No heat

I have a 94 chevy camaro I've replaced the thermostat the heat sensor the heater core and the water pump car will heat up after it runs for 20 min but as soon as you start to drive the temperature Guage goes down and the car starts to cool off inside there is no heat control valve all hoses are warm this is really frustrating and I live in Illinois it's cold can you please help
Experienced mechanics share their insights in answering this question :
Hi there:

In some instances, this problem is caused by a simple electrical issue, such as a faulty electrical relay or blown fuse to the heater core. It’s also possible however, that you have a blockage inside the coolant system that is causing the no heat problems. There are two things I’d do first; flush the radiator (and make sure it’s properly primed while filling) and check all electrical connections to the heater core, and blower motor. If you complete those checks and still can’t find a solution, feel free to contact one of our professional mobile mechanics to complete a heater is not working inspection.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

The most common reasons a Chevrolet Camaro heater isn`t working are a broken heater blower motor, a problem with the thermostat, or a failed heater blower motor resistor. Search our network of RepairPal Certified shops near you to speak with a technician about your issue. Oops!
The average cost for a Chevrolet Camaro Heater Core Replacement is between $1,252 and $1,479. Labor costs are estimated between $741 and $935 while parts are priced between $511 and $544.
If your blower only works on the highest setting, your blower motor control module probably needs to be changed. If the fan isn`t working, you probably need to have the blower motor fixed or changed. If the air coming through isn`t hot, the heater core is probably clogged.
Low Coolant Level

If there isn`t enough coolant in your system, the heater core will blow cold air into your car. Solution: If you confirm that a low coolant level is the source of your problem, you simply need to top off your coolant. You may want to check for leaks as well if you just recently refilled your coolant.

If you think the cause for your car heating not working is related to the blower fuse, be sure to replace it with one of the same amperage. The fuse may have blown due to age, or it may suggest an underlying problem. If the replacement fuse (of the same amperage) does not blow, you may well have identified the problem.
If the heating system isn`t working at all (no hot or cold air is being blown into the car), this is likely due to a faulty blower motor or an issue stopping power from reaching the blower motor, but that`s not the only possible reason. In general, car heater issues can be caused by the following: Low antifreeze.
Clean Filters

One of the most common issues with a heating system not functioning is dirty air filters. If your air filters are extremely dirty, then the airflow can be blocked. Check for clean air filters, vents, and registers. Make sure there are no rugs or furniture blocking vents or registers as well.

Some heater control valves will be located in the engine compartment at or near the passenger side firewall. Others are located behind the dashboard near the passenger footwell. Refer to the factory service manual for your vehicle to determine the exact location.
Below are the signs of a bad heater control valve: No heat coming out. Heat always on and cannot be turned down. Heat output changes with no changes in the heat setting.
2) Turn on your boiler/programmer and central heating, making sure your hot water is turned off. 3) Turn up your room thermostat or boiler thermostat, and make sure the boiler fires up. 4) Wait for 5-10 minutes, and feel the top and bottom of you radiators in each room, make sure they warm up evenly.
The blower fuse is a 40 amp fuse located in the engine compartment`s fuse box.
In most cars the heater motor is situated under the centre of the dash, which makes it rather inaccessible. In some cases, however, the motor is under the bonnet at the rear of the bulkhead. The most common cause of any problem is a blown fuse .
A heat pump consists of two major parts – a “wall cassette” that is mounted inside your home, and a condenser unit that stays on the outside of your home.
The thermostatic valve `senses` the temperature in your room and once the temperature you want is reached, it will automatically stop the flow of hot water to your radiator and prevent it from getting any warmer, wasting heat and energy.
Heater control valve bypass is not standard on vehicles; it is a modification. When bypass hoses are installed, the coolant in your car will always be circulating through the heater core – that means that if the core starts leaking, you won`t be able to turn it off.
As the engine heats up, the thermostat should open up and allow the coolant to flow from the radiator to the engine. If you see the coolant flowing through the radiator, then the thermostat opened and is working properly. If not, then it is most likely stuck closed.
If the heater control valve fails or gets stuck, it will not be able to allow hot coolant into the heater core so that the heater can operate. If the heater does not have hot coolant the AC system will not be able to blow hot air, and the front defroster may not work.
If your car`s air conditioning isn`t blowing cold air at all (or it tries, then turns warm), you could have a clogged expansion valve, a faulty compressor clutch, a leak, or a malfunctioning fuse in the system.
Turn your thermostat to HEAT mode and adjust the temperature until the thermostat triggers a heating cycle. Once the heating system is running, go back outside to the exterior unit – if this equipment is on and blowing air, it`s a heat pump.
A fuse is a device that works on the heating effect of electric current. It consists of a fuse wire which has low melting point. It is connected in series with the appliance in a circuit. Whenever there is high electric current, more heat will be produced and it leads to the melting of fuse wire.
If your car`s air conditioning isn`t blowing cold air at all (or it tries, then turns warm), you could have a clogged expansion valve, a faulty compressor clutch, a leak, or a malfunctioning fuse in the system.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

A/C and heat are not working properly. Car blows heat in summer and cool air in winter.
ANSWER : Common causes of no cabin heat include malfunctioning blend door(s) (part of the in-dash ventilation network), a faulty or stuck heater control valve, a plugged heater core, stuck open engine cooling thermostat, collapsed hoses, and low coolant level. The cost to resolve the problem depends on which of the foregoing faults is the cause. If you desire a diagnostic to determine exactly why there is no cabin heat, please request a non functioning cabin heater diagnostic and the responding mechanic will come right to your location and get this resolved for you promptly.

With regard to your air conditioning system, if merely re-charging the system restored normal operation but the a/c ceased to function after a month or so, that scenario typically suggests a leak. Some leaks are really cheap to repair, like if a couple o-rings need to be replaced in system piping but if the leak is at the compressor shaft seal, that repair is more costly. It is not expensive to find the leak and diagnose the system and once the leak is found the mechanic can let you know of the exact cost to repair the leak and re-charge the system. If you desire that service please request an a/c system diagnostic – suspected refrigerant leak and the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you

Read Full Q/A … : No heat

Heat inside car stays warm for minute then blows cold until I turn heat off for a minute and try again.
ANSWER : Hi there. The engine always at operating temperature leads me to believe, the thermostat is not the cause, for no heat inside the vehicle. There are several possibilities for no heat inside, the heater control valve is malfunctioning, the heater core is restricted, the temperature blend door actuator is malfunctioning. Replacing components without diagnoses, can be expensive and time consuming without resolution. I recommend having your vehicle’s inoperative heater be diagnosed and repaired by a certified technician, such as one from YourMechanic.

Read Full Q/A … : No heat

Heater not working reliably, is it caused by a bad thermostat?
ANSWER : From what you’ve described, it sounds like you have a stuck open thermostat. I’d recommend replacing the thermostat to see if this is the cause of the slow heat up of the vehicle since it’s a relatively quick repair. In an area like that it sounds like you’ll will need the heat in the winter very badly and as soon as possible. I would also recommend getting a coolant flush as it may help clear any possible blockage in the heater core. To avoid any unnecessary repairs, consider YourMechanic, as one of our mobile technicians can come to your home or office to diagnose your heating issue and make the necessary repairs.

Read Full Q/A … : No heat

Vehicle at running temp, turn on heat, no heat – stomp on gas, there is heat – ??? 2004 Jeep Liberty
ANSWER : Hello – regarding your lack of heater function unless the engine is revved up a bit, you have a coolant flow issue. This could be caused by a worn water pump (engine might be running warmer than normal?), a partially blocked heater control valve (adjustment problem or failed heater control switch), or clogged cooling system that simply has poor flow. I would recommend an inspection of the heater & cooling system by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.

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Car heat is cold until I add water and over heating with out telling me
ANSWER : Hello, thank you for writing in. There seems to be an issue that we need to take on first and foremost. This is the fact that you are having to add coolant to the system. This means the coolant is leaking either externally (onto the hot engine), or internally (being consumed with the air/fuel mixture). The best way to tell is to simply run the vehicle and watch for the leak. If the engine is consuming the coolant, you are likely seeing white smoke from the exhaust. This is most commonly resolved by replacing the head gasket. Common components to look for an external leak with are the thermostat and the water pump. Both would cause the symptoms you are explaining. Fore more help with the issue, contact our service department to schedule an appointment.

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My heat and air turns on without a problem but does not blow very hard (heat blows harder than air). Rattling noise.
ANSWER : The heater and the air conditioner both use the same blower motor. However, Nissan does have two separate fuses for the same unit. One of them can be blown. There are also resistors in the system that can fail. There are several electrical tests that can be done, but depending on the condition, it may be more practice to change the entire unit. Due to the age of your vehicle, and the Juke’s history of blower motor issues, it’s very likely a simple fuse issue. These can (for the most part) be visually inspected, and are cheap.

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Engine is over heating and I’m not getting heat. 2001 Pontiac Grand Am 3.4 V6
ANSWER : Hello – I agree with your diagnosis – a water pump failure is a prime candidate for both overheating and a "no heat from the heater". Lack of water flow will cause both symptoms, and cause damage to the engine in minutes. I would recommend a thorough examination of the cooling system immediately. A mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.

Read Full Q/A … : No heat

Car won’t drive after over heating on the highway
ANSWER : Hi there. Most of the time when you overheat this engine it will also cause the transmission to get too hot. When this occurs it can easily cause transmission failure. I would suspect this if the vehicle does not move at all. If it move but is severely lacking power then you either have some serious internal engine damage or a failure in the catalytic converter from the overheating. It sounds like it is the transmission though. I would recommend having a transmission specialist take a look at it.

Read Full Q/A … : No heat