Category Archives: Hybrid

Electric Car Servicing: A/C and Heating

Electric Car Servicing: A/C and Heating

Air conditioning has become the mainstream on cars since the 1990s, and of course, a car with a premium price tag and showcasing the latest technology can’t be sold without it. Traditionally, a refrigerant compressor is driven by a belt from the engine, and an electromagnetic clutch allows the compressor to be disconnected when the pressure is outside the limits, when full engine power is demanded, or when the driver switches it off. In recent years, this has been replaced by the variable displacement compressor on many cars, which controls the flow of refrigerant similar to a suction control valve on a high pressure diesel pump.

When a hybrid engine stops, there is no way to drive the refrigerant compressor. The first generation Toyota Prius avoided this particular problem by keeping the engine running when the air conditioning was on. This rather inelegant solution was much improved on the second-generation car, by the addition of an electric refrigerant compressor.

An air conditioning compressor draws a similar amount of power to a starter motor, so when running for long periods it’s far more practical and efficient to run this from the high voltage system than attempt a 12V supply. Toyota’s system uses a three-phase motor, powered by an A/C supply from the inverter. There’s no need for a clutch, because of course the car can spin the compressor’s motor at whatever speed it desires.

These days, air conditioning compressors tend to have built-in inverters, so are fed by a fused high voltage DC supply, and internal circuitry operates the motor, typically on a LIN network.

So, what about heating? In the case of a hybrid vehicle, we have the same source of waste heat as traditional cars, so our heating system is largely conventional, save for an electric pump to circulate coolant when the engine is hot but not running.

Electric cars are different, as the big source of waste heat is no longer available. A heating element can be used for cabin heating. In some cases, this is fitted directly in the heater box, similar to a fan heater. It’s more common for the heater unit to be located under the bonnet, and liquid coolant to be pumped around a heater matrix – although slightly less efficient and requiring more parts, this does keep any high voltage wiring out of the interior.

Another solution to cabin heating is to use a heat pump. This uses the existing air conditioning components with a few extra parts (typically a second condenser inside the car, and a few electrical valves) in order to pull heat into the car, rather than pulling it out. The heat is normally sourced from the outside air, sometimes in conjunction with waste heat from power electronics cooling.

Electric heating and cooling gives us numerous other benefits. If you leave at the same time every day, you can set a timer to pre-heat or pre-cool the car ready for you to leave. If the car is plugged in, this power can be drawn from the mains, so not only is your windscreen clear and your car a comfortable temperature, but your battery is still fully charged as well. Some models also use the air conditioning system as part of the battery cooling system, which of course uses further valves to direct refrigerant to the required part of the circuit.

From a servicing point of view, the most important thing to be aware of is the variation of different systems and how it works on the car you’re working on. Even a regas is not as straightforward as it once was – normal air conditioning oil conducts electricity, which doesn’t go down well in an electric compressor, so as well as using the right oil, it’s essential to flush all machine pipework to ensure no contamination. Many models also have specific procedures for regassing to ensure that valves used for battery cooling or heat pumps are in the correct position – if the valves are shut, you may only be regassing part of the system!

A guide to understanding and offering a safe hybrid service

Regulatory demands for better fuel economy and reduced emissions will continue to drive the increase in hybrid vehicles on the road in the future.

In fact, by 2020, it is projected that volumes will nearly triple from the two-million vehicles produced in 2012, so there is no doubt we will continue to see an increase in the number of hybrids entering the aftermarket once the warranty period ends.

Due to the high-voltage circuits contained in most hybrid vehicles, proper service takes on a whole new approach. Improper handling of the hybrid system may result in electrocution and damage to vehicle components, so it is important to closely follow the service procedures found in the approved VM repair manual when servicing these vehicles.

Each hybrid is unique and the proper processes need to be followed for locating/removing or switching off service plugs/switches prior to servicing the vehicle. There are a variety of tools required to help diagnose and service hybrid vehicles.

First, and foremost, a quality diagnostic scan tool is critical for accurate repairs. Additionally, a Category III DVOM is a must for diagnosing high voltage hybrid vehicle circuits. Meters such as the Fluke 1587 allow for insulation testing as well as performing all the other functions of a CAT III meter.


1. Always wear high-voltage insulated gloves rated to 1,000V (minimum) while diagnosing and servicing hybrid vehicles and systems. Use gloves that are in good condition, even as pinholes, can be very dangerous. One way to ‘method-test’ a rubber glove for leaks is to blow into the glove and hold it tight by squeezing or rolling the open end tight. If the glove has a leak it will deflate.

2. High-voltage circuits are typically identified by bright orange cables or wires. The wiring may also be covered by bright orange covers or conduit. When hybrid vehicles are in a workshop, the vehicle may need to be moved, so it’s important to remember that if you’re rolling a vehicle in the garage, with the drive wheels on the ground, the motor generator may be providing power to these circuits. To avoid this condition, wheel dollies are recommended to move hybrids around the workshop.

3. Always remove all jewellery, including watches, necklaces and earrings, when working on a hybrid vehicle. Metal objects conduct electricity and could be a hazard if it inadvertently contacts a voltage source. You should also wear the appropriate protective clothing (high-voltage rubber gloves, face shield, insulated boots, protective coat or apron) when servicing these vehicles.

4. During diagnosis, do not drive the vehicle when it is in “Service Mode”, as it may damage the transmission or other components of the hybrid system. To reset the vehicle, shut it off and restart.

5. If a hybrid is equipped with a “smart key” system, technicians need to be sure the system is disabled prior to performing any servicing work. When in “Ready Mode”, the engine can start at any time, which could create a safety concern if this occurs during vehicle service.

How do Stop-Start systems work?

The last few years have seen the introduction of Stop-Start systems by many manufacturers across various vehicle models to improve fuel consumption and reduce exhaust emissions.

One of the main problems the introduction of Stop-Start systems has caused is that when the starter is operated the voltage in the vehicle’s electrical system can drop. In normal circumstances this is not a problem, the vehicle is not usually in “driving mode” and it doesn’t matter if some of the vehicle electrical systems do not function during starter motor operation (exterior lights, heating & air conditioning and audio systems, for example). However, during driving this is not acceptable for reasons of safety and driver convenience.

To counter this problem most systems use an additional power supply to ensure that voltage-critical equipment will not stop operating during starter motor operation. For some models this consists of a large capacitor that is charged by the alternator using engine power, or kinetic energy generated during deceleration and braking.

Considerable thought has been given to the safety mechanisms; most, if not all, Stop-Start systems will not operate if any of the doors or the bonnet is open and will only operate if sufficient vacuum is available to ensure the normal operation of the braking system.
As the use of Stop-Start technology is increasingly adopted, there are now as many systems as there are manufacturers, but they can be categorised as follows:

  • Those using a “conventional” starter motor
  • Those using a combined starter motor/alternator

Although some models use a conventional starter motor for cold start and Stop-Start operation, it is usually modified to ensure it can withstand the extra use it will encounter. However, the time taken to start the engine with this system is thought by some to be too long so other models are using a different approach.
Battery technology is also changing, with the extra starting cycles requiring a more robust battery construction. Absorbent glass matt (AGM) batteries, Gel batteries or the slightly cheaper enhanced flooded batteries (EFB) variants can be found in most vehicles with Stop-Start systems. Replacement of these batteries may necessitate programming of the vehicle’s computer system to allow the battery degradation process to be monitored. On many models the Stop-Start system will be disabled for up to 24 hours following battery disconnection or replacement to allow the battery condition to be evaluated.

Which Stop-Start Application Do They Use?
Toyota Yaris

The Stop-Start system of the Toyota Yaris has its starter motor in constant engagement with the flywheel ring gear and then the ring gear is connected to the engine flywheel with a one way clutch. This, together with recognition of the engine’s static crankshaft position, allows instantaneous ignition of the correct cylinder, thereby reducing starting time.

It is interesting to note that the number of starter motor operations is recorded and the calculated “end of starter lifespan” is indicated by a flashing warning lamp on the instrument panel. After replacement of the starter motor the counter has to be reset.

PSA group

Using a conventional type of starter motor for cold start, the Peugeot/Citroen group employs a combined starter motor and alternator assembly (so called reversible alternator) for the Stop-Start system. Connected to the engine crankshaft with the auxiliary drive belt, it provides silent operation and short starting time.

Unlike conventional alternators, diodes are not used; instead voltage rectification and motor operation use metal–oxide–semiconductor field-effect transistors (MOSFETs). Presently, it would appear that it is only the “e-HDi” models that use the aforementioned capacitor.

3 Essential Items That You’ll Need When Servicing Stop-Start Systems

Starters & Alternators 

Used in many modern vehicles, StARS (Stop start Alternator Reversible System) consists of a reversible alternator that replaces the conventional alternator and starter motor. The reversible alternator provides the function of alternator and starter combined with the new design allowing the conversion of electrical energy into mechanical energy, and visa-versa.

StARS works similar to the conventional alternator where the later applications would have the charge rate controlled by the vehicle ECU (computer controlled and smart charge systems). The new variation now has a separate ECU which administers the reversible alternator and the vehicle’s engine.
When the vehicle is slowed down by the user the ECU analyses the speed of the car and if/when the speed falls under 5mph the ECU switches off the engine. Once the brake pedal is released the ECU then gives an order to start the engine again. The reversible alternator plays the part of the starter motor to achieve this.

The system is designed to work in 5 phases:
1. The vehicle is switched on and the ECU will crank/start the engine. This is achieved by the battery providing electrical energy and the reversible alternator then acts as a starter motor to help crank the engine.

2. During normal driving (when the vehicle is not being slowed down) the reversible alternator then acts as a conventional alternator by converting the mechanical energy into electrical energy and charging the battery.

3. Once the vehicle speed has been reduced below 5mph by braking the StARS ECU gives a command to stop the engine.

4. Once the brake pedal has been released the StARS ECU then gives a command to start the engine again. The battery provides electrical energy and the reversible alternator plays the part of the starter motor and cranks the engine.

5. The vehicle is switched off and the ECU will stop the engine

AUTOELECTRO provides a whole array of replacement starter motors and alternators for modern Stop-Start systems and applications.

Servicing Data 

AUTODATA has enhanced its online product offering to include technical information on vehicles with Stop-Start technology.
The technical information provided by Autodata on its online system enables technicians to identify the specific location of key elements such as the main battery, additional battery and the Stop-Start capacitor.

Procedures for disconnecting and reconnecting each element are clearly explained along with additional information for servicing the system.

Replacement Batteries
EXIDE has expanded its coverage of the UK car parc with new AGM and ECM batteries. The new products cover vehicles from VW, Audi, Toyota, Ford and a slew of other brands.
Exide’s AGM batteries are claimed to have around three times the lifecycle durability of standard batteries. Parts of “matching quality”, they are designed for cars with Start-Stop and regenerative braking systems. They are also used in standard vehicles to increase endurance and performance.

AGM battery coverage: Audi A1, A4, A5 and Q5; BMW 5, 6, 7, X5 and X6; VW Golf, Polo and Touareg; Chrysler Voyager; Dodge Caliber; Jeep Cherokee and many others.

ECM battery coverage: Ford Fiesta, Galaxy, Focus, Mondeo, B-Max, C-Max and S-Max; Toyota iQ; Mazda CX-5 and a range of other models.

Hybrid manufacturing and servicing requirements

Air Conditioning
In some hybrids, the compressor used in the A/C system is powered by a high-voltage three phase electric motor. This motor is located inside the compressor case and is in contact with refrigerant oil. The refrigerant oil that the vehicle manufacturer specifies will have unique electrical properties that will protect you from electrical shock off the motor.

Ordinary PAG refrigerant oils cannot be introduced into many hybrid A/C systems. The use of the wrong oil will contaminate the A/C system; the severity of the damage will depend on you switching the A/C on. If you do not run the A/C, then only the compressor will need to be replaced. However, if you do run the A/C, you will need to replace the compressor, condenser, evaporator and pipework.

Just 1% contamination can lead to electrical problems such as fault codes or, in extreme cases, total vehicle shutdown. UV dye that is used in standard combustion vehicles shouldn’t be added to systems that use an electrical compressor. The adding of any standard UV dye can considerably reduce the refrigerant oil’s electrical insulation properties.

A number of A/C machines available from Autoclimate are designed to work with hybrids as standard. Failing that, the company can provide Robinair customers a ‘hybrid conversion kit’ which allows their existing machine to carry out the work.

Insulated Tools

Darwen Diesels has introduced a range of insulated socket sets, specifically for use with hybrid/electric vehicles.
Kits are available in both 3/8” drive and ½” drive variants and are manufactured to the highest standard with a working tolerance of 1,000 volts. A reversible ratchet, T bar, extension bars and Allen Keys are all included in the sets and the 3/8” kit has sockets ranging from 8 – 22mm with the ½” drive kit consisting of sockets ranging from 10 – 32mm.

Tony Shoard, Owner of TSG Motors in Slough recently put this great range through its paces. Here’s what he had to say:

“We have recently carried out repairs on a Lexus RX400H hybrid using the insulated socket set from Darwen. We found the kit to be extremely well made and reliable and this gave us confidence when working in a confined place without the worry of injury to ourselves.”

“Excellent quality and versatile, the socket set is a great bit of kit and one that I’d recommend to other technicians who are contemplating taking on hybrid servicing/repairs.”

As part of its 2014 catalogue of safety footwear, Dickies has introduced an ESD trainer into the range. The Alford trainer, which is suitable for people working near or with electricity, provides a safe and controlled method of discharging static electricity that can accumulate in your body.

Engine Lubricants
Pro-NRG 0W-20 – a ’bespoke’ fully synthetic hybrid engine lubricant with a notably Japanese-American formulation – was recently added to the Comma Performance Motor Oils (PMO) range.

Because fuel efficiency in the US has been an increasingly important purchasing influence ever since gasoline breached the psychological $1 a gallon mark, (it’s now around $3, which frightens the life out of many Americans) an engine lube appropriate to the ‘economy’ ethos of hybrid technology was needed to make its contribution. This arrived in the form of the API SN and ILSAC GF-5 specifications used mainly by US and Japanese manufacturers, and appears on the Comma Pro-NRG label.

Representing a significant advance over previous inceptions, these specifications are designed to provide improved high temperature deposit protection for pistons and turbochargers, more stringent sludge control, improved fuel economy, enhanced emission control system compatibility, seal compatibility, and protection of engines operating on ethanol-containing fuels up to E85.

With the fuel economy requirements of these specs and a very low 0W-20 viscosity, Comma says Pro-NRG lends itself nicely to the hybrid message.

If you’re thinking of setting up your business to work on electric vehicles, it will be useful to reassure potential customers with a recognised accreditation.

Handily, the IMI has a solution in its ATA Electric Vehicle accreditation. ATA Electric Vehicle is intended for technicians whose job role involves the inspection maintenance and repair of light vehicles, as well as those involved in accident repair bodyshops (i.e. MET, Panel, Paint, VDA).

In order to achieve the accreditation the technician must be able to work unsupervised and have the knowledge and experience necessary to enable them to complete modules covering safe working practices, high voltage battery replacement and high voltage component replacement.

Find out more at

The requirement for solutions that manage noise output levels in Electric (EVs) and Hybrid Electric Vehicles (HEVs) has created a number of challenges for friction manufacturers, such as Ferodo. Essentially, because the vehicles are driven on electric power, there is no engine noise so all other noise sources become more prominent.

The challenge with EVs and HEVs is amplified because they are often in the premium sector and may be relatively heavy. Add the substantial weight of batteries, and the vehicles can carry a lot of kinetic energy. That means they need powerful braking systems; typically ‘high steel’ with excellent integrity, high friction and consistent performance at high temperatures.

High-performance brake systems need very careful NVH management. A small change in specification can result in a reduction in performance or in noise-related warranty work that can more than eliminate the original profit for the garage.