
11
Quick Reference Guide
Characteristics of Fuel Cell Vehicles
A fuel cell vehicle (FCV) converts hydrogen gas into electricity which is used to power an electric motor. The FC (fuel cell) system comprises 
of hydrogen tanks and an FC stack, as well as other components,  and requires a constant supply of hydrogen fuel, and proper cooling and 
ventilation to generate electricity.
The FC stack is the main power unit which comprises of a series of fuel cells joined together or “stacked” on one another. With in each fuel 
cell, hydrogen reacts with oxygen to create an electric current whic h is used to not only power the motor but also charge a High Voltage 
battery. This High Voltage battery provides supplementary power to assist the FC power system when the vehicle is subjected to  heavy 
acceleration.
Unlike vehicles that use internal combustion engines,  FC vehicles emit no harmful emissions such as CO
2 and NOx, and are thus considered 
environmentally friendly. The only substa nce discharged from the tailpipe is water,  in the form of both liquid and vapor.
FC Stack
Fuel cell power output may decline faster th an usual under the following circumstances:
● The vehicle is frequently used in sub-zero temperatures over extended periods of time.
● The vehicle is repeatedly left in stand by state for extended periods of time.
● The FC system is subjected to frequent starting and stopping.
● Salt water has permeated the air cleaner element.
u Replace the air cleaner element and clean the surrounding area.
● The vehicle is driven extensively in areas whose air contains high levels of:
Dust
Sulfur (common to hot spring and volcanoes)
Organic solvents, e.g., paints and thinners
Amine-related substa nces, e.g., ammonia
Chlorinated substances, e.g.,  salt and snow-melting agents
u Once the vehicle is driven in a normal environment again, fuel cell power output will return over time.
In the following circumstances, power output may be temporarily limited:
● You are repeatedly accelerating and decelerating aggressively.
● You are ascending a slope or driving at high altitudes above 6,562 feet (2,000 meters).
2 Driver Information Interface Wa rning and Information Messages  (P104)
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19
Quick Reference Guide
Fuel Cell Insulating Fluid
Fuel cell insulating fluid (FC insulating fluid) uses a specifically designed fluid with high electrical insulation properties in order to safely cool 
the fuel cell.
Never add water, other commercial coolants, or genuine Honda inverter coolant to the cooling system. Doing so will cause damage to the 
fuel cell.
Consult an authorized Honda Clarity Fuel Cell dealer to replenish or change the fuel cell insulating fluid.
FC Insulating Fluid Reserve Tank
Inverter Coolant Reserve Tank
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459
uuMaintenance Under the Hood uInverter Coolant
Continued
Maintenance
Inverter Coolant
This coolant is premixed with 50% an tifreeze and 50% water. Do not add any 
straight antifreeze or water.
We recommend you check the  inverter coolant level every time you refuel. Check 
the reserve tank. Add the in verter coolant accordingly.
1. Make sure the motor and radiator are cool.
2. Check the amount of coolant in the reserve 
tank.
u If the coolant level is below the  MIN 
mark, add the specified coolant until it 
reaches the  MAX mark.
3. Inspect the cooling system for leaks.
Specified coolant: Ho nda Long Life Antifreeze/Coolant Type 2
■Reserve Tank
1Inverter Coolant
NOTICE
Genuine Honda inverter cool ant is a 50/50 mixture of 
antifreeze and water that can withstand freezing at 
temperatures as low as a bout –31°F (–35°C). If your 
vehicle is consistently subjected to temperatures 
below this, the concentration of antifreeze in the 
coolant should be  increased. Consult an authorized 
Honda Clarity Fuel Ce ll dealer for details.
If Honda antifreeze /coolant is not available, you may 
use another major brand of non-silicate coolant as a 
temporary replacement. Check that it is a high quality 
coolant recommended fo r aluminum motors. 
Continued use of any non-Honda coolant can result 
in corrosion, causing the cooling system to 
malfunction or fail. Have  the cooling system flushed 
and refilled with  Honda antifreeze/coolant as soon as 
possible.
3WARNING
Removing the expansion tank cap while the 
motor is hot can cause the coolant to spray 
out, seriously scalding you.
Always let the motor and radiator cool 
down before removing the expansion tank 
cap.
MAX
Reserve 
TankMIN
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uuMaintenance Under the Hood uInverter Coolant
460
Maintenance
1. Make sure the motor and radiator are 
cool.
2. Turn the expansion tank cap 1/8 turn 
counterclockwise and  relieve any pressure 
in the cooling system.
3. Push down and turn the expansion tank cap 
counterclockwise to remove it.
4. Pour coolant into the expansion tank until it 
reaches the  MAX mark.
5. Put the expansion tank cap back on, and 
tighten it fully.
■Radiator 1Inverter Coolant
Do not add rust inhibitors  or other additives to your 
vehicle’s cooling system. They may not be compatible 
with the coolant or with the motor components.
1 Radiator
NOTICE
Pour the fluid slowly and ca refully so you do not spill 
any. Clean up any spills immediately; they can 
damage components in the motor compartment.
Expansion 
Tank Cap
MAX
Reserve 
TankMIN
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480
Maintenance
Climate Control System Maintenance
Air Conditioning
To ensure proper and safe operation, th e Society of Automotive Engineers (SAE 
J2845) recommends that the refrigerant  system only be serviced by trained and 
certified technicians.
Never repair or replace the air conditioning evaporator (cooling coil) with one 
removed from a used or salvaged vehicle.
New replacement mobile air conditioning  evaporators must be certified (and 
labeled) as meeting SAE Standard J2842.
Dust and Pollen Filter
The climate control system is equipped with a dust and pollen filter that collects 
pollen, dust, and other debris in the air. The Maintenance MinderTM messages will let 
you know when to replace the filter.
We recommend that you replace the dust a nd pollen filter sooner when using your 
vehicle in areas with high concentrations of dust.
1 Climate Control System Maintenance
NOTICE
Vented refrigerant is harmful to the environment.
To avoid refrigerant from  venting, never replace the 
evaporator with one re moved from a used or 
salvaged vehicle.
Refrigerant in your  vehicle’s air conditioning system is 
flammable and can be igni ted during servicing if 
proper procedures  are not followed.
The air conditioner labe l is found under the hood:
2 Safety Labels  P. 83
2 Specifications  P. 530
1Dust and Pollen Filter
Using an air freshener  may reduce the deodorizing 
effect of the dust and polle n filter, and may reduce its 
life.
If the airflow from the climate control system 
deteriorates noticeably, and the windows fog up 
easily, the filter may need to be replaced. Please 
contact an authorized Honda  Clarity Fuel Cell dealer 
for replacement.
The allerfree hi gh retention deodor ization filter 
collects pollen and dust, has allergen treatment 
ability and reduces exhaus t gas odor that may be 
present in the air.
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uuOverheating uHow to Handle Overheating
510
Handling the Unexpected
■Next thing to do
Inspect the coolant level, and check the 
cooling system components for leaks.u If the coolant level in the reserve tank is 
low, add coolant until it reaches the 
MAX  mark.
u If there is no coolan t in the reserve tank, 
check that the radiator is cool. Cover the 
expansion tank cap with a heavy cloth 
and open the cap. If necessary, add 
coolant up to the base of the filler neck, 
and put the cap back on.
■Last thing to do
Turn the power system on, if the message  Power System Problem. Stop Driving 
When Safe disappears from the driver informatio n interface after you have started 
the power system, resume driving.
If the message does not disappear, contact an authorized Honda Clarity Fuel Cell 
dealer.
1 How to Handle Overheating
If the coolant is leaking,  contact an authorized Honda 
Clarity Fuel Cell dealer for repairs.
Continuing to drive with the  Power System 
Problem. Stop Driving When Safe  message on the 
driver information interface may damage the motor.
3WARNING
Removing the expansion tank cap while the 
power system is hot can cause the coolant 
to spray out, seri ously scalding you.
Always let the motor and radiator cool 
down before removing the expansion tank 
cap.
3CAUTION
Never pour water or other commercial 
coolants into the inve rter coolant reserve 
tank. Doing so will cause damage to the 
motor.
MAX
Inverter Coolant 
Reserve TankMIN
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