Xantia Heater Fan Stays On Full Blast!!

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Post by Peter.N. »

Thanks for all the info, didn't know there were so many electronics engineers out there. I was unaware of the originals being darlingtons as only one junction of one transistor was still in tact, which was how I discovered that they were PNP. I can only reiterate that at least twice I have replaced them with 15A rated bipolars, (on different cars!) and have covered a considerable mileage without further problems, maybe i've just been lucky! As someone else commented, when they are switched hard on, they are dissipating very little power (app .6v x amps ) they work harder at lower speed
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Post by AndersDK »

BonceChops wrote: 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.
The relay is fitted on the blower motor assembly ?
Thought there was no relay on Xantia type blower fan controllers ?

If that is so - the base drive current could be just in-adequate to drive the relay coil.
This is because the circuit must be a type where the relay coil is in parallel to the PNP base and +12V. Thus the driver circuit must provide approx the double relay coil drive current - as the base-emitter current on a standard power transistor are rather high driving collecto-emitter currents of 5-10Amps. Mind you the current gain on these standard power transistors are rather low - some 20x. Compare this to a darlington which is at least 10x higher.

In other words : a low gain power transistor may eat up all the drive current not leaving enough drive to put on the relay.
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Post by dennis.Y »

Hello, first post, got redirected from other forum, while seeking help.
Same problem as in title, but in xantias predecessor.
At the end, I settled for bad transistor, type MJ 900 - non deliverable.
Could get MJ 901.
Any other alternatives?
blower fuse is 25A
http://www.digchip.com/datasheets/parts ... s_mj02.php
If helpull.
thanks, Denis.
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Post by Clogzz »

MJ900 and MJ901 are rated at 8 Amps.
MJE2955 is rated at 10A according to this list, and will give you more ‘margin’:

http://www.digchip.com/datasheets/parts ... s_mj04.php

Talk of MJE2955 in posts higher up, should be OK for the BX heater blower.
Don't use MJ11015 or other 30A transistors here, as they may lack drive current when replacing an 8A transistor.
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Post by dennis.Y »

Will try to verify those codes this week!
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Post by AndersDK »

Clogzz wrote:MJ900 and MJ901 are rated at 8 Amps.
MJE2955 is rated at 10A according to this list, and will give you more ‘margin’:

http://www.digchip.com/datasheets/parts ... s_mj04.php

Talk of MJE2955 in posts higher up, should be OK for the BX heater blower.
Don't use MJ11015 or other 30A transistors here, as they may lack drive current when replacing an 8A transistor.
The MJ11015 would certainly be OK in the BX regulator too, as a darlington transistor type always would need LESS drive current than a non-darlington.

BTW : do you have the spec for the series II CX blower fan regulator transistor too ?
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Post by Clogzz »

Was thinking of that too, but with no certainty then as to what an MJ900/901 was, it now looks like they are darlingtons, and even 10 Amps, contrary to the 8A on the previous list:

http://www.datasheets.org.uk/specsheet.php?part=MJ900

As for the CX II, don't know yet, will have to explore, probably in Shane DoubleChevron's direction. :)


Addition at 12.10 PM GMT:

Went exploring on Planète Citroën Forum ... found nothing ... so put the question to them:

http://www.planete-citroen.com/forum/sh ... hp?t=38501
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Post by dennis.Y »

Clogzz wrote:MJ900 and MJ901 are rated at 8 Amps.
MJE2955 is rated at 10A according to this list, and will give you more ‘margin’:

http://www.digchip.com/datasheets/parts ... s_mj04.php

Talk of MJE2955 in posts higher up, should be OK for the BX heater blower.
Don't use MJ11015 or other 30A transistors here, as they may lack drive current when replacing an 8A transistor.
MJE2955 is visually completely diffrent from MJ 900..."E" goes for flat black housing with 3 legs and "MJ" for round housing with 2 legs.

So I installed MJ 2955 (resembling name, correct housing)but fans didnt bother to work.
Which should I go for now? It must be MJ.
characteristically they go in this order 900, 901, 2955, 11015 (rising current and power) so since 2955 didnt work, why 11015 should?
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Post by Clogzz »

Bad news ! :(

MJE2955 was used by a previous poster, but it then looks like he must have done what we call a 'plumbing' job to get the transistor in.

If MJ2955 doesn't work, it's likely that there is another fault.
2955 is close to 900/901 in spec, and should work.
All I can suggest is to go back over the job, to see if all phases still show the same symptoms.
Does the original transistor measure faulty ?

More ideas here, especially Tom Sheppard's posts, 2 pages:

http://www.aussiefrogs.com/forum/showthread.php?t=19229
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Post by dennis.Y »

OK, thanks.
If it should work, Ill try locating other fault.

Not really into measuring (electricity argh), but at garage with my citro fanatic mech, we tried several diffrent plates from non aircon BX and neither worked, even found one from an aircon model, but all dead.
Connect mine back and here goes full speed rotating.
Ill play more with current one, because had very little time to test.

Relay under steering is OK, speed selecting knob was opened, checked, seemed OK.
I believe there is nothing else, that can go wrong.
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Post by Clogzz »

More ideas in these threads.
Try particularly to get into Tom Sheppard's 'BXPress' pages:

http://www.bxclub.co.uk/forum/viewtopic.php?t=536

http://www.bxclub.co.uk/forum/viewtopic.php?t=1531
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CX II transistor FW26025A

Post by Clogzz »

AndersDK wrote:BTW : do you have the spec for the series II CX blower fan regulator transistor too ?
Better late than never, something came in at last.
Transistor for CX II blower motor:
FW26025A - PNP darlington - 20 Amps - 100 Volts - 160 Watts.
That's the same one as the originals on the Xantia.

http://www.planete-citroen.com/forum/sh ... stcount=20
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Post by BonceChops »

Clogzz wrote:MJE2955 was used by a previous poster, but it then looks like he must have done what we call a 'plumbing' job to get the transistor in.
I used a pot to supply the base current while I obtained the MJ11015 that should be in. I finally got round to fitted them this morning and now the fan works perfectly. I susspect the 2955's needed for base current than the air con ecu wanted to supply them so it didn't work.
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Re: CX II transistor FW26025A

Post by AndersDK »

Clogzz wrote:
AndersDK wrote:BTW : do you have the spec for the series II CX blower fan regulator transistor too ?
Better late than never, something came in at last.
Transistor for CX II blower motor:
FW26025A - PNP darlington - 20 Amps - 100 Volts - 160 Watts.
That's the same one as the originals on the Xantia.

http://www.planete-citroen.com/forum/sh ... stcount=20
Tx -
We just need to follow postings by Peter N. then to remember the replacements 8)
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Heater problem

Post by KennyW »

Hi Gang<

Just a little aside , while disamntling a Xantia Mk2 at the Scrappie today (Friday14th) I saw the relay fitted by Citroen for the problem encountered by earlier Xantia's. Fitted in steering column shroud, grey in colour.

But strangely enough when doing my Matrix!!!!!!!!!! I don't recall seeing one on my Xantia MK 2 .

There is only approx 2 mths diff. in manufacture.

This would suggest maybe mine was one of the last prior to modification.
(I've Swallowed a dicnotionary!!!!!!!!!!!!!!!!!!!!!!!!!!!)

Regards

Kenny.
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Xantia 2.0 Hdi 90hp 1999 only 189,000 and rising!!!!!!! Moved on to a new home
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Xantia TD 1.9 Mk 2 Estate LX 1998 model over 210,000 miles now and still rising!!!!!!!!!!!!! now deceased 17/12/2010.
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