I have a golf 2000reg 2.3 v5. The problem is that the engine overheats. yesterday i went to the shop stuck in the traffic, water temp. came up to 120, fan wasn't blowing to cool the engine, and it never turns it self on. I read alot of info about thsi kind of rpoblem one says its the temperature switch another one says its the thermostat others say its water pump or a air block somewhere in the seastem. Can someone tell me what actualy could be the solution tu this. By the way when i turn the heating on it blows hot air. so i don't think its the thermostat, but might be i'm wrong.

SOURCE: coolant temperature sensor?????

um...strange ...engine temp reaches 210 before thermostat opens and lets water circulate ..fans go on before that normally..180 or so..hot air from heater going to cold air? strange...could you elaborate for me /us?

SOURCE: 1986 VW Golf GTI 1.8 SOHC cooling issues, and heater blows cool

try changing cooland temp sender,your heater matrix maybe blocked(common)what temp is it running at have you checked it with a gauge?

SOURCE: 1986 VW Golf heater blows cold air

The heater in your car depends upon a flow of hot coolant going through the heater core in order to get hot air into the car. If the heater core is partially plugged, it will restrict the flow. If you have a head gasket that is putting exhaust into the cooling system, it will eventually get into the heater core. When this happens there is no coolant in the heater core to make the air warm. If the water pump vanes have corroded away the result will be very poor coolant circulation causing the heater to not blow hot air. If your car is equipped with a heater control valve that is not functioning properly, the coolant flow will be restricted. One or a combination of these factors is likely the culprit in your case.
if the car is not overheating, the thermostat is working fine.... replace or flush the heater core multiple times to try and eliminate sediment build-up.

SOURCE: OVER HEATING

In the fan circuit...You have a temp switch screwed on the radiator, a fuze and a relay in the fuze box plus a fan.  Swap the relay with another relay, replace the fuze.  The other fan should come on when the a/c is turned on.  If you fix the fans and it still overheats, you may have a BLOWN HEAD GASKET.  ALSO ARE YOU BLEEDING THE AIR FROM THE SYSTEM?  DO YOU SMELL EXHAUST IN THE COOLANT?   

SOURCE: 2002 New VW Beetle is only blowing hot air out of

My 03 conv. beetle did the same thing .My cousins 02 coupe also . He told me it was a lever on the bottom of the heater unit that switches between hot and cold. The problem is the lever falls down out of the unit .More cheesy ''engineering''. I fixed mine by cutting a short piece of copper pipe centered over the screw to prop up the lever in postion .That was about a year ago. Been working great ever since . The best i remember i took the glove box and the cover at the very front of the console out .You should be able to see it then.