Mechanics

BATTERY AND BRAKE LIGHTS

1998 Ford Contour • 193,000 miles

Today my battery light came on, I took it to get checked out and it was the alternator that was failing. I risked the drive home without getting the repair(will get the alternator replaced Tuesday). While on the freeway the brake light and ABS lights came on. What/why would those come on?
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Dsmddn11
October 15, 2012.



MOST LIKELY LOW VOLTAGE TRIGGERED IT

A LOT OF TIMES GAUGES START GOING CRAZY TOO, AS THE NON-CHARGED BATTERY STARTS DEPLETING

YOU GONNA DO THE REPAIR YOURSELF?

A FRIEND?

A PAY SHOP?

THE MEDIC

Tiny
CJ MEDEVAC
Oct 15, 2012.
I'm going to do the repair myself.
That would explain why some of my gauges have been going crazy.

Tiny
Dsmddn11
Oct 15, 2012.
Depending on how the diagnostic tests were done there's more than just saying it's a bad generator. Before you stick a new one on and have the same problem, measure the voltages on the two test points on the back. If you find 0 volts on both, you have a blown fuse. If you find full battery voltage on one and 0 volts on the other, replace the brush assembly. That can usually be done without removing the generator from the engine. I'm pretty sure you have to buy a new voltage regulator to get the brush assembly that's attached to it.

If you find full battery voltage on one test point and less, but not 0 volts on the other one, that part of the circuit is working. In that case measure the voltage at the output terminal with the engine off and with it running. That will tell us where to go next.

Caradiodoc
Oct 15, 2012.
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LET ME KNOW IF YOU'RE GONNA BUY MY LUNCH NOW!

THE MEDIC

Tiny
CJ MEDEVAC
Oct 15, 2012.
All that was done was the battery voltage was measured and it came out at about 13.5V while the car was running, when the fan turned on it went down to about 12.3V. With the engine off the battery was at around 12.2V. After that I was told it had to be the alternator. I just replaced the alternator a little over a year and a half ago. The battery was replaced a little before the alternator.
Lucky for me if either is failing they are both under warranty, the battery for another 3 years and the alternator has lifetime warranty.

Could this be caused by a simple loose cable? I only ask because that happened once 4 years ago. I was never told what cable so I couldn't check this time.

Tiny
Dsmddn11
Oct 15, 2012.
13.5 volts is a fuzz too low unless the battery was run down, and that's what 12.2 volts indicates. Low engine speed will aggravate that. Part of the test procedure involves raising engine speed to 2000 rpm during the load test. However, 13.5 volts proves the generator was working. Ideally the voltage should be between 13.75 and 14.75 volts but that quarter volt isn't the cause of a problem.

There's a number of ways a generator can fail, and given the warning light turned on, yet the 13.5 volts says it was charging while it was being tested, but dropping to 12.3 volts suggests it can't keep up with demand. That's the result of one defective diode of the six. That will reduce its maximum output to exactly one third of its rated output current. Replacing diodes isn't easy or cost-effective, especially if the generator is under warranty. All of your observations suggest simply replacing it will be the end of the story.

Caradiodoc
Oct 15, 2012.
Thank you guys for the answers, in the end I did just replace the alternator and problem solved. When I took it to replace it, they tested it first to make sure it didn't work, and as it turns out it was completely dead. Had a bit of trouble getting it out because the repair manual said there were 3 screws to remove it, there were only 2. Putting it in was a piece of cake. But again, thank you guys. I got another question up if you guys want to help. Noise related this time.

Tiny
Dsmddn11
Oct 19, 2012.