Skip the auto shop - Our mechanics make house calls

Q: Heater does not work

asked by on

Ok so my heater is inoperable. Check all fuses, good. Connected power to the blow motor that works. I'm getting power going into the relay but when I test it at the resistor I'm only getting a low voltage of 5 but 12 are going into the relay.Is this a bad relay or a ground problem

My car has 180900 miles.
My car has an automatic transmission.

Your vehicle’s blower speed selector controls voltage to the blower motor using two different circuits. When high speed is selected the blower control switch bypasses the resistor and operates the blower relay sending full battery voltage from the blower fuse to the blower relay to the blower motor. When tested at the blower motor on high speed, battery voltage should be present at the blower motor connector.

On blower speeds other than high, battery voltage flows from the fuse to the control switch then to the blower resistor. Depending on the speed selected, the blower resistor sends different voltage amounts to the relay which transfers that same voltage to the blower motor. When speeds other than high are selected, different voltage amounts will be present at the blower motor connector. Based on the information you provided, a ground circuit or the control switch and/or relay connections (internally or externally) could be open. If you would like a technician to come to you and inspect your blower system, please consider YourMechanic.

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
  1. Home
  2. Questions
  3. Heater does not work

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 only works on highest speed. 2008 Volkswagen Passat

Hi there, thanks for writing in about your 2008 Volkswagen Passat. If the blower motor resistor and connector are good, then the only other thing that can cause the problem is the blower control switch or connector. Check the resistor...

Q: Grinding from rear brakes

Hi there. Sounds to me that your brake pads have worn past their limit causing the metal base to press against the brake rotor which is leading to metal on metal contact. A brake service is due for your car....

Q: How to change battery cable connectors

Your Battery Saver Light comes on because your car is seeing a lower than expected battery voltage. When you see the light, your car will turn off certain electrical loads in order to save the battery from being unable to...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
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...