P0D68: Air Conditioning Compressor Motor Voltage Sensor A Circuit
What to do
Expect no air conditioning, and on a car with a heat pump, no cabin heating either. The car will drive. In warm weather watch for slower rapid charging as well — on many cars this compressor also cools the battery.
What this code means
The circuit for the sensor measuring the supply voltage at the electric air conditioning compressor's motor is faulty.
An electric car's air conditioning compressor is a high-voltage machine, and almost everything that follows from that surprises people who know conventional systems.
A belt-driven compressor stops when the engine stops. That is tolerable on a petrol car because the engine only stops when the car does. On a hybrid the engine stops at every set of lights, and on an electric car there is no engine at all — so the compressor has to be driven by its own motor, fed from the traction pack at several hundred volts, with its own inverter to turn that direct current into the three-phase supply the motor needs. That inverter is why this block has phase current codes for an air conditioning part.
Two consequences change what a fault here means. First, on many cars this same compressor cools the battery, so an air conditioning failure becomes a charging and power failure in warm weather — the driver reports a hot cabin and the car quietly reports reduced rapid-charging. Second, a heat pump runs this compressor in reverse to heat the cabin, so on a car with one, losing the compressor loses the heating too, in winter, when nobody suspects air conditioning.
And the repair carries a hazard that has no equivalent on a conventional system: the oil. A high-voltage compressor is lubricated by a specific non-conductive polyolester oil carried in the refrigerant. The PAG oil used in every belt-driven system absorbs moisture and conducts — put it into a high-voltage compressor and it degrades the motor's insulation, which can energise the refrigerant circuit and the metal pipework running through the car. This is a real and repeated workshop error, not a theoretical one, and it is the reason these systems must be serviced with dedicated equipment that has never seen PAG oil.
This particular sensor is how the compressor's inverter knows what it has to work with, and without it the inverter cannot set its switching correctly, so it shuts down rather than guess.
The base circuit fault: no plausible signal at all.
Likely causes
Start here
- Faulty electric air conditioning compressor · specialist
- Corroded or loose connector · specialist
Less common
- Open circuit in sensor wiring · specialist
- Damaged wiring harness · specialist
- Failed sensor reference voltage supply · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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