Fan blower works ok but no heat , lots of small debris coming out of defrost and vents. 1999 vw beetle

replace the switch its self.. you can search ebay motors under electrical and find one easily.. also they remove easily and just plug in the back..

does the car have automatic climate control?

I had a very similar problem on a Buick recently. Like mine, your blower's fan blade assembly may have come loose from the motor shaft. There is a very small washer type clip that holds the fan blade part to the motor's shaft. Usually the whole blower assembly is pretty easy to get to and take off...usually. A lot of GM cars had the assembly accessed from the firewall behind the engine. You would need to pull the blower motor out and check the fan assembly.

Did you check the coolant level? if your low on coolant the sensor for the fans won't work, also could be a bad fan motor or just a fuse, if you continue to over heat the car you can do a lot of damage to the engine, blown head gasket, and the VW's are expensive to repair, take it to a good shop and have them check it out.

blower motor relay or resistor needs replaced

Did you check fuses located on battery?
Possible causes , fan itself , but it would have nothing to do with overheating.
Fan resistor (final stage controller) , not for overheating either.
And the most common on this cars is radiator fan control module , basicly a few relays in one.
You can check fuses by yourself but for the rest of it probably mechanic shop is preferable.

Replace the dash controls. A common problem on beetles.

if its work in only low speed u have to replace the blower motor resstor which located close to the blower
let me know have a good one

Look in your owner's manual index and turn to the page about Fuses.  It will tell you where to find the blower motor fuse.  Use needle nose pliers to remove it, hold it up to the light and look to see if the aluminum strip inside is blown.  Replace with a fuse of the same amperage rating, it should be around 20 Amp, the numbers are stamped on the fuse.  Fuses are widely available at car parts stores and department stores Kmart Walmart ect.

My daughter has a 99 Beetle GL and the A/C and fan went out. It's the A/C haeadunit that needed to be replaced. The switches short out and you have to replace the whole piece. VW charges about $225 for the part Hope that helps