Looking for pictures or where the heater core is located on my 1991 Audi 100.I have no heat coming out of vents.Dash Temp display showing higher than mid line area,and electric radiator fan does come on.

 

It's probably the climate control temp flap unit located over behind the glove box. Sometimes they stop working and will not move the flap in the air box to allow hot air in. Or.. The cable is disconnected.

Also for the rest of your questions, if you're going to be going this deep into fixing it (I have an 87 5000S Quattro that I've been restoring) you need to locate the Bentley repair manual or at least the Haynes repair manuals for that car. The Haynes manual will show most of the basics. The Bentley manuals are relatively expensive but are the official Audi Repair manuals and have just about EVERYTHING in them.

 

Is it rather easy to remove the glove box,and how is it done?And is the cable easy to access?

 

I'm not sure on the 100's but there is a shelf of sorts on the lower part of the dash that you must remove first. It's just a couple of three screws and slides out rearward. Once you remove it, you can see the climate control flap actuation servo. It's basically small black box with vinyl vacuum lines and an electrical connection on it. On top of that box is a little arm attached to a cable that runs to the airbox. The other end of the cable can be accessed from under the rain tray just ahead of the windshield under the hood.

But do go ahead and pick up a Haynes manual on that car. It will help quite a bit. Keep your eye out on Ebay for the Bentley Manual (those are the ones you REALLY want) because you can score them at good prices from time to time. I bit the bullet and dropped about $70 for the ones for the later 80's 5000S. Worth it's weight in gold.