Volkswagen Repair: overheating 1985 Golf, prong plug, thermoswitch

Question
Dear Paul,

I own a 1985 Golf 5-door 1.8L with very low milage (around 60K) but it is ungaraged.  I live in NYC and have taken good care of the car.

For the last several years, the red LED overheat light comes on intermittently when the engine is cold.  Invariably, when idling in heavy traffic or when parked the temperature gauge hits the roof.  This was especially true when my a/c working (the compressor has sprung a leak and I have not gotten a rebuilt unit yet).

My mechanic discovered that the auxiliary fan was not kicking even after he replaced a faulty relay and installed a new thermostat and a lower temp thermo switch.

He discovered that the fan does indeed operate and he rigged a manualy-operated toggle switch on the dash board.  When the temperature goes up, I flip the switch and the temp gauge drops to normal.

The radiator, recently replaced because of a leak, is circulating the coolant, but the hose near the thermo switch is always cooler than it should be. My mechanic does not think that the water pump is bad.

Can you suggest a possible reason for my overheating problem?  As a related question, is a heavy duty radiator available?

Thank you.

Jason  

Answer
Jason,

The hose near the thermoswitch? There isn't a hose over there.  I've never heard of a low temp thermoswitch?  I think you mean a low temp thermostat. The thermoswitch is located below the battery, halfway down the rad, you should have a three prong plug, not a two prong.   Have your mechanic check the wires just below the relay, they get brittle from the battery acid and break in the three wire black plug (red wire). Installing the original thermostat should bring your engine back up to regular temperature.

Good luck,

Paul