DANGER: High Voltage!

Are you ready for hybrids in your fleet? Well if you are not, or you just want some more information, read on. We will be covering what you need to know about servicing and maintaining hybrid vehicles. First, a word of caution! We need to start with safety, because we are dealing with high voltage.

Now don't fear, because if you follow basic safety rules, get some hybrid training and follow manufacturer recommendations, you will be safe. Every day utility companies work with high voltage without anyone being injured. When was the last time you heard that a utility worker was shocked or killed by high voltage? Most likely your answer will be never. The reason why is that utility workers are trained on how to work with high voltage and are provided with the proper equipment.

Work Smart - Work Safe! Remember: don't fear high voltage (HV)--respect it.


First, because we are dealing with vehicles whose wires carry lethal voltages and current capacity, we should be able to identify what kinds of wires we are dealing with.
• Low Voltage (Below 30V): RED or BLACK means these wires are safe to work with.
• Intermediate Voltage (Below 60V): BLUE or GREEN means you should take caution.
• High Voltage (Above 60V): ORANGE means that if you don't take precautions, that's all she wrote.

Second, avoid wearing metal objects when servicing hybrids. Remove jewelry, watches, phones--even your wedding ring. Better to have your spouse mad at you than be killed or hurt.

How is this so? Simple. Metal objects increase contact surface area and conduct current, thereby leaving us exposed to the dangers that come with electricity such as burns and electrocution. Furthermore, there are powerful magnets in hybrid components like the motor generators, and as we well know, metal is attracted to magnets.

Here are a few safety tips:
• Wear HV (1000V) gloves near ANY open connections
• Check gloves for pinholes by sending them out to a qualified tester
• Wear goggles to protect your eyes from sparks
• Be sure to have a yellow "rescue hook / pull pole." What's it for? It's an insulated hook / pole that is used to pull someone that is being electrocuted off the hybrid he is working on.
• Use a CAT III certified DVOM and leads on ALL cables and capacitors--other meters are not built to do the job.
• "Power down" before towing a damaged vehicle.
• Be sure to de-energize/shut down the high voltage system before servicing anything on this side of the vehicle. This is of paramount importance!
• Remember, high voltage orange or blue cables run under hybrid vehicles from their engine compartment to the rear of the vehicle. BE AWARE! Setting the lift wrong can do major damage to the HV system.

Precautions must be taken before attempting to diagnose or repair any component that has orange (or blue) wires connected to it. Remember the equipment that is needed: a CAT III meter and scope that is capable of handling 1,000 volts, correct vehicle information, 1,000-volt gloves with protective liners, and safety glasses.


Okay, so now that we know we should be wearing gloves and not haphazardly servicing a hybrid's electronics, let's discuss how we should disengage the high voltage (HV). Consult the information that can be found on the manufacturer's websites. Having a hard time remembering all those websites? If so, just go to www.nastf.org, on this site you will find links to all of the manufacturer's sites. The hybrid safety information is free. You should always disable the HV and wait five to ten minutes before working on ANY hybrid system electronics. Check the hybrid system with a DVOM to make sure voltage is at a safe level (about 12 volts).


Oil Changes: Every 3,000 to 5,000 miles, hybrids will require a run of the mill oil servicing with a proper oil type/weight. For customers with particularly high environmental concerns, recommend that they switch to fully synthetic oil, besides most hybrid recommend it. It will improve fuel economy and cut down on their necessary oil changes.

Inspecting and Rotating Tires and Brakes: Every 5,000 to 6,000 miles, not only do the tires have to be rotated, but the rotors need to be inspected. Rusting is a common problem with hybrids' rotors, because of they are not used as often due to regenerative brakes.

ANNUAL MX (EVERY 12,000-15,000 MILES)

Throttle Body Service: If you are dealing with a Toyota Prius or any hybrid with an electrical throttle, maintenance of the throttle body every 12,500 miles is especially important.

HVAC System-Cabin Filter: On Ford hybrids, there is a rear filter for the battery HVAC behind the rear seats that needs to be replaced.

Battery Starting/Charging Test: During the winter, do a State of Charge (SOC) test on the 12V and HV batteries with a scan tool. Also, on Toyotas, don't forget to purchase a special battery charger for the glass-mat 12 volt battery. The maximum charging amperage is 3.5.

A/C System Service: During the summer, hybrids will require run of the mill maintenance. But not so fast! Hybrid A/C systems are a different beast than non-hybrids. Toyota hybrids (2005 model year and up and Hondas 2006 and up) have electric compressors. In some cases, this eliminates the need for an A/C clutch or belt, and full A/C operation even with the ICE off is now possible.

Many Honda, Ford, and GM hybrids have dual scroll compressors. Such a compressor is in fact two compressors in one: one belt driven off the engine and one electric. They can work both independently or combined, but when combined the autostop feature of the hybrid is deactivated.

The preceding means that if there is a compressor problem with a hybrid, you are going to have to look at the high voltage circuit. The compressor, whether it is fully electric or dual scroll (in autostop mode), can be inoperative because of an electrical problem. As the old adage goes, a technician has to wear many hats, and this is especially true with hybrids.

Another difference be- tween hybrid and non-hybrid A/C is that there is no single universal PAG oil/lubricant. Hybrids use different kinds of oils, mostly POE (polyol ester) oils, and no dye. If PAG oil or a PAG dye are put in, severe damage and possible high voltage problems will exist, and this can be DANGEROUS.

A/C maintenance is not something optional on hybrids. Let your customers know if they own a Ford/Mercury hybrid that the A/C system actually cools the HV battery and the HV battery is the most expensive piece of equipment in the vehicle! So, make sure the A/C is fully functional.

Computer Systems Check: Check the hybrid controllers, because not all DTCs turn on the dash lights.

Coolant Service: Note that some hybrids have dual systems, one for the engine and the other for the inverter. Furthermore, this means that many of the hybrids require special coolants. In order to service such systems, you should consult the manufacturer's recommendations and use the correct coolant.

Spark Plugs: Be sure to use the OEM recommended plugs and apply a small amount of anti-seize to the plugs every 30,000 miles.

Brake Fluid: Flush or bleed the hydraulic brake system. We should remind our customers that proper brake service for hybrids is essential for their safety.

Bleeding the brakes on a hybrid requires a special precaution: many hybrids' brakes have a self-test. As long as the 12V and HV batteries are connected or "SBSM" (Safe Brake Service Mode) is not activated on Ford Escapes, you run the risk of having the brakes pressurize without you commanding them to.

You will need to deactivate and depressurize the brakes before working on the system. Consult the manufacturer's information before work on any Teves brake system.


Unlike a normal repair facility, you have a vested interest in your hybrid vehicles. You already made the investment in purchasing them, so it is wise to take care of them right. To get the most MPG from hybrids, implementing a driver/operator training course may be a good idea. Most importantly, the proper maintenance of hybrid vehicles increases their fuel economy and their longevity. So, invest in educating your techs and operators, and you should be fine!