why isnt my heater working?! no hot air coming out.. only cold!

[NY EURO S4]

hey i have a 2000 audi s4

i just recently tried to turn the heating on because the weather in NY is turning pretty chilly.

i turn it on, and put the temp to the highest it can go, and only COLD air is coming out.. no warm / hot air at all.. i tried everything...

any suggestions of why this is happening?

thanks in advance!

[falconcrest32]

hey i have a 2000 audi s4

i just recently tried to turn the heating on because the weather in NY is turning pretty chilly.

i turn it on, and put the temp to the highest it can go, and only COLD air is coming out.. no warm / hot air at all.. i tried everything...

any suggestions of why this is happening?

thanks in advance!

try changing ur thermostat

[AMC]

its your heater core...its a bitch to replace

[NY EURO S4]

oh god.. how much can it run me?

[orttauq]

oh god.. how much can it run me?

Hold your horses before you get all worked up. It MAY not be your heater core.

Thermostats are a common failure which would cause the same thing. The other possibility is that you have an air pocket in your heater core. Did you recently do the timing belt/water pump service or a coolant flush?

What happens is that your heater core is the highest point in the cooling system plumbing. If you get an air pocket in the system, it usually travels and traps itself in the heater core. You have to burp the system. Also a trick it to rais the front of the car and the air pocket will naturally move and you can burp it out if the expansion tank.

[kiellish]

sounds like an air pocket if the heater never starts working even after the engine is warmed up fully for a while (gauge is in the center). if it's the heater core, it is a huge job to replace. i replaced the evaporator and heater core on my b5 a4 and it took a couple days. the more you tear into the project, the more parts you have to remove. not sure if it was completely necessary, but i had to remove the main crossmember that goes behind the dash. huge amounts of work.

[b5s4tt]

it may be your climate control as well. my car is having similar issues. search elsewhere there is a test menu for the climate control that displays errors as well. i have many errors in mine. im going to replace mine tomorrow and see if it fixes it.

[mholme]

It sounds silly, but make sure when you turn up the Temp button, that it actually moves the degrees up. The buttons like to stick on the climate control. If the button is stuck on a previous cooler setting and you just crank up the fan speed, you'll still get nothing but cold air. Just a thought.

[jakecro]

You could try reverse flushing the heater core by reversing the coolant lines, running for a bit and then draining the system. If it was clogged there will be a lot of flaky debris in the coolant.

[DoGGRoBBer]

Your heater core may just be clogged, its a common problem with Audis. Look for the two heater lines that run into your firewall. Disconnect them, add some normal citrus style degreaser into them. Let it sit for 10-15 min. Then force water from your outdoor hose thru them. This gets messy but its worth a try. Repeat till the fluid coming out is clear or atleast clearer that before. Just a thought, my mechanic does atleast 1-2 audis a month with this issue.

An easy DIY.

Hope this helps.

-Mike

[YBLEGL]

I would suggest what doggrober said becuase that will at least tell you if the core is clogged, if water runs through it no problem and its clean its not the core, it could be your thermostat and or climate control unit. Start with the core first its easy to remove those hoses on the firewall.

[obijohn22]

I vote temperature sensor. there are several sensors used for the climate control system. If any are faulty the system will not work properly. for instance. the system may think it is 95 degrees in your car or that is is 95 degrees outside. First VAG and see what comes up. then let's go from there. And also as Mholme said, the sticky button. I have had this happen to me persanally.

[orttauq]

I vote temperature sensor. there are several sensors used for the climate control system. If any are faulty the system will not work properly. for instance. the system may think it is 95 degrees in your car or that is is 95 degrees outside. First VAG and see what comes up. then let's go from there. And also as Mholme said, the sticky button. I have had this happen to me persanally.

There's an easy way to see if this might be the problem without diagnostic equipment. If the air temperature sensor(s) are failing, the speed of the fan won't change if you turn the temperature up/down. If it's REALLY 50 degrees inside the car and you turn the temp up to high, the fan speed should turn all the way up. If the car already thinks it's 85 degrees inside, the fan won't come on.

[obijohn22]

There's an easy way to see if this might be the problem without diagnostic equipment. If the air temperature sensor(s) are failing, the speed of the fan won't change if you turn the temperature up/down. If it's REALLY 50 degrees inside the car and you turn the temp up to high, the fan speed should turn all the way up. If the car already thinks it's 85 degrees inside, the fan won't come on.

good plan. it should def. work to check and see what is up!

[ECS Tuning-Audi]

If it were a thermostat the heat would eventually come on after a long drive, 20-30min. Does your car's temp display on the dash properly?

Also, step 1 is check your coolant level.

[NY EURO S4]

is there already a thread on the forums that is a tutorial for doing your self for the un-clogging and heater lines? sorry but i am a noob lol and i need some help with this..

as far as my temp gauge, it DEFF works 100%. even when i am driving for a good 20-30 min and try turning the heater on, it doesnt give out hot air... =[

THANKS so much though for all replies so far..

[CrazyRobCustoms]

I would say heater core is part clogged or you have a air pocket. I'm a Audi/Vw tech, audi's and vw passats mainly start floating in now with the lovely no heat complaint.Corrosion and sediment build up in the heater core. Most of the small passages will be restricted but some will flow fine. So you'll go to flush it and think wow it has good flow. I have heard that a lot of techs are having great luck using CLR (calcium lime rust) cleaner. fill the heater core with it and let it sit for awhile.Half hour maybe. Then flush it out with a hose.to bleed it put the right hose on, then look at the left side hose. Theres a hole in the hose about 3/4 of a inch back. Slide the hose back untill the hole is past the end of the heater core tube and run the motor at 2-3 k untill coolant comes out of the hole.Then push the hose back all the way on. May need to do it twice. Good luck

[DoGGRoBBer]

^^^^ Didn't I already say that? Does anyone read my posts?.. Geez. Face in palm......

[orttauq]

^^^^ Didn't I already say that? Does anyone read my posts?.. Geez. Face in palm......

And it was said a couple of times before you said it. What's your point? Is this a competition or are we just trying to help the guy here?

[witwer4444]

It sounds silly, but make sure when you turn up the Temp button, that it actually moves the degrees up. The buttons like to stick on the climate control. If the button is stuck on a previous cooler setting and you just crank up the fan speed, you'll still get nothing but cold air. Just a thought.

Not to thread jack, but my buttons have been slowly starting to stick in my 01 climate control unit in the dash.

I have found that if the car is cold inside, they are very hard to push and most of them either wont work or wont come back out when I push them in.

What do you suggest I clean the buttons with?

thanks and go on with the original OPs questions if you cant answer mine

[B5BiTurboS4]

There was a DIY on this. How to remove the whole button assembly and clean it...
Search it up... It should be moved to the DIY section but I havnt seen it. Its very detailed...

[BoostinonYOU]

Does anyone elses ambient air temp readout go haywire sometimes ? Mine will go to like -58 degrees... wtf is that all about, IT did the same thing in my 99 a4 as well.

[Juliebenton]

I would say heater core is part clogged or you have a air pocket. I'm a Audi/Vw tech, audi's and vw passats mainly start floating in now with the lovely no heat complaint.Corrosion and sediment build up in the heater core. Most of the small passages will be restricted but some will flow fine. So you'll go to flush it and think wow it has good flow. I have heard that a lot of techs are having great luck using CLR (calcium lime rust) cleaner. fill the heater core with it and let it sit for awhile.Half hour maybe. Then flush it out with a hose.to bleed it put the right hose on, then look at the left side hose. Theres a hole in the hose about 3/4 of a inch back. Slide the hose back untill the hole is past the end of the heater core tube and run the motor at 2-3 k untill coolant comes out of the hole.Then push the hose back all the way on. May need to do it twice. Good luck

Hi ,
I just bought a 1999 VW Passat and this may be one of the problems that have popped up. Also do you know, is the mass air flow sensor and ignition module a possible cause for the car shaking and stalling occassionally?

[AWD87]

http://www.audiworld.com/tech/eng.html
First article "Heater Core flush"

[ECS Tuning-Audi]

Does anyone elses ambient air temp readout go haywire sometimes ? Mine will go to like -58 degrees... wtf is that all about, IT did the same thing in my 99 a4 as well.

Yes, you likely need one of these: Outside Temperature Sensor. They are a common problem.

[Scotty@Advanced]

hey i have a 2000 audi s4

i just recently tried to turn the heating on because the weather in NY is turning pretty chilly.

i turn it on, and put the temp to the highest it can go, and only COLD air is coming out.. no warm / hot air at all.. i tried everything...

any suggestions of why this is happening?

thanks in advance!

There's any number of things that could be wrong.

Air bubble in heater coil coolant circuit
Bad thermostat (will show as engine running too cool)
Dirty heater coil
bad Climate control head
Mixer flap actuator not working
Plugged up heater core (internally)

[1.8Tcaddy]

Sticky button DIY link:

http://zener.com/audi/HVAC_cleaning/

[DanS4]

Yes, you likely need one of these: Outside Temperature Sensor. They are a common problem.

I replaced mine and the temp is still 184 outside. I believe there is two sensors the one described and one near the cabin filter.

[Scotty@Advanced]

DanS4 your Avatar rules!