Q: Heater blower surge

asked by on December 31, 2016

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.

Heater Blower Motor Resistor Replacement $106.80 - $693.71 Get a Quote

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.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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


Experienced Mechanic?

Earn up to $70/hr

What others are asking

How much fuel can my car hold?
Your vehicle has a fuel tank with a capacity of 13.2 gallons.
Key won't program
Greetings! Your truck is considerably new, therefore the key, ignition, and the immobilizer system will have to be reprogrammed by the special equipment that is only available at the dealership, or by a licensed locksmith.
Misfiring cylinder
Hi there. There are a couple of different reasons why a single cylinder would be misfiring. A common issue would be a lack of continuity throughout your spark plug coil, wire, and plug. Another problem you may be having is...
Steering wheel is locked
The battery in the keyless remote may be dead and will need to be replaced to see if this cures the problem. If you have a second one then try it and see if it works. If neither work then...
Knock Sensor issue
The sensors are doing their job and telling you there is a knock in the engine. Even though it may seem like the sound went away, you may not be able to hear it when you drive but the sensors...
My car makes a subtle squeak and minor clunk when driving over bumps slowly.
If you just had a shock replaced and the noise did not start until the shock was installed, then I suggest having the shock mounts checked to make sure they are seated properly when they were put in. If the...
Truck starts then immediately dies
Hello, thanks for writing in. Most of the time this is caused by a fuel system issue. I would usually start by installing a scan tool to see if there are any codes in the computer pertaining to this problem....
I am trying to replace the dc converter in my 2006 Honda Civic Hybrid. I bought used one online and put it in but not working.
Hi there. Unfortunately, there are too many variables we are not aware of, including the type of component you are using (OEM or aftermarket), the installation process or condition of the vehicle prior to the service completed to provide you...
I have a 2006 cadillac cts 2.8L. Swapped the motor only after rocker arms a d other issues. I now have the motor in and it won't s
Hey Chris. Thanks for sending the question tonight. Unfortunately, anytime the OEM engine is replaced, it pretty much falls outside of our areas of expertise. We stick to providing advice on common repairs, maintenance and service recommendations for original OEM...

Related articles

Symptoms of a Bad or Failing Blower Motor Switch
If your blower motor switch only works on certain settings, gets stuck, or has a broken knob, you may need to replace your blower motor switch.
Symptoms of a Bad or Failing AC Thermistor
If your car's AC only blows cold air for a short amount of time or the blower is not functioning properly, you may need to replace the AC thermistor.
Mercury Certified Pre-Owned (CPO) Car Program
Drivers Drivers who are shopping around for a used Mercury vehicle may want to check out cars under their certified pre-owned program. Many manufacturers have a certified pre-owned (CPO) program, and each one is set up differently. Read on to...