Impreza electrical problem

[zint]

My 2002 Impreza 2.5RS has the brake light and the battery light coming on after driving for 5 minutes. I recently got a new battery, new alternator installed and new brake pads. But the car's battery light and brake light continue to come on and stay lit after approx. five minutes of driving. Now the car won't start - has a drained battery - after sitting for about a week. I have noticed that the radio display had been staying lit when the car is not running and didn't think this was normal, but also didn't think it was drawing enough power from batter to hurt anything. Anyone have a clue as to what's going on with my Impreza???

[idosubaru]

interesting. time to start checking for a drain.

 

the radio light should not stay on, i'd just unplug the radio and fuse and see if that does it.

 

technically you should probably test for a drain from the radio by checking the draw with it unplugged and plugged in. the ghetto method would be to disconnect the stereo or it's fuse and see if the battery stays charged.

 

it's not impossible to get a bad batt or alt too, but unlikely given the same exact symptoms before and after.

[Cougar]

The warning lights being on indicates a bad alternator even though it was replaced. To verify things remove the rear connector on the alternator and see if the warning lights are off after you start the engine. If they are off that will verify that there isn't some other grounding problem on the lamp lead and the alternator needs to be replaced. Whenever the battery warning light is on it indicates the alternator isn't working.

[Durania]

I strongly suggest taking the alternator back and getting a replacement.

[Fairtax4me]

Cheap alternator maybe. Where did you get it?

 

There is a plug on teh back of the alternator where a few wires plug into it. Make sure that is connected tight and the pins/sockets inside it are 100% clean.

[SubaruAlliance]

time to start looking for a short. i would start with the charge circuit since that was the last thing replaced, and now it's starting to drain the battery. the radio light being on isn't gonna drain a brand new battery in a week. the radio light staying on, the charge light, and the brake light being on are indications of the circuits being affected by the short, so while they may be getting annoying, there are signs showing you where to look. simply unplugging the radio won't fix the problem, it will only fix one of the symptoms of the problem. (unless of course the radio is the source of the problem lol)

 

i would jump start the car, while it is running put a volt meter on the battery terminals and see what the voltage is. if it's 12.6 or lower that means the alternator isn't doing anything. ideally you wanna be in the 14.25-14.75 range. at least that will tell you if the alt is working. if it is working, then you know a short is draining the battery. I might have mis read it, but i assumed the battery and brake light came on after the battery and alternator swap? i would start with the newest symptom first.

 

in my experience 80% of shorts are ground issues, not power. look for a power wire that is grounding out.

 

also if the short is in the radio circuit, it must be BEFORE the ignition circuit, otherwise turning off the key would kill the power to whatever is causing the short. (correct me if i'm wrong guys, but it seems if it is something that is normally off with the key then turning off the ignition would stop the short? or something that is hot all the time.)

 

also the brake light being on should refer to the e-brake being set, and if it's off, it should be signaling low brake fluid level, not the wear of the pads.

Edited December 29, 2010 by SubaruAlliance

[Cougar]

The battery warning light really isn't a check for shorts on the power bus though if that lead gets shorted on the alternator side of the lamp it would cause a charging problem and turn the light on.

 

Shorts as they are normally refered to are caused when a power wire touches a ground point and hopefully will blow out a fuse that is there to limit the current to a safe level that the power wire can handle without damage to it. To me, they are a power wire issue because the trouble is usually due to insulation damage on the power wire, not the ground.

 

I think the lighting issue in the radio is most likely due to a problem with the way the light display is hooked up or with the lighting control module. If none of the other lights are a problem then I suspect the radio is the trouble. I don't believe the power for the radio display light is controlled by the on/off switch of the radio. The light circuit needs to be isolated from ground since the dimmer circuit controls the ground side of the display lighting. If the radio display doesn't dim along with the rest of the lights on the dimmer then I suspect it is wired directly to the light power and ground. If this is correct it would drain the battery over time.

Edited December 29, 2010 by Cougar

[nipper]

My 2002 Impreza 2.5RS has the brake light and the battery light coming on after driving for 5 minutes. I recently got a new battery, new alternator installed and new brake pads. But the car's battery light and brake light continue to come on and stay lit after approx. five minutes of driving. Now the car won't start - has a drained battery - after sitting for about a week. I have noticed that the radio display had been staying lit when the car is not running and didn't think this was normal, but also didn't think it was drawing enough power from batter to hurt anything. Anyone have a clue as to what's going on with my Impreza???

 

You don't know what else is powered when the radio light is on. There could be a few lights that are very dim. Unplug the radio for a week, live with a ipod, and see what happens.

 

Another possability is a crap Alt. there are quite a fe really poor rebuilds (read China again or Mexico) and that may have a short in it.

 

Can you fully charge the battery, disconect the Alt at the Alt and let it sit for a week to see what happens?

 

After that we will suggest the next step.