Interior Fan Not Working

Hi,

My beloved C3(03 plate) is now beginning to fail me. Hopefully I can get a few years out of her yet. Anyway my interior fan blower has stopped working(as in, it doesn't blow on any setting).

After doing a fair bit of reading up on the subject(I also have a Haynes manual) I thought I'd look at the easy thing first, the Resistor Pack. I found this was blown. So I replaced it, hoping it was that simple(although I wasn't hopeful as I assumed, if the resistor pack was blown then the fan should still work on setting 4). Sure enough it made no difference. So next stop was the switch unit. The plastic was heavily melted around Pin A4. Although interestingly not around A6. The Switch did not switch A4 to any of the A side pins(i.e. the resistor pack pins) or A6(earth)

So I then started confirming the fan was working. It was blowing air fine. So I started rigging up a switch to put the fan full on, that I could then turn on and off. Expecting that would get me by until I found a new switch unit. It was at this point that I noticed how hot the wires were getting when switched on. So this then led me to think the motor must be drawing huge current, therefore I went to the hassle of removing the fan to check it out. I found the fan is taking more than 20 Amps(My Ammeter can't measure anymore than this) when in situ. I can't believe this is right, but, apart from the huge current, the fan seems fine.

I have measured the static DC resistance of the motor to be 0.4 Ohms. This seems low to me, and is probably why such a huge current is flowing. With this resistance figure, stall current would be 35 Amps.

Does anyone what the DC resistance of the motor should be? Does anyone know what current should flow. My car uses a 20 Amp fuse(Not the 40A that I had wondered) but does not blow either.

I need a new switch unit, but there is too much current flowing and I don't want to burn out a new switch unit, so I'd guess the problem is the fan but again I don't want to spend money on a new fan without being sure that the fan is the problem.

All help and advice is very much appreciated!! Below is an image of the switch type from my car.

Hi 927465, welcome to the forum!

It can be worth checking the bearings are not seized up a bit, the fan should turn easily by hand. If you have the thing out, it wouldn't be tricky to feel the fan spins easily by hand.

Hi C3driver52,

Thanks for the welcome and thanks for the reply.

The fan is back in the car, connected to a heavy duty switch I had, in line with the full resistance of the Resistor Pack. So that I could reduce the current to stop the wires getting hot and at least have some fan action to demist my car.

What I meant by "the fan seems fine", is that the bearings don't appear to be seized up, the brushes are fine. I can turn it easily by hand but it does stop quite quickly when you stop turning it(not sure if this is normal for this type of fan).

I had it powered outside the car, with an old House Alarm battery. It was drawing 10 Amps using this battery(obviously the voltage across it was 12V and not 14V like it would be with the alternator across the battery). I forgot to take a note of the fan part number(but I'd guess from the part number is says 6 Amps) Hindsight is a wonderful thing, but I should have powered it using the battery from the car, with the engine running to see if the current was different from when in the car. Also note there was plenty of airflow(hence why I say it appears to be fine). On position 4 of the fan it should run the fan with 14V across it, therefore I wouldn't have thought 20 Amps is right(because the fuse should blow at 20Amps, even though the fuse hasn't blown)

I am beginning to wonder if I have some problem with the heater matrix, that maybe blocks air flow causing the fan to work a lot harder, which causes more current to flow and hence blew the switch and resistor pack.

I'm beginning to think I need to trail around car breakers and hopefully find a c3 with the same switch, fan and resistor pack and just buy them at least then I'll know what they do outside of the car. I was just wondering if anyone knows what current should flow normally?? That would help me immensely.

Have you changed the cabin air filter? As you've found, fan motors can be quite powerful and will try to overcome resistance. A 'blocked' filter will add significantly to the load on the fan.

A friend of mine has a facelift C3, his fan draws reasonable current on positions 1, 2 and 3 but jumps to over 40 amps on setting 4 (his model has a 40 amp fan fuse). He thought it was a faulty resistor pack until we temporarily removed the cabin filter and the current dropped to below 20 amps on setting 4.

I wonder if Citroen increased the rating of the fan fuse because of current issues when the system gets a bit older and the filter isn't new?

Missing Lincs wrote: I wonder if Citroen increased the rating of the fan fuse because of current issues when the system gets a bit older and the filter isn't new?

This could well be the reason for the 2 different fuse ratings. Well spotted.

Yeah I had checked the filter. It was a bit clogged up but not hugely. Sorry I should have said I had taken the filter out when doing my testing just to ensure it wasn't related. I have now got a new filter in.

Tried a few scrap yards today, without much luck. Only found 2 C3's in total and both with different fan and switch control unit, from my car. Will need to do some searching for big scrap yards in Glasgow. Does anyone know of big Car scrap yards/car breakers in Glasgow??

Did get prices from Citroen for the parts, just so I knew how much it would be from them. But wasn't expecting the prices to be so high.

Resistor Pack - £59
Switch Control Unit - £250
Fan - £222

Do you think Citroen increased the fuse rating? I think a 40A fuse was for most models. The 20A appears to be for HDI cars with air conditioning(using the Haynes manual as my reference for this). Not sure why that would be the case. I have a populated 40A fuse(guess they just populate the fuse box with fuses regardless of whether they are used or not), but its definitely not used(know for a fact because I'd thought it was this fuse but after reverse engineering the wiring, found it was definitely the 20Amp fuse that was in line with the fan).

Will need to do some searching for big scrap yards in Glasgow. Does anyone know of big Car scrap yards/car breakers in Glasgow??

I don't know Glasglow, but I have used ebay for used C3 parts in the past.

try another Heater Control Panel, C3 Blower Motor and C3 blower resistor pack. All with delivery

Yeah thanks I've tried loads of internet/ebay searching but I cannot find the parts.
I had already purchased a resistor pack, from ebay, it said it was for my car but it definitely wasn't the right one. I modified it to fit my car(I am an experienced electronic engineer in my day job).
I don't know if the resistances are the same but they are certainly in the right ball park and affect the amount of airflow in the right proportions. Although the fan is blowing harder than I
remember(which again would tie in with my theory of the fan having a reduced resistance to what it should have)

Just in case anyone is interested. I got a 2nd hand fan, control unit and resistor pack from a scrappy.

Please note my original thought(and reason for joining this forum) was that my old fan had too small a static dc resistance and therefore caused too much current to flow in the circuit, blowing my resistor pack and control unit.

DC Resistance of old fan - 0.4 Ohms
DC Resistance of new fan - 6 Ohms

Current flowing with the new fan - 11 Amps. Due to this and the fact the dc resistance was so different I didn't try to measure anything else. I just put everything back into the car and it all works a dream. Hopefully it stays that way

I'm going to experiment with a smaller fuse, because the fuse never saved the original resistor pack or the original control unit. Hopefully if something similar develops in the future, it will just blow the fuse, and therefore cause me to look into the problem. Although I'm hoping I won't get a problem with this again.