Im having this same problem... I havent flushed my coolant, but i was thinking that may help.. Replacing the coolant temp sensor didnt help... LMK if you find anything!
2002 A4 3.0 6 SPEED
I have been having a problem with my heat the last few years. I live in Wisconsin and when I am on my way to work my heat will not kick on at all. It seems to work when the temp outside is around 50 degrees. If I take my car on a long drive, (last weekend to Chicago) about half way there I can shut my car off and go get food or whatever, and it will suddenly work. For the rest of the day no problem. Then I will park it overnight. Get in start it up no heat.
It cant be the blower motor right? It blows great, sometimes.
The heat is as hot as you could ever want it to be when it works. Its not blowing warm or cold air. ITS HOT when turned all the way up.
The coolant in the vehicle has to be G12. I purchased a gallon of g12 from the dealer and was just going to flush out the heater core and add any more coolant I need. Before I was going to do this I tested the TEMP of the coolant and it was maxed out to like -45F. That seems high. Could that be my problem? Too high of a coolant/water mix. Both tubes that run to the heater core are warm when the car is warm.
I don't see how it could be a thermostat because the heat gauge when warm is always the same right in the middle.
I also know about the flap that is in there too. I have done much reading and investigating and don't know where I should start. Any help would be GREATLY appreciated.
You aren't very clear on what the problem even is. If air comes out of the vents when you have the fan on, it's not your blower motor. The blower just blows, it has zero effect on the temperature of the air coming out. What exactly is the problem? Always blows, just not always warm? Or sometimes blows, and sometimes doesn't?
Assuming it always blows air, but doesn't always blow hot air the way you describe, I'd definitely consider the thermostat. If it's sticking open sometimes, your engine may never get to proper operating temp, and you also may not get heat. If that's your problem, fix it ASAP. If it decides to stick in the closed position you'll be in even more trouble. Your temp gauge isn't the most accurate thing in the world. The needle will indicate "normal" over a fairly wide temperature range, so don't go by that.
Assuming it doesn't always blow air, start looking at wiring as a fuse isn't going to be intermittent like that.
It will NOT have anything to do with coolant temp sensors, or the quality of the coolant; A flush would just be a waste (for resolving this issue anyway. I'm not saying changing coolant isn't important for other reasons). My money is on thermostat.
OK, So it's a bit of work, if you are nearly due to replace the timing belt, that may be good excuse to replace it as it's part of the job. That being said, coolant( the G12 stuff), thermostat assembly( yes it's neat looking lil gaffer).
Holy cow, this is freaking easy...:
- Remove the air intake hose from the rad support to the air box.
- Remove the center front cover on top of the engine( the one that says 3.0l V6).
- Remove 2 hose clamps that hold the flexible coolant hose to the thermostat.
- Remove the hose clamp that hose the hose to the hard coolant passage that follows up the right timing cover.
- Remove the 2 allen key's ( 6 mm) that secure the thermostat to the engine.
** when installing the new thermostat assembly to the engine, lube the O-ring with ( rabestos brake silicon). This will make sure it presses into the engine with out a fuss and makes for a much for positive feeling fit.
** if you are doing this job, I'm sure i need not inform you that I'm not responsible for any mistakes you make.
This how too description from another thread.
-I'll add to it, suspend the front end, remove the front tires, remove the fasteners ( T25 torques bit )that hold up both left and right wheel wheels, you need only to remove the front half( up to the middle of the fender, then peal them back behind the brake rotors.
-3 10 mill nuts between the front of the fenders and the front bumper cover. then remove only the front lower fasteners for the splash pan, the splash pan doesn't need to come off the car.
-Now stretch your back and remove the headlamp assemblies( T30 i think), Two on top, remove these bolts, the ones on the bottom and behind the headlamps( two each) loosen them about 4 turns. Unplug the headlamps, and remove the headlamps from the car.
-Sit back down in front of your car use a medium sided flat blade screwdriver and push the tabs that hold the fog light trim pieces.
-Next, use an 8mm all keyed socket to remove the to bolts that hold the front bumper support to the bumper shocks.( these bolts are in the upper, inner( towards the center of the vehicle) of the fog light openings.
- Now on the drivers front corner there is a hose that goes to the headlight washers, clamp the hose from the windshield washer reservoir. Pull up the brittle plastic clip that holds the connections together and separate them.
- Remove the 3 fasterners for the front bumper/rad support. ** use the 2 allen bolts that are from the bumper support( they are long enough to allow you to pull the rad support forward and away from the car. This is placing the vehicle into the service position allowing you more room to move.