Skip the auto shop - Our mechanics make house calls

Q: Heater/ac blower resistor

asked by on

The fan (blower) sometimes works and sometimes does not work. When I jiggle, the wire cable connection to the resistor, the blower will go on sometimes. Is my problem most likely with the wiring, connection, or the resistor itself? And, how would I find out for sure? Thanks.

My car has 44000 miles.
My car has an automatic transmission.

A: This may be either the resistor or the wiri...

This may be either the resistor or the wiring connection to the resistor. i would recommend first eliminating or confirming the resistor as the problem since this is much easier to test than faulty wiring. Many blower resistors control current to the blower motor in all speeds except high. In high speed the resistor is bypassed and power is fed to the motor directly from the switch. The resistor itself can be tested by doing the following:

Place one lead of the Ohmmeter on terminal 1 of the resistor. Place the other lead on terminal 2 and check against specifications. If this circuit is open, showing infinity on the Ohmmeter, the blower resistor must be replaced. Move the lead from terminal 2 to terminal 3 and check this reading against specifications. If this circuit is open, showing infinity on the Ohmmeter, the blower resistor must be replaced. Move the lead from terminal 3 to terminal 4 and check this reading against specifications. If this circuit is open, showing infinity on the Ohmmeter, the blower resistor must be replaced.

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

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: Fan blower motor not working replaced resistor and blower motor but I don't know we're the fuse or relay is located

The fuse and relay is in the power distribution center which is mounted under the hood on the left side of the engine compartment. Remove the top cover and look on the under side of the cover. You will see...

Q: How do I know if it's my blower motor resistor or the resistor switch that's not working?

The referenced parts are tested with an ohmmeter. The resistor block must have a specified resistance across each element on the block. However, if any resistors are open (infinite resistance), the block is just condemned and replaced automatically. Occasionally, you...

Q: Lost power driving in traffic

This model year F-150 engine has had a few concerns that relate to the problem you are having. The first step in diagnosis is to verify if problem only happens during wet, damp or humid conditions. YourMechanic will then need...

Related articles

P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.