Skip the auto shop - Our mechanics make house calls

Q: Heater blower surge

asked by on

My heater blower works at all speeds,but continues to jump from any fan speed to high momentarily,then back to the selected speed-just continues to surge like that,while driving or sitting still

My car has 170000 miles.
My car has an automatic transmission.

Hi There,

It sounds like you may have a faulty blower motor resistor. Blower motor resistors are used to control the fan speed of automotive blowers. The fan speed can be changed either by switching the blower resistor resistance mechanically, using a rotating lever, or electronically by the air conditioning system. The change in resistance then limits the current through the motor, which dictates the speed at which the blower fan works. Blower resistors, being a mechanical component, are prone to wear and are the most common point of failure in a car’s heating system. I would recommend having a professional from YourMechanic come to your location to diagnose and inspect your vehicle.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. Heater blower surge

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: I have an engine code to replace the cylinder head temperature sensor. Do I also replace intake manifold gasket?

Hi Ebenezer. Thanks for writing in tonight to YourMechanic.com. I have forwarded your inquiry with our sales and service team to help streamline the process of receiving an accurate estimate to have one of our mobile mechanics replace the cylinder...

Q: Heater not working

This may be related to a faulty blower motor or blower motor relay. The blower motor is a unit inside your vent system that blows warm air from the heater core to the vents when the heater is on or...

Q: Car doesn't start after sitting a few weeks.

Sometimes a battery can be so badly undercharged that it wont even take a jump, and if its around 3-5 years old its probably just that. Have a certified mechanic take a look at it, it might only need a...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.