Rad Fan motor connections

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simmit
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Rad Fan motor connections

Post by simmit » Fri Jun 17, 2016 2:30 pm

The Rad. Fan loom on MB50 has 3 wires going to the motor but only 2 are connected. Is this intended or simply, has one come adrift?
Looked at Peter's excellent wiring illustrations but can hardly read the text and can't find the Fan motor.



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Re: Rad Fan motor connections

Post by philhoward » Fri Jun 17, 2016 2:35 pm

I thought the MB had a 2 speed fan - or was I dreaming it?


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Re: Rad Fan motor connections

Post by peter freeman » Fri Jun 17, 2016 2:35 pm

My MB fan is a two speed - perhaps yours has been replaced by a single speed fan. Unfortunately we are at the international at the moment so I cannot check things out for you. Peter



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Re: Rad Fan motor connections

Post by Roger Pennington » Fri Jun 17, 2016 3:24 pm

Rad fan is towards the top right corner on Peter's diagram and has three wires brown black and orange, and two speeds, operated by two relays (which if I'm reading the diagram correctly, switch the output from the motor?)


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Re: Rad Fan motor connections

Post by philhoward » Fri Jun 17, 2016 3:27 pm

It's switching either one or two earth paths. I'm guessing there's two sets of windings in there fed from the common (brown) supply internally. Think of a 2 speed wiper motor but instead of switching the +ve, they switch the -ve instead. It has the same effect electrically.


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Re: Rad Fan motor connections

Post by Roger Pennington » Fri Jun 17, 2016 3:30 pm

Black is slow, and orange is fast according to the diagram :)


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Re: Rad Fan motor connections

Post by philhoward » Fri Jun 17, 2016 3:42 pm

Yep - that's how I read it too.


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Re: Rad Fan motor connections

Post by scimjim » Fri Jun 17, 2016 4:08 pm

simmit wrote:Looked at Peter's excellent wiring illustrations but can hardly read the text and can't find the Fan motor.
Open the wiring diagrams entitled a or b which are better resolution.


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Re: Rad Fan motor connections

Post by simmit » Fri Jun 17, 2016 9:24 pm

scimjim wrote:
simmit wrote:Looked at Peter's excellent wiring illustrations but can hardly read the text and can't find the Fan motor.
Open the wiring diagrams entitled a or b which are better resolution.
Thanks Jim, much clearer now. I hadn't realised the a and b were independent links.

My fan motor has 3 connections so probably original and one of the loom connections simply came adrift.

Am currently replacing coolant hoses (found very helpful silicone manufacturer less than 1 mile away and he's knocking out set of hoses for the MB) so not able yet to run the motor and try things out. In passing, my local radiator repair guy is also good egg and put a drain tap in the radiator so I won't get coolant all over the place when next I drain down.

Incidentally, why have a two speed rad. fan and how is it controlled (automatic or manual)? Being new to the MB I'm still finding my way round and further, I claim no electrickery knowledge (strictly clockwork is me).



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Re: Rad Fan motor connections

Post by AJL Electronics » Fri Jun 17, 2016 10:24 pm

The Otter switch is a two stage device. It switches to earth at two different temperatures, so the fan has an ignition live and two earth feeds switched. Should you fit an aftermarket fan, you may have to use relays to invert it.


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Re: Rad Fan motor connections

Post by simmit » Sat Jun 18, 2016 8:09 am

AJL Electronics wrote:The Otter switch is a two stage device. It switches to earth at two different temperatures, so the fan has an ignition live and two earth feeds switched. Should you fit an aftermarket fan, you may have to use relays to invert it.
Thanks for the explanation. All good stuff!



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