Blower Fan Repair

Venting your frustrations with a clogged blower fan

It can slowly creep up, intensifying with each passing day, or hit from seemingly out of nowhere. It can be barely noticeable, easily ignored, or so hugely annoying that you don't even want to turn it on. It can be characterized by an alarming shake at high operating speeds, and sound like a garbage disposal chewing through an errant utensil.

No, we're not talking about the neighborhood kid's garage band. This noise hits even closer to home, because it goes with you wherever you drive, emanating from a deep recess under your vehicle's dash. So the potential for repair expense may seem more daunting than the thought of just living with it.


But for those who have experienced these symptoms when they turn on their vehicle's interior fan for any HVAC (Heating, Ventilation, Air Conditioning) function, it's usually a problem that just has to be remedied right away. What you may not realize is that, often, removing the blower motor assembly and repairing it is not all that difficult.

Blower fans are basically an electric motor with a fan impeller attached to the motor's shaft. The impeller more resembles that of a water pump than a radiator fan, in fact, being nicknamed the "squirrel cage." It really does resemble the rotating exercise wheel often found in a pet rodent's cage. This design excels in moving a large quantity of air in a confined space.

Some manufacturers mount the motor with the shaft positioned horizontally, with the unit located behind the lower center of the dash, just above the center tunnel. This design works just fine, but is often difficult to service.


The design we will focus on employs a vertically positioned motor shaft, with the unit in a housing that mounts under the lower right dash, just above the front passenger's right foot. Depending on mounting design, and clearance between the housing, the dash and glovebox (if so equipped), it can be surprisingly accessible.

Believe it or not, the most common cause of noise and vibration is debris lodged inside the fan impeller. Often, due to the fan's recirculation air inlet being in close proximity to the back side of the glovebox, small items can sometimes fall out of the box and be ingested into the fan impeller when the air inlet is switched to "Recirc" or "Max A/C." This mishap can happen when the glovebox is overloaded, shut with excessive force, or the vehicle is driven on a bumpy road.

On other occasions, you may find nuts lodged in the impeller, as in chestnuts, acorns, etc., which, along with other "droppings," indicate the enterprising activities of actual rodents (including real squirrels!).


The net effect of all this debris is that the impeller will spin imbalanced, much like an unevenly loaded washing machine on spin cycle. Of course, the higher the fan speed, the more the imbalance will be noticed, usually accompanied by noise coming from actual contact between the impeller and the housing.

If this problem isn't corrected quickly, the impeller-usually constructed out of plastic-will become deformed, and will continue to cause vibration and noise even after the debris is removed.

Sometimes, just due to aging and use, the impeller will become deformed. It can also become deformed due to the fan motor running excessively hot, overheating the shaft and causing the impeller's mounting hub to melt. In such a case, not only will the impeller have to be replaced, but the motor as well. In some instances, the impeller and motor are sold as a single unit.

For purposes of illustration, here is a '98 Toyota Corolla, which is about as easy as it gets when it comes to R&R of a blower motor. Phase One involves removal of the glovebox and lower cover (if so equipped). Phase Two involves disconnecting the electrical connectors and removing the mounting bolts.


Phase three involves careful removal and inspection of the unit, paying close attention to accumulated debris and its source, as well as checking for evidence of contact between the impeller and the housing. If possible, it can be helpful to reconnect the electrical wiring to the motor and operate it while it is down for inspection, if in doubt about its performance. In the case of our Toyota, even after the debris was cleared, the impeller was still out-of-balance. The motor and impeller had to be replaced as a unit. When installing a new motor, here are a few things to keep in mind:

> Make sure that the motor is indexed to the same position as the original. On some models, the motor will mount to the housing only one way, due to mounting screw "stagger."

> Sometimes, the replacement motor's wiring connection will be different, because of upgrade or other manufacturing changes. This will mean that the installer will have to splice into the existing wiring harness. Although there are usually only two wires to the motor, there is still a 50-percent chance of getting it wrong.

> If possible, test the fan's operation before reinstalling the blower/housing unit. Keep in mind that, although the motor will operate either way it's wired, the airflow will only be in the correct direction when the motor is wired correctly.


Phase Four is the reinstallation of the assembled Blower/Housing unit, which is pretty much a reversal of the removal phase. Here are a couple of additional things to keep in mind:

> As the blower/housing unit is being fitted, use care when mating it up to the evaporator housing (if A/C equipped), so as not to damage the rubber seal.

> Review glovebox-stuffing habits, making sure to eliminate any and all "contraband!"

With your blower fan repaired or replaced, your driving comfort should be noticeably improved...ahh, now that's better! No more cringing every time you reach for the fan switch. Nothing but good vibrations happening here. If only an annoying garage band were as easy to repair.

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