Diagnosing a Battery Charging Problem on a Carrera 4

Tools used

Referenced tools without an associated photo: Multimeter

If there is a charging problem even though the battery, alternator/regulator, and ground strap are in good condition, check the D+ excitation circuit and the battery warning light. The warning light should normally come on when the ignition is turned on and then go off when the alternator is charging.

Figure 13.1 — Simplified diagram of the alternator excitation circuit via the battery indicator light. — Figure 1 — Simplified diagram of the alternator excitation circuit via the battery indicator light.

Overview

Figure 13.2 — Relay No. 11 located in the fuse box of the Carrera 4. — Figure 2 — Relay No. 11 located in the Carrera 4's fuse box.

Explanation

In the case described, a voltage of 9 V was measured, and relay No. 11 was no longer receiving power. The diagram shown illustrates the principle observed on this vehicle. Verify the circuit path in the documentation for the specific model year. A potential idle-speed recalibration procedure should only be performed if it is specified for the installed control module.