High voltage when running in hot weather

2002 FORD F-150

250,000 MILES • 5.4L • V6 • 4WD • AUTOMATIC

BRUCE GAFNER

MEMBER
1 POST

Newer battery and replaced alternator a few months back due to regulator error. Bench test of alternator okay, but in vehicle test regulator error at one parts store. Another parts store no errors.

High voltage caused electrical failure of dash gauges, windows, radio, etc. Battery discharged. Charged battery and now starts, but high voltage (gauge and icon) under acceleration in hot 100+F weather.

Aug 11, 2020 at 8:24 PM

JACOBANDNICKOLAS

✓ASE Certified Mechanic
110,194 POSTS

Hi,

How many volts is it showing? The voltage regulator is the only thing that controls voltage. Is it over 15v?

As far as testing, here are directions for checking for an overcharging system. Take a look through it and let me know if it helps. The two attached pics are actually the test procedures.

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2002 Ford Truck F 150 4WD Pickup V8-5.4L SOHC VIN L
Test C: System Overcharges (Voltage Greater Than 15 Volts)
Vehicle Starting and Charging Charging System Testing and Inspection Pinpoint Tests Pinpoint Tests Test C: System Overcharges (Voltage Greater Than 15 Volts)
TEST C: SYSTEM OVERCHARGES (VOLTAGE GREATER THAN 15 VOLTS)
C1
See pic 1

C1 - C2
See pic 2
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Let me know.
Joe

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Aug 11, 2020 at 10:31 PM

Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.