2004 c70 electrical/sound problems

jbcastello · Post by **jbcastello** » 10 Jan 2014, 01:26

MAIN QUESTION: The stock CD player while playing CDs or tapes, all of the speakers would stop working except the drivers side, but when playing radio it'd work fine. Went to a store, had new radio put in, had to get a second amp put in for some of the speakers so they'd still work. About a week later the drivers side speakers work, but they don't get very loud, and they also have lots of engine noise coming through them (I've always had engine noise coming through them but now with the new amp on the passenger side they don't get it but haven't had the speakers not getting very loud until the new CD player) BUT eventually the speakers will kick in at normal volume, and the engine noise will disappear. Amp going bad, or is it a wiring issue?

OTHER QUESTION: that if answered would be phenomenal but I think my car is just haunted.

I've been to a volvo dealership, and 3 different repair shops about these issues, not one has been able to give me a definite fix. Was having problems with my alternator, car would just shut off if I wasn't giving it any gas, or any big electrical pull, convertible top, rolling all the windows up/down(especially if the windows were all the way up or down it'd instantly turn the car off) Or if I turned my vents on high. Had my alternator replaced, problems still persisted, but only sometimes. Took it to another repair shop, had it looked at, for broken window regulator and about the power issues, they told me to replace the battery so did that, problems still persisted. Then a few new issue came up. The car would NOT stay started, and sometimes I would lose all power to everything for acouple minutes, or until I opened the door back up...

The day that the car not staying started unless I fed it gas, but would immediately turn off the second I stopped, I got it started and stayed started, drive it to the dealership that second and dropped it off. They told me I should replace my alternator/battery, (which I had already done) So I told them that, they tested everything and everything was fine.

The second new issue, with the car losing all power sometimes, I haven't been to the shop yet but I'll get in the car, lights from the door being open turn on, insert key, turn to start ignition, and ALL lights will turn off, try turning the key again, nothing turns back on, open the door, the lights stay off for acouple seconds, then they'll come back on, or I just wait a few minutes and the power will come back. Very frustrating when you're in a hurry.

Every once and awhile the car WILL just turn off while driving, but It'll start right back up with no issues and won't do it again.

Any and all help would be appreciated, I'm tempted to have the dealership put in the alternator, and not a local repair shop, but I really don't want to have the same problems occur after I replace an alternator for a second time in a year...

socompsp · Post by **socompsp** » 10 Jan 2014, 10:01

it sounds like you may have a serious short problem. in my 98 c70 ive had a similar radio issue that continues to this day. my issue is a little different, the sound from my radio just cuts out completely, sometimes if i switch to radio from casset (have an adapter for phone), it will start working again, and sometimes i can even switch back to casset and it will work, but not always. and sometimes i cannot get the sound back at all. most the time the sound cuts in and out and doesnt out-right quit. my issue is completely random. i did notice that it happens when i hit a bump or turn sharply, but this is not always the cause. head unit seems rather warm to the touch while this happens as well. i have not yet been able to track down a cause although i suspect a short in my case as well. did your issue start happening after a repair? i suggest you yourself look for any wires with stripped or missing insulator before you have a shop do the trace, cause im sure that costs alot of money. oh and btw i have the sc-901 (or 902 cant remember) head unit with 4x100 amp.

Post by **kcodyjr** » 10 Jan 2014, 16:29

Start with checking the ground strap. For engine noise to transmit into the radio like that, there has to be a shitty ground turning the engine block into an antenna.

socompsp · Post by **socompsp** » 10 Jan 2014, 16:55

kcodyjr wrote:Start with checking the ground strap. For engine noise to transmit into the radio like that, there has to be a shitty ground turning the engine block into an antenna.

lol is this even possible? i dont think engines transmit radio wave frequencies. but it is possible that the loose ground is causing static, or there are vibrations coming through to the dash and doors.

Post by **kcodyjr** » 10 Jan 2014, 17:44

Who told you there has to be a radio frequency signal? A DC source is sufficient to screw with a nearby AM receiver, once when you touch the wire to it, and once when you take it away. How many times per second is there a coil discharging through the block? Right. It's in the AF range, so you don't get those higher level RF behaviors, but it's still a radiated electromagnetic signal.

The radio is (electrically) on the other side of that crappy ground, where the charge dumps to after overcoming the resistance of the strap, pulling it slightly above ground in the shape of the combined coil signal. That's straightforward noisy power source interference that a cheap enough radio will happily send along to the speakers.

There's also several circuit traces inside the head unit carrying low voltage audio signal, which would also serve as a remarkably poor sensitivity AM receiver, but well enough to pick up what the engine is radiating, especially since it's probably well inside the near field.

Point is, the two ground straps are the two most important electrical junctions in the car, and oft neglected.

socompsp · Post by **socompsp** » 10 Jan 2014, 19:04

i guess it can happen then haha, that makes since, i just wasnt sure if there were too many barriers between the two.

Post by **anjill182** » 11 Jan 2014, 03:43

Bad ignition switch?

socompsp · Post by **socompsp** » 11 Jan 2014, 11:12

im not sure about that, so let all ask ourselves, if he states it happens in second gear, does the ignition switch know what gear the trans is in? another thing im not sure about but i think could be worth some checking into, is if its in second while it happens, is it possible one or more of the shift hardware is shorting intermittently?

jbcastello · Post by **jbcastello** » 11 Jan 2014, 23:50

UPDATE: It was the first warm day in the area since i've had the issue and driven my car (warm= above 50f) the speakers started up fine, no engine noise, definitely starting to think its an amp problem of some sort.