Fan always on - 84 500SEC

[S11YBM]

Should the big fan in front of the engine bay always be on? I've only tested this when the car is on idle..not sure whether this should come on only when needed or like mine, which is on all the time.

 

[ivan1983]

Yep it always spins, there is a clutch that engages should it go over a certain temperature the it really spins and you will hear the air flow increase.

I assume you are talking about the one connected by a belt to the engine rather than one mounted to the radiator?

 

[S11YBM]

Yep it always spins, there is a clutch that engages should it go over a certain temperature the it really spins and you will hear the air flow increase.

I assume you are talking about the one connected by a belt to the engine rather than one mounted to the radiator?

oo...maybe im getting confused with my fans! I've only noticed one, which is basically directly in front of the engine, where's the radiator fan?

 

[W210Virgin]

It will be the fan with a viscous coupling and always spins.

Sent from my SM-G935F using Tapatalk

 

[S11YBM]

It will be the fan with a viscous coupling and always spins.

Sent from my SM-G935F using Tapatalk

OK, I'll check this again tonight... Im surprised that I've not noticed the fan on the radiator!

 

[W210Virgin]

This fan will be engine driven and obviously will be in the space between engine and radiator. With a/c, the fan is most likely directly behind the front grille at the very front acting on the a/c condenser (radiator).

Sent from my SM-G935F using Tapatalk

 

[190]

No specific knowledge of an 84 500 SEC but some time in the 80's MB started using engine driven fans with an electromagnetic clutch which engaged the fan when a certain temperature was exceeded. If the fan is of this type it may still turn slowly at idle but if you grab the fan it will stop. Obviously I don't recommend you grab the fan but if it is of that type you could try spinning it by hand with the engine off to check the clutch is free.

A wiring diagram would clarify if there is an electromagnetic clutch and associated temperature switch.

 

[grosser panzer]

On my 1990 w126 500sel the fan is viscous coupled type. When the engine is stopped it should be possible to turn the fan on the hub. When doing this it will not spin freely but a slight drag should be noticeable. When the engine runs it is not loud but when the engine reaches the required temperature the viscous coupling locks and drives the fan at engine speed causing a loud blowing noise.

Normally the a/c fan(s) are in front of the radiator. My car has two plastic ones driven by electric motors.

 

[grober]

Use the carrot test-- a viscous fan can be stopped with a carrot or similar object if the clutch is not engaged. When the VC is fully engaged it will dice the carrot.

 

[S11YBM]

Thanks all for your input! I checked last night, and I was getting confused. I didn't realise the fan was driven of the engine, and there would spin all the time.

I believe mine is a viscous fan, but will check to see if i can see the clutch.

 

[grober]

Thanks all for your input! I checked last night, and I was getting confused. I didn't realise the fan was driven of the engine, and there would spin all the time.

I believe mine is a viscous fan, but will check to see if i can see the clutch.

# The viscous clutch forms part of the metal central hub of the fan where it mounts to the engine. Its controlled via a bimetal strip which reacts to the temperature of air coming through the radiator. It bends acting ona pin actuated valve which routes the viscous fluid into certain internal chambers of the coupling causing it to engage.
K6JRF Auto Page

 

[S11YBM]

Thanks Graeme,

Is there a way to "spoof" the temperature reading to see the clutch being engaged?

 

[grober]

First thing is to see its not clogged with dirt[ effectively insulating it] from any hot air. iF there's room you could try heating the bimetal strip with a hair drier [ possibly through the radiator even{ engine off !!! for heating it up but on to test when hot} --- BUT unless you are experiencing engine overheating problems its likely to be working OK
ps viscous fans should never be stored horizontal always vertical.