I keep having overheating issues in my 94 Jetta 2.0 litre USA market automatic.
It heats up normally, but keeps going until it the gauge is pegged.
The fans don't engage. I replaced the thermoswitch twice with OEM Behr units.
if I shove a paperclip into the plug, I can get the fans running on a speed, perhaps high speed or low. I cannot get the "other" speed to engage. There are three contacts, so only if I bridge two of them will it run, if I do any other two combination I get nothing. Unless "high" speed is all three jumpered, haven't tried that.
If I drive the car around 50 mi/h or 80km/h indicated in 3rd gear of the autobox it usually won't overheat. But go less and heats up quick.
If I jumper the fans to low speed when I first start the car cold, and drive around, it usually will overheat as well, just I can drive much further before that happens. It hasn't gone significantly beyond 1/2 way point just because I don't want to risk that.
The car also appears to have a slight leakage of water, but can't pinpoint it.
Once after driving, the coolant temp slightly higher than normal, I had a weird milky substance visible on the dipstick. My heart sank as I thought headgasket. But the oil looks nice and squeaky clean when it is cold, just after I drove it that one time it looked weird...