w124 electric radiator cutting in cutting out problem

ssohotra

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Hi All,

Firstly i have tried searching all posts to see if anyone has the same problem, but alas no....!

I have a 1992 W124 230TE with a healthy 204k miles. When the car gets up to temp [80-85 deg] it fine, and no electric fan cuts in. If the car does become hotter than this the fan cuts in... but really strangely.

Its as if it cuts in then cuts out then cuts in then cuts out etc etc, in very quick succession. It still cools the engine down, but surely it should stay on... cool, then switch off??!

It is a bit annoying as it puts the engine under strain and the engine hunts when idling.

It sounds like an electrical/fuse issue as i can hear clicking every time it cuts in and out... any help would be most appreciated!!!

Apart from this... 204k and still drives like its floating!

Simpson
 
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Bolide

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Assuming the car is standard the electric fan is for the aircon. The viscous-coupled fan deals with the normal engine load and the electric a/c fans cut in at about 100 C

Ordinarily, with a/c off, a W124 won't go over about 90 C unless it's being pushed hard up a long hill or is sitting in traffic on a hot day with a less-than-perfect cooling system

So, do you have a/c, is it on and how silted-up is your radiator?

Nick Froome
www.w124.co.uk
 

television

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Nicks post above does suggest the the cooling circuit is now too small to cope,,, What is the visco engine fan doing,,is that cutting in correctly.
 
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ssohotra

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Hi Nick,

The radiator and thermostat were replaced less than a year ago with a Beru radiator so that should be fine. Coolant [MB] is fresh at a 50/50 mix.

The a/c won't be on when the electric a/c fan kicks in [i.e the black plastic one mounted on the front of the radiator - near the Benz grille].

In fact i very rarely use the a/c.

When town driving [averaging 30-40mph], and even if crawling, the temp remains fine [80-85deg].

The elec fan kicks when the temp does go near 100 C [when sitting in traffic], but the problem lies how it kicks in. Its switches on/off/on/off in very quick succession - its as if it can't make its mind up whether it should be on or not.

Once the engine has cooled back down to 80-85 deg, it also won't switch off... it keeps on running in this funny way... switching on/off/on/off in very quick succession... regardless of the temp.

Hence I'm thinking a sensor or relay could be on its way out????

Simpson
 
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ssohotra

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yes the viscous fan operates as it should and passed the carrot test[!]
 

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OK it is clearer now and you do have a fault on a sensor some where,, I do not have that much info on a 124 but I will check on what I do have
 

Bolide

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There should be a fair amount of hysteresis in the way the fan switches on & off - ie it shouldn't do it so frequently. Assuming there's no electronics involved it has to be the temperature sensor or dodgy wiring

Nick Froome
www.w124.co.uk
 
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ssohotra

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Really appreciating this. I'm just one minor problem away from a super ride.

Any ideas on where these sensors live?
 

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Just a little on the workings of these things,,the electric fans do not cut in until 100c this is for the single stage fan version

I will check on what info I have
 

Bolide

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Just a little on the workings of these things,,the electric fans do not cut in until 100c this is for the single stage fan version

That's right. But why are they cutting in? It must be overheating to get to 100C in normal use. Or the temp sensor is fubared

I think the two temp sensors are front right of the head by the elbow that feeds the radiator

Nick Froome
www.w124.co.uk
 

E280T

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I have the same issue with my 124 e280t.
Sometimes the aircon fans even start running full speed when I turn the key - regardless of the engine temperature or if I have the heater / ac on or off... It's obviously not linked to the coolant temp or whether or not I have the ac switched on. I also hear a loud clicking (relay?) under the dashboard or in the fuse box, and then the ANNOYING fans go on. I'm really getting irritated with it, and it can't be good for the fans. But then sometimes days go by and they don't come on...

Help.
 

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