cripti0n

I recently purchased a 1998 1.8T A4. This morning was the first cold morning since I have purchased the car, and it turns out the heat does not work.

From what i have discovered it can be a couple things that have gone wrong. ie. Temperature sensor, Air Flow Flap, or the actual heater core itself, or others im not aware of.


Here is what i know:

The A/C system works great, and the fan speed is adjusted automatically when set to auto, so this makes me think the temperature sensor is fine.

There is no heat AT ALL that comes out of the vents, even after a good 10minute drive to work.

When i put the heat on when starting the car, the fan speed was at minimum, and after a couple minutes of driving the fan speed increased, but the air wasnt any warmer. (i think this mean the computer knows the coolant temp has increased, which means the heater core has warm air waiting... just a guess though)

And finally...
No Fault Codes




So if anyone has any ideas or has experienced this problem before i would appreciate the help.


Thanks

cripti0n

Just an Update..

I checked to see if the flap motor is working and it seems to be. I can hear a motor/servo moving and i can see a lever moving if i get down under the glove box.

Second i checked both coolant hoses that are between the battery and brake fluid reservoir, and they were both warm after the drive home from work.

One last thing, if i drive around with the blower off, and then turn it on with full heat, there is some heat that comes out but it quickly turns to cold air.

So is this a sign of a bad heater core? or is it reading the inside temperature wrong?


I am out of ideas and could really use some help.

rocky.ca

iTrader: (1)

had that prob in my old jeep. flush out the heater core with a hose.... both ways a couple of times. see if that works, if not, replace it. most likely your prob

frob

Thats a good idea- and easy to do, as those hoses have easy wire clips and pull right off.
assuming the coolant level is normal and your coolant temp gauge is acting normally - if that doesn't work i'd be concerned something worse is reducing or preventing the coolant flow- like a bad pump impeller, a common problem, but then your coolant temp gauge would not be acting normal, unless you only do very short trips that don't let the engine build up a lot of heat. also your thermostat could be dead in the open position.
If you have never changed the coolant, it may be time to do an engine flush and change the thermostat - an easy and inexpensive DIY project. what color is the coolant and is there any dark deposits in the coolant overflow tank?

also - have you ever changed the cabin air filter?

cripti0n

Thanks for the replies,


I had the coolant flushed by the dealership a the week before i had this issue. I rechecked the hoses to the heater core (with the heater running) and one was hot and the other was not. So it was clogged.

brought it back to the dealership because the heater core should be flushed when the coolant is flushed. Turns out they had to flush it twice to fully remove the clog.

The heat works now, although i think it is still a bit clogged as it takes some time for the heat to get really hot.

There is crap in the coolant expansion tank, which turns the coolant more brownish.


-Coolant temp takes a while to reach the middle, usually 20-30mins of driving. but i have never seen it pass 90 (2+hours driving).

I think im going to clean the coolant expansion tank to get the crap out of it, and do a coolant flush myself.... i dont think i will ever go to the dealership again.



Frob you mentioned the cabin air filter, i should probably change it now that i think of it.

frob

If the coolant isnt bright fluorescent orange after a recent flush/replacement, they didnt do a very good job if they even did it at all.
If you DIY, consider doing what i just did - run a coolant system cleaner - i used prestone "super cleaner" (Can. tire) which in mild and non-corrosive, aluminum safe etc. run it mixed with pure water (distilled if possible) for a week or 2 (400-600km), then flush and replace with proper G12 coolant @ 60% w/distilled H2O. it worked well for me, it might help dissolve any remaining crud in the heater core (and elsewhere you may not yet know about but if you do this, do it before the weather drops below 0 Celcius!
last bit of advise - if you disconnect the heater hoses, look out for the o-rings, they tend to fall out- better to get replacements anyway, as they swell over the years and are hard to reinsert properly.

tb426

My car was out of heat for a while, i bring it to a car shop, they told me my thermostat need to be change, coz it stay up in open position even the engine is cold.

so they charge me aound $24 dollars for the parts, and told me the labour cost is about an hour.

after 3 hours, they call and told me for the A4, is really hard to change it, is like changing the timing belt labour, they need to take away the bumper and alot of thing in order to change the thermostat. so at the end they charge me total $200 for larbour and parts. now the question is did i get ripped off? i really dont know about this car alot. please advise. thanks alot.

frob

I'm not a professional mechanic, but i know it would take me about 15-20 minutes to change my thermostat, including jacking up the car: With the plastic belly pan off and the coolant drained, just undo the 2 bolts holding the plastic elbow connecting the lower rad hose to the water pump. the thermostat is tucked inside the elbow and should just pop out. very easy to get at from below, there's nothing really in the way. Its that easy, at least on mine (AEB engine). I don't know if its different on the other engine versions, but 3 hours is certainly a ripoff, no doubt about it.

By the way, even you had to take off the bumper (which you don't) , that only adds another 5 minutes: its 2 bolts and a chiropractic maneuver and voila! its off.

p.s. here's the DIY writeup: http://www.audiforums.com/forum/showthread.php?t=100442

carinc

checked to see if the flap motor is working and it seems to be, well this generally happens in the cold mornings

cripti0n

Hey Frob,

Thanks for finding that DIY, that is a huge help.

I thought i should mention, although i dont know if it is 100% needed. The FSM mentions that you should remove the drain plug from the waterpump when draining the coolant. Which is the bolt to the bottom left of the thermostat (30Nm/22ft lb).

Also Torque for the two bolts for the thermostat cover is 10Nm / 7ft lb ! And stripping them would be bad.

Hope this helps anyone changing there thermostat, i will be doing mine this weekend.