5 Signs of a Failing Land Rover MHEV DC-DC Converter

Is Your Land Rover MHEV Behaving Strangely? 5 Signs of a Failing DC-DC Converter

A faulty 48V to 12V DC-DC converter in a Mild Hybrid Land Rover can cause a host of confusing electrical problems. Recognizing the signs early can save you from being stranded. Here are the top five symptoms pointing to a failing converter.

1. The Obvious: ‘Charging System Fault' Warning

This is the most direct symptom. The car is telling you that the 12V battery is not being charged. In an MHEV, this almost always points to the DC-DC converter.

2. Repeatedly Dead 12V Battery

Have you replaced your
12V AGM battery, only for it to die again a few days or weeks later? This isn't a sign of a bad new battery; it's a classic symptom that the battery isn't being replenished. The converter is failing to do its job as the car's charger.

3. Widespread, Seemingly Unrelated Electrical Gremlins

As the 12V system voltage drops, various control modules can start to malfunction. You might see random warning lights (ABS, SRS, etc.), a flickering infotainment screen, or power windows that are slow to operate. This chaos is caused by modules not receiving the stable voltage they need to function.

4. Automatic Start/Stop System is Always Unavailable

The MHEV's auto start/stop feature requires healthy voltage in both the 48V and 12V systems. One of the first things the vehicle disables when it detects a charging problem is the start/stop function to conserve power.

5. A ‘Click' But No Start

Even if the 48V MHEV system is healthy, your vehicle relies on the 12V battery to power up the computers (ECU, BCM, etc.) and engage the starter relay. If the 12V battery has been drained by a faulty DC-DC converter, you'll hear a click from the relay, but there won't be enough power to start the vehicle.

If these symptoms sound familiar, it's time to have your charging system professionally tested. A failed DC-DC converter is a likely diagnosis, and replacing it with a new genuine unit is the correct repair.