Heater fan always on full speed - common citroen problem?

[AirCooledHeaven]

Hi

I've owned a synergie HDi SX from new, it's the one with climate control. Now for the third time I have a problem that the heater fan is permanently on full speed. Even with climate control switched off completely the fan is still going. With climate control switched on I can press the fan speed up and down buttons and the little bargraph display goes up and down accordingly, but the fan only has one speed, flat out.

The first two occasions it was fixed under warranty, I believe the fan blower unit was changed, now of course I'm looking for a diy fix. I'm sure this is probably a simple electronic component failed, and as an electronics engineer myself I'd like to fix it. Just wondering if anyone here has had a similar problem.

Thanks

[myglaren]

It is certainly a common enough problem with Citroens and Peugeots and you will find quite a few threads devoted to it.
The cause is not always the same, there are a few variations that depend somewhat on the type of air conditioning/climate control that is installed.

I have mine die completely and had to replace what is generally known as the `resistor pack' - although it wasn't really, a heap of surface mount components and a triac by the looks of it. Chucked it out now unfortunately.

In mine it was located above and to the left of the clutch pedal, yours may be different but your symptoms seem to be more akin to the real resistor pack and easier (and much cheapper) to fix. Once you manage to locate the actual module it really is just a matter of replacing the open circuit resistors and a thermal link IIRC.

You will find quite a few threads in the "Aircon-French" forum that deal with it, not sure if the Synergie is covered specifically but it won't be radically different from the others.

[Clogzz]

The air-conditioned cars have the transistorised heater fan drive that doesn’t use the resistor pack.
Hope these Xantia topics will be of use:

http://www.frenchcarforum.co.uk/forum/v ... hp?t=22398

http://www.frenchcarforum.co.uk/forum/v ... hp?t=22348

http://www.frenchcarforum.co.uk/forum/v ... hp?t=25122

[AirCooledHeaven]

The air-conditioned cars have the transistorised heater fan drive that doesn’t use the resistor pack.
Hope these Xantia topics will be of use:

http://www.frenchcarforum.co.uk/forum/v ... hp?t=22398

http://www.frenchcarforum.co.uk/forum/v ... hp?t=22348

http://www.frenchcarforum.co.uk/forum/v ... hp?t=25122

Hi Clogzz

Thanks a lot for those links. Just a couple of questions, first do you know where I could find a wiring/circuit diagram for a climate control synergie? I'd like to verify that the transistor contro unit is in fact getiing a variable input signal. I also need a wiring/circuit diagram for the indicator stalk area, as my car has just started the random ticking sound which I believe is a problem in this area. Secondly I'm curious about those transistors, they're rated at 30amps, so to go short circuit they must be getting damned hot, any idea where the design flaw is?

Cheers

ACH

[CitroJim]

If the Synergie is anything like the Xantia at all, the instructions in the last of Clogzz's links will do to see if the module is seeing the right control voltages.

Yes, the transistors are a pair of 30A PNP Darlingtons in parallel and yes, they get very hot in use. In fact, run the module outside of the fan unit and in minutes it is too hot to hold The module relies on the fan running to keep itself cool

If yours are short-circuit (you'll have to isolate the bases and emitters to be sure) then I hold a small stock of spares, the MJ11015. they may not be marked as such but that'll be what they'll be. Alternatively, if you don't feel confident to repace them, I can for you..

This is the Circuit Diagram of the blower module.

They used PNP Darlingtons so the collectors could be connected direct to the heatsink..

[AirCooledHeaven]

If the Synergie is anything like the Xantia at all, the instructions in the last of Clogzz's links will do to see if the module is seeing the right control voltages.

Yes, the transistors are a pair of 30A PNP Darlingtons in parallel and yes, they get very hot in use. In fact, run the module outside of the fan unit and in minutes it is too hot to hold The module relies on the fan running to keep itself cool

If yours are short-circuit (you'll have to isolate the bases and emitters to be sure) then I hold a small stock of spares, the MJ11015. they may not be marked as such but that'll be what they'll be. Alternatively, if you don't feel confident to repace them, I can for you..

This is the Circuit Diagram of the blower module.

They used PNP Darlingtons so the collectors could be connected direct to the heatsink..

Thanks for the info Jim and the offer of help, I found the transistors at CPC for 2.75 each so I'll give it a go. If I get into trouble I'll be in touch

ach

[CitroJim]

I found the transistors at CPC for 2.75 each

They're getting cheaper! Time to stock up Back along they were only available from Farnell and they had a rather uneconomic minimum order policy.

CPC Link to the MJ11015

[AirCooledHeaven]

I found the transistors at CPC for 2.75 each

They're getting cheaper! Time to stock up Back along they were only available from Farnell and they had a rather uneconomic minimum order policy.

CPC Link to the MJ11015

Jim

Just wondered if you've come up against one like this:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 0305285093

Looks like the pcb is potted which means getting the trannys out will be a no-no

ach

[Clogzz]

Delayed reaction … the diagram shows how top speed bypasses the transistors with the relay, and ‘TDRV’ shows which way the voltages go.
The finding over the years has been that transistors go short for good.
Picture of module with MJ2955 transistors:



The ticking sound of the indicator may be caused by the emergency flasher switch needing a clean of contacts by switching it on and off a few times.
The indicator current always passes through the switch when it’s off, but the switch contacts hardly ever get any self-cleaning activation.

The Haynes book has a map of the indicator circuit.
Scanned pages somewhere in here:

http://www.shanescitshed.com/xantia/xantia.html

[AirCooledHeaven]

Delayed reaction … the diagram shows how top speed bypasses the transistors with the relay, and ‘TDRV’ shows which way the voltages go.
The finding over the years has been that transistors go short for good.
Picture of module with MJ2955 transistors:



The ticking sound of the indicator may be caused by the emergency flasher switch needing a clean of contacts by switching it on and off a few times.
The indicator current always passes through the switch when it’s off, but the switch contacts hardly ever get any self-cleaning activation.

The Haynes book has a map of the indicator circuit.
Scanned pages somewhere in here:

http://www.shanescitshed.com/xantia/xantia.html

Thanks cloggz, i've found tapping the indicator stalk can set off the wild indicator ticking sound so I've assumed its a problem with the stalk or a connection in that area. Strangely the problem is worse when its damp, leading me to think there's some electrical leakage involved in the problem. The stalk looks like a 'sealed unit' so maybe a diy fix is not possible??

ach

[Clogzz]

The stalk is prone to carbonisation, but if it’s sealed, how does the dampness get in ?
Seven stalk pictures from ImageShack:

http://img106.imageshack.us/my.php?imag ... o11cb8.jpg

http://img106.imageshack.us/my.php?imag ... o07mz4.jpg

http://img106.imageshack.us/my.php?imag ... o05rm2.jpg

http://img106.imageshack.us/my.php?imag ... o03sw0.jpg

http://img106.imageshack.us/my.php?imag ... o12jw0.jpg

http://img106.imageshack.us/my.php?imag ... o09es8.jpg

http://img354.imageshack.us/my.php?imag ... o08me7.jpg

[louisamason18]

Im having the fan stuck at 1 speed, Flat out,
ive bought 3 new resisters , 1st one didnt work at all, 2nd one fan will run at half speed but cant control speed, same for the 3rd new part,
so i can get flat out with original part or half speed with new part, om completely baffled,
can anyone advise please

[admiral51]

Hi and welcome to the forum
I think this thread is for older vehicles than your C5 X7.
I will have a dig around to find a more current one as i do know there a few topics regarding this issue.


Right have a look at this Search Link

All i did was to pop into the google search bar top left of this thread C5 X7 interior blower on full and hit search, it will bring up everything in the posted link.

Lots and lots of good information within all of them

Hope this helps

Colin

[GiveMeABreak]

Im having the fan stuck at 1 speed, Flat out,
ive bought 3 new resisters , 1st one didnt work at all, 2nd one fan will run at half speed but cant control speed, same for the 3rd new part,
so i can get flat out with original part or half speed with new part, om completely baffled,
can anyone advise please

Be aware that a lot of the cheaper sensors are notoriously bad quality - if they work at all! There have been many here who have wasted time on replacing these with cheap Chinese ones and they have regretted not getting a decent branded Heater Blower Control Module (as they are called). One other bit of advice - purchase anything from Eurocarparts at your peril - they have an extremely poor reputation here for parts.

[admiral51]

Agree with Marc, we call them Eurocraparts lol