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Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 35482
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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2004 Ford Crown Vic 44,500 miles I'm a 72yo retired 30 vet

Customer Question

2004 Ford Crown Vic 44,500 miles
I'm a 72yo retired 30 vet (USN Aviation Electronics Techinician)
who attended the Delco-Remy Electrical Auto Training way back in 1967.
Discrepancy: On the way home last week, Alternator dash warning light
came on and the alt-gauge was at the top (Over-Charging). I continued
home since I was about a mile from the house. One of my auto manuals
indicated that it could be the alternator so, I borrowed a rebuilt
from my buddy at O'Reilly's. No joy, still overcharging. I checked
resistance of heavy battery charging lead from top of alternator back
to battery (fusible link) when changing alternator & it was 0.1 ohms
on different 2 Fluke meters. I also tested the battery with a heavy
load tester to see if cell was opening up. it was good,
i.e. green for 40 seconds.
1- Max alternator overcharging/high voltage out at all times.
2- Ignition switch dead in all positions.
3- No power indication in vehicle at all.
4- No power to fuse box on passenger side fender-well.
5- If I jump power from battery to RH fuse box, car cranks
& runs but, with high-alt-output for 15-20 sec test.
Sounds like a power relay, but which one??
Submitted: 1 year ago.
Category: Ford
Expert:  Ron replied 1 year ago.

Hello James and thank you for your question, my name is ***** ***** I can help you with this,

The alternator charge rate on your 2004 is controlled by the duty cycle from the PCM (computer) with your back ground are you able to do some testing If I send you the steps?

Customer: replied 1 year ago.
I assume so
Customer: replied 1 year ago.
Are you doing via this mode or via email?
Expert:  Ron replied 1 year ago.

Im suspecting you have a problem with the PCM but to be sure you are going to need to do some testing, see the complete file in the link below. You will want to start your testing at pinpoint test C 1.

See the first link below for those steps , copy and paste the link to your browser to open and view them

See the charging system diagram for reference in this link as well.

Customer: replied 1 year ago.
James Rewis is back after printing the 2 schematics, 1st hot link was only 1 page vice 3 pages of data.
Expert:  Ron replied 1 year ago.

Try this link, it has all you need for the pinpoint test C1