Cooling fan doesnt work, overheating

[lowandslowdiesel]

Hi guys, my 91 jetta 1.6na cooling fan doesn't turn on when engine starts getting warm.
Car does have AC and fan does work when AC is turned on.
I put a new thermo switch (on the bottom of the rad.) with no luck.

I searched about this issue and I believe its the sensor in the thermostat that is causing this issue. But there is two sensors located in the thermostat. Could someone please let me know which one is for the cooling fan? The one on the top of the housing or on the one on the side? Also, parts store says their is multiple sensors, I think 2 or 3. Not sure which one I have to get?


Thanks I appreciate it,
Nate

[the caveman]

Have a look at the wires to the relay which is screwed to the top of the fan housing. The hot wire corrodes there alot. I've fixed many

[rallydiesel]

Could be as simple as a poor connection between the thermoswitch and the fan terminal. Since the fan comes on with a/c on, the whole a/c sensor/resistor etc. circuit should be good. The circuit for the fan without a/c on is very simple, just power to thermoswitch to fan. Which leads me to believe it's just a continuity issue. Also check the fan terminals to see if the metal ends haven't been pushed back. And do the jumper test to make sure the fan motor functions at both speeds.

[Baron VonZeppelin]

The part you are refering to as thermostat (housing) is not the thermostat housing.

Its just a water outlet / neck for cooling hose attachments, etc...

The 2 small sensors on the water outlet, one does the glow plugs, one does the in-dash temp gauge. Most have a 3rd larger sensor that shuts off the a/c compressor if coolant temp gets too high.

The thermostat and its housing are at the bottom of the engine on the passenger side.

The thermostatic switch / sensor you replaced on the radiator - is what does the thermostatic brain work for the fan. Other than the a/c-on-run function.

Could very well be what the caveman or rallydiesel suggested.

Also check for coolant flowing good in your plastic expansion tank.
If no, or only little flow, could be bad thermostat.

Check for both sides of radiator feeling about the same approximate temp range.
Could be blockage.

Another "to check for" is the temperature range of the new thermostatic switch you just installed. There are 3 or 4 heat ranges for these.