Here are some reasons why a car’s heater may suddenly stop working. I just have to find the blower relay and its fuse. There is no battery to operate the blower. You should see a valve near the furnace that controls the gas flow. Check the coolant level. When winter arrives, the last thing you want breaking down is your car's heater because not only is a frosty car inconvenient—it's also dangerous. If your blower only works on the highest setting, your blower motor control module probably needs to be changed. Rotated all the PDC relays around, they have the same ID, other than ABS pump. Check if the blower motor receives power. In the case of this Dodge's blower, the answer was fairly easy to discern. Switch the thermostat from hot to cold and listen. I noticed the fan was not blowing any air through the vents. My blower motor does come on. Your vehicle should have a complete relay diagram showing the location of all of the vehicle's electrical components such as fuses and relays. Coolant travels through several parts of your engine. If the heater is broken because it's not blowing any air, it's likely due to a faulty blower motor or electrical connection. Follow these steps to fix the problem. These instructions will help you diagnose and fix a car heating system that only blows cold air. To find out what's wrong with your car's heating system and what you can do to fix it, you first need a basic read of the situation. Filling the coolant may fix the problem in the short term. Lift the hood and check the temperature around where the heater core hoses enter the heater core box. Actually, you might have blown two fuses: the literal fuse connected to your thermostat and, if you're angry about your AC not working, an internal "fuse." That means a trickle out of your vents instead of the rush you asked for. It will however work when you turn the key all the way back or forward but not when the engine is running. This is usually because the coolant has not been replaced in … To that end, if your owner's manual is incomplete, buy a proper repair manual. Some reasons can be an easy fix while others may need the assistance of an auto repair shop in the Longmont area. Checked continuity of 40 amp blower fuse; it's okay. A motor failure will obviously may cause the fan failure, causing an overall car heater failure. So when I first start the truck AC/heat blows fine, but after about 10 to 15 minutes I am getting little to no air. It has A/C but is a short body and has no rear heat or A/C. If you determine that hot antifreeze flows through the heater core, there may be debris in the heater box. Of course, any central residential HVAC system is supposed to provide cool air when it’s warm outside and heat when the outside temperature drops. I have a 2000 Honda civic ex. The Front Blower Motor Relay (also known as the AC Relay), located behind the junction block with a black connector, B05, is the culprit. Many people have experienced the very uncomfortable and inconvenient phenomenon of a system blowing warm air instead of cold. Is the heater blowing cold air into the car, or is the car heater not blowing any air at all? 2. Rotated all the unmarked relays around in the junction box. Then all of a sudden it started blowing full blast, while the recirc, ac, rear defrost button lights all came on and were flashing...then it all turned off.... - 1996-2000 Honda Civic There is also an electric fan , which can be switched on to blow air through the system when the car is stationary, or when extra ventilation is called for. However, attempting this without all of the info you need, destines your electrical troubleshooting process to failure. But the narrow passages can become clogged. Therefore, if major problems in the heating and air conditioning system fail, as if the power supply to the motor was completely cut off due to overheating or corrosion, the motor will simply not work, which in turn will render the entire heating and air conditioning system unusable, as no air will flow through the vehicle’s air vents. Matthew Wright has been a freelance writer and editor for over 10 years and an automotive repair professional for three decades specializing in European vintage vehicles. My radio, windshield wipers and ac/heater fan will not work. It should have level indicators that show how full or empty it is. A blown fuse often indicates a different underlying problem, so never replace one with a larger fuse to prevent it from blowing out again. However, low coolant often indicates another problem, such as a leaking gasket or hose. Haynes say it is located in the PDC under the Hood, along with a 40 amp blower fuse in the PDC. If your car has no heat, not only would the inside of your car feel like an ice box, but a broken heater can prevent your defroster from blowing warm air to your windshield to eliminate ice and fog, which can pose a hazard while driving. All the relays in the PDC have designated legends on the cover, but none indicate they are for the front blower relay.