Viscous fan on 124

[diy_dan]

Stupid question but how does the viscous fan detects the water temp in the rad? or does it works on the temperature in the engine compartment? I want to remove the viscous fan and replace it with an electric one. but cant see a water temp sensor like on other cars. I would assume the air con fans run continuous while the air con is working, I just bought this car and it needs topping up but is using r-12 and I was told I need to convert to r-134a, europarts sells a kit for doing this but on the yanks equivalent of this site I've seen comments about changing seals as well. does any of you know the procedure? The r-12 gas is quite low so there isnt really anything to recover. Anyway back to the fan question, how does it work?

 

[jibcl500]

it uses expansion of metal in the fan to bite so it spins when hot.
jib

 

[C220GJS]

Not exactly the same unit ,but it works on the same principle.
http://www.vintagemodelairplane.com/pages/Rover_Technical/Viscous01.html.

 

[Bolide]

The a/c fans run off their own temperature sensor and normal come on together at 100 C

I wouldn't replace the viscous fan with an electric one as the viscous fan works well and is reliable

Unless you have a very unusual W124 it should be running R134a already

Nick Froome
www.w124.co.uk

 

[wireman]

There are some severe legal things to do regarding older refrigerant gasses, you must abide by the recent HAVAC regs when dealing with the gas, if there is none in your system there wont be a legal problem. Get the advice of a decent air con bloke regarding the newer gasses although Im sure there are some posts around here about it.

The viscous coupling has an oil filling between the plates of a clutch like arangement when the hub gets hot either a bimetalic strip or wax capsule diverts the flow of the oil and engages drive from the shaft to the hub. To test the fan get the car hot and hold a carrot into the fan, if the coupling is good there is torque the carrot will be smashed. Avoid smashing your fingers whilst testing.

 

[diy_dan]

The a/c fans run off their own temperature sensor and normal come on together at 100 C

I wouldn't replace the viscous fan with an electric one as the viscous fan works well and is reliable

Unless you have a very unusual W124 it should be running R134a already

Nick Froome
www.w124.co.uk

I was hoping to get an extra 3mpg if I converts to electric. The car is H reg and there is a green sticker under the bonnet that says r-12

 

[diy_dan]

it uses expansion of metal in the fan to bite so it spins when hot.
jib

What I wanted to know is how does it detect the coolant temp for the metal to expand. The electrically operated ones (nearly all cars) have a sensor in the radiator

 

[Bolide]

I was hoping to get an extra 3mpg if I converts to electric. The car is H reg and there is a green sticker under the bonnet that says r-12

Only the very early cars - like yours - have R12. You need a competent a/c guy to sort this out

If it's a 200 or 230 I'd leave well alone. If it's a 300 I can understand you wanting better economy - but I don't think you'll gain 3 mpg by replacing the fan

I'd start with tyres at the top end of the pressure range, a new air filter and some injector cleaner followed by new plugs and an Italian tune-up. A new distributor cap & HT leads will probably help too but they're quite expensive

I believe the temperature sensor is at the top front right of the engine in the alloy take-off for the top radiator hose. It's not on the rad like in a modern car. Without knowing what car you have it's hard to say where it is

Nick Froome
www.w124.co.uk

 

[diy_dan]

Only the very early cars - like yours - have R12. You need a competent a/c guy to sort this out

If it's a 200 or 230 I'd leave well alone. If it's a 300 I can understand you wanting better economy - but I don't think you'll gain 3 mpg by replacing the fan

I'd start with tyres at the top end of the pressure range, a new air filter and some injector cleaner followed by new plugs and an Italian tune-up. A new distributor cap & HT leads will probably help too but they're quite expensive

I believe the temperature sensor is at the top front right of the engine in the alloy take-off for the top radiator hose. It's not on the rad like in a modern car. Without knowing what car you have it's hard to say where it is

Nick Froome
www.w124.co.uk

Thanks for the info, Its a 300ce but if the fan wont make that much of a diff I might leave it for now but I have some iridium plugs which I will put in and its going to have an lpg kit installed but I'd be interested to know what an italian tuneup is

 

[kth286]

The fan just senses air temperature between engine and rad. It does not sense water temperature.

AS your fan is hardly ever in the "on" position, it just free-wheels, there is no economy saving to be had.

Do not change your plugs from the recommended Mercedes spec. for your car.