Xantia Heater Blower - fixed, but why??

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markw
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Xantia Heater Blower - fixed, but why??

Post by markw »

Hi all,
As seems to be fairly common, the fan on my '97 Xantia stopped working.
Having read the numerous postings, I decided to fit a relay in order to take the current off the ignition switch.

On the first test after fitting the relay, the fan still didn't operate. Testing it out, it was obvious that there was no 'closed circuit' on the ignition switch. Then I coupled the feed and load together on the fan side, and expected the fan to operate irrespective of the ignition switch. Very strangely, this isn't the case. The fan will only operate with the ignition turned on - despite the fact that the switch is out of the circuit! However, the heated rear window can now be operated without the ignition on.

I'm delighted that the fan is operating, but am concerned that I've done something wrong.

a) is there any risk in leaving the feed and load to the fan permanently connected?
b) does anyone know why the fan is now switching with the ignition switch?

I'm baffled!
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Post by Peter.N. »

If it is an auto temperature control fan (temperature control claibrated in degrees) it has a speed regulator module on the motor that requires a voltage from the control panel to turn it on and regulate the speed, if this is missing the transistors are switched off and the motor wont run.
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Clogzz
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Post by Clogzz »

The risk when the motor fan is permanently supplied is that since it wasn’t what you had planned for, you may not have the correct fusing in the feed, if any fusing at all.
The modification with relay is to turn the fan supply off when the ignition is off, so something didn’t go according to plan there, least of all if the rear demister works with the ignition off.
The fan does stop when the ignition is off because the climate control board that controls the fan speed is operating only with the ignition on, and the engine running.

Ideas here: http://www.frenchcarforum.co.uk/forum/v ... hp?t=17322

This map from RichardW: http://www.geocities.com/tricky992002/fanmod.xls
2002 C5 2.0i AL4 230,000 km 76372389
markw
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Post by markw »

Thanks for the help. I'm pretty sure the circuit is fused (according to
the wiring diagram the fuse comes after the ignition switch), but I'll
check this by removing the fuse that controls the heater fan. I would
much rather have the fan circuit switched by the key, as this is is a
safer option. I did install a relay as per that excel file, but it wasn't switching with the ignition; it seems that the switch in ignition barrel isn't closing.

Without the key being able to complete the fan circuit, do
you reckon I could pick up a feed from one of the other switched
circuits (not the starter one!) and use this to control the relay?
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Clogzz
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Post by Clogzz »

Black plug NR wire 1: Unfused permanent 12 Volts from battery.
Black plug NR wire 2: 12V out when starting only.

Grey plug GR wire 1: 12V out on ignition and accessories.
Grey plug GR wire 2: 12V out on starting and ignition.

Brown plug MR wire 1: Unfused permanent 12V from battery.
Brown plug MR wire 2: 12V out on ignition only.
:mrgreen:
Yes, you could use either of the grey plug wires.
Wire 1 has power on 'ignition' and 'accessory', but with the engine and climate control ECU turned off, the fan won't spin on the 'accessory' position.
Wire 2 has power to it on ‘ignition’ and ‘start’, but the fan motor speed control won’t operate until after the engine is running.
Since the rear demister works with the ignition off, it means that you’ve tapped into an unswitched wire.
Wire 2 of the brown plug is usually still good to operate the modification relay and demister timer after it no longer has to pass the high fan motor current.
2002 C5 2.0i AL4 230,000 km 76372389
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