Xantia Heater Fan Stays On Full Blast!!

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vagabond
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Xantia Heater Fan Stays On Full Blast!!

Post by vagabond »

Hi All.

Wonder if anyone can help. 2000 HDI Xantia.

Put Heater fan on full this morning to move frost. Turned it down and it just stays full on!! IE it wont turn off at all. The sliding knob does not do anything!

Can anybody tell me the likely cause and what I can do?

Am at present puting the fuse in and out!! Its always really hot, or really cold in the car!!

Really appreciate any help.

Thanks.

Peter.N.
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Post by Peter.N. »

There are two speed control transistors mounted on the blower casing, one or both have probably failed. If you are handy with a soldering iron and drill, replacement of these is the cheapest option, or you could get a secondhand blower form the scrappies.

vagabond
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Post by vagabond »

Thanks for the reply.

I've searched for a blower removal process but can't find one for the xantia.
Where is the blower, and is it easy to remove? Also are the transisters obvious once the blower is out.

Any help would be appreciated.

Thanks.
Paul.

mezuk04
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Post by mezuk04 »

The heater blower motor is located under the front passenger footwell carpet on the left handside (its the big round unit)...held in place by about 3 screws (well on my spec of car at least) with a couple of wired connectors to it.

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Clogzz
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Transistors MJ11015

Post by Clogzz »

The original transistors are, of course, unavailable. :evil:
The replacements are MJ11015.

Peter.N.
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Post by Peter.N. »

Thanks clogzz, someone else was asking about them yesterday and I couldn't remember, I'll make a note of that.

vagabond - The transistors are riveted to a plate on the motor, If I remember correctly, you have to remove the motor from its housing by compressing the three rubber blocks around the circumference, you will then see the transistors. Unsolder the leads, two on each,make a note of their positions, drill out the rivets, fit the new transistors with suitable nuts and bolts, and resolder the wires.

Peter.N.
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Post by Peter.N. »

There you are clogzz, I dont think I will lose them now! they are a darlington pair, does it make any difference? I used ordinary bi polar transistors on mine.

Peter.

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AndersDK
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Post by AndersDK »

A darlington pair transistor is also a standard bi-polar transistor. Difference is that a darlington pair has 2 transistors in series (hence the designation) to decrease the required base terminal current drive. This in turn makes for double the base-emitter forward bias voltage - as you in effect then have 2 forward biased diodes in series.

In such a "simple" application as this fan speed controller, the difference does not mean anything to the function.

BonceChops
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Post by BonceChops »

So will my 2 MJE2955 ( the PNP equivalent od 2N3055 ) be ok? They are rated at 15A each

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AndersDK
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Post by AndersDK »

BonceChops wrote:So will my 2 MJE2955 ( the PNP equivalent od 2N3055 ) be ok? They are rated at 15A each
Sorry ? -

The MJ11015 is rated at 30Amps - whereas the MJE2955 is rated at 15Amps. It will pop out first time you set the fan at full blast.

Peter.N.
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Post by Peter.N. »

Anders - Thanks for the info for the transistors, I knew the configuration of the darlington pair but not how it would work in this application.

BonceChops - I have only just learnt of this new 30 amp rated transistor from clogzz, but I have always used 15 amp rated transistors in the past with no problem, I certainly have not had them fail again. The old 2N3055 is almost indestructable, so I would think they would be OK.

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Clogzz
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Transistors

Post by Clogzz »

Hello all,

As it happens, the original transistors FW26025A1 are darlingtons, rated at 20 A.
I get my stories from Planète Citroën Forum, where I got this:

FW26025A1 sont des PNP Darlington Vce=100V Ic=20A Pdisp=160W
MJ11015 sont des PNP Darlington Vce=120V Ic=30A Pdisp=200W


No idea as to what the current is at maximum speed.
There also has to be allowance for higher than normal current when the pollen filter is very dirty.
The blower motor fuse is 30 A.

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Mandrake
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Post by Mandrake »

Peter.N. wrote:BonceChops - I have only just learnt of this new 30 amp rated transistor from clogzz, but I have always used 15 amp rated transistors in the past with no problem, I certainly have not had them fail again. The old 2N3055 is almost indestructable, so I would think they would be OK.
I don't think indestructable is quite the right word for the 2N3055/2N2955..... :roll: I've lost count of how often I've replaced those things in things like regulated power supplies :)

If you want something a bit more indestructable, try something like the MJ802/MJ4502, specifically designed for medium voltage high current applications like linear regulators. 90 volts, 30 amps, 200 watts, same package. Very rugged transistor in actual fact as well as just in paper specs.

One thing that concerns me a bit though is that if the original transistors are indeed darlington, it may not be a good idea to replace them with non darlington types, without knowing what the driving circuit is like.

The extra base current required either may not be supplied (preventing the fan from going at the correct speeds) or it may even blow up the driver stage. Cavet Emptor....

Edit: Just read Cloggz post, looks like they are darlington, so the MJ11015 could be a good bet...

Regards,
Simon

BonceChops
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Post by BonceChops »

AndersDK wrote:The MJ11015 is rated at 30Amps - whereas the MJE2955 is rated at 15Amps. It will pop out first time you set the fan at full blast.
When almost at full speed a relay operates on the speed control board that shorts the collectors and emmiters so no current is conducted through the transistors.
Mandrake wrote:One thing that concerns me a bit though is that if the original transistors are indeed darlington, it may not be a good idea to replace them with non darlington types, without knowing what the driving circuit is like.
The relay coil is connected between the transistor base and +12 volts. The driver circuit must be capable of supply enough current to operate the relay. Would the current needed to energise the relay coil be more or less than the base current of the non-darlington type transistors.
I will change mine but they are on a 3-4 week lead time and the MJE2955's were only 80 pence each and in stock.
I had wondered if by fans intermittant running was being caused by too high a base current.

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Clogzz
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MJ11015

Post by Clogzz »

Peter.N. wrote:There you are clogzz, I dont think I will lose them now!
Image


Hello Peter,

The transistors will feel at home in your signature, brilliant idea !