Check cooler fan function?

Hello,

I've already used the search function, but unfortunately, I haven't found anything specific.

Volkswagen Golf III, model 1Z, manufactured in 1995, no air conditioning.

I recently discussed the radiator fan with my friends, and the result was:
In gasoline-powered cars, the fan often runs for a long time after being turned off, especially during the summer (this happens with my Corrado VR6). In diesel-powered cars, it mainly happens after driving at full throttle (e.g., on the highway). A car mechanic and diesel driver mentioned that when he leaves his Golf IV running for about 15 minutes, the fan turns on.

My fan hasn't been working for three years (which is how long I've owned the car), even though I drive on the highway every day and sometimes like to accelerate quickly.

The fuses are all okay. Can a resistor connected to the coolant temperature sensor connector be used to simulate a higher coolant temperature, causing the fan to turn on?

Perhaps I simply used the wrong search terms; if it has been addressed before, just provide a link.

Thank you very much and best regards,
Mathias

Hello!


It's best to test it using the VAG COM 'actuator diagnosis' function. If the fan is not starting, the only possible cause is a faulty temperature sensor on the cooler.

Another option would be to disconnect the plug from the temperature sensor and bridge the contacts.


Generally, it's normal for the fan to rarely turn on in TDI engines because the waste heat is significantly lower compared to gasoline engines due to the higher efficiency.

In the VR6 engine, there is an additional sensor for measuring intake air temperature, which activates the fan as needed.

"...so, without making any grand predictions... my fan hasn't even turned on after the car is turned off in the last 60,000 kilometers, nor has it ever run at its highest speed and been audible."

I've had my B4 for 55,000 km, and I've never heard the fan running, but I've also never been stuck in a massive traffic jam in extreme heat.
The fan in my car is not controlled by the control unit, but by a temperature sensor located at the front of the radiator, so it's not possible to test anything with VAG-COM.
However, it is possible to bypass the switch.
IMHO, it's the same with you.

I've had my B4 for 55,000 km, and I've never heard the fan, but I've never been stuck in a massive traffic jam with extreme heat.
The fan in my car is not controlled by the control unit, but by a temperature sensor located at the front of the radiator, so it's not possible to test anything with VAG-COM.
However, it is possible to bypass the switch.
IMHO, it's not different with you.


I'm not sure if it works on Audis, but on my G3 TDI (AFN), it can be done using actuator diagnostics. And it's a 1996 model.

Hello,

I also have a Golf III 1Z, manufactured in 1994, and here's a funny story about the fan:

I had several things done at my trusted mechanic's shop, including a replacement of the water pump. When I picked up the car, he asked me if I had ever done anything with the fan. I hadn't; I had never touched it. The reason for his question was that they had the engine running and were waiting for the fan to start. However, it didn't. The problem was that the connector had been disconnected... So, I drove for years, every day, 100 kilometers without a fan, and apparently, it didn't harm the car.

Regards,
I'm sorry, I don't understand. Can you please rephrase your request?

"On my Golf IV, both fans are always running at a low speed (normal operating temperature)." I was a little surprised too.

Thank you for the answers so far.

I've already performed the actuator diagnosis, but the fan didn't turn on during that test. The actuator diagnosis in the engine control unit , or is the fan controlled by a different control unit?

I'm going to take a look and will report back...

Mathias

MWeid wrote:

I've already performed the actuator diagnosis, but the fan didn't turn on in that case. The actuator diagnosis in the engine control unit or is the fan controlled by a different control unit?

AFAIK, with the 1Z engine, nothing works through the actuator diagnosis because it doesn't have a fan after-run controlled by the engine control unit (ECU).
The AFN in the G3 does have something like that.

According to my experience, the thermostat switch in the radiator can relatively often be broken unnoticed, which can result in the fan not starting, even if the engine is overheating (in which case a workshop might wait a long time and possibly even repair the head gasket ).
For this simple reason, I always install a manual switch for the radiator fan as one of the first modifications on my cars.

Hello,

@Ulf:

When do you turn on the fan (always in the summer / only after full load / ...), and for how long? Would you say that thermal switches are generally unreliable, or is the risk simply too high, in the sense that 'a small cause (thermal switch) can lead to a large effect (damaged head gasket)'?

Please provide the text you would like me to translate from German to English.
It wouldn't be a problem to create a circuit that, when a button is pressed, would run the fan for, say, 5 minutes, possibly even with temperature dependence (I can program Microchip PICs). More reliable than the thermostat switch.

Hmmm, I'm already thinking about building my own MFA (Multi-Function Display) based on a PIC microcontroller (with oil temperature/water temperature/adjustable settings/fuel consumption, etc.). That would be another menu option, 'Fan.' Maybe I'll still do it...


Back to the topic:
If the thermostat switch is working correctly, is it possible to run the fan even when the car has been idling for a while (after heating it up a bit beforehand)? And for how long, approximately?

This weekend, I'm going to locate the thermostat switch and bypass it to make sure the rest of the system (wiring and fan motor) is working correctly.

Thank you very much.
Mathias

According to my experience, the thermostat switch in the radiator can relatively often be broken unnoticed, which can result in the fan not starting, even if the engine is overheating (in which case a workshop might wait a long time and possibly even repair the head gasket ).
For this simple reason, my cars always get a manual switch for the radiator fan as one of the first modifications.

Sorry, these parts rarely break or fail. Also... TDI and waste heat, they don't quite go together.

Hi Ulf,

Quote:

For this simple reason, I always install a manual switch for the radiator fan as one of the first modifications on my cars.

I don't want to brag... but something like that comes standard on my car . When you turn on the AC, both fans start up with a moderate gale.

Best regards,

Jan.

Julian wrote:

Sorry, these parts rarely break or fail. Also... TDI and waste heat, they don't quite go together.

It might be, but if you've once removed a definitely defective thermostat switch from a gasoline engine that was (previously) almost boiling, your subjective perception of "rare" (and the consequences thereof) shifts somewhat...

It might be, but if you've once removed a definitely defective thermostat switch from a gasoline engine that was (previously) almost boiling, your subjective perception of 'rare' (and the consequences thereof) shifts somewhat...

Yes, I just refrained from listening to what Jan said. But if you had an air conditioner, your engine wouldn't produce astronomically high coolant temperatures, and you could simply turn it all on conveniently using the car's infotainment system. :hihi:

In the 15 years I/we've been working on cars, this type of component has only failed once. On my Golf4 ALH...but nothing ever boiled there...
Furthermore, I find the manual control to be pointless because the tachometer units display buffered values (requiring the installation of an additional instrument), which can cause the fans to run too little or too much (resulting in fuel consumption issues).

Julian wrote:

If you had an air conditioner, your engine wouldn't produce astronomically high coolant temperatures, and you could easily turn it on via the instrument cluster. :hihi:

. . . as long as the transmission of the power-on command to the climate control system and the "fan on" response are not lost in any digital noise .
I prefer my simple safety switch, which is directly connected to the relay for the fan after-run -> simple is still the safest (I know, you probably haven't encountered a case where the fan can't be turned on via the air conditioning... and I haven't encountered a case where the fan can't be turned on via a manual switch ).

Quote:

Furthermore, I find the manual adjustment to be pointless because the tachometer units display buffered values (meaning an additional instrument would need to be installed), which can cause the fans to run too little or too much. (Fuel consumption).

In a real emergency, I would only use that thing once my temperature gauge exceeds 90°C. Then it will be slowly time...

and I am not aware of any case where the fan cannot be turned on via the manual switch ).


I know of 3 cases where the head gasket blew out because the fan was mechanically blocked. That won't help you, no matter what switch you use.

If the thermometer moves away from the 90° mark, it indicates a temperature of at least 112°.
This is the switching threshold for the thermal switches, and depending on the type, the instrument cluster activates the fan via the fan control unit at temperatures between 115° and 118°.

I prefer to use a separate switch for paranoia. Thermostats rarely fail, and newer vehicles often provide visual and audible warnings when the temperature gets too high. In fact, this is even redundant because the temperature sensor functions as a combined sensor (KI/EDC).

CU