Xantia A/C

Post your Cit/Peu/Ren air conditioning queries or advice.

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admiral51
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Re: Xantia A/C

Post by admiral51 »

Okay i have had a little play and ended up feeling like i wish i had not bothered and then came in doors and thought about it.
Sorry if i am going to say stuff i already have but...........
Just for clarity so when i read this back i understand it L/H and R/H fans are from looking at them from the front of the car :)
The R/H fans appears to be a little weak, whilst the L/H fan spins up the R/H needs a little nudge to start, after that it spins up the same as the R/H with the Blue stat plug removed, tried it 6 or 7 times and once after the first nudge it no longer needs any help to spin up, they both go full pelt.
However both fans will only spin at full speed, tried the bridge trick on the dryer/receiver and both full speed.
So Relays are working, power is getting to them the issue now is why no slow speed.
And then i remembered the following, i even replied but missed the point totally #-o #-o
xantia_v6 wrote:
15 Mar 2020, 19:05
To get the low speed fans to operate at low speed, you need to get the engine to the correct temperature, or turn the A/C on, I don't think that you can trigger low speed by unplugging sensors.
So yes i can get them to run at full speed but i need to get them to run at slow speed, so maybe 2 ways of doing it ?
1. Have the A/C on
2. Get it upto temp to trigger it.

1. A/C does not work need,to get it regassed/pressure checked but need fans working to make sure the the compressor engages ?
2. Bit late for a sunny Sunday afternoon to sit and rev the nuts out of it, HDI never gets above 80 ish even on a long drive :)

So off to work tomorrow morning early and going to sit in the empty car park and see if i can get the temp up a bit over 90 :-D

So as for the STOP and Over temp light flashing when interior blower is set to demist, now i have changed the 3 relays and cleaned up contacts what was an intermittent issue i can recreate it at will by putting blower on and set to demist, move setting to anything but demist it goes away,move it back to demist and within 10 secs it starts flashing again.

My apologies and thanks in equal measures to everyone who has helped me get this far, fingers crossed i was chasing a fault that never existed, knowing my luck it wont be that simple but...... :rofl2:

Colin

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white exec
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Re: Xantia A/C

Post by white exec »

Hi Colin,

LH & RH is always (for all parts) as seen from the driver's seat.

You've done the Fast speed test, so that's ok.

In Fast speed, the two fans are in parallel, so even if one of then was duff (open circuit), the other one will work, full speed.
If one fan is 'weak' (stiff, or stuck/worn brushes)
- (a) the other will work
- (b) the full 12v applied to it might well overcome stiffness (or poor bush contact) and get it going, fast.

Now, Slow speed...

Here, the fans are in series, and
1 - both have to be in decent condition, as the current flows though each in turn + •—FAN→FAN—• – .
2 - the voltage across each fan is only half the normal 12v (so they run at slower speed), and for that reason a stiff or lazy fan might (i) not turn at all, but allow the other one to function, or (ii) might not turn at all, and prevent the other one from operating.
For Slow speed, BOTH fans must be in decent working condition.

To trigger Slow speed...
Cooling - Fans Slow v1.jpg
...power up Relay #1502 by Grounding its pin 2 (the 1550 line from the ECU)
Do this by applying +12 to relay pin 1, and Gnd to pin 2.
This will turn the relay on, and should make the fans run at Slow speed.
Note - You can do this with IGN OFF, and with the double relay #1304 unplugged, if you wish.

Try that, when you can, and fill in the usual Report. :wink:
If you do have a lazy fan, you might have to nudge it for it and the other one to work.

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Re: Xantia A/C

Post by admiral51 »

Thanks for the support Chris, report in about 6 weeks ;)
It was a good few years back i remember doing the bridge trick/unplug the stat plug and both fans went slow then fast, that is what my knoweldge is based on.
Looking at what Mike says being ECU not WTCU (Bitron) controlled i have to atleast get it up to temp to prove/disprove it.
Have left the cover panel removed as its easier to give the fan a flick if needed lol

Colin

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Re: Xantia A/C

Post by white exec »

The test described above (unplug double relay, and power up the relay) doesn't require the engine to be run, nor got up to temperature. Could help.
Have re-labelled the circuit diagram in two places: WTCU now also labelled Injection ECU, and the RH fan properly labelled (there were two LH ones! #-o).

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Re: Xantia A/C

Post by admiral51 »

Chris you have been awesome in all your help, as has everyone else ( please forgive for not naming you all, my age i think ) but i along with everyone else called the WTCU as the Bitron so please do not think i was picking at your diagrams, maybe if i could understand them i may,just may,have queried it but =D> =D> :)

Colin

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Re: Xantia A/C

Post by xantia_v6 »

The Engine ECU and A/C ECU have no means of knowing that the fans are not running at low speed, so lack of fans does not stop the A/C clutch form engaging. On the other hand, if the engine ECU has a stored fault code relating to a previous fault (such as overheating), it may decide that the A/C clutch should not engage (although I doubt that the Xantia ECU is that clever).

admiral51
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Re: Xantia A/C

Post by admiral51 »

Okay so tried my best this morning high revs in 3rd and 4th gear along the dual carriageway for 15 mins and this blinking car will not go much above 80 ish on the gauge, got to work a short 8 minute drive off the dual carriageway and the gauge is quite happy sitting at just a tad over 80, 10 mins spent sat revving and maybe a couple of degrees higher, i even drove with blower off and heater set to cold for the whole journey.
What do i need to do to get this cracking engineering master piece to get hot, it just laughs at me saying go on then try some more :(

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Re: Xantia A/C

Post by white exec »

Thermostat up for replacement? Or have we been there before?
Getting a diesel to run extra-hot by normal driving can be a chore (they are very frugal on fuel), and fast driving can just ram cold air through the radiator, and so be completely self-defeating.
If you want to do a fast drive test, blank off the radiator with a sheet of cardboard in front of it, but keep an eye on that gauge!
Just leaving the engine to idle - maybe for 45 mins or so - should bring the fans on Slow, eventually.

Check the actual water temp with an infra-red thermometer pointed at the water-outlet/thermostat housing, preferably at something black (bit of black tape or marker pen, if nec.).

Take it you've given up on switching on the fans on Slow speed by powering up the relay.

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Re: Xantia A/C

Post by admiral51 »

Not given up Chris just time ran out and i had to go back to work so thought i would try to get it hot.
Within 1 mile it is getting warm air from the heater, 2 miles i get nice toasty heater and temp gauge does not move, give it 5 miles miles and i get close to roasty heater and it creeps upto 60 after 10 miles it just sits at 80 laughing at me, been like that since i had the car, summer winter whatever the outside temp it never gets above 80 unless i rag it but never seen it get even close to 90 :)

admiral51
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Re: Xantia A/C

Post by admiral51 »

And just for posterity update was less than 6 weeks :)

Think i need to 1 of 2 things
A .upset the neighbours this easter weekend and use the alternator to charge the battery whilst having some cardboard covering the rad
B. do the relay grounding test.

Or do both and see what happens :rofl2:

Colin
Last edited by admiral51 on 06 Apr 2020, 21:44, edited 1 time in total.

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Re: Xantia A/C

Post by xantia_v6 »

I think that it may be time to take a different tack, and try to get the A/C compressor to engage (at least for test purposes). I have not re-read all of this topic, but I don't think we have discussed the state of the A/C system in any detail (or if we have, a new summary would be useful).

Is the A/C pressure switch open or closed? If open (lack of pressure), does anything happen if you bridge the contacts?

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Re: Xantia A/C

Post by admiral51 »

Quick Summary of the A/C system and what has been done.
No engagement from the compressor when doing the dryer bridge trick but both fans ran full speed with the L/H needing a little nudge bridging those pins.
Replaced all 3 relays,cleaned contacts etc and whilst L/H fan is still weak once nudged it spins up full speed every time afterwards, R/H fan spins up full speed no issue.
Once all relays had been replaced i did get a click from the compressor doing the bridge trick with engine running, not tried it again but i did get a click 3 times in a row whilst testing but only a second, as soon as i heard the click i removed the bridge.
Normal circumstances i would get the A/C regassed but i need the fans to operate ( maybe i am missing something ) to complete the circuit, no gas in A/C (LP) will not engage A/C regardless if fans are working or not.
Colin

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Re: Xantia A/C

Post by admiral51 »

Okay so i kinda left this issue to one side as i have been using the C5 as the wife has been unable to work due to covid 19 and it needed a good run :)
This morning i decided to give the old girl a clean out, check fluid levels etc etc and do some serious Citroebics and i thought i would take the time to see if i could actually get the car up to temp to get the fans to come on at slow speed.
Now just to recap with the Blue stat plug i had never removed it with the engine running before, only with ignition on and this i think is important as is the fact that with engine running and blower on and setting at demist no fans working, or with blower on and A/C button switched on, no fans working.
The following has confused me totally lol
With engine running whilst doing Citrobics i managed to remove the Blue Stat plug and both fans spun up at full speed, plugged back in and a few moments later they stopped as they should, did it another 3 times and the same result, full chat and then stopped.
Managed to get the temp up to just over 93 ish and still no fans running so thought i would put blower on full chat on cold to add some load to the engine, went to front of the car and both fans were spinning at slow speed result, they both work and doing what they should or so i thought.
I had a brain wave and thought maybe it was the blower that put them on so i switched the blower off and fans stopped within 40 secs but the temp had dropped so no better off apart from fans both work.
With blower off i got temp back to 93 ish and no movement from fans, a little reluctant to keep going as i had it in my head it should be 95+ before fans kick in so put blower on and hey presto both fans kicked in on slow, blower off fans stopped and temp was still 92+.
And then i realised i had pushed the A/C button in so decided to do some tests lol
Engine running, blower on A/C off no fans, blower on A/C on both fans running at slow.
Engine running A/C off and blower on set to floor no fans, switch setting to demist and fans spinning at slow :)
The only thing i can think is that by removing the Blue Stat plug with the engine running has somehow reset/cleared any issues within the A/C + Ignition ECU's as i have previously changed all 3 relays and got nothing from the fans at slow speed, even with A/C on and blower on nothing, not until i removed the Stat plug with engine running.
Over to you guys to explain it all, as i think next step is going to be an aircon regass, do not want to play about with it now that the fans appear to be working as intended lol

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Re: Xantia A/C

Post by white exec »

admiral51 wrote:
25 May 2020, 14:57
And then i realised i had pushed the A/C button in so decided to do some tests lol
Engine running, blower on A/C off no fans, blower on A/C on both fans running at slow.
Engine running A/C off and blower on set to floor no fans, switch setting to demist and fans spinning at slow :)
That ↑, so far as I recall from some of Marc's posts, is the correct operation:
- AC, when switched on, brings on fans at slow speed
- Demist screen, when activated, brings on AC, which brings on fans at slow speed

Pulling the temp sensor (engine running) will put both fans on full speed, and switch them off when re-connected.
That's how it should work, too.

admiral51
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Re: Xantia A/C

Post by admiral51 »

Yes Chris that is what i understood, however the temp sensor pulled with ignition on does the same, it was only after doing it with the engine running that i now have fans running as they should, it never did so before, french cars hey :)