2007 Ford Focus Alternater

Tiny
ALVLARWHITE14
  • MEMBER
  • 2007 FORD FOCUS
  • 2.0L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 88 MILES
Had altern. Rebuilt 2 days ago. Was told there was a PCM problem, but not mandatory presently! Not 2 blocks after leaving shop, low battery light comes on. Shop is closed- weekend- and car is beginning to stall out once again! HELP!
Do you
have the same problem?
Yes
No
Saturday, January 11th, 2014 AT 10:14 PM

5 Replies

Tiny
CARADIODOC
  • EXPERT
What was diagnosed as being the cause of the problem? What was replaced in the generator? What kind of help do you want? Do you want to diagnose this yourself? If so, do you have a voltmeter?
Was this
answer
helpful?
Yes
No
Saturday, January 11th, 2014 AT 10:32 PM
Tiny
ALVLARWHITE14
  • MEMBER
Once again, the Alternator was bad- diagnosis. Alt. Rebuilt- diods and rotor were bad and were replaced. Was then told the pcm was malfunctioning and would eventually- not now- need replaced. Problems are occurring again when the shop told us it would be ok for time being. My question is, did we get screwed by having alt. Rebuilt and is $ 292.00 est. On pcm repair a reasonable estimate!
Was this
answer
helpful?
Yes
No
Saturday, January 11th, 2014 AT 10:42 PM
Tiny
CARADIODOC
  • EXPERT
I have no way to know how they diagnosed a problem with the computer, but I can't help but wonder how they think it can be okay but needs TO BE replaced later. Most mechanics aren't psychic.

A failed diode is somewhat common. One bad one of the six will reduce the maximum output current to exactly one third of the generator's rated current. 30 amps from the common 90 amp generator is not enough to run the entire electrical system under all conditions. The battery will have to make up the difference until it slowly runs down over hours or days.

A rotor is one of the last things to fail. The commutator bars the brushes ride on could get chewed up, ... I suppose, but in 40 years of repairing electrical problems, I've never come across a bad one yet.

Ford had a really nice charging system throughout the '90s, but it's anyone's guess what problem they found a solution for when they added an unnecessary and unreliable computer circuit to it. The charging system on a 2007 model doesn't do anything they didn't do in the '70s.

As for the cost of that computer, that seems rather low, but I don't replace many computers. Wiring problems, like corroded splices and connector terminals cause a lot more trouble than computers.

To figure out where to go next, I need test results to analyze. You can start that process if you have a digital voltmeter. Measure the battery voltage with the engine off and with it running. With it running, you must find between 13.75 and 14.75 volts. If that is okay, the next step requires a professional load tester. Those will measure maximum output current and "ripple" voltage. Those values will point us in the right direction.
Was this
answer
helpful?
Yes
No
Sunday, January 12th, 2014 AT 12:00 AM
Tiny
ALVLARWHITE14
  • MEMBER
NO REPLY! No answers?
Was this
answer
helpful?
Yes
No
Sunday, January 12th, 2014 AT 12:26 AM
Tiny
CARADIODOC
  • EXPERT
Are you saying you have no answers until later, or did you not see my reply?
Was this
answer
helpful?
Yes
No
Sunday, January 12th, 2014 AT 2:20 AM

Please login or register to post a reply.

Recommended Guides