Xantia A/C

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

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white exec
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Re: Xantia A/C

Post by white exec »

Hi Colin,

Parts diagram for your fans...
Motors are shown as 200W each.
The three relays (6, 6 & 7) also on the diagram.
[7 is the 5-pin changeover one; ok to have all three of this type, as already noted]
admiral51's Xantia cooling fans.JPG

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Re: Xantia A/C

Post by admiral51 »

Thanks Chris gives me something to look for before the weekend.
I have changed my plan on the relays, still getting the 5 pin ones but not those i linked to, had a brain freeze moment and realised they have a moulded lug on them for bolting to something, and not sure if there is room for that in the housing so ordered same spec but ones without the moulding :)

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Re: Xantia A/C

Post by admiral51 »

Just a very quick update as it is raining cats and dogs here today :(
I have replaced all 3 relays with new 5 pin ones, however all 3 removed were 5 pin so someone has been there before .
The lower centre ( must be 5 pin ) did have some green corrosion on it and on the contacts of its plug.
I have cleaned this up and whilst before the RH fan would lag behind the LH fan and at times not keep full speed they both now go full chat in sync.
However neither fan runs at slow speed, there is a 2-3 second delay when removing the stat plug before they both go full chat.
In my head i have crossed off the fans being at fault and the contacts are clean and new relays so that leaves what ??

Are there separate fuses for high and slow speed, i keep looking back at old posts and diagrams and maybe i am getting confused by them.
The fans should be able to keep running on slow even with ignition off so as they work on high what am i missing ?

Due to the location of the Stat plug i have yet to do this with the engine running just an idle thought maybe i should do the bridge trick on the HP/LP switch to see if they start on slow then fast ?

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Re: Xantia A/C

Post by admiral51 »

Okay had time to think, i really need to work out what fuse powers the slow speed fan set up, and the wire that goes to the relay as i think that is my problem, not the fans/relays but power to set them on slow.
It may take a few weeks for me to be able to strip the front of the car ( easter lol ) but just trying to understand the power feed

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Re: Xantia A/C

Post by white exec »

These should be the circuits, fusing etc included...
Xan 2.0HDi cooling RHZ_Page1.jpg
Xan 2.0HDi cooling RHZ_Page2.jpg
Xan 2.0HDi cooling RHZ_Page3.jpg

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Re: Xantia A/C

Post by xantia_v6 »

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.

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Re: Xantia A/C

Post by admiral51 »

Thanks Chris will print them off at work tomorrow in big print so i can see it properly:)

Mike i see the logic, by unplugging the sensor it should throw them into fast mode as by default if the temp is at the level or A/C is on then both fans should be on slow speed already ??

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Re: Xantia A/C

Post by white exec »

Agreed: unplugging = fast.
Reconnecting the sensor might leave the fans running fast, but turning IGN on then off resets everything (on the XM here, at any rate).

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Re: Xantia A/C

Post by admiral51 »

Okay i just had to try something just cos it was bugging me :)
Now i have proved both fans run at full chat when blue stat plug is unplugged with no slow speed
When trying before to do the bridge trick engine running with the A/C HP/LP switch i could get RH fan full chat nothing from LH and not a murmour from the A/C compressor when bridging those 2 pins.
Now when doing the same bridge trick i still get RH fan full chat and nothing from the LH fan but when bridging the A/C clutch pins i get an audible click from the compressor.
Confussed well yes and no lol
I think i will have to remove the fan housing to get good access to the relay sockets and wiring as i think this is where the problem lies, a connection good enough to tell the ECU everything is ok but not a good enough connection to provide the power to get things running.
And yes after doing the bridge trick with the above results, i removed the blue stat plug ( engine off ignition on as before ) and both fans go full chat :)
Colin

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Re: Xantia A/C

Post by xantia_v6 »

Do you have a current meter that is capable of handling about 20A ?
If so, can you measure the current through each of the fuses in BMF2 with the fans running at high speed? There is one fuse for each fan motor.
Does it look like someone has previously played with the wiring (especially behind the relays)?

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Re: Xantia A/C

Post by white exec »

Have spent a little while looking in detail at that Xantia cooling fan circuit above, and it seems to contain something interesting.

Traditionally, twin fans, with their associated three relays, have received one of two +12v (or Gnd) commands to operate the fans:
- Go Slow . . . fans in series
- Go Fast . . . fans in parallel
This was done by a +12v (or Gnd) signal from either a thermo-switch (early cars) or a Water Temperature Control Unit (WTCU) (later cars). In both cases, only one control line operated (+12v or Gnd) at a time.

The Xantia circuit above, it seems, is subtly different.
Twin fans, three relays and a WTCU still, but . . .

Slow speed is achieved by line 1550 on the WTCU (#1320) going to Gnd. This switches on relays #1503 and #1504, putting the fans in series.

Fast speed is achieved by both lines 1540 & 1550 going to Gnd together, putting the fans in parallel. So, two command lines in operation together.

Interestingly, if line 1540 were Gnd'd on its own, the LH fan (#1512) would remain Off, but the RH fan (#1511) would operate a Full speed. In practice, this might well never be an operational condition, but could, I suppose, occur as a fault.

We've been used to understanding that twin fans will always operate simultaneously and indentically, either Fast or Slow. This last (maybe oddball) condition throws up something else.
____________

I'll post some annotated versions of the above circuit in the next day or so, to illustrate current flow for the Slow and Fast conditions, and the Oddball one too.

Perhaps others might look at the circuit too, if in lockdown at home #-o.

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Re: Xantia A/C

Post by white exec »

This is the same circuit, annotated to show how the two fan speeds operate . . .
Cooling - Fans Slow v1.jpg
Cooling - Fans Fast v1.jpg
And, just out of interest, the oddball case where one of the control lines (1550) fails to go to Ground...
Cooling - Fans Oddball-fault-state.jpg

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Re: Xantia A/C

Post by admiral51 »

xantia_v6 wrote:
15 Mar 2020, 21:34
Do you have a current meter that is capable of handling about 20A ?
If so, can you measure the current through each of the fuses in BMF2 with the fans running at high speed? There is one fuse for each fan motor.
Does it look like someone has previously played with the wiring (especially behind the relays)?
Not yet but it should be winging its way to me via Amazon some time this week :)

No i idea on the wiring but my guess is now looking at the diagrams posted by Chris that i really need to find and fix the slow speed issue before i go any further.

Thank you both for all the input, i would be reaching for the sledge hammer without both your help.
Colin

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Re: Xantia A/C

Post by admiral51 »

Having re read the wiring diagrams Chris has posted, particularly the OddBall one this may have got lost, although i think you both had an input into the thread at the time.
The link is back on page 3 of this thread just after they got merged, but i will copy and paste this from it as DickieG had both fans running at slow but only RH on full unless he pulled the Blue stat plug :)

"Post by DickieG » Sun Jul 04, 2010 5:28 pm

The mystery is now solved :D
thorter wrote:
Thanks for your reply, the way I've been testing the fans speed is by using an actuator test with my Lexia, if its confirmed that both fans on a HDi should run at high speed together I'm tempted to work around the "problem" by way of using a fourth relay
Perhaps the Lexia only sets or clears the discrete output for each relay separately. That would make sense for diagnostics. So the fans may well work in tandem in the real situation that the water temperature is over 107C or whatever.

Fred
You were right there Fred, well done :D instead of using my Lexia to trigger the fans at high speed I removed the blue connector form the sensor on the thermostat housing and both fans operated at high speed together :lol: so after a weekend of dismantling the car and head scratching it was working correctly all the time :roll: Doh!

Thanks for your help and suggestions chaps, I've now learned something extra about Lexia actuations :evil:"

Maybe the OddBall is not so OddBall just owners do not realise it :)


Just to keep things together as the link to the above quote was a link within a link so it can be found Here starts half way down page 2 and continues onto page 3

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Re: Xantia A/C

Post by white exec »

Well done in digging out that previous report - and from 10 years ago!

As well as Lexia actuator tests on the relays/speeds, there is the possibility of testing fan operation by good old-fashioned means:

1: Make a ground connection* to line 1550, which should bring on Low speed (both fans)
2: Add a ground connection to line 1540, which should then bring on High speed (both fans)
3: And, for good measure, try grounding just 1540, which should run RH fan only, at High speed

* Grounding could be achieved by piercing the insulation with a needle, and grounding that. Grounding should not damage the control unit.

IGN on (or engine running) needed for these tests.