The fourth generation Volkswagen Jetta, also called the MK4 or the Bora, is Volkswagen's family sedan.

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Why isn't my heater actually heating?

hi i have a 2001 volkswagen jetta and well my problem is that i am not getting very hot air when i have the heater on and i am getting very annoyed with my mom always complaining about how she doesnt like the car and i can put it at max air and max heat and still only gives warm air. i have asked a few people and they say that it can be the thermostat or the the a/c button isn't working but the a/c is. and when i press the button to turn off a/c, a/c stays on even if it says it's off.

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What model Jetta is it and what engine does it have?


it is a 2001 volkswagen jetta gls 2.0L 4 door sedan


Probably it's broken and you have to fix it.


good answers


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josue villarreal, yes, it is possibly that it is your thermostat. It is also possible that your heater core is clogged or the your fan is not working properly to forced air through the heater care. Also, make sure that you have enough antifreeze in your vehicle. Check the heater hoses, the lower hose is where cooled coolant reenters the engine. it should not be cold but will not be as hot as any other cooling system component. If there is no circulation (hose, radiator and heater core cool) then you may have a bad coolant pump. If both hoses are hot that would mean you have enough flow through the core, check the servo that opens and close the vent doors. If they do not open properly, you would not get enough flow to heat up your interior.. Hope this helps, good luck.


Just looked at the service manual for your specific model. thanks for letting us know which one it is. Check your Temperature Flap cable. Make sure that it is properly adjusted.

Temperature flap cable, installing and adjusting


Heating and ventilation controls are installed.

Connecting duct removed

Turn temperature rotary control knob to left onto stop.

Attach center wire of cable -1- to the temperature flap lever -2-.

Push temperature flap lever -2- to stop -arrow A- and secure outer cable -1- with clip -3-.

Turn temperature rotary control knob to left and right onto stops.

When turning the rotary control knob, both end stops must be reached.

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great article!


THX this working!


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Regarding the a/c button, if you have the selector on defrost, the a/c should stay on. If you turn the a/c off, and turn the selector to one of the other settings (such as floor or vents), does the a/c turn off then?

Regarding the heater temperature, if the fan is blowing normally, it is likely either the thermostat is stuck open or the heater core is clogged, either internally (not allowing the coolant to flow through it properly) or externally (not allowing the moving air to pull the heat off of it properly). Does the car warm up to its normal operating temperature? If you have a temperature gauge, check to verify that it warms up to the middle of the normal range. If it does not, chance are good your thermostat is stuck open. If it does, then the thermostat is probably working correctly, and it is more likely that the problem is with the heater core.

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There is a remarkably common problem with Jetta heater boxes. I have discovered it in my own 2003. When we purchased the car used we noticed a flurry of foam from the vents when heat or A/C was turned on, and thought not much of it. I just figured it was probably a lining of some vent that had worn over time. Since that time...with extremely poor heater performance my research led me to discover that the vent doors, once sandwiched with foam deteriorate over time and leave stamped metal doors with huge holes punched in them. These now obvious holes leave hot air to mix with outside air, and never divert hot air as they would if they were solid.

Since a pic...and a very helpful video is worth more than a thousand of my words...check this out if you discover all else recommended has failed. I believe you would want to take a look at this before you go replacing the heater core.

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Where can I get the material that you used on the doors when the foam has blown out in my face? Thank you so much for your post. You saved me a lot of money.


Don't bother replacing the foam, but if you choose to do so 3M has a very thin foam that can handle the temperature range required. My advice? Go get HVAC Duct tape..actual HVAC tape is metal. Duck brand is pretty thick, but any mallable metal tape will do. The foam was a way of keeping mold from growing in the vents and blowing smelly air in your face....if this happens just use lysol, about one can in your windshield vent should take care of enough of it; run your ac on high and to the floor and console, spray in. That works...just ask any Neon owner.


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josue villarreal will be eternally grateful.
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