i just bought a 97 a4 2.8 a couple of days ago. this is my first audi to ever own so evrything is new to me maintenance wise. we ll i found out the other day that my heater doesnt work. no matter what setting i turn it on, it blows cold air. the fan works cause it changes speeds, and you can here valves in the dashboard move to direct the air, but its still always cold. the rear defrost and my water temp gauge doesnt work either. could they be connected somehow? any help would be great as i am new to audi's and have never worked on these kinds of motor's before. thanks

 

very dodgy mate, temp gauge doesn't work and only cold air "this sounds like an air lock/failed thermostat/head gasket" air lock is the first to check out, heated rear window could be a fuse

 

ok what exactly is an air lock??? i checked all the fuses and they are all good....rear defrost included. but i am totally confused. i'm a pretty good mechanic but i have never touched a motor anything like this. its like trying to read japanese for me. so any more details would be great. where is the thermostat housing located so i can check out the thermostat?

 

an air lock is caused by filling the coolant and not bleeding the system, thermostat follow the radiator top hose to the engine which leads to the thermostat housing

 

to confirm an air lock you will find the top hose stays cold which is probably why the temp gauge in the dash isn't working because the radiator is cold at the top

http://images.google.com/imgres?imgu...005-44,GGLG:en

 

so not burping the coolant system could make the heater not work? i've never heard of that. i mean, every other car overheats a little bit if there is air in the system. it doenst make the heater not blow hot air. this just isnt making any sense to me. but thanks for the location of the thermostat. i'll take a look at that tomorrow

 

burping the system lol never heard it said like that but that is exactly what I mean, the temp stat housing is where the temp probe is "air rises to the top of the engine" which prevents water reaching the stat or the probe/sensor "AIR LOCK",

if all the coolant pipes don't get hot especially the top hose and heater matrix pipes the how can the heating work

all systems do overheat to a critical point that's why the engine coolant fans cut in to reduce the pressure by cooling the coolant

 

for the rear defroster I'd say check for (very tiny) breaks in the line. you get this sometimes when someone removes a rear-tint job and isn't careful about cleaning off all the leftover goop that stays on teh window. There are repait kits, available at justa bout any auto parts store, for fixing minute cracks in rear-defroster grids. If NONE of teh lines heat up I'd recommend checking at/near teh bottom, or one of the sider, depending on where the lines originate...

 

thanks. i'll check that out today. my CEL came on today when i let my wife drive my car. so i went and had the codes ran and it showed up as "input from coolant temp sensor changed too much or too little in a short period of time" which totally explains the temp gauge. cause it will say full cold 95% of the time but then sometimes it will jump up to regular operating temp so that explains the code. and the also means that my temp sensor is bad. but my question is this, will that sensor affect the heat? if that sensor is bad, does the engine think its temp is really cold and therefore the heat be cold? or is this 2 seperate problems?? also does anyone happen to have an extra temp sensor or know how much they are from the dealer?

 

pity you didn't get the fault code number?? but I would still check for air lock first before replacing the heater matrix

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