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HDGENE, Ford Senior Master/Diesel/Trans
Category: Ford
Satisfied Customers: 5704
Experience:  25 years Auto experience, Ford ,GM, Chrysler, Asian & European
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My name is ***** *****. I have a 2008 F150 4.6l It was

Customer Question

My name is ***** *****. I have a 2008 F150 4.6l It was custom build in Feb 2008 because it's a reg cab 8' box and all pick ups now are shopping carts with 5 or 6' At 4200 rpm my dash gauges all go to 0 and the dash lights go off. The headlights increase in intensity to the point where it blows the lightbulbs. The Ford dealer told me to replace the alternator. I had it tested with the reg on it and it put out 14.1 V at all ranges up to 6200 rpm. I replaced the regulator regardless. No change. I had a licened mechanic go with me on a test drive with his diagnostics computer from work. At 4200 rpm the voltage spiked to 15.1 V. He suggested it could possibly be the PCM. I got a used PCM and had it flashed and programmed by the Ford dealer. Still no change. At the Ford dealer I can't seem to get any answers other then bills. Any ideas? My email is***@******.*** Thx for taking the time to read this, scratching your head and I'm just hoping you can give me some sort of clue. Thx, ***** *****
JA: Thanks. Can you give me any more details about your issue?
Customer: I think that is all the details I have
JA: OK got it. Last thing — Ford Mechanics generally expect a deposit of about $28 to help with your type of question (you only pay if satisfied). Now I'm going to take you to a page to place a secure deposit with JustAnswer. Don't worry, this chat is saved. After that, we will finish helping you.
Submitted: 1 year ago.
Category: Ford
Expert:  HDGENE replied 1 year ago.

Hello, are any generator codes stored with the increase of charging system voltage? Why did you only replace the regulator and not the complete altenator assembly?How many miles are on the vehicle? No codes stored in any of the othe rmodules? Instrument cluster, pcm, etc?

Customer: replied 1 year ago.
I have 193000kms on the truck. The alternator was in perfect shape and tested 100 % ok and therefor didn't get replaced. The regulator has been switched back and forth, and both old and new are ok. The only code was for a ground to the driverside door. No other ones were found.
Expert:  HDGENE replied 1 year ago.

Well if it is overcharging there is an issue with it I would think and the dealer recommended replacing it. Thats where I would start first for sure and see if the 15 volt issue is resolved

Customer: replied 1 year ago.
But then why only at 4200 rpm?
Customer: replied 1 year ago.
Always and every time and only at 4200 rpm
Expert:  HDGENE replied 1 year ago.

Diode trio dropping out would be suspect in the altenator cant hold field

Customer: replied 1 year ago.
Replaced alternator and still the same results..