Can anyone explain exactly how this thing works? I assume it has a temp sensor in the radiator (Pass side perhaps) that when the temp gets hot it triggers the fan... When temp goes down the fans stops...
Thing I dont get is there are no wires that go to the fan clutch so where does the fan get its signal from?
Mike
Explain the Viscous fan
Moderator: martauto
got me wondering about this so used google.. stole this from another forum so dont know if its 100%
"The fan clutch is an automatic device that is often used in a vehicle’s cooling system. So, when the engine is cool or even when it is at a normal operating temperature, the fan clutch will partially disengage the engine’s radiator cooling fan (which is mechanically driven).
This is normally found at the front of the waterpump and it is driven by a belt and pulley that is connected to the engine’s crankshaft This process will then save power because the engine won’t have to fully drive the fan.
But, if the engine’s temperature gets hotter than what the settings for the clutch are, the fan will then become fully engaged, this will then maintain or even lower the temperature of the engine.
You will find that most fan clutches are viscous or ”afluid”a (the internal friction of a fluid that is produced by movement of its molecules against each other. It is what causes the fluid to resist flowing) couplings that are combined with a bi-metallic (it’s a strip that is used to convert a temperature change into mechanical displacement and it usually consists of two layers of iron and copper) sensory system that is similar to that in a thermostat."
"The fan clutch is an automatic device that is often used in a vehicle’s cooling system. So, when the engine is cool or even when it is at a normal operating temperature, the fan clutch will partially disengage the engine’s radiator cooling fan (which is mechanically driven).
This is normally found at the front of the waterpump and it is driven by a belt and pulley that is connected to the engine’s crankshaft This process will then save power because the engine won’t have to fully drive the fan.
But, if the engine’s temperature gets hotter than what the settings for the clutch are, the fan will then become fully engaged, this will then maintain or even lower the temperature of the engine.
You will find that most fan clutches are viscous or ”afluid”a (the internal friction of a fluid that is produced by movement of its molecules against each other. It is what causes the fluid to resist flowing) couplings that are combined with a bi-metallic (it’s a strip that is used to convert a temperature change into mechanical displacement and it usually consists of two layers of iron and copper) sensory system that is similar to that in a thermostat."
Yep, it simply picks up the hot air off the rad blowing over a bi-metalic strip which activates the viscous fluid to tighten up, or something like that. Unfortunately i have found them un-predictable and converted to an electric fan off a 206.
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Brianmoooore
- E30 Zone Team Member
- Posts: 49358
- Joined: Mon Jan 10, 2005 11:00 pm
Until the viscous fluid eventually leaks out, they are one of the most reliable self contained devices on the car. Far, far more reliable than any electric fan!
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mrLEE30
- E30 Zone Team Member
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- Location: Sweating buckets in Bahrain
already told you this mike!!!
the temp sensor on the side of the rad will only make the additional AC fan turn on if you have one fitted, and then only at a high temp (about 90C or 3/4 of temp gauge IIRC)
the viscous fan is very reliable but if concerned and getting overheating isses when stationary then they are very cheap and easy to change - compared to a Head gasket or worse!
the temp sensor on the side of the rad will only make the additional AC fan turn on if you have one fitted, and then only at a high temp (about 90C or 3/4 of temp gauge IIRC)
the viscous fan is very reliable but if concerned and getting overheating isses when stationary then they are very cheap and easy to change - compared to a Head gasket or worse!
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m_jermyn
- E30 Zone Team Member
- Posts: 4208
- Joined: Sat Mar 14, 2009 11:00 pm
- Location: Sydney Australia Mate
Thanks guys.... problem with the viscous fan is its hard to tell if its working or not... Electric fans either work or they dont... All Aussie cars use a twin thermo set up and they cool our big V8s just fine..