Electrical Gremlin

[Scomber]

Here I thought I was just about all set with this car. But today I'm having the radio and speedometer drop out. They go dead, then come back a few seconds later. Several times it's happened just as I signal a right turn.

 

Where do I look for the short? It's a 98 Legacy Brighton Wagon. The radio isn't the original, but it is Subaru, with cassette and weather band.

 

Scomber Sanctus.

Edited October 20, 2011 by Scomber

[Scomber]

DAMNIT!

 

Mayday Mayday Mayday.

 

The car died in the middle of traffic. I had to push it to get rolling down the side street, and it's now in the back post office lot in town.

 

So, what would cause radio, speedometer, brake lights, and turn signals to cross? Battery now reads about 9 Volts.

 

Scomber Sanctus

[Rooster2]

DAMNIT!

 

Mayday Mayday Mayday.

 

The car died in the middle of traffic. I had to push it to get rolling down the side street, and it's now in the back post office lot in town.

 

So, what would cause radio, speedometer, brake lights, and turn signals to cross? Battery now reads about 9 Volts.

 

Scomber Sanctus

 

I am thinking you have a bad battery, prolly one cell is dead in the battery, so voltage is low, but battery is not dead. I had this happen on a VW years back. The battery still had enough amperage to barely get the motor started, but low voltage resulted in crazy dash instrument readings, and caused turn signals to go nuts.

 

If you can, and have the tools and know how, pull the battery, take it to an auto parts house that will check the quality of the battery. Chances are, it is bad. If so, install a new battery, and your problem is solved.

[1-3-2-4]

Sounds like the alt went.. Mine did that really bad when I drove down to VA.. it only did it once when I was leaving work but I thought I could do it again but nope..

 

in the end I think the alt output wire was grounding to the alternator body and did it in..

 

I should of known because I changed all my dash lights to LED's and they were flickering like mad in the days it got really bad and it burned out a good few of them..

[Scomber]

Bad alternator or bad battery. The things I like about these two options are that they both explain how loads that are touchy about voltage dropping out when other, larger, non-voltage dependent loads are engaged.

 

Because the issue was briefly intermittent, I'm guessing alternator.

 

I have jumper cables on board, and a friend is coming to get me eventually. So I can bring the battery into a parts shop to be tested, or I can test the alternator once it's jumped.

 

I'm guessing it's the alternator.

 

How do I test the alternator? It has to be pulled, doesn't it.

 

Scomber Sanctus

Edited October 20, 2011 by Scomber

[Scomber]

Potentially Important Clue:

 

The timing belt was replaced this afternoon. The alternator belt was also replaced.

 

Scomber Sanctus

[1-3-2-4]

Stick the red probe from the volt meter to the post on the top of the alternator and stick the other to the battery negative terminal and if you don't see 14V with the engine running the alt is week or shot.

 

Also another test is to set the meter to AC and see if it's outputting AC (should not) when running.. that can cause odd things to happen and nasty things.

 

if the belt was replaced it does not mean much.. in order for it to not work the belt would have to be so loose that the PS pump would squeal before the alternator did.. besides the PS would feel heavy when turning if the belt was loose.

[Scomber]

So does that mean I should have continuity with the positive terminal from there? The wires have a bit of corrosion and a few strands are broken, but I don't see why they shouldn't carry current.

 

Scomber Sanctus

[1-3-2-4]

I'm saying with the car running and you see something like 12V output from the alternator then it's NOT charging the battery and the car will soon then die again.

 

You can clean up the terminals

[Scomber]

I am home. A friend came and got me. Once we jumped it, the system voltage stayed at 7 volts. Clearly there's an alternator issue, most likely a bad wire from when the timing belt was changed today and the alternator was temporarily moved out of the way. Tomorrow I will bring a fresh battery and drive it on battery electrical power alone (no headlights) to where I need to go to get the issue fixed.

 

Thank you all for your diagnostic help.

 

Scomber Sanctus

[Cougar]

Make sure the battery warning light turns on when you turn the ignition on. Current has to pass through that light to the alternator field to get the alternator action working. If that is ok then check the voltage at the alternator output lead. It should be between 13 and 14.8 volts.

 

Charge the battery up with a battery charger before using it in the car again with the alternator.

[Scomber]

I replaced the alternator this morning. One thing I noticed driving home tonight was how bright the headlights were. Obviously (20/20 hindsight) the reason the headlights were so dim before was that the alternator wasn't putting out enough juice. The accessory belt that drives the alternator was slipping, and I had it replaced as part of the timing belt job. So the new belt overcame the resistance in the alternator, overworked it, and finished it off.

 

If your headlights seem dim, check your system voltage. Lesson learned.

 

Also, I learned that my multimeter (the old one that happened to be in the car) is inaccurate, so Last night when it said I was down to 7 volts, I was actually around 11.

 

Scomber Sanctus