Handling hybrid repairs

March 5, 2012
Servicing hybrids requires a commitment to keeping up with the pace of evolving technology

The U.S. seems to be hybrid-crazed. Everywhere you look these days, hybrid-drive vehicles seem to be all the rage. This sensationalism certainly has grabbed a lot of media attention about the environmental aspects of hybrid technology.

Despite all the fanfare, hybrid technology took it on the chin recently. Reports of battery fires on the highly touted Chevrolet Volt--punctuated by a full-blown investigation from the National Highway Transportation Safety Administration (NHTSA)--serve as a reminder that this technology is still emerging and you should stay on top of the latest developments.

Although the Chevy Volt fires were linked to crash testing and not service procedures, they do suggest that a healthy amount of respect is in order for the batteries and high-voltage electrical system. With that as a backdrop, along with the growing numbers of hybrid vehicles, we bring you this issue's Tool Q&A.

Q. We want to perform cooling system maintenance on hybrid vehicles. Are there any differences from regular cars and light trucks?

A. For the most part, the cooling system of hybrid vehicles is substantially identical to conventional vehicles, since hybrids use an internal combustion engine (ICE) as part of the drive system. You'll find the typical array of radiator, pressure cap, reservoir, water pump and so forth. However, there may be differences on particular vehicles that you need to be aware of. For example, let's say you're diagnosing a no-heat or low-heat problem. Many hybrids use an electric assist pump to move coolant when the engine is in the idle stop mode. To be thorough, you'd need to include this assist pump in your diagnostic regimen to get to the heart of the problem.

Q. We run an air conditioning specialty shop. Do hybrids have any major differences in their A/C systems that require specialized equipment?

A. The air conditioning systems used on hybrid vehicles are virtually the same as conventional vehicles, with a few key exceptions. Since hybrid drive systems often employ the strategy of shutting down the engine when the vehicle stops, the compressors on these vehicles must have another type of drive system so that refrigerant flow doesn't stop with the engine off (idle stop mode). Given this scenario, some hybrids use compressors driven exclusively by a high-voltage motor. In other applications, the compressor may use a conventional belt drive when the engine's running, and then switch over to high-voltage electric drive when the engine's off. Regardless, troubleshooting poor A/C performance on such a vehicle becomes more involved due to the change-up in compressor drive technology. In such applications, you'll be required to use a scan tool to look at compressor engagement parameters and operation.

Q. When charging an A/C system on a hybrid, are there any special things to keep in mind?

A. First, make sure you refer to the system label that specifies refrigerant and refrigerant oil. The refrigerant is a no-brainer, since R-134a is the current refrigerant of choice. Refrigerant oil, however, is a different story. Hybrids with high-voltage electric drive compressors use special, non-conductive refrigerant oil that insulates the high-voltage motor. Make sure you use only what's specified by the manufacturer. Both Honda and Toyota warn that using the wrong refrigerant oil—no mattter how small the amount--compromises the insulation capabilities of  the oil itself and increases the risk of high-voltage shock when working on the system. It can also trigger a diagnostic trouble code. Both manufacturers also caution that if the incorrect oil is added to the system, the main components of the entire system will need to be replaced. Finally, due to the the risk of cross-contamination of refrigerant oils, it's best to keep a separate set of manifold gauges on hand to eliminate the chances of a oil mix-up.          

Q. What kind of battery charger should I use to charge the high-voltage battery in a hybrid?

A. In normal use, a dedicated vehicle module takes care of the charge in the high-voltage battery. While it's true that specialized high-voltage chargers are available, especially in the dealer network, your best bet is to make sure the hybrid ICE gets started, and let the battery module and the rest of the hybrid high-voltage system in the vehicle itself take care of charging the high-voltage battery.

Q. How do I determine which parts of the electrical system are high-voltage and low-voltage?

A. Always proceed with caution when working around the electrical system. Generally, the 12-volt, low-voltage part of the electrical system will use red and black to represent positive and negative polarities, respectively. Blue or yellow cables typically signify circuits with a somewhat higher voltage of 42 volts. Although 42 volts does not present a shock hazard, its circuits can cause arcing when opened. Finally, and most importantlly, orange cables along with accompanying warning labels signify high-voltage circuits, ranging from 100 to 600 volts or more. Failure to exercise caution around high-voltage circuits can cause injury or death, so be careful.

Q. We're hesitant to jump into hybrid service because we're uncomfortable with working around the high-voltage electrical system. What kind of safety measures can I put into place to protect my technicians?

A. First, invest in technician training for all your staff who will be working on the high-voltage electrical system. Remember, the overwhelming majority of hybrid vehicles still require many of the same maintenance procedures as a conventional vehicle, and don't involve the high-voltage circuit at all. For those planning on servicing the high-voltage circuit, they should wear insulated rubber gloves, similar to those worn by utility linemen. The gloves should be rated to a minimum of 1 kV (1,000 volts), and carry a class 0 designation by ANSI and ASTM.  

Q. Are there dedicated testers for taking voltage readings in a hybrid’s high-voltage electrical system?

A. You bet; the voltages found in the high-voltage electrical system of a hybrid require that you use a meter and leads meeting a CAT III standard. A meter meeting this standard, rated at 600 to 1,000 volts, offers the best personal protection when working around the electrical energy potential found in high-voltage hybrid drive systems. Do not use a conventional multimeter intended for low-voltage circuits or you may suffer severe shock and related injuries.

Q. We run a towing company and work in conjunction with emergency crews at the scene of a vehicle accident. What special considerations apply when first responders appear on the scene of an accident?

A. This is a great question, because hybrids demand special handling due to their high-voltage electrical system. There are special training programs for these scenarios, as we highly recommend you take all the training you can to ensure your safety and to provide the best assistance you can at the scene. While the specifics of individual training programs differ, there are some general guidelines that can be followed at the scene:

  1. Identify whether the vehicle is in fact a hybrid.
  2. Disable the vehicle using a manufacturer-approved procedure.
  3. Secure the vehicle to prevent movement.
  4. Access the occupants using one more more methods to ensure their safe removal.
  5. Turn the ignition off.
  6. Open the 12-volt circuit by disconnecting or cutting the battery cables. Please note that providing first-responder assistance requires the use of manufacturer approved/recommended equipment that requires special training.

Q. When performing cooling system testing on a Toyota Prius, we 'd like to disable the idle stop mode to ensure continuous mode operation of the cooling system. Is there a way to do this?

A. Yes, you can use a Toyota Diagnostic Tester to disable the idle stop mode. If yoU have a different scan tool, check with the manufacturer to see if this capability can be added through a software update.

Q. Are there any special considerations that need to be made when jacking or hoisting a hybrid vehicle?

A. Like any vehicle, look up the recommended lift points for that specific make and model beforehand.  Then, when positioning the jack or hoist, watch for any high-voltage cables that may run along the undercarriage of the vehicle. As an example, some Honda hybrids encapsulate high-voltage cables in a bright orange jacket that runs fore and aft along the unibody. Steer clear of this or you'll be asking for trouble.

Q.  One of my techs says we need to depower the high-voltage electrical system on hybrids whenever we perform service. Is this true?

A. No, most routine hybrid service doesn't require depowering the high-voltage electrical system as part of routine service. However, that may change if you need to perform more involved service procedures on certain systems. Always consult service information first before proceeding and if you do need to depower the high-voltage system, follow the manufacturer's procedure to the letter.

Hybrid service routines and tools will continue to develop at a rapid pace as technology dictates. As long as you make a pledge to stay current and follow proper safety procedures, you'll be able to stay in stride with the changes coming your way. 

Sponsored Recommendations

Snap-on Training: ADAS Level 2 - Component Testing

The second video for Snap-on's comprehensive overview of Advanced Driver Assistance Systems (ADAS), covering the fundamental concepts and functionalities essential for automotive...

Snap-on Training: Intro to ADAS

Snap-on's training video provides a comprehensive overview of Advanced Driver Assistance Systems (ADAS), covering the fundamental concepts and functionalities essential for automotive...

Snap-on Training: Guided Component Tests Level 2

The second video for Snap-on's comprehensive overview of Guided Component Tests, covering the fundamental concepts essential for diagnostic procedures.

Snap-on Training: Data Bus Testing and Diagnosis Part 1

Learn the basics of vehicle data buses and their diagnosis with Snap-on's Jason Gabrenas.

Voice Your Opinion!

To join the conversation, and become an exclusive member of Vehicle Service Pros, create an account today!