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300Tdi electric fan switch mod?


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I need to fit an electric fan onto a 300Tdi conversion I've just done, and was wondering if I can use one of the AC switch ports on the thermostat housing to screw in a suitable thermostat switch - has anyine done this and know if any suitable switches will match the thread size?

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Yep. That's what I did.

I had a super switch in there and it went apex over base.

Getting another of the same temp setting proved impossible.

As my Defender isn't at home I can't look. If I have the book I keep info in then I'll let you know.

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Found notebook....Why doesn't what you wrote down five years ago make sense now ????

Have a look at Intermotor 50160 that should be 100/ 90 Deg C

I also have written under that

5012225 and 131082

a good partsman should be able to tell you what they are.

HTH

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Electric fan switch should really go in either the radiator bottom-tank or the outlet-hose, not the top hose or thermostat-housing.

Putting it in the top will probably result in the fan triggering about 10x more often than it needs to.

--Tanuki

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Yes M22. There is an old post on here about that. Also the switch settings. You'll need to go back a long way for it though.

There should also be an Intermotor switch list on here IIRC.

Tanuki

Yes I know you should. The same a a radiator should allow the coolant to use all of the matrix, something the 300Tdi rad doesn't do.

I've not had a problen in the short time mines been in there.

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Electric fan switch should really go in either the radiator bottom-tank or the outlet-hose, not the top hose or thermostat-housing.

Putting it in the top will probably result in the fan triggering about 10x more often than it needs to.

--Tanuki

But your fan wont trigger if your engine gets towards boiling point. The fan will just thinj the engine it only warm.

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it shouldnt get towards boiling point! Thats what you have a functioning water pump for :blink:

idea behind it being in the bottom hose is this -

Say your travelling at 60mph and with the airflow over the radiator with no fan on you have the following readings....

water temp in top hose - 95C

water temp in centre of rad - 90C

water temp in bottom hose feeding engine - 82C

therefore if the vehicles radiator and airflow through the rad is sufficient to keep the incoming water temp of the engine to the right level - your fan doesnt switch on. its only when that airflow doesnt keep up with the generated heat and the water temp going into the engine exceeds your prefered temp that the fan comes on. If you had it in the top hose, your fan will be thinking the engine is cooking and overcooling the thing so that the incoming water temp to the engine might be down to 70C or lower. that can overcool the engine and make it run less efficiently.

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Cooling is full of misconceptions.

So long as the *bulk-coolant* temperature of the engine is right you don't want the fan to trigger.

Imagine you're driving up a long hill, towing a trailer. The engine's kicking out a lot of heat and the temperature of the water coming out of the engine is 110 Centigrade. But because you're moving, the ram-effect is providing plenty of air into the radiator and the water coming out the bottom of the rad is at 70 Centigrade.

You don't want to start the fan under these circumstances - everything's doing just fine!

Modern vehicles always put the temp sensor in the bottom tank. Often they put the thermostat in the return-pipe too. The car I'm currently driving has no thermostat - it uses a variable-speed electric water-pump.

--Tanuki.

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But your fan wont trigger if your engine gets towards boiling point. The fan will just thinj the engine it only warm.

Depends which switch you use.

Funny thing here. I'm being told it's not in the right place in the top hose. Then why is the temperature gauge sender in the same place as the thermo switch

TheRecklessEngineer

Hammer, nail, head. You got it in one

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On my 200 tdi (after I removed the aircon) i simply used the sensor/switch thingy on the thermostat housing to trip a relay to bring in the electric fan. I also added a manual over-ride so I could turn it on earlier if I wanted. Fan always comes on when needle rises just above half and goes off again when temp falls. Perfect

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Well I popped into my local old school motor factors - such a shame there are less and less of them these days -

he bought out a box of thermostatic switches, and I'm in business.

he had quite a range that close the contacts from 80 up to 105 degrees. I picked one that closes the contacts at 95 deg, If that seems to be tripping the fan on too early I can always go back and get a higher value one - only £9 per switch so no biggie.

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Yep. You can only try. A 92/ 87 is far too low.

Please let me know what you eventually end up getting.

As there's two places there that the switch will fit. You can leave that one in as you try another one. I did and it came in handy when the one I use failed.

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