BX dash ventilation fans stopped dead!

JohnW

JohnW

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Greetings!

This week was to be "sort out a few BX matters" week. Instead I bought a CX Pallas. Now, instead of fixing a couple of things on the BX, the AC ventilation fans have stopped and it is a tad difficult to get to the bottom of it.

Has anyone had to solve this one? Just to save us re-inventing the wheel...

thanks

JohnW
 
A process of elimination I suspect!

If the fans do not work on any of the three speeds, then it may be a poor connection at one of the relays near the battery - there are several relays in the AC circuit so begin by wiggling the connectors and see if anything happens.

If you have the Behr heater from about 1978, the switch in the centre console will presumably direct current through a simple wire resistor pack that is located inside the heater box and under the small terminal cover that you see when you remove the spare wheel. I can't recall if you can get at it without prising the top of the heater box up. If that fails (corrosion / open circuit) you may only get one speed working.

CX electrics can provide endless amusement if the coloured tags at the ends have been lost. Preserve these whenever you can or you will have a tangle of wires in only about 5 colours. It's probably sensible to clean the connector blocks in the engine bay and check them for security as a preventative step.

David
 
John,

I'd suggest you do a search on Andyspares forum as this one has been covered several times over the years and apparently it can be done two ways;

#1 Is to buy a switch at enormous expense from Citroen

#2 Is to fit a transistor from Dick Smith for about a buck 50.:D :D

Alan S
 
I think John wants to repair the fans in the BX not the CX.

Here's some basics - the fans in the BX vents stop because the non replaceable motors die. I replaced one on my ex BX by removing the fan and motor and replacing it with a 12V computer fan - about 100mm diameter. Requires some drilling of the tubing and mounting but nothing drastic. It is fun (not) getting the ducting out as you have to remove the cover over the plenum chamber, then the washer bottles then the ducts but it is tricky but of course entirely possible. You will see where the two halves connect together in the middle - disconnect this joint before proceeding as it is the only way to get them out.

The OTHER problem may be that the speed switch is shorted or dirty. Alan can point you at previous discussions on that job.

Then again, doing both jobs should ensure a fix:D

BTW - the XM aircon is finally working sweet - a trip to Dubbo and back over XMas :wink2: tested it well. A detailed description of events and parts will follow - a couple of G&Ts is hampering my typing ability tonight:cheers::crazy:
 
UFO said:
I think John wants to repair the fans in the BX not the CX.

Here's some basics - the fans in the BX vents stop because the non replaceable motors die. I The OTHER problem may be that the speed switch is shorted or dirty. Alan can point you at previous discussions on that job.

Then again, doing both jobs should ensure a fix:D
QUOTE]

Thanks to all of you. The BX it is. Both fans have stopped at once so I'm suspecting controllers - switch, or more likely the resistor/transistor device, the location of which is still a bit of a mystery. I can see how to get the grill off I think - remove windscreen wiper arm, undo huge nut and prise off two press in rubber/plastic things at each front end of the grill, and this gives access to the vent/fan system and the washer bottles (themselves in need of replacement!). Somewhere in there is this mythical electrical device if I read the Andyspares threads correctly - I'll go there and look in more detail Alan, as there certainly are threads on the subject. Not totally clear whether they fit our late TZi with two fans mind you.

Cheers

(I barely need to drive the CX as we all seem to go weak at the knees just looking... Tomorrow it will have insurance, which might help.)
Click to expand...
 
Ah, I see. In that case ... I'm anticipating a future question re your newly acquired the CX. You will find youself in that CX department sooner or later!

David
 
David S said:
Ah, I see. In that case ... I'm anticipating a future question re your newly acquired the CX. You will find youself in that CX department sooner or later!

David
Click to expand...

Thanks David - no doubt I will!

Cheers

john
 
Scarey! I spent the last spring fitting aircon to my own BX (Which is going back to the town of its construction very soon,) and I have also just bought a CX which is a beautiful and comfortable car (although it is starting to show its age with arthritic heating and ventilation and lousy visibility.)
 
tomsheppard said:
Scarey! I spent the last spring fitting aircon to my own BX (Which is going back to the town of its construction very soon,) and I have also just bought a CX which is a beautiful and comfortable car (although it is starting to show its age with arthritic heating and ventilation and lousy visibility.)
Click to expand...

Scarey indeed! I've had the CX for two days now and am extraordinarily lucky with its condition due to the previous owners' care and attention. Always wanted one I suppose, and quite by chance a good one (pretty rare) appeared.

Thanks for yesterday's input. We'll have another go at the BX fans on Friday.

JohnW
 
JohnW said:
UFO said:
I think John wants to repair the fans in the BX not the CX.

Here's some basics - the fans in the BX vents stop because the non replaceable motors die. I The OTHER problem may be that the speed switch is shorted or dirty. Alan can point you at previous discussions on that job.

Then again, doing both jobs should ensure a fix:D
QUOTE]

Thanks to all of you. The BX it is. Both fans have stopped at once so I'm suspecting controllers - switch, or more likely the resistor/transistor device, the location of which is still a bit of a mystery. I can see how to get the grill off I think - remove windscreen wiper arm, undo huge nut and prise off two press in rubber/plastic things at each front end of the grill, and this gives access to the vent/fan system and the washer bottles (themselves in need of replacement!). Somewhere in there is this mythical electrical device if I read the Andyspares threads correctly - I'll go there and look in more detail Alan, as there certainly are threads on the subject. Not totally clear whether they fit our late TZi with two fans mind you.

Cheers

(I barely need to drive the CX as we all seem to go weak at the knees just looking... Tomorrow it will have insurance, which might help.)
Click to expand...

OK, now have better picture - first serious look at the BX electricals. About 1/10 for layout and access!!

I have 12V going in (at the double wire pin on the left hand side of the fan unit) and about 56 ohm to earth on the ground wire, regardless of the position of the fan speed rotary knob. I also have two separate wires going in to the unit on the opposite (drivers) side. Can't get either of these separate pins out, full stop. Any ideas on how to shift these things without breaking anything?

Separate question - can't find the oil pressure sender unit - this particular gauge isn't working. Manual gives no clues. I've found the oil temp. sender unit - a bit abraded so it's been grounded at some time, so may be the reason the oil temp gauge doesn't work. Other instruments do work so it isn't the instrument panel earthing or power supply I guess.

Best wishes for 2005 of course.

Thanks

JohnW
Click to expand...
 
Hi John, what kind of CX have you acquired? What kind of condition is it in, and is it roadworthy?? :confused:
Cheers...George 1/8th. :cheers:
78 CX 2400 C-Matic. (Unregistered now....soon to be registered...I hope) :D
 
George 1/8th said:
Hi John, what kind of CX have you acquired? What kind of condition is it in, and is it roadworthy?? :confused:
Cheers...George 1/8th. :cheers:
78 CX 2400 C-Matic. (Unregistered now....soon to be registered...I hope) :D
Click to expand...

George,

I've acquired that CX 2400 Pallas that was advertised in Perth and about an equivalent amount in spare parts. It's gorgeous and very much running and registered.

I've now 3 C-matic transmissions, a manual and all the gear to convert to manual, three blocks and a large amount of other bits and pieces. There's a bonnet too. Luckily, I disposed of 5XRenault 16TS doors at the same time...

This query is about our BX not the CX however.

Cheers

JohnW

Cheers

John
 
fifty six ohms to deck? Let me think. If the transistor was open circuit (OR BIASSED OFF!) then the beast would be open to deck but the transistor is in series with the negative of the fan. 56 ohms to deck would allow about 200 milliamps through the fan which wouldn't get out of bed for that!
I reckon that you need to start by finding out whether the transistor is connnected to ground at all. It is a big PNP type so measure if the can of it is connected to earth. it ought to be. If it isn't, you won't blow the planet up if you hard wire the can of the transistor to earth and try it out. I've seen mysterious earth line breakages on BXs. the route to ground is tortuous and it is a good idea to run a thick wire from the Transistor to a stout earth connection. Relay 745 could be part of the problem, too. It sits(electrically) between the negative of the fan(s) and the emitter of the transistor, one of the 2 leads poking through the metal plate but that is getting towards the difficult end so start by grounding the end of the motor that is 56 ohms to earth. Should run.
Then ground the transistor can instead. should run. If not the transistor most likely went to its ancestors.
 
tomsheppard said:
fifty six ohms to deck? Let me think. If the transistor was open circuit (OR BIASSED OFF!) then the beast would be open to deck but the transistor is in series with the negative of the fan. 56 ohms to deck would allow about 200 milliamps through the fan which wouldn't get out of bed for that!
I reckon that you need to start by finding out whether the transistor is connnected to ground at all. It is a big PNP type so measure if the can of it is connected to earth. it ought to be. If it isn't, you won't blow the planet up if you hard wire the can of the transistor to earth and try it out. I've seen mysterious earth line breakages on BXs. the route to ground is tortuous and it is a good idea to run a thick wire from the Transistor to a stout earth connection. Relay 745 could be part of the problem, too. It sits(electrically) between the negative of the fan(s) and the emitter of the transistor, one of the 2 leads poking through the metal plate but that is getting towards the difficult end so start by grounding the end of the motor that is 56 ohms to earth. Should run.
Then ground the transistor can instead. should run. If not the transistor most likely went to its ancestors.
Click to expand...

Thanks Tom. All good advice for which I'm most grateful. Can't get at the car for a week now (it lives away from home!) so will have a go next weekend. I haven't actually found this transistor yet - presume it's in (i.e. inside) the middle of the fan unit somewhere - and will also need to find that relay 745. I find I can't get the fans out as the two separate cables that plug into the casing on the drivers side are so tight that nothing non-destructive will shift them (as opposed to the two in a common plug on the casing on the opposite side, which does come out). This BX of ours is lovely apart from the wiring...

What I'm going to try first is to run a new earth to the appropriate pin on the fan body (that for the double plug on the left hand side), switched with an inline fuse, and see if that helps. In the meantime, some more study of the manual and hopefully someone who knows a practical way of getting those wires out!

Regards

JohnW
 
tomsheppard said:
fifty six ohms to deck? Let me think. If the transistor was open circuit (OR BIASSED OFF!) then the beast would be open to deck but the transistor is in series with the negative of the fan. 56 ohms to deck would allow about 200 milliamps through the fan which wouldn't get out of bed for that!
I reckon that you need to start by finding out whether the transistor is connnected to ground at all. It is a big PNP type so measure if the can of it is connected to earth. it ought to be. If it isn't, you won't blow the planet up if you hard wire the can of the transistor to earth and try it out. I've seen mysterious earth line breakages on BXs. the route to ground is tortuous and it is a good idea to run a thick wire from the Transistor to a stout earth connection. Relay 745 could be part of the problem, too. It sits(electrically) between the negative of the fan(s) and the emitter of the transistor, one of the 2 leads poking through the metal plate but that is getting towards the difficult end so start by grounding the end of the motor that is 56 ohms to earth. Should run.
Then ground the transistor can instead. should run. If not the transistor most likely went to its ancestors.
Click to expand...

Ran switched earth and separate +ve to the double pin on left (passenger) side - fan runs. So it's the controller. Now to find it!!

Thanks.

JohnW
 
It ain't necessarily so! You have grounded the fan (Which is in parallel with the other fan BTW) and if you now run the system without the separate +12
feed, it should run. The neg of the fan goes to relay 745 before it gets to the controller. THe Controller (But let's call it the speed regulator transistor)
is behind the multiplug into the passengers' side fanbox whrer it is cooled by the fan's airflow. This means removing the fan to get at it so off with the wiper arm and scuttle grille, out with the washer bottle and remove the nut that holds the recirculator flap motor assembly, 'cos you'll need to slide it about to wiggle the fan box out.
Some further tests: From within the car, you have pulled out enough bits to find the circuit board. Two of the connections (There's five of them) obviously run the instrument lights. they are one and two. Three should measure direct to earth. If it doesn't, you've found the problem. if it does then measure the voltage at five whilst you turn the fan control(White disc)
It should read from 0V fully clockwise to somewhere under 10 fully anticlock.
If it does, then one of the wires to the speed regulator transistor, (Number 5, so it will be at one end of the connector) should do the same. If not, busted wiring.
 
tomsheppard said:
It ain't necessarily so! You have grounded the fan (Which is in parallel with the other fan BTW) and if you now run the system without the separate +12
feed, it should run. The neg of the fan goes to relay 745 before it gets to the controller. THe Controller (But let's call it the speed regulator transistor)
is behind the multiplug into the passengers' side fanbox whrer it is cooled by the fan's airflow. This means removing the fan to get at it so off with the wiper arm and scuttle grille, out with the washer bottle and remove the nut that holds the recirculator flap motor assembly, 'cos you'll need to slide it about to wiggle the fan box out.
Some further tests: From within the car, you have pulled out enough bits to find the circuit board. Two of the connections (There's five of them) obviously run the instrument lights. they are one and two. Three should measure direct to earth. If it doesn't, you've found the problem. if it does then measure the voltage at five whilst you turn the fan control(White disc)
It should read from 0V fully clockwise to somewhere under 10 fully anticlock.
If it does, then one of the wires to the speed regulator transistor, (Number 5, so it will be at one end of the connector) should do the same. If not, busted wiring.
Click to expand...

Thanks Tom - you should work for Haynes!! You mean the circuit board on the back of the instrument panel I presume?

Much obliged for the excellent description. Next weekend for this one, maybe the one after, looking at my schedule for 2005!

Cheers

JohnW
 
JohnW said:
Thanks Tom - you should work for Haynes!! You mean the circuit board on the back of the instrument panel I presume?

Much obliged for the excellent description. Next weekend for this one, maybe the one after, looking at my schedule for 2005!

Cheers

JohnW
Click to expand...

Done. That wasn't too hard and it allowed me to vacuum out 10 years of compost. Not a trace of rust anywhere!

That circuit board in the airflow has signs of heat......

Thanks for the advice. All I need is the designation for the transistor now..

Cheers

JohnW
 
PNP3055 is a pretty universal beast that will do but there are other trannies that may be better and more available in Oz.
If you know a tron with a multimeter, get him to test the transistor for you first to ensure that it really is duff.
 
tomsheppard said:
PNP3055 is a pretty universal beast that will do but there are other trannies that may be better and more available in Oz.
If you know a tron with a multimeter, get him to test the transistor for you first to ensure that it really is duff.
Click to expand...

Many thanks Tom - your Sunday morning Citroen "fix" is clearly in progress!

Cheers

John
 
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