X-Fan wiring

[jcwcooper]

Right ive wired up my new fan like this.

Im having problems that the Thermostatic fan switch isnt turning the fan on but i can override it, i cant see anything wrong with the wiring diagram, The only thought is that the switch in the bottom rad hose maybe has an airlock by it? Its only just been filled up with coolant. Is my diagram right?

[simonr]

Your circuit is fine. Try testing the sensor - very occasionally they are faulty. Stick it in a pan of boiling water (while actually boiling) and see if the contacts close?

If not, give me a ring & I'll send you a replacement.

Regards,

Si

[Roverdrive]

Isnt the switch supposed to be in the top rad hose?

Thought the top was the engine outlet, and the flow was down through the radiator?

Standing by to be corrected.

[Debs.]

Isnt the switch supposed to be in the top rad hose?

Thought the top was the engine outlet, and the flow was down through the radiator?

Standing by to be corrected.

I put my thermoswitch in the top hose (`seems to work as expexted); but, standing by to be gutted if it`s in the wrong place!

[Pete Attryde]

I don't think there is a right or wrong about which hose to put the switch in, but having it in the bottom hose allows the fan to assist the radiator in cooling the engine when it can't cope rather than when the water coming from the engine is hot enough to operate the switch but the rad hasn't cooled it. if you see what I am trying to say.

Pete

[roguevogue]

With the switch in the bottom hose, the fan only runs when the radiator can't disipate the heat without the fan added air flow.

The top hose is not wrong just the fan will run more than actually required.

[GBMUD]

As they say above, it is no surprise if the water is coming out of the engine top hose hot, that is to be expected and is why there is a radiator fitted to the car. You need the fan if water is coming out of the bottom of the radiator hot.

In my experience people are often disappointed with how little their fan comes on - a psychological thing IMHO as having spent their cash they want to see it doing something. This can lead some people to fit switches with deliberately low temperature settings or just to worry that there is a problem when there is not.

With a Tdi you should expect never to hear the fan come on under 'normal' driving conditions. In traffic in summer you will hear it come on occasionally but in winter, when the heater is on and you are in a traffic jam, expect the engine to be unable to make enough surplus heat to run the heater, never mind need a fan - mine used to drop off the temperature gauge while winter greenlaneing! While working hard off-road or when slogging up a hill with a heavy trailer on you would expect to get the fan running.

A Tdi, on a normal day (neither very hot nor very cold!), left ticking over may take up to an hour to get hot enough to start the fan up, depending on how much breeze there is. Best to test the sender in hot water as Si says, but do not be surprised, once fitted, if the fan does not come on regularly. In general this means that the radiator is working well, not that there is a problem with anything else.

Chris

[jcwcooper]

I have tested the Thermo switch and it didnt work but i have another one which does work, so Ive popped that in, the only thing thats been making me wonder why the fan hasnt come on is because on my Temp guage its going up to 90+ish obviously its not going to be 100% accurate so im guessing this is the problem and im just being paranoid, its proberly not actually hot enough for it too come on.

Just would be nice that i knew it worked.

Thanks for you help chaps

Dave.

[JST]

As they say above, it is no surprise if the water is coming out of the engine top hose hot, that is to be expected and is why there is a radiator fitted to the car. You need the fan if water is coming out of the bottom of the radiator hot.

In my experience people are often disappointed with how little their fan comes on - a psychological thing IMHO as having spent their cash they want to see it doing something. This can lead some people to fit switches with deliberately low temperature settings or just to worry that there is a problem when there is not.

With a Tdi you should expect never to hear the fan come on under 'normal' driving conditions. In traffic in summer you will hear it come on occasionally but in winter, when the heater is on and you are in a traffic jam, expect the engine to be unable to make enough surplus heat to run the heater, never mind need a fan - mine used to drop off the temperature gauge while winter greenlaneing! While working hard off-road or when slogging up a hill with a heavy trailer on you would expect to get the fan running.

A Tdi, on a normal day (neither very hot nor very cold!), left ticking over may take up to an hour to get hot enough to start the fan up, depending on how much breeze there is. Best to test the sender in hot water as Si says, but do not be surprised, once fitted, if the fan does not come on regularly. In general this means that the radiator is working well, not that there is a problem with anything else.

Chris

yep agree totally with the above, the only time my fan kicks in (xEng Switched) is during towing or winch/DRD - ie very slow speed for a heavy engine load.

[jcwcooper]

It works! It came on as everyone said under heavy load with no speed. Thanks again everyone.

Dave.

[Roverdrive]

Cheers Rougevogue and Raceface, That made perfect sense when you explained it like that.

My only experience was with a Kenlowe kit many moons ago, that put the sender in the top hose. FWIW it worked fine, but I can see from your reasoning that it would have been doing a lot less running if the sender had been in the bottom, allowing the radiator to do its job first.

My only other question, ( at risk of a hijack ) would be what temp gradient you could expect across the radiator, ie is there a risk of overheating the engine before the fan gets a signal to cut in?