Car died on freeway... Electrical problems?

[Lethal GST]

Had a similar issue almost exactly a year ago. Past couple months, the battery light would come on when starting the car, but go away after revving the motor past 3500 rpms. This seemed to be an intermittent problem. Also, while cruising, sometimes the voltage would read around mid 12s to low 13s, and some days it would read high 14s, sometimes even hitting 16.

Today, while driving home from work, noticed that voltage was reading around 11.5. Almost made it home when realized voltage went extremely low on the freeway (around 9). Car finally just died while exiting. A tow trunk came to give me a jump and charge, during which the voltage read a a steady 12.5-7. Once disconnected from the truck, voltage dropped to mid 11s again. I was able to drive the car home, but when I parked, I noticed that the voltage was once again around 9.

I'm assuming it's an alternator problem? When it happened last year, I replaced the battery, and had the alternator tested, which was from fairly new from Autozone. It passed their tests fine, so it wasn't replaced. You guys think that since I didn't replace it a year ago it's finally coming back to bit me in the arse now?

Thanks in advance!

 

[xdsmlaser93x]

I had the same problem you did with my old laser 1.8, i put in a new battery and an alternator and everything was good for about a year or so. the stereo in it would smoked it.

 

[luv2rallye]

Sounds like a bad alternator but it could also be a bad battery or a massive short or combination.

Let's test the battery first: Charge it up if you can. Then disconnect the battery negative first and then the big + cable on the alternator and tape it up so it can't touch metal. Now reconnect battery negative and measure battery voltage (should be 12V or higher). Now turn high beams on for 30-60 seconds and again measure battery voltage with them on (should be 11.5V or higher and within 0.5V of last measurement or bad battery). Now turn off headlights, start car and measure battery voltage (should be 11.5V or higher). Now turn high beams on for 30-60 seconds and again measure battery voltage with them on (should still be 11.5V or higher and within 0.5V of last measurement or bad battery).

If battery ok let's test alternator (read next post about checking alternator fuse first before continuing): Stop engine and everything off. Disconnect battery negative and reconnect alternator. Reconnect battery negative and measure battery voltage (should be 12V or higher). Start engine and measure battery voltage (should be around 14.4V within 0.5V or bad alternator). Now turn high beams on and again measure battery voltage with them on (should still be around 14.4V within 0.5V or bad alternator).

A massive short can sometimes make an alternator or battery appear bad while testing it when actually there is nothing wrong with it. If you suspect a short see here: http://www.dsmtuners.com/forums/showthread.php?p=1496998#post1496998 and start with the small light bulb in series with the battery test.

Note A: For those reading this post for just a quick and dirty way of testing the battery without disconnecting anything:
With car off, measure battery voltage (should be 12V or higher). Now turn high beams on for 30-60 seconds and again measure battery voltage with them on (should be 11.5V or higher and within 0.5V of last measurement or bad battery).
Note that this test is not as complete as above test and it assumes there is no short in the alternator (which the above test accounts for by disconnecting it). But it sure is very quick and easy and a bad battery usually fails. Of course taking the battery to an auto store or a shop will test it better (they put a large load on it and a shop may even check it's charging rate and capacity), but this is something easy that you can do at home and a place to start.

 

[steve]

I just want to add that if the alternator fuse is blown the second set of test would also fail so make sure to check the fuse before pulling the alternator.

Steve

 

[Lethal GST]

Thank you DSM Wisemen

I will take all your recommendations under consideration.

One more question, could an electrical short also be responsible for the high spikes in voltage I was getting last week (while the car was still running)? On a couple of night drives I would get high 15s-16's, and a couple of times I even hit 17!

 

[steve]

If they were short spikes maybe, but it they were longer than fractions of a second then no, it would be from the voltage regulator going out.

Steve

 

[Lethal GST]

If they were short spikes maybe, but it they were longer than fractions of a second then no, it would be from the voltage regulator going out.

Steve

Thanks for the info. They weren't spikes, the car was actually maintaining those high levels. So that problem was definitely the voltage regulator.

Came back from work a few minutes ago. Tried to start car, but wouldn't turn over. All the electrical systems seemed to be functioning, but voltage was reading around 8.3. I gave it a jump, kept the revs around 3500rpms, and the voltage was staying steady around 14.1.
As soon as I let off the gas, they would drop down to the 12s.

I also noticed that the alternator was making a much louder "whirrrrring" noise; in fact I could hear it over the engine.

Could a bad voltage regulator be the source of all these problems? The issues first started about a year ago and were basically left untreated.

 

[Lethal GST]

We pulled the alternator and it was covered oil. Replaced it and the car has been running fine ever since.

However, today I hit a bad bump in the road which caused the idiot lights to come on, and all the interior stuff (locks, windows, radio) stopped working. Then I tried turning on the headlights and the horn started going off. Worst part is that I work on a Coast Guard facility and this all started right near the admiral's office!

Anyway, so I finally parked, yanked out the horn fuse, and saw that the 100A alternator fuse was blown. I'm thinking that when I hit the bump, my interooler pipe might hit something connected to the alternator, causing it to ground out.

My question is, do I have to remove the battery before I replace the alternator fuse?

 

[freshlane]

I would disconnect it.

 

[DSM-Franek]

We pulled the alternator and it was covered oil. Replaced it and the car has been running fine ever since.

However, today I hit a bad bump in the road which caused the idiot lights to come on, and all the interior stuff (locks, windows, radio) stopped working. Then I tried turning on the headlights and the horn started going off. Worst part is that I work on a Coast Guard facility and this all started right near the admiral's office!

Anyway, so I finally parked, yanked out the horn fuse, and saw that the 100A alternator fuse was blown. I'm thinking that when I hit the bump, my interooler pipe might hit something connected to the alternator, causing it to ground out.

My question is, do I have to remove the battery before I replace the alternator fuse?

I had a similar problem with my 100A alternator fuse.

Every time I would make a left turn my fuse box would short against my frame and pop the 100A.. And then the horn would go off constantly, people would look at me like I was laying on the horn at them and my lights were stuck on blah blah blah .. Haha. Anyway. My problem was that I did not have the bottom cover on the fuse box in the engine bay.

But back to your question,
I poped the 100A twice so far and never took the battery out to swap the fuse

-Frank

 

[Lethal GST]

Thanks for the help everyone!

Another problem though. I'm stuck here at work and none of the local shops within walking distance have a 100A fuse in stock. Their computers keep pulling up the part number for the 80A. Will that be good enough for a temporary fix?