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Weird electrical issues.. Bad battery, alternator, or shorted wire
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Scotty.p
New User
May 10, 2014, 10:50 AM
Post #1 of 7
(1595 views)
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Weird electrical issues.. Bad battery, alternator, or shorted wire
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I have 04 Volvo S80 T6 w/2.9L 6 cyl w/twin turbo. Ever since I got it the dash would display a message that there is a headlamp failure, dry running bulb & sometimes it says multiple bulb failure. I just cleared the message and went on because Ive checked all the lights and all lights work. last week I was on the highway and my rpms were at a steady 2500 & all of a sudden it climbed to 3500 and went back down, it did this by itself, then the message displayed on my dash that I have a bulb failure the message appeared right after the rpm's climbed. This happened again about 5 minutes later, then it happened a 3rd time and all the lights on my dash went out, my turn signals didn't work anymore, my ac blew warm air, my radio went off, my steering got tight, it displayed a message that the abs Brakes is failing and to pull over immediately. I pulled over, shut the car off, turned it back on started right up, it said the srs airbag system needs serviced. These messages never came up before, only the bulb failure messages appeared previously. I finally got home, shut car off, went inside and came back out to the car and the car wouldn't start, the lights on the dash lit up but car wouldn't start. I disconnected the battery and reconnected it and it started no problem. Sometimes it won't start and I'll disconnect the battery and reconnect it and it will start. I took it to autozone twice, first time it was a bad diode in alternator, second time it was a bad battery. Got it tested at OReilly's and they said battery and alternator are good but could be a shorted wire. What could it be? Thanks
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Discretesignals
Ultimate Carjunky
/ Moderator
May 10, 2014, 11:09 AM
Post #2 of 7
(1583 views)
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Re: Weird electrical issues.. Bad battery, alternator, or shorted wire
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Don't know how savvy you are with working on charging systems, but you should monitor system voltage and also check for excessive alternator ripple.
If you get a runaway alternator, 15 volts or higher, due to bad alternator regulation, that will reek havoc with computer modules in the vehicle and they will do some odd things.
The same applies in the other direction. If the system voltage gets too low, things will start acting flaky and shutting down.
Excessive alternator ripple means that you are getting too much AC current in the DC electrical system. Solid state DC control modules don't act right when they are supplied with too much AC. The job of the diodes in the alternator are to rectify AC into DC. If you have a shorted diode, that will allow AC current to pass through.
Could be that Autozone caught it when the problem was occurring and OReilly's didn't. I suggest you take it to a reputable shop that specializes in electrical diagnosis. There may be codes stored in those computer modules that may give direction.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on May 10, 2014, 11:16 AM)
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Scotty.p
New User
May 10, 2014, 11:15 AM
Post #3 of 7
(1577 views)
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Re: Weird electrical issues.. Bad battery, alternator, or shorted wire
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Don't know how savvy you are with working on charging systems, but you should monitor system voltage and also check for excessive alternator ripple.
If you get a runaway alternator, 15 volts or higher, due to bad alternator regulation, that will reek havoc with computer modules in the vehicle and they will do some odd things.
The same applies in the other direction. If the system voltage gets too low, things will start acting flaky and shutting down.
Excessive alternator ripple means that you are getting AC current in the DC electrical system. Solid state DC control modules hate AC and it will cause some very weird things.
Could be that Autozone caught it when the problem was occurring and OReilly's didn't. I suggest you take it to a reputable shop that specializes in electrical diagnosis. There may be codes stored in those computer modules that may give direction.
OReilly said the alternator had excessive Ripple. If i remember correctly, it was at like 14 or so
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Scotty.p
New User
May 10, 2014, 12:22 PM
Post #5 of 7
(1565 views)
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Re: Weird electrical issues.. Bad battery, alternator, or shorted wire
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Yeah 14v. He said it should be at 0 so there could be something using power when the car is off. My battery level was at 86% at that time too
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Discretesignals
Ultimate Carjunky
/ Moderator
May 10, 2014, 12:38 PM
Post #6 of 7
(1564 views)
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Re: Weird electrical issues.. Bad battery, alternator, or shorted wire
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Ok wait....if something is draining the battery while the vehicle is off, that is completely different than if there is too much AC in the electrical system.
This is getting confusing. You should have a shop check it out.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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