Balancing Act

DIY: How to Clean Your 3rd Gen Prius High Voltage (HV) Hybrid Battery Cooling Fan

After visiting my local Toyota service center for the Prius’ 120,000 miles check up, I was handed a costly laundry list of recommended maintenance. The easiest but most expensive service on the list is “Hybrid cooling fan service” at the cost of $389.00 and I’ve heard quotes from other Prius owners ranging as high as $497 in other parts of the state. If you have all the basic tool set, the only cost for this simple but crucial maintenance is your time. It essentially involves removing your back seat cushions and removing the HV Battery Cooling Fan Assembly to access the cooling fan centrifugal blower.

The HV Battery Cooling Fan, as with any fans (ceiling fans, floor fans, air filters, etc.) will eventually experience build up of dust, lint, pet hair and other debris that can impair the proper operation of the HV Battery Cooling System or even jam the fan. When this happens, it can burn out the cooling fan motor, cause the HV Hybrid Battery to overheat and trigger DTCs in addition to diminished fuel efficiency and in worst case scenario, trigger premature HV battery cell failure. How quickly the fan will build up with lint and dust depends on how severely the Prius is used or driven.

According to Toyota, the cooling fan should be serviced every time the HV Battery Assembly is replaced OR every 5,000 miles under severe driving condition.

Toyota documents severe driving condition as meeting one or more of the following criteria:

  • The vehicle is used for over 15 hours per day
  • The vehicle is used over 6 days per week
  • The right rear seat is used over 50 times per day
  • The vehicle used in a dusty environment or driven in dusty roads

If you live in extreme temperatures, commute long distances or carry loads that generally would cause intake of dust, hair or other small debris – e.g. if you carry furry pets or children in your car, you should clean the HV battery cooling fan every 5,000 miles.

If you use your Prius as a taxiing vehicle, it qualifies as a severe-use vehicle and the HV battery cooling fan should be cleaned every 5,000 miles.

If the Prius is driven in light to normal condition, a 30,000 mile check up interval is sufficient. If you’re a solo driver most of the time driving in normal condition, a 60,000 mile check up interval would even be okay.

Materials and Tools Required

  • Handheld vacuum (if available)
  • Needle nose pliers
  • Household multi-surface cleaner, such as 409
  • Flathead screwdriver
  • Nylon pry tool (optional, if not available, use needle nose pliers, wire stripper or Flathead screwdriver – to remove trim clips)
  • Ratchet with 10 mm and 12 mm sockets
  • Q-Tip, cotton swab
  • Shop towel
  • Hook, if necessary (only needed if your HV Battery Cooling Fan is so clogged up with hair [e.g. from pets] or lint that the aid of a hook is necessary to effectively scrape off from the impeller).

Step 1

Remove the retractable cargo privacy tonneau cover.

Remove the cargo mat or all-weather liner if you have one.

Unlock and remove the rear floor board.

Remove the rear deck floor box (and accessory organization tray, if you have one).

Step 2

Remove the rear seat cushion pad by lifting the seat vertically with force. The seat cushion is held onto the floor board by two clips and two hooks.

Step 3

Fold down both rear seat backs so it lies horizontally. Fold down the rear head rests for clearance if necessary.

Step 4

Remove the right rear side seat back assembly with air inlet by unbolting a 12 mm bolt at the base.

Lift up and pull the panel outward to remove it. The base is stapled to the carpet material and cannot be completely separated.

Step 5

Separate the rear seat back covers from the rear floor board sub-assembly, then lift the floor board sub-assembly up.

This floor board sub-assembly is attached to the HV battery cover by six retainer clips:

Some of these clips may become brittle with time, so it’s a good idea to have replacements ready.

Replace the clips back in the floor board sub-assembly:

Step 6

Remove the HV Battery Cooling Fan cover by lifting it up. It is held down by two push clips:

Step 7

Remove the 10 mm bolt from the luggage hold belt striker assembly hook from the right quarter trim and set both aside:

Step 8

Remove two black push retainer clips from the air inlet duct. Disengage the inlet duct then set duct and clips aside:

Step 9

Remove the single black retainer clip from the exhaust duct on the HV Battery cover and set aside.

Step 10

Disconnect the cooling fan cable.

Dislodge the black cable clip that’s securing the motor cable onto the metal bracket using a pair of needle nose pliers:

Step 11

Remove the HV Battery Cooling Fan from the HV Battery Cooling Fan Assembly; do not attempt to clean the cooling fan while it is still attached to the vehicle as dust may enter the HV Battery case.

To remove the cooling fan, remove two 10 mm bolts and one 10 mm nut in the highlighted locations:

Using a vacuum and an air duster, clean any dust, lint and debris build up from the HV Battery, cooling fan impeller, control module and air ducts of the HV Battery cooling system.

Step 12

Once the HV Battery Cooling Fan is removed and isolated, take a vacuum cleaner with crevice attachment and run it along the impeller blades to suck out loose debris. Do this for 1 minute.

Step 13

Separate the impeller from the blower shell by removing three Philips screws and carefully unmounting the two plastic tabs from their clips that are holding the shell together.

You now should have full access to the impeller.

Step 14

If the HV Battery Cooling Fan is clogged with lint and hair, you will need a small hook or pick tool to scrape and remove it from the impeller blade. Do this until the impeller blade is clear of any large blockage of debris or hair.

Step 15

Once the impeller blades look relatively clean, grab a bottle of household multi-surface cleaner spray, such as 409 or Windex. Cover the cable connector to protect it from liquid.

Hold the impeller facing the ground and begin liberally spraying it with the multi-surface cleaner  inside and out. Avoid spraying the cable and the motor.

As you spray, the excess liquid will pull the dirt off the impeller and drip.

At this point, you really do not need to do any manual scrubbing. The constant spraying of the multi-surface cleaner should be enough to lift and self-clean the impeller blades.

Continue spraying until the impeller looks clean. Wait between 1-2 minute between each spray to allow the cleaner to penetrate the dust build-up. There may be some tough spots where you’ll need to manually scrub with a Q-tip cotton swab to remove.

Step 16

Once you are done cleaning the impeller blades with the multi-surface cleaner, dry the blades off by spinning the impeller to centrifugally spin off any collected liquid. Once liquid stops spinning off the impeller, run a shop towel through the impeller blade and areas around the shell to thoroughly dry. Spray and clean the other half of the impeller shell.

Allow to air dry for at least 30 minutes, preferably in direct sun light.

Verify visually and physically that the HV Battery Cooling Fan is indeed dry.

Step 17

Continue and clean the exhaust duct and side intake vent. Spray a shop towel with multi-surface cleaner and run it through the ducts.

Air dry in the sun when done cleaning.

Step 18

Wipe the HV battery cover and air duct inlet that connects with the cooling fan with shop towel to remove additional dust:

Step 19

Take a vacuum cleaner with crevice and brush attachments and start vacuuming the chassis in and around the HV battery. Continue vacuuming the spare wheel compartment, the rear quarter trim panels, the entire rear passenger footwell, the floor beneath the rear seat cushion and anywhere else you see signs of debris, such as hair. Use the brush attachment to lift embedded sand and lint. You won’t believe how much debris you’ll pick up with the vacuum after years of accumulation.

After a thorough vacuum, reinstall the HV Battery Cooling Fan Assembly and ducts. Replace all the rear seat components and parts that were removed in the the reverse order of removal.

At close to 120,000 miles, I’ve experienced no issues with the high voltage hybrid battery and this will be the first time I’ve performed this maintenance procedure. For the most part of the six years owning the Prius, it was strictly a solo driver. It had a build-up of dust and a total of two strands of hair lodged in the shaft, but nothing drastic.

Before and After Comparison

Before cleaning:

After cleaning:

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