before I redid the radio harness related to the wiring hackjob?
2)is the right channel not working most likely due to me messing up those connections when redoing the harness, or is it possible a fuse or something of the like was blown/tripped?
3)what would be the fastest/most efficient way of determining whether the speakers are bad, the wiring connections, the connector to the head unit, or the head unit itself is bad?
4)what wires an I missing, and how hard is it gonna be to restore this section of harness to stock?

[Mstrshkbrnnn]

I forgot to add the biggest problem! The way the previous owner set up this head unit was causing it to draw power even with the car completely off! Back in 2019-2020 I went through two batteries and an alternator because of this drain. Back then I didn’t understand electrical systems to the level I do now, so tracing the problem seemed impossible to me. After replacing the alternator etc etc a couple weeks ago, I used my multimeter to trace the parasitic draw, and the radio fuse was pulling over .3! After pulling it the reading dropped to <.02. I’m kinda lost and feel like I’m being pulled in quite a few different directions so any and all guidance would be greatly appreciated.

[scot850]

Your current draw now of 20mA is normal level. The radio always has a draw on the standard car to maintain the memory of settings and the likes. I have seen draws as little as 10mA. My V70R draws about 45mA due to the aftermarket security system.

I would find a wiring harness drawing section for the radio connections and check you have all the wires present.

There is a wire on the standard radio for lighting which is run from the dashboard lights and switches on the lights in the radio when the lights are turned on.

Check the dashboard light brightness slider as those become flakey with age and can cause the dash lights to be intermittent.

At this age, there is a good chance the speakers could be bad. You can try removing them. I use a 9V battery with a couple of wires to test the speaker. The wiring diagram will tell you which is the +ve and -ve terminals. Connect one wire to the speaker from the battery using tape, and the other tape to the battery end and then dab the wire on/off the other speaker terminal and see if the magnet on the back flexes the speaker. If it doesn't move it is likely bad. I haven't tried it on an 850, but try swapping the speaker with the opposite one and see if it works over there is another option.

Check also the wiring to the door speakers. Wires break with age in the door harnesses. Do continuity checks from the radio to the end of the speaker wires and see if they are all good. If a wire turns out bad, remove the multi harness at the door pillar and buzz the wire out from there to the speaker to check the harness wires have not broken in the door harness. Typically that would happen in the section from the pillar down into the door as that flexes most over the years.

Finally on current drain. Check the glove box light is not staying on. Put your cell phone in the glove box on video mode and check the light goes off when the lid is closed.

Neil.