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Ford F150 Heater Not Working – 7 Easy Troubleshooting Methods!

Is your Ford F150 heater not working? Don’t stress! I’ve got you covered.

In this article, I will discuss the potential reasons why the heater is not working on your truck and how you can troubleshoot and fix this problem.

The main reason might be the low coolant level in the reservoir – others include a bad fuse, bad relay, faulty blower motor, or blower motor resistor.

So without further ado, let’s dive into it.

Please Note: This guide applies to any Ford F150 truck, regardless of the model year.

Common years with this problem are Ford F150 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, and 2019.


7 Reasons Why Ford F150 Heater Not Working!

The main reasons why the Ford F150 heater is not working are:

ProblemSolution
Blown blower motor fuseReplace the fuse
Bad blower motor relayInstall a new relay
Faulty or stuck open thermostatReplace the thermostat
Low coolant levelRefill the coolant within the cold fill range
Coolant flow restrictionFree the hose restriction
Clogged heater coreFlush the heater core
Faulty blower motorReplace the blower motor
Faulty blower motor resistorReplace the blower motor resistor
YouTube video

1. Blown Fuse

First thing first, look for any blown fuses in the battery junction box under the hood.

Locate fuse number 51 (40 Amp) – the blower motor fuse. Look for any damages, and test it with a test light or a multimeter.

For quick verification, you can swap it with an identical one and check whether the heater is working.

If the swap fixes the heater, you need to replace the fuse to solve the problem.

2. Bad Relay

Next, you need to ensure that the relays are working properly, especially the blower motor relay.

First, find the appropriate relay position (usually number 3) that controls the blower motor and remove it from the box. Look for any physical damage or buildup that might cause the relay not to work properly.

If the relay has dirt, debris, or gunk, you must clean it up and install it back. Additionally, you can swap it with another relay from the box and check whether it fixes the problem.

In terms of a faulty, or damaged relay, you need to replace the relay to fix this heater problem on your Ford F150.

3. Stuck Open Thermostat

If the engine doesn’t reach the operating temperature after 15 to 20 minutes of running, you need to check whether the thermostat is working properly.

And if this continues to happen after 30 minutes of running the engine, the thermostat might be stuck open or faulty.

So, first, you need to replace the thermostat, and if there are no other problems, replacing the thermostat will fix the heater issue.

4. Low Coolant Level

This is the most common reason why the heater doesn’t work. And it might be the case for your truck as well.

To verify the low coolant level, open up the hood, and do a visual inspection to see whether the coolant reservoir has an adequate amount of coolant.

If the coolant level is low or the reservoir is completely empty, go ahead and refill the reservoir with appropriate coolant within the cold fill range when the engine is cold. And you should get the heater up and running again.

After filling up the coolant, if you see the problem still persists, you need to concentrate on the heater core, blower motor, and resistor.

5. Clogged Up Heater Core

If you have adequate coolant, yet there’s no heat, the heater core might be clogged up, or the coolant flow is restricted.

Look for any twister or pinched heater core hoses in the engine bay. If you find any, make sure you fix the coolant flow.

Now, the heater core can be clogged, and you can get an idea from the radiator. Open the radiator cap, and look inside.

If there is rust or debris in the radiator cap and inside the radiator, the heater core might also not be in good condition.

Additionally, you can measure the temperature difference between the two hoses with an infrared thermometer. If the difference is more than 30 to 35, the possibility of being clogged up is higher.

In this case, you need to flush the coolant system, or at least the heater core, to fix this problem.

6. Faulty Blower Motor

If the blower motor is faulty, you won’t get any hot air. So, make sure the blower motor is working properly.

To verify the motor, put the ignition key in the ON position, and turn on the heater switch. Get a test light, and check the voltage at the blower motor connector.

You can test them with a test light. Watch the following video for a better understanding.

YouTube video

If both the power and ground are fine, then the motor is faulty. In this case, you need to replace the blower motor, and the heater will be fixed.

7. Faulty Blower Motor Resistor

The blower motor is working properly? Alright, now, you need to verify whether the resistor is fine.

With a test light, check the voltage at the resistor connector. Test the power and ground with the test light and the signal wire with a multimeter. If all of them are fine, the resistor is faulty.

In this case, you need to replace the blower motor resistor to fix the heater problem on your Ford F150.


Final Words

I hope you have all the information on why the Ford F150 heater is not working. You can try all the troubleshooting methods I have discussed above, and hopefully, you’ll get the heater problem fixed.

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Kevin Shaw

Editor-in-Chief at F150Lab

Kevin Shaw is an automotive enthusiast and expert specializing in Ford F150 pickup trucks. With over ten years of experience in the automotive industry, he has the knowledge and expertise to help you maintain and troubleshoot your F150.

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