P0626 Alternator and charging: signal or voltage too high

By: Diagno editorial team · Updated: 2026-10-15

P0626 means: Alternator and charging: signal or voltage too high. The computer monitors battery voltage and charging. Drive gently and have the car checked soon. The repair usually costs about €30–300 in Estonia. The most common cause: connector loose, damp or corroded. Other possible causes: wire shorted to power or ground broken, faulty battery or alternator.

What it means

The computer monitors battery voltage and charging. The voltage is too low, too high or unstable. A weak battery can also cause other odd faults. The signal voltage is too high. Usually a wire is shorted to power, the ground is broken or the part itself has failed.

What you may notice

• Hard starting
• Lights dim
• Battery light may be on
• Random warnings on the dashboard

What could be wrong

1. 1Connector loose, damp or corroded
2. 2Wire shorted to power or ground broken
3. 3Faulty battery or alternator
4. 4Engine computer fault (rare)

Repair difficulty: Easy

What you can check yourself

First look at the connector and wiring: anything loose, melted or green with corrosion? Check that the battery terminals are clean and tight. With the engine running, battery voltage should be about 13.8–14.7 V. You can do the simpler checks yourself.

How we fix it

1. We read the fault data on the diagnostic tool and check whether the fault is constant
2. We measure the circuit's supply, ground and signal
3. We repair the wire or replace the connector
4. If the wiring is fine, we replace the battery or alternator

Standard SAE description: Generator Field/F Terminal Circuit High