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Car Forum / Volvo Cars / February 2005The stereo's connected to the... taillight?
My 1990 240 has been acting oddly. Specifically I had an aftermarket stereo installed at Best Buy about 3 1/2 years ago. A couple of winters ago it started cutting out- the sound would stop, the display would go out and eventually it would come back on. It would lose the radio presets and the clock would not keep good time. It seemed to be random. It would happen if the car was parked, sometimes would happen if I turned right, sometimes happened if I hit a bump. I haven't had time to take the car back to Best Buy to have them check it out, but have assumed it's a problem with the wiring, specifically the power supply. (I know what you're thinking- "two years you've put up with that? You slacker!" True.) Three days ago I noticed an intermittent "light out" indicator on the dash. I traced this to the right rear taillight. Wiggling the socket rendered the light operative and I noticed as I got back in the car that the stereo had cut out and was just coming back on. "Huh" thought I. Well, ever since then the stereo has been performing perfectly. The clock keeps time, it doesn't cut out. My question is: WTF? How does an intermittent connection in the taillight affect the stereo? Does this indicate bigger problems? Thanks in advance to people who actually understand car wiring and elecctricity... I am not one of them. > My 1990 240 has been acting oddly. > [quoted text clipped - 23 lines] > Thanks in advance to people who actually understand car wiring and > elecctricity... I am not one of them. If you have corroded fuses in the fusebox you'll get all sorts of weird electrical gremlins since voltage will sometimes feed back through unexpected paths. Loose or corroded ground connections can cause wierdness too. >> Three days ago I noticed an intermittent "light out" indicator on >> the dash. I traced this to the right rear taillight. Wiggling the >> socket rendered the light operative and I noticed as I got back in >> the car that the stereo had cut out and was just coming back on. >> "Huh" thought I. Well, ever since then the stereo has been >> performing perfectly. The clock keeps time, it doesn't cut out. <snip> > If you have corroded fuses in the fusebox you'll get all sorts of > weird electrical gremlins since voltage will sometimes feed back > through unexpected paths. Loose or corroded ground connections can > cause wierdness too. I'll check the fuses more closely- they looked OK when I looked at them but it was fairly cursory for the most part. I really only checked the one for the stereo closely. Hmmm, ground connections... I popped the stereo out of the dash to check to see if there were obvious problems with the wiring of that, and I did see that the negative ground wire for the stereo wasn't connected to anything. Could that be the culprit? What should it be attached to? However, why would the taillight affect it (assuming that's the cause and it's not just coincidence)? Nothing else in the car seemed affected. > >> Three days ago I noticed an intermittent "light out" indicator on > >> the dash. I traced this to the right rear taillight. Wiggling the [quoted text clipped - 19 lines] > connected to anything. Could that be the culprit? What should it be > attached to? Yes that most certainly will cause a problem, assuming you're *sure* that wire is the negative, connect it to ground, there's some screws with other ground wires on them behind the center console with the switches and heater controls, just put a crimp-on hoop connector and stick it on one of those screws. >> Hmmm, ground connections... I popped the stereo out of the dash to >> check to see if there were obvious problems with the wiring of [quoted text clipped - 7 lines] > switches and heater controls, just put a crimp-on hoop connector and > stick it on one of those screws. Well, the wire has a pre-printed label on it that says "negative ground" so I assume that's what it is. It's got a "C" terminal on the end of it. How do I tell which is the screw with ground wires attached to it (just so I don't screw it down to something else and fry things)? >>> Hmmm, ground connections... I popped the stereo out of the dash to >>> check to see if there were obvious problems with the wiring of [quoted text clipped - 14 lines] > How do I tell which is the screw with ground wires attached to it > (just so I don't screw it down to something else and fry things)? If it is the body of the car (usually painted the same color as the exterior) you have the right place. Scrape away any paint under the screw first, even if there are other wires already there. Mike > "Tim McNamara" <timmcn@bitstream.net> wrote in message >> How do I tell which is the screw with ground wires attached to it [quoted text clipped - 3 lines] > exterior) you have the right place. Scrape away any paint under the > screw first, even if there are other wires already there. Thanks! > >> Hmmm, ground connections... I popped the stereo out of the dash to > >> check to see if there were obvious problems with the wiring of [quoted text clipped - 14 lines] > How do I tell which is the screw with ground wires attached to it > (just so I don't screw it down to something else and fry things)? Any screw that goes into metal attached to the body of the car will work, it'll be fairly obvious when you get in there. > How do I tell which is the screw with ground wires attached to it >> (just so I don't screw it down to something else and fry things)? > > Any screw that goes into metal attached to the body of the car will > work, it'll be fairly obvious when you get in there. Simple enough. Thanks! >>> Three days ago I noticed an intermittent "light out" indicator on >>> the dash. I traced this to the right rear taillight. Wiggling the [quoted text clipped - 23 lines] > cause and it's not just coincidence)? Nothing else in the car seemed > affected. The ground should definitely be stuck under a screw in the metal part of the body. Relying on the mounting to provide a ground is bad form. Mike > My 1990 240 has been acting oddly. > [quoted text clipped - 23 lines] > Thanks in advance to people who actually understand car wiring and > elecctricity... I am not one of them. Some stereos have a connection to the taillights for dimming the display when the lights are on (on the theory it will be dark when your lights are on). Exactly how this relates to your problem I sure don't know. You slacker ;-) Mike > Some stereos have a connection to the taillights for dimming the > display when the lights are on (on the theory it will be dark when > your lights are on). Exactly how this relates to your problem I sure > don't know. Interesting. How common is this? > You slacker Sad but true... >>Some stereos have a connection to the taillights for dimming the >>display when the lights are on (on the theory it will be dark when >>your lights are on). Exactly how this relates to your problem I sure >>don't know. > > Interesting. How common is this? The backlighting on the radio in my S70 is bright when the headlight switch is all the way to the left (daytime). Any other position, and it adjusts to the bright...dim dash light switch. >> Some stereos have a connection to the taillights for dimming the >> display when the lights are on (on the theory it will be dark when >> your lights are on). Exactly how this relates to your problem I sure >> don't know. > > Interesting. How common is this? Pretty common - I'd guess about half the models available do that. >> You slacker > > Sad but true... We should form a club, maybe have jackets! Mike >>> Some stereos have a connection to the taillights for dimming the >>> display when the lights are on (on the theory it will be dark when [quoted text clipped - 4 lines] > > Pretty common - I'd guess about half the models available do that. Wow. Who knew? Not me, obviously! >>> You slacker >> >> Sad but true... > > We should form a club, maybe have jackets! I'll get around to that when I have time. My "new" 89 780 has the old Sony cassette/equalizer setup, and just has a couple of indicator lights on, very faint high frequency noise, thought i actually heard a radio station it today, but have a wiring issue some where in the setup. (Car had water damage previously, and just now getting into the stereo issue, since I need sound other than the usual and unusual mechanical sounds I here) I did notice that the wiring diagram for mine shows this dimmer wire connection, too. Although I don't think that's my particular problem, it is interesting so see that feature. Alas, I will probably opt for a good aftermarket stero even if I get this one working, since my cassettes are pretty dusty these days and cd's are so much better sounding. Wlil keep the original stereo and 2 Sony amps in case I want to replace them as original equipment in the far off day I actually sell the black beauty of a Bertone. This vehicle definately has some extensive wiring harnesses running all through it I am discovering! Good luck with yours. I'd always check the voltages into the radio before going further, should be I think a constant 12V. line (green), another 12v. line that's on when the key is on (red) and of course the grounds, which are usually black in most 12volt negative ground systems. A cheap volt-meter can save you some money over the long haul. Of course a really good meter will last a good long time.... >>>> Some stereos have a connection to the taillights for dimming the >>>> display when the lights are on (on the theory it will be dark when [quoted text clipped - 14 lines] > >I'll get around to that when I have time. |
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