heater not working properly?

try pulling HVAC fuse with key on leave out for 60 seconds and reinstall wait another minute it may reset your actuators if not then check for actuator not getting power. This guide can help us fix it as well:

https://www.2carpros.com/articles/car-heater-not-working

Please run down this guide and report back.

I have a 2003 GMC Sierra 1500 4WD 5.3L
And my AC\HEATER only blows from the defrost.
it doesn't work on the front four vents or the floor. I just replaced the control moduel located below the stereo. And it made no difference ' I've also checked all the fuses. What else can i do to repair or troubleshoot this problem?

did you check the door actuator that controls where the airflows its prolly a bad mode door actuator

Jacob is correct. Check to make sure it is working whey you switch air flow direction. I believe they are electon your vehicle; however, they may still be vacuum actuated.

Sitting at idol I have no heat. The faster I drive the more heat I get. In return the slower I go the cooler it gets. The fan works and both lines going into the firewall are hot. I have changed the sensor that goes in the fan under the dash. All the fuses look to be good. I do not smell antifreeze nor are there any wet spots on the floor board. Any ideas.....

What you are describing sounds like it is low on coolant. Is the blower motor running?

Let me know.
Joe

Yes the blower motor is running and the collant level was low. but I only added about a cup to bring to cool full line. The warning light would come on every now and then so i added coolant. a short time after that the heater started to act up. Could it now be over full by just enough to do the same as needing coolant?

You didn't overfill it. It will push out what isn't needed. As far as the heater, is the engine running at a normal operating temp? THere is a chance the thermostat is stuck open and the engine isn't warming up enough to create good heat.

Let me know.

Joe

The engine is running at a normal operating temp.

2001 gmc sierra 4x4

Recently had the coolant system flushed, now i notice that the heat is not blowing hot air like it should be. Not sure exactly what the issue could be. Both hoses are warm like they should be, the heater/air door opens and closes like it should when switching from air to heat. I'm thinking it might be the thermostat but not positive???

You could have some air trtapped in the system.
Try the link below as it will guide you to the procedure to release air from a cooling system. If that does not work, the thermostat is most likely stuck open and needs replacement.

Her is the link;

https://www.2carpros.com/articles/vehicle-bubbling-noise

2001 gmc 150000 miles heater does not blow warm air. Blower moter working on all speeds .Engine tempature normal.

Check heater hoses by the fire wall if both hot suspect blend door and or its actuator


If hoses not hot or one cool suspect heater core clogged

Heater problem
2000 GMC Sierra V8 Four Wheel Drive Automatic

I have a 2000 GMC Sierra 1/2 ton. I am not getting any heat in the cab. The engine coolant temp. gauge reads normal, but I still get no heat in the cab. i have always noticed cold air on the passenger side, but this year there is no heat, is there a vent stuck open

Verify that the thermostat is operating properly replace if needed check and verify that heater hoses kinked free and getting hot if not remove hoses and flush heater core if heater hoses hot suspect blend door in the HVAC box

Heater problem
1999 GMC Sierra V8 Four Wheel Drive Automatic

heater blows hot than cold. return heater cor line gets cold after blower is turned on. lower radiator hose is cold too. if you leave blower turned off the return hose from core stays hot. replaced the thermostat and problum is still there. also the nipple on the inlet side broke. can that be replaced?

check your water level, it's probably low. then have your radiator cap checked as this is on e of the big failures on coolant systems. if it's not full your heater won't work right.

Heater problem
1999 GMC Sierra Two Wheel Drive Automatic 108k miles

does the 1999 GMC need a thermostat or something else. it's winter and i lost the heat in my truck.

Hello, does the engine reach operating temp normally? Does the blower motor work? If you feel of the heater hoses under the hood, are they hot?

yes, and still blows cold air.

The only other thing I can think of is to check the mode or temperature actuator under the dash.

thanks, wiil check it. btw where is it located under the dash?

They are directional doors, I'd have to look.

the temp gauge on the engine reads normal, but i replaced the thermostat anyway and then the waterpump. the air in the cab remains cold. the line running to the heater core feels hot, the return line seems cold. could there be something plugging the H.C.? If so what is the best way to flush it out. Thank you much. Ben

Hi there,

The heater tap may not be opening at all, disconnect the two hoses and using a garden hose on LOW pressure try and flush core with tap open, if no flow, try and access the heater tap and check operation, also check that the heater controller is working.

Mark (mhpautos)

My hubby's truck blows cold air, yet the temp gauge seems to be working fine, the fluid levels are good, so I don't know what could be wrong. It doesn't matter how long the truck's been running, the heater never seems to warm up. Any one else encounter this problem or know how it could be fixed? Thanks much! :-)

Try warming the Vehicle, then carefully feel the heater hoses, are they both hot? If one is cooler than the other, You need to flush the core, or do a replacement job on the heater core. Also if the system has a heat control valve on the heater hose, make sure it is working! Also check the thermostat, and the temperature blend door, thats under the dash, in the heater plenum...

problem resulted from faulty water pump. I replaced water pump, thermostat, radiator cap, and heater core. had a difficult time getting air out of system. I now have heat coming from vent at dash not sure if its the same good heat I had before but its heat. temp gauge seems to stay at 165-175 degrees not sure if that's where it should read. the heat only comes from the dash vents wont change from the indicator dial and the windshield defrost blows cool air

I think you installed the wrong thermostat.the temperature rating is marked right on the thermostat,.I'm thinking it should be around 190. Go to the parts store and have them look it up.

I have a 1995 GMC Sierra that the heater is not working properly on. The only way you can change the temp and the air direction from vent to floor is to turn the fan off. It also will not go to defrost and does not have the high mode on the fan. I have already change the A/C control head

you'll have to check to see if the actuators are getting power ornot. they are under the dash. i'll send a pic of a generic heater to give you an idea where to look. theblower may not be working on high due to the high blower relay notworking. here are the thingsto look at.

temperature running hot. replaced heater core, thermostat and water pump. doesn't appear to have any water going to thermostat hose not sure how long I should have left car running but temperature ran high and do not have any heat blows cold air. no water on dip stick.

First look for a bleeder screw on the thermostat housing. The thermostat wont open if there's air under it. If there's no bleeder screw, look for a sensor on or near it that can be removed while you fill the coolant.

If you get the air out but coolant still doesn't circulate, bleed it again while the engine is running. If you continue to get air, suspect a leaking cylinder head gasket. The combustion gases will pool under the thermostat preventing it from opening. Your mechanic can perform a chemical test at the radiator or reservoir to verify a leaking head gasket.

Heater problem
1995 GMC Sierra V8 Four Wheel Drive Automatic

i have the truck above and my heater will only sometimes come on most the time only have the first 3 fan speeds but every now and then the forth fan speed will work and then it blows hot air otherwise it is always cold air that come out regardless of where my heat control is any ideas, the fan speed resister shouldn't be broken if it works sometimes.

When it doesn't operate on high, check the switch and the resistor this way:
BLOWER MOTOR OPERATES AT LOW &/OR MEDIUM SPEED ONLY

Turn ignition on. Set blower switch to high speed position. Connect test light between Orange wire at blower switch connector and ground. If test light glows, go to next step. If test light does not glow, replace blower switch.

Connect test light between orange wire at blower resistor connector and ground. If test light glows, replace blower resistor. If test light does not glow, repair open Orange wire between blower resistor and blower switch.

I have not heat so I swapped out my thermostat for a 165 and my truck runs at 160 an sometimes shoots up to 180 and now I have no heat and in this twenty degree weather seriously not good. should I switch it out for a 195?

normal thermostat for this vehicle is 195 then when cooling system Is full run at 2500 rpm's until truck heats up let engine cool and recheck coolant level.