406 Heater Blower Fan

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MostWanted - 21 Sep 2005 11:17 GMT

Hi.

I am really getting frustrated with this now.
My heater blower fan of my 1998 406 ONLY works on full power.
I was told I needed a new blower fan, so I replaced it.
Still no joy.
So I replaced it again.
Same problem.

Then I was told it would be the digital control unit (with all the
buttons on it). Put in a new (expensive) one of those together with
another new fan.
Again.
Same problem.

What could the problem possibly be?

It works, but only on full power and its really annoying because things
like a/c you would rather have working on low-medium fan which I cannot
do.

ANY ADVICE PLEASE??

Thanks

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Nom - 21 Sep 2005 13:48 GMT

> Hi.
>
[quoted text clipped - 18 lines]
>
> ANY ADVICE PLEASE??

Is there a resistor pack to offer differing voltage levels to the fan, based
on what the "digital control unit" tells it to do (ie, "digital control
unit" simply replaces the physical switch, and the speed is still adjusted
by resistors as in a "normal" car) ?

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MostWanted - 22 Sep 2005 11:59 GMT

the resistor pack is built onto the fan unit no?
So everytime I changed the fan unit, effectively I was changin the
resistor pack aswell right?

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G.T - 22 Sep 2005 13:03 GMT

Hi,

> the resistor pack is built onto the fan unit no?

I don't know for AC-equiped cars, but often an external pack, due to
dissipation imperatives. Often made of 3 resistors (the 4th speed being
direct) and a thermofuse / thermodiode acting like a fuse.

I've got a part called "module" next to blower fan for AC-equiped Mk1 406s
(codename D8). I don't know if it's the resistor pack.

BTW, I'd like to drop a line about this : don't you, guys, think it's
incredible to see resistor packs fit nowadays ? Bad efficience (useful
power/used power ratio) for a speed variation, they'd better fit a DC/DC
converter, which isn't more expensive, if you see the price for a set of
power resistors.

HTH,
G.T
205 Diesel & turbo-Diesel : www.205d.com

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Nom - 23 Sep 2005 08:50 GMT

> Hi,
>
[quoted text clipped - 5 lines]
> I've got a part called "module" next to blower fan for AC-equiped Mk1
> 406s (codename D8). I don't know if it's the resistor pack.

I think it probably is. You should soon be able to find out, with a bit of
wire-tracing and multimeter work.

> BTW, I'd like to drop a line about this : don't you, guys, think it's
> incredible to see resistor packs fit nowadays ? Bad efficience (useful
> power/used power ratio) for a speed variation, they'd better fit a
> DC/DC converter, which isn't more expensive, if you see the price for
> a set of power resistors.

No idea - I'm no electrician :)

Car makers always use "If it aint broke, don't fix it". Resistor packs may
well be crap - but if they're cheap and reliable, then there's no point in
Peugeot spending £££ on researching and developing a replacement.

Reply to this Message

G.T - 23 Sep 2005 12:08 GMT

Hi,

> > I've got a part called "module" next to blower fan for AC-equiped Mk1
> > 406s (codename D8). I don't know if it's the resistor pack.
> I think it probably is. You should soon be able to find out, with a bit of
> wire-tracing and multimeter work.

That's my idea too, but removing parts to have an access could well be a
pain. Glad I don't have to do it myself !

> > power/used power ratio) for a speed variation, they'd better fit a
> > DC/DC converter, which isn't more expensive, if you see the price for
> > a set of power resistors.
> No idea - I'm no electrician :)

You don't know what you're missing ;-)

> Car makers always use "If it aint broke, don't fix it". Resistor packs may
> well be crap - but if they're cheap and reliable, then there's no point in
> Peugeot spending £££ on researching and developing a replacement.

I do agree with you, but trust me, such an electronic module takes about 2
hours to design (and it's a max value) and costs about £5 to build (and
that's a large amount, too).
Just for fun, I've just designed such a PCB. My crappy design (took me 10
minutes) fits on a PCB which is only 48*25mm (18.9*9.84mil) - I could do
even better if I wanted to.

Regards,
G.T
205 Diesel & turbo-Diesel : www.205d.com

Reply to this Message

Nom - 23 Sep 2005 08:48 GMT

> the resistor pack is built onto the fan unit no?
> So everytime I changed the fan unit, effectively I was changin the
> resistor pack aswell right?

I don't actually know - I was just trying to establish how the system works,
so we could work out what was bust :)

This is the sort of thing an auto-electrician should have no trouble with -
I'd be looking in my Yellow Pages.

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Hendrik Skarpeid - 23 Sep 2005 11:14 GMT

I don't know if this is the case with the fan i the 406 but it is the case
on 605's and 205's at least.

The fan i equiped with a electronic regulator, with a bypass relay.
The bypass relay is operating only at full speed, otherwise the electronic
regulator is powering the fan. The electronic regulator is probably faulty.
This could explain the symptoms you are describing.

The engineer that developed the regulator did not have sufficient electronic
skills to understand that placing two bipolar transistors in paralell
without some kind of arangment for current sharing, can be a recipe for
disaster.

The transistors in the fan are probably blown, (both of them).

If you, or any of your friends have the necessary skills, you can find
replacements, and repair the regulator yourselves. Just replace both the
TO-3 transistors. Otherwise, you will have to try to get hold of a working
fan, or a working regulator.

Hendrik

> Hi.
>
[quoted text clipped - 20 lines]
>
> Thanks

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