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jupiterroom

Cooling fan wiring

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jupiterroom

Currently unpicking a previous owners handy work with the wiring.  What I had:

 

1.  No cooling fan resistor

2.  A two pin cooling fan switch, so fan was either on or off (no slow option)

3.  A relay connected straight into the battery to control the above

3.  A number of old connectors flapping around the engine bay

 

I'm now trying to put this right by sourcing the correct cooling fan switch with three pins and a resistor, but needed a bit of help with the wiring.  If anyone is under the bonnet of theirs today or happens to know, could you please share here?

 

Essentially what I'm now left with:

 

1.  A small section of loom with a blue three pin plug (I assume goes onto the cooling fan switch) that was unconnected when I purchased the car

2.  On the same section of loom is a brown plug, does this go to the resistor?  This was also unconnected.

3.  The cable that goes to the fan itself which is a plug (like the ones that go into the shunt box) with a positive and earth wire.  Where about's is this supposed to go?

 

Thanks in advance,

 

Rich.

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Tom Fenton

I'd be inclined to leave it alone in all honesty. The fan switches these days are garbage to the point that I've been changing them once a year or more on my cars. A solid state switch handling full fan current is a terrible idea, it used to work OK but I can only conclude the quality of the fan switches these days isn't what it used to be.

 

I rewired one of my cars to use the twin speed set up using a pair of relays, OK if you can do it yourself, otherwise it would prove costly if you are paying someone else to do it for you.

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jupiterroom

Thanks for the tip, Tom.  Do you have a rough idea of the schematic for that two-relay approach?

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jackherer
Posted (edited)

It connects the fans in series for low speed then parallel for high speed.

 

 

edit: that's the diesel setup with two fans, with one fan the wiring will obviously be different.

Edited by jackherer

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SRDT

You can use a diesel fan loom:

motovent.jpg

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DrSarty

I'm not sure why anyone wants or needs 2-speed fan cooling? Arizona desert, Dubai or Australian outback maybe, but otherwise a single 10 or 11" fan which is on or off should be plenty. Why complicate things?

 

Agree with Tom on using a proper sensor which goes to a switching relay, and would recommend a pull rather than push fan layout.

 

Come on at maybe 92/93 degC and go off at 87/88, or thereabouts. Sensor/switch kits can bolt to rad or get feed from coolant for temp, or if you have an aftermarket ECU, let that control the fan.

 

KISS!

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wicked

For modified cars, I tend to disagree. On my tct I had a single Spal pull fan and that could barely keep the temperature in control after spirited driving. For standard engines the single fan should be sufficient. 

 

Iirc the single fan setup doesnt use a relay and runs the full current through the sensor. Lesser quality sensors might fail early because of the high current. 

I replaced it with a relay that switches on (fully) at the first temperature of the sensor (no high current through the sensor) and had never reliability issues... 

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DrSarty

Mine is modified. 217bhp Mi16 on bodies which doesn't really know what unspirited driving is.

 

The Ring, road rallies, M25 standstills on a hot day, mapping sessions etc; my single fan controlled by the Emerald has never let the temp go above half.

 

I may concede that a turbo'd engine bay may be hotter, although I have never heard the fan (or fans ?) on my Mazda 6 MPS. But I'll still aim for 1 fan on the Xsara turbo.

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jupiterroom

Thanks for all the help guys.  Will look at a more efficient solution as mentioned above but also managed to grab the entire cooling fan loom from a 205 that was being broken at my local scrappy.  I've now got a "new" cooling fan switch (three ping, blue connector) and resistor.

 

Shall post back here with the details once/if I get it working.

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DrSarty

The available wiring diagrams are ok, but to simplify the standard set-up:

- batt positive (or shunt box) to the live feed pin on the in rad, 3-pin thermo switch. I think it's the bottom one.

- low speed pin goes via resistor to fan positive feed

- high speed pin goes direct to the same fan positive feed

- fan negative to ground

- to establish pins on the thermo switch, if needed, a jug of hot water or pan on the stove plus a multimeter on continuity will help out

 

Good luck; but you've been warned about those switches....

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jupiterroom

@DrSarty you point is very much taken re: switches.  I guess I'm still at the giddy lets-restore-everything phase and an hour or so in the garage is a welcome break from the kids.  It might break again in a year?  Even better, I get to do it all over again ;)

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wicked
Posted (edited)
On 6/1/2019 at 7:25 PM, DrSarty said:

Mine is modified. 217bhp Mi16 on bodies which doesn't really know what unspirited driving is.

 

The Ring, road rallies, M25 standstills on a hot day, mapping sessions etc; my single fan controlled by the Emerald has never let the temp go above half.

 

I may concede that a turbo'd engine bay may be hotter, although I have never heard the fan (or fans ?) on my Mazda 6 MPS. But I'll still aim for 1 fan on the Xsara turbo.

 

With a soaking hot turbo you add a heat source via the cooling of the turbo and the oil, via the heat exchanger. Last one you can circumvent by using an oil cooler. 
Next to that you might have (at least I have) an intercooler in front of the radiator, which could reduce the radiator efficiency. 

All in all, on most occasions my single Spal fan is sufficient, but after a blast through the mountains or hot trackday, I can see the temperature going to 100 degrees. On those moments I regret I did not put in a second fan. Now I lack room for it. With NA 16v I never had these issues. 

So on a new build like your Xsara (with plenty of room?) I would fit 2 fans for peace of mind. 

 

@jupiterroom

Maybe your current setup with relay is nicer for the switch and in the end what you want to have. If it is really annoying that kicks in with full speed, you could make a use the 3 pin switch and add a relay with the resistor in line on the low temperature. 

Edited by wicked

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petert

The 405 and Motronic GTi (DKZ) do it slightly differently (by switching the relays to earth), but still with three relays to provide low (series) and high (parallel) functions. It's a clever design, as it moves lots of air at low speed, without being noisy. Every 205 and 405 sold in Australia had the twin fan setup. Engaging the AC compressor will also turn the fans to low speed. DKZ 205's still have the blue radiator switch, whereas 405's use a Bitron controller, which reads the resistance of a sensor in the thermostat housing

Screen Shot 2019-06-03 at 9.14.07 pm.png

Screen Shot 2019-06-03 at 9.18.33 pm.png

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Nobbly
On 5/30/2019 at 11:39 AM, SRDT said:

You can use a diesel fan loom:

motovent.jpg

That's what I did ;-)

Got everything from a really rotten M-reg diesel in my local scrappy, so now have two speed twin fans running via relays and it all looks factory.

 

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