Question about Air Conditioning and Heat for Toyota Yaris

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Heater hoses Car is fully heated but heater blows only slightly worm air. Checked both hoses that go from the engine inside of the car both equally worm but not hot at all.

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Start by identifying engine size and auxillary extras on this car for us all. basic thought... is the coolant level full??? and any air bubbles purged from the system? now measure the coolant temperature. now the heater duct temperature. identify the components in the system. locate and inspect them. now you must find any control for the coolant to flow or not flow. or flow at a reduced rate. is there a heater control valve on your car? is it cable operated or do you have automatic temperature control? or is it vacuum operated? toyota products i have experience with use a cable operated valve located at the entrance to the heater core. this is at the firewall,or, bulkhead .behind the engine on most front engine, front wheel drive cars. There is a wire type cable that operates a lever. its adjustable when its snapped into place. these often bind up when they are exposed to weather and miss their maintenance. Try to lubricate and readjust the wire. With it disconnected, operate the lever and turn it both directions. Take new duct temperature measurements and compare them to the readings you got before. Is the coolant temperature of the engine at operating temperature? Did the duct temperature change? Are you familiar with the components used on your car? If your system uses different parts and method the principle is still the same. Get it to let the coolant pass thru and circulate till it takes on the same temperatue as the engine. You can also report your findings so far. There are service bulletins for technicians available at your local library... for free!. also, ask for service manual information regarding your system. Follow safety recommendations. Protect yourself and your vehicle as you go. Be sure your engine cooling fan operates in cycles to cool the engine. If the coolant temp is below operating temp specification, your thermostat is possibly stuck open. Be sure your heater blower operates as designed. Several speeds are the norm. There has been no recent change to the controls on the instrument panel... like the warm/cool lever wont go all the way over to warm anymore... this tells you the cable is out of range. On automatic systems, the controller uses sensors to decide before actuating. Your car may need professional help. So you see, there's a ton of information required for the technician to test and consider or look up. When you are satisfied the coolant is flowing and the blower is running, there is the matter of temperature mode doors in the heater A/c system. They control airflow. The temperature blend door is often cable operated and adjusts like the control valve. If not, there's vacuum operated ones or the kind with electronic actuators. At any rate, it has to be open to let the air flow thru the heater core. Verify and identify this as well. There are also fresh air /recirc doors on these systems if yours is stuck open then cold ambient air is its supply. That will reduce the duct temp considerably.

Posted on Nov 19, 2013


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If the fan is moving air at the proper velocity, it is most likely a clog in the heater core or the hose leading into it. Generally, there are 2 hoses about 1 inch in diameter going through the firewall. Those hoses go into a small radiator inside the cars passenger compartment. Go to YouTube and look for 2002 Silhouette heater core removal for specifics. If warm radiator water won't flow freely through the core, that's the problem.

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Hi Shannon, IM AL the owner of Big As Auto Repair.

Shannon, it looks like you have ruled out the coolant side not heating properly with the thermostat replacement and coolant flow through the heater core because you replace it as well. Let's first make sure coolant is getting to the heater core. Here's an easy way to check this issue. Start the engine and drive it until completely warm then park and leave the engine running, open the hood and check each heater hose that is connected to the heater core at the firewall. If both hoses are equally hot then the coolant is getting to the core and working properly. If one is a lot cooler then the other then you could have a heater valve on the system "OR" a water pump flow issue. BUT, if they are equally hot, then you most like have a heater door issue inside a/c housing. If the heater door is not working properly and staying on the cold side you will not have heat. Lets stay in close contact buy you going to my auto-repair-website and work together. Just click on "CONTACT US" and I'll work with you until we resolve this issue.

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Heater in my car blows slightly worm air

no year stated. nor engine.
the engine must be 180F or more and hold
we use what is called a tool, called a thermometer,
we measure the engine heat first. at the thermostat housing
180F is typical. if not fix that first.
check fuses if the fan "blower" is dead , is it?
blows cold in all lever positions? hot + recirc, + defrost ,high or low vents?
all vents cold? (warm)

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There are 2 systems for making heat in your vehicle. One is the water system and the other is the air ductwork.

Check both heater hoses for equal heat when the engine is at normal operating temperature. Careful not to burn yourself, but you need to grab each hose and compare the heat. If they are not equal, then your problem is water flow. There are flow valves which need to open to circulate the water through the heater core.

If both hoses are equally hot, then the problem is inside the cabin and in the ductwork. An air passage is blocked by an inoperable flap mechanism.

With some Digital Climate controls, self diagnostics is possible. You will really have to dig for the info on the Web or go to a Dealer. Certain keypad sequences can be entered to release the Codes. But the Code numbers are in a different table of Codes separate from the typical engine Codes. Depending on who made the Climate Control can affect how to do everything.

The net result for the diagnostics is to identify any small solenoids that are not opening the flaps in the ductwork, or other defects.

Please rate my info.

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Heater is not blowing hot air

How old is the coolant in your car? If you haven't changed the coolant in a couple of years, you may have sediment build-up in the heater core that is restricting full circulation in the core and preventing good heat output. Feel both hoses at the firewall that go to the heater core. Are both equally hot when the engine is warmed up and heater controls on high? If only one is hot, and the other lukewarm, the core is partially plugged. Pull off both hoses there and run a garden hose at low volume backward through the core. If not sure what is backward flow just run the garden hose through both openings and see if you can remove any sediment or blockage.
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Have you checked the coolant level? What you describe is exactly what happens if the coolant level is low. When stopped at idle, hot coolant is not circulating through the heater core, so no heat. As the engine increases in rpm's when you pull away from the light, the water pump is spinning quicker, and some coolant is making it to the heater core. So check the level, and if it is low, keep an eye on it to see if it drops again. That of course indicates a leak somewhere. Get it fixed, as overheating the engine leads to costly repairs and worse case a new engine. Let me know how you make out with this.

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