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Jeep Heater Not Working (13 Reasons Why)

There are many reasons behind a Jeep heater not working, including issues with the heater core, blend door actuator, and electrical components. And while Jeeps are often used in a top-down fashion, it is equally important to ensure its in-cabin features – like its A/C and heating system – are functional. This article will go over the usual triggers of a non-working Jeep heater and how to fix them.

Below are 13 of the most common reasons behind your Jeep Heater not working that you should be aware of:

  1. Heater core difficulties
  2. Insufficient coolant
  3. Blend door actuator failure
  4. Dysfunctional thermostat
  5. Water leaks
  6. Contaminated coolant
  7. Water pump issues
  8. Melty blower switch
  9. Clogged or defective heating controls
  10. Faulty blower motor or resistor
  11. Obstructed vents
  12. Dirty air filters
  13. Bad casting process

Note that this list isn’t exhaustive and only covers common reasons behind your Jeep heater not working. In reality, there are hundreds of things that could lead to a car heater going bad.

This guide aims to give you the right tools and knowledge of the most prevalent causes of this issue. But ultimately, taking your Jeep to a licensed mechanic or technician would be the best course of action if these recommendations do not help solve your problem.

Reasons Your Jeep Heater Does Not Work

Car Air Vent

1. Heater Core Difficulties

Comparable to compact radiators, a heater core is part of the cooling system that serves as the passageway for hot coolant and is usually of brass or aluminum tubing material. Since the heater core (view on Amazon) is responsible for balancing heating actions inside your Jeep, it is crucial to keep it clog-free. Otherwise, you would end up with a wet floorboard or a non-functional heater along with one of these signs:

  • Abnormally quick coolant usage
  • A sweet-smelling, fruity odor
  • Fogging inside your vehicle
  • Overheating engine

Even without these indicators, it would be clever and pre-emptive to check the heater hoses for heat. A warm engine should mean heater hoses that are warm to the touch as well. If they are not, it would mean one of three things – the engine coolant is not circulating correctly, air is in the lines, or your heater core needs a flush.

2. Insufficient Coolant

Like any other vehicle, your Jeep uses coolant to cool down your engine in warm weather and blow warm air into your car through the heater core during winter.

The ratio of antifreeze to water the coolant has is typically 50:50. So long as this ratio and the manufacturer-recommended coolant capacity are met, your vehicle’s heat transfer in and cooling system should function seamlessly. The reverse would happen when your engine runs low on coolant and would come across as your Jeep heater not working.

To check on your Jeep’s coolant level, simply take a peek at the overflow reservoir, which connects to the radiator (view on Amazon) through a tube coming from the right side of the radiator cap. Seeing no coolant in the overflow reservoir would automatically indicate low coolant levels.

A word to the wise: If there is no coolant in your overflow, refill the radiator by adding more coolant through the reservoir and never directly through the radiator cap.

The only instance you can add coolant through the radiator cap would be one of two things – either you suspect the hose going from the reservoir to the radiator is clogged, or the radiator cap is ice cold. Outside of these exceptions, always assume that the radiator is hot and that its fans can kick on at any time (even if you have taken the key off the ignition).

3. Blend Door Actuator Failure

One other significant part of your Jeep’s cooling system is the A/C blend door actuator. This component controls the air temperature blowing through the vents and into the cabin.

It is also naturally subject to fail at some point – like in any other vehicle. When this happens, the blend door loses its ability to change the air temperature inside your cabin, causing your heater to seem like it has stopped working. Problems with the blend door actuator resulted in various Jeep blend door recalls, including the Jeep Liberty heater core recall for 26 units in 2012.

What I find interesting is that the majority of Jeeps with this dilemma seem to be 2011 Jeep Grand Cherokees, not Liberty models. Furthermore, it seemed like the stigma associated with the Jeep Cherokee heater not working was further aggravated by another problem – visibility issues coming from as early as its 2000 model caused by a non-working defroster that posed a potential rider hazard on the road (especially when riding at night).

4. Dysfunctional Thermostat

Your thermostat gauge is another component that will be worth your while to check. The reason for this is that it’s its responsibility to regulate the temperature of your engine.

That said, a broken thermostat would not be able to signal to your vehicle that its engine is warm. In turn, this prevents the engine from sending the coolant over to provide heat to the heater core, resulting in the air staying cool inside the cabin. Luckily, thermostats are a relatively inexpensive fix and among the easier items to address in this list.

Aside from a non-working heater, apparent symptoms of a bad thermostat include staying stuck open, only working when the car isn’t moving, the engine temp gauge rapidly shooting into the red after you start driving, or the blower giving colder air than normal.

Meanwhile, an overheating engine would point to a thermostat valve that is stuck closed. In most cases, a new thermostat installed in your vehicle will eliminate these problems and get your heater properly functioning in no time.

5. Water Leaks

Leaks are naturally part of the reasons your Jeep heater would stop working because your engine’s required coolant consists of part antifreeze and part water. When a leak happens, the 50:50 ratio between the antifreeze and water components gets disrupted, causing the whole cooling system to be dysfunctional.

What is troublesome about this is that leaks can surface anywhere, making them difficult to spot. When narrowing down the leak source, make sure to check for damage in your vehicle’s radiator, water pump, cylinder head gaskets, or hoses first, as these are the most common areas where leaks occur.

6. Contaminated Coolant

In some situations, your Jeep heater not working can be traced back to an impure or contaminated coolant. When your coolant contains rust particles or other contaminants, it will block the heater core from circulating air into the cabin properly. It may also result in your radiator and heater being clogged with rust. Some causes of coolant contamination that you should look out for are as follows:

  • Bad head gasket or cracked cylinder head, resulting in oil and coolant mixture
  • Breach in the engine-cooling system, resulting in contamination by transmission fluid

7. Water Pump Issues

A high engine temperature reading and little to no heat coming from your heater are both indicative of water pump problems. But if you’re having second thoughts, then take your Jeep out of gear and rev the engine for a bit.

Feeling the heat blowing hot for a few seconds after you do this would either confirm a faulty water pump or having a low coolant (also discussed in this list). Another tell-tale sign that something’s wrong with your pump is if your vehicle’s serpentine belt (the one that goes to the water pump) does not turn as fast as it should. A more obvious indicator is if your water pump (view on Amazon) has corroded impeller blades.

8. Melty Blower Switch

Black Jeep Wrangler Off-Road Snow Trail

Often overlooked, a common cause of Jeep heater problems is a defective blower switch. This switch has a plastic housing with four female metal clips that slide over copper male posts.

From the factory, the four wires coming from the switch would be wired into the wiring harness. If you see otherwise, it would mean that the original switch was toast and had been replaced.

Because the blower switch is seldom paid mind to, you will rarely see resources online and forums that share details on how to get this component fixed. Hence, I will be sharing steps on how to go about diagnosing and replacing your blower switch should you discover that it is shot:

Step 1:

Have your vehicle’s wiring diagram handy and on standby for troubleshooting reference.

Step 2:

When switching the Climate Mode Selector on your dash to any of these options – vent, heat, or defrost – listen for a fan start noise and feel for air blowing out of the vents.

If you have neither sound nor air blowing, you could be dealing with either a broken Climate Mode Selector Switch, a blown fuse, or a faulty blower motor (you can narrow this down by process of elimination). Otherwise, go to the next step.

Step 3:

Move the blower switch from bottom to top, coming from either the vent, heat, or defrost option. Feel for a click as you go through each of its four modes.

If you don’t feel all four clicks, prepare to fix either a mechanical or electrical failure. At the same time, listen for changes in fan speed as you go through the different modes. Depending on which mode works, you may need to repair or replace the switch (low) or the resistor (high).

Step 4:

Test the resistor coils individually and see which ones need to be replaced. If there are any, it would be ideal to replace the blower switch with it. Then retest the resistor and see what happens.

Tip: When buying a replacement for the blower switch, make sure to also get a five-wire relay plug with same-size clips and butt splice connectors. Use these extras to splice into your wiring harness and connect to the newly installed blower switch.

Step 5:

Repeat step #3 and see if all four modes on the blower switch work. If all four modes still do not click, then you have a fault in the wiring of your Jeep and would be better off taking it to a licensed technician for repairs. If all modes work, but you are not getting warm air in your vehicle when turning on the heater, flush your heater core.

9. Clogged or Defective Heating Controls

Another thing worth inspecting if you have sufficient coolant levels in your engine and no obstruction is in your heater core is a non-working heating control. Although one of the least suspected causes, gummed-up or non-working heating controls can be the reason why your Jeep heater is not working. And if your Jeep is a 1987 model, this is very likely to happen.

While you’re at it, check under the hood and examine the condition of your heater control valve. It is another vital component of your vehicle’s cooling system, acting as the switch that turns the heat inside your cabin on and off. This switch must work properly for your heater to blow warm air inside your vehicle.

10. Faulty Blower Motor or Resistor

As its name suggests, the blower motor is in charge of blowing air across the heater core, through the ventilation system, and into your vehicle’s cabin. You may still get warm or cool air through the vents when this component fails. However, the air pressure it will give off would be noticeably lower regardless of the fan speed you select.

Sometimes, it may even work only at certain speeds. You know there is a problem with your resistor and no longer with the blower motor when this happens. Either that or you may be dealing with a blown fuse or faulty power relay.

11. Obstructed Vents

Closed or clogged vents can make you feel like your heater is not producing enough heat, as some of the hot air cannot pass through the vents into your Jeep’s cabin. Fins or louvers that are jammed shut or stuck in the closed position do the same.

So, before you jump into troubleshooting more difficult items in this list, make sure that the fins or vents of your heater are not dirty, damaged, or badly in need of a replacement. You may also want to replace that carpet with an all-weather floor mat or liner like Rugged Ridge All Terrain Floor Liner Kit (view on Amazon) to cover your floorboards.

12. Dirty Air Filters

Out of everything enumerated in this guide, this is the least likely cause of a bad heater. However, we cannot disregard the fact that dirty air filters lead to airflow problems and prevent heat from effectively moving through the vehicle ductwork and passageways into your cabin.

When airflow is restricted, you may feel like not much heat is coming off your heater – even if there is nothing wrong with your Jeep’s cooling system. 

13. Bad Casting Process

Based on collective data from Jeep forums and, this seems to be a known issue for 2007 – 2017 Jeep Wranglers.

For owners with affected vehicles, the problem started with their Jeep Wrangler heater core not working. The vents on the driver’s side (left) were particularly not blowing warm air. There were also cases where the heater would work perfectly fine when air is on recycle but not when normal air was used.

Something was warped from the inside of the vents. And as it turned out, excess sand was left from the engine casting during the manufacture of the Jeeps.

Consequently, this residual sand circulated through the vehicle’s cooling system and eventually formed a sludge-like buildup that settled in the heater core, radiator, and oil cooling systems. Jeep owners who were fortunately still within warranty when they encountered the problem did take their vehicles to Chrysler’s service department for repair. Those who were not so fortunate had to shell out between $600 and $2,500 in repair costs to get their tank ready for the next winter.

A complete tear-down had to happen for the service department to access cylinder heads and other components. Additionally, the entire engine block, including the heater core, had to be flushed. Worse, some Wrangler owners even needed a new heater core, water pump, and radiator (despite the thorough clean) due to the severity of engine damage the sludge from the casting sand had caused.

Conclusion – Reasons Behind Your Jeep Heater Not Working

Jeep Interior Dashboard Instrumentation

To review, here are the 13 most common causes of a non-working Jeep heater:

  1. Heater core difficulties
  2. Insufficient coolant
  3. Blend door actuator failure
  4. Dysfunctional thermostat
  5. Water leaks
  6. Contaminated coolant
  7. Water pump issues
  8. Melty blower switch
  9. Clogged or defective heating controls
  10. Faulty blower motor or resistor
  11. Obstructed vents
  12. Dirty air filters
  13. Bad casting process

Seeking assistance from a reputable auto repair shop or professional technician after you have exhausted all the initial troubleshooting shared in this guide will help stop the recurrence of your Jeep’s heater problem.

Additionally, through inspection of secondhand Jeep purchases, religious upkeep, adherence to manufacturer recommendations, and proper vehicle care can save you unnecessary headaches and expensive repair costs.