Darned Xsara Blower (+a/c and recirc) still does not work

[mpdevice]

Another look at the blower tonight in total darkness. We originally assumed the ignition lock as the problem and so did I because it appeared the blower once came to life after moving the key. Anyway, took the lock switch to bits, cleaned it, re-assembled it and blower never worked since. BUT:
Measured the switch (when disconnected from remaining harness: Does what it says on the circuit.

Bad symptoms: Blower dead on any climate control setting.
Recirculation flap dead and does not respond to switches
A/C compressor does not cut in upon switch press.

Good symptoms: Ignition key lock appears to work as mentioned.
All supply voltages as per the wiring diagram: attached (I hope it is more or less the correct one) are present on the fuses F14,12,2,21,5 which are not blown.
Blower Relay 8048 works so:
Supply volts to blower 8045 speed control module present between pin 4,2 so ext. blower relay 8048 OK
Brushes to motor look good, no traces of shorts, overheating etc.
passenger compartment air temperature fan sensor runs.

Questionable symptoms: 13.8V on speed control input on blower speed module pin 3 regardless of setting of the speed on the dial. That must be wrong. Looks like something is pulling it up to supply. 0.8V or so on blower thermistor to ECU pin1. Maybe OK.

The circuit diagram that I have found on the net (not quite sure if it's correct) does not appear to show the recirculation flap motor, and 8065 I believe must be the hot cold control flap.
So it appears that a whole supply rail has somehow failed and perhaps the a/c or climate control ECU is down, too (but the temp sensor fan works so I doubt that as it seems to be supplied throught he ECU).
So I will test the blower assy on the bench when I have some time and I fully expect it to work.
So, to work myself forward has anybody got a CCT with the recirculation flap motor on it? That might show me which rail is down. The pressostat for the a/c, is it shown in resting position i.e. aircon off?
I suppose the ECU then turns the blower on a few seconds after the engine is running?
This is becoming more mysterious each time I look at it.

(This is a T-reg Xsara non Picasso with a/c and climate control.)

[Peter.N.]

The usual problems with the XM were failure of the 30A under bonnet fuse holder, failure of the connecter to the blower or the usual transistor problem, on the only occaision I had that it wasn't any of those it was a fault on the control panel so I just fitted another secondhand one and it was fine. If you short the control lead to earth and it works, that will be the problem.

Peter

[cc101]

I had similar problems with our other car (xsara Picasso) I topped up the ac and hey presto it sprung into life. The system was so low on refrigerant the pressure sensor cut the compressor etc. Once refilled everything worked fine. I bought the top up from halfords, with the trade card was about 17 quid.

[mpdevice]

Well, I took the blower to work and ran it on the bench. All seems fine. Back in the car-nothing. I cut the orange wire (control) and when engine runs and the wire is grounded on the fan end the Fan ECU relay cuts in and the fan runs merrily at full speed as expected.
[BEWARE of a circuit that goes around showing the Blower ECU. This circuit is not quite correct and the relay of course switches ON when the control line is at ground potential and not the other way around. Also some of the transistors are shown incorrectly but thanks anyway to the guy who tried to figure it out - must have been a pain to get this far with SMD semis. When the relay is ON the transistors are bridged to avoid excess transistor power dissipation which would be very high because of the current.]

Well as before I am not much the wiser, all power lines are OK, all fuses, blower relay, ignition switch, too, but the recirc flap motor, compressor activation and blower of course still don't work. While all is connected I have 12 V on the orange control line which of course turns the fan OFF.

So I will have a look at the pressostat as mentioned, that is one of the last ideas. I might just link the connections. But I would think the design is rather poor if the blower doesn't work just because the a/c gas is low! Colleague has a Peugeot 306 and I am sure the the circuit is more or less the same and his a/c is dead for years and the blower works happily. I am sure people would really moan (especially here) if low gas means blower off from then on.

Guess I will have to go to Citroen and beg them for a copy of the relevant circuit that shows the recirculation flap motor as well.
Anybody knows where to find the climate control ECU?

Thanks to all so far, M

[Clogzz]

The pressure switch cannot affect the blower.
It can only prevent the compressor from starting.

[Mandrake]

Guess I will have to go to Citroen and beg them for a copy of the relevant circuit that shows the recirculation flap motor as well.
Anybody knows where to find the climate control ECU?

Send me your VIN number by PM and I should be able to send you a PDF copy of the correct version of the relevant diagrams for your car.

By the way I assume you don't have a Lexia, but if there is a forum member near you with a Lexia it could help immensely to troubleshoot this problem - if you get no dialogue with the ECU you know you either have a power or ECU problem, if you can get a dialogue you can get readings from all the sensors and controls, and manually operate the fan, temperature flap and air con clutch via the ECU to confirm their operation.

One other suggestion is that if its the same as the system in the Xantia, the climate control ECU has a connection to the alternator exciter wire (the same one that powers the charge light on the dashboard) and if it thinks the alternator is not charging (exciter wire voltage is low) it will not enable A/C, the blower fan, nor will it move the temperature flap motor, so it will appear almost dead, but you would still get a Lexia dialogue with it.

[mpdevice]

Thank you Simon, I will have a look for this wire on the CCT and hot wire it if necessary. No warning lamp regards battery comes on, though. I have been to my local Citroen and begged them for a copy of the correct CCT - which I now have ! Hurrah! Anyway, I am actually not much the wiser, I have been pulling plugs, buzzing and measuring all over the place. I also hot wired the pressostat with no effect to the problem.
The ECU has powers on all the lines where one would expect to see it, it also has ground. The recirculation flap motor and the a/c compressor are both switched by the ECU, so is the blower control line. So the only thing left now appears the ECU or perhaps the control pane but I doubt that. I opened the a/c ECU to look for smoke signs but it looked good apart from some minor corrosion on the connector soldering which I have brushed away. Some SMD capacitors look a bit odd though but are not shorted. Guess I got to find another ECU to try or talk to our LEXIA man!
Thanks to all!

[mpdevice]

Resoldered all conenctor joints and otehrs that looked suspicious on the a/c ECU today. Plugged it back in, still does not work. Guess I'm getting nowhere.

[Peter.N.]

It was the panel that failed on my XM, I was a TV engineer for 50 years but I don't think I would try and repair one.

Peter

[mpdevice]

Possible, Peter but I believe there is not much more than a few pots on there and the two switches (see CCT). So the likelihood that one small fault on the panel brings down the whole ECU is a bit low IMHO.
I have no real idea how to get to the panel - I have no decent repair manual. Looks like the whole fascia needs to come off.
First I'd like to see if I can talk to the ECU.
M

[Peter.N.]

Mine just had no control voltage so I just changed the board. There were plenty of secondhand ones about then. Mine came out quite easily but don't know about the Xsara I'm afraid.

Peter

[mpdevice]

Well, I measured on the ECU circuit board in the darkness this evening and I got as far as knowing that some of the ICs don't have any proper supply voltages, e.g. the micro. The 12-14 V makes it in past the protection devices , diodes onto the board. So far so good, then I get lost not having a circuit. I can't spot any clear voltage regulator on the board but some SOT-23 device may do that but that's just guesswork with the SMD codes. The motor driver bridge chips run on full rail anyway I would have thought. But Opamps on less than 2V that's not right!

[Peter.N.]

With TVs we used to change the suspect chip first - but it usually some peripheral component that was the problem but you needed a decent circuit diagram to find it and a lot of patience. I'm pleased I am retired - not that there's no job to go to now anyway.

Peter

[mpdevice]

I'm sure you are, although this ECU is full SMT it is just two layers. Heck knows where it gets the 5V from, I will have a closer look in the lab tmw.
M