Cooling fan doesn't work?

1st December 2013, 19:27

Just after a bit of advice on this if anyone can help.

I've got a mk2 vtr that's had an engine conversion to the 100bhp mk2 vtr engine.
Since the conversion was done the cooling fan has never worked. There's a multiplug coming from the main loom that plugs into the fan loom with the relay so guessed the cooling fan works off the switch in the thermostat housing?

I know the fan works as connected directly to the battery.
Today found there's actually a cooling fan switch in the radiator aswell so I've disconnected the fan wiring from the loom and got rid of the relay and made my loom by running an earth to the radiator fan switch, then other side to the fan and then the live to the fuse box.

Had the fan come on for a couple of secs but then nothing again? Checked the voltages and found once the temp gauge goes above half the radiator switch switches the earth and there's 14 volts going to the fan plug but still doesn't cut in?
Took the wires off the radiator switch and then joined together and fan cuts in?

Initially would've said its the radiator fan switch but seems to be switching the earth so seems to be working!
As there's a radiator switch in the rad surely I don't need the relay and plug into the engine loom?

Any help is appreciated as just confused now

1st December 2013, 19:29

if there is power going to the fan plug, it should work.
take the fan off and power it up manually by giving it an earth and a live.
if it still doesnt work, you have a dead fan motor.

1st December 2013, 19:55

Are you sure you`re using the correct cooling fan for your car?

1st December 2013, 20:48

I've powered the fan just using the battery so know the fan works.

Obviously the radiator fan switch just switches the earth to power the fan, and using multimeter checked it switches when the temperature gets up which it does but the fan still doesn't power up? But if you bypass the radiator switch and join the two wires (effectively the radiator fan switch working) then the fan powers up!

Surely if wrong fan then wouldn't work when wires joined?
As I said earlier the fan did come on momentarily when I put the wires on the radiator switch but then hasn't come on since, only when power applied to it directly and not through the switch?

1st December 2013, 21:04

Could be a shite earth.....

So when the temp gets up and temp switch does what its suppose to do,there might be a break in the circuit so the fan never comes on.

I had this on my nc30,the rad switch worked as it should but because the rad was not earthed correctly the fan never came on.

1st December 2013, 21:29

do a continuity chect on the wires from the fan to wherever they join.
Would be advisable to get a wiring diagram to help trace it

1st December 2013, 23:04

I've run an earth to one side of the rad switch, and once the temp gets over 1/2 the other pin on the rad switch, switches to an earth as it should.
I then checked the voltage going to the fan plug and its 14 volts.

This is why I'm confused and can't work it out? Thinking of trying another rad switch but it seems to be switching across.

I've checked the Haynes wiring diagram and a single sped fan (non a/c) doesn't need a relay so see no need for it. Wiring diagram just shows an earth going to one side of the rad switch, other side going to the fan. Then live from the fan going to the fuse box which is what I've done

2nd December 2013, 00:36

So bypassing the fan switch the fan powers on? Adding it in the circuit and it stops? Is try a new one if so they aren't expensive

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2nd December 2013, 21:12

Bought a new one today and fitted it and still nothing, so checked the new switch and found its faulty, no continuity through it when hot

going to exchange it tomorrow and try again, waste of an evening!

3rd December 2013, 20:24

Got the new one fitted and found what appears to be a problem.
Temp warning light comes on at 98 degrees, then the cooling fan switch kicks in at 101 degrees....but then doesn't turn off again?