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A. Penland
A. Penland, Ford Senior Master Technician, ASE
Category: Ford
Satisfied Customers: 6212
Experience:  ASE Master Certified, ASE Advanced Gasoline Engine Performance
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I have an 2003 Lincoln Navigator and I just bought a new

Customer Question

I have an 2003 Lincoln Navigator and I just bought a new battery with 600 cranking amps and I had my alternator check and they said everything check out fine but when I turn on my school or my defroster my check charging system light comes on do I need
to get a bigger battery since everything in my car is electrical
Submitted: 1 year ago.
Category: Ford
Expert:  A. Penland replied 1 year ago.
Who checked the charging system and alternator?
Dealership, auto parts store or aftermarket repair shop?
Customer: replied 1 year ago.
Auto parts store and I had an after market repair shop take the alternator off and took it to the auto Supply store and to have the alternator check and it checked out fine. But when I turn on my AC or defroster the check charging system light comes on
Expert:  A. Penland replied 1 year ago.
Your alternator is controlled by the PCM (Engine Computer). The PCM acts like the voltage regulator. The PCM needs to see the alternator output to be 14.3 volts or better when the engine is running. If it drops below 14 volts, the battery light will come on and the AC system is considered a load on the charging system. Your Navigator should have a 750 CCA battery also.

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