Citroen XM Forum

And the High Coolant Temp warning light/message on the dash is switched on by its own thermal sensor on the engine, completely independent of the fans. Low road and engine speed (eg your 20mph), without fans working correctly, will cause coolant temp to rise - water pump probably working gently under these conditions, too.

If the three relays are working ok, and have clean contacts, and both fan motors are operational, then the system should work correctly.

Road test done with right results. With replaced fuse and engine warm (one fan on) I switch AC and second fan join the first one. First slowly and then booth start with full speed. Engine off and fans stays on for 30-60 seconds so everything seems to be ok now.
Didn't get any warning about coolant but for further issue/investigation can you tell me where that sensor is located (maybe some photos)?
Many thanks.

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Interesting, and good that you have rotation from both fans, but that isn't right.
With twin fans, the two of them should always work together and identically, not separately.

There are just three modes of operation:
- both off
- both running at Lo speed
This is triggered either by AC being turned on, or by a moderate rise in coolant temperature
- both running at Hi speed
This last is triggered solely by coolant hitting the higher specified temperature.

The two fans are connected via 3 relays, connected together.
The relays have just two (cable) inputs:
- "Run at Lo speed"
- "Run at Hi speed"
The first of these puts the two fans in series, for Lo speed
The second puts them in parallel, for Hi speed
The two command connections (inputs) come from the temperature control ECU.

It is possible to test these two command connections, and the correct operation of the relays.
I will post the circuit diagam of these shortly for you, with details of how to test.
It is not difficult to do.
>>> EDIT: See post below, with link to Ebaman pages.

Maybe it was just coincidence. After that they both working at same speed. I'm always happy to get more information about xm and how it works so please fell free to pass some more details.

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OK, that's good.
If you did observe the two fans working at different speeds/times, it could have been either your 'new' fan settling in (doubtful), or maybe a less-than-perfect connection somewhere (maybe relays) which has sorted itself.

To save me posting details again, you could just download a pretty-full XM manual from here:

Either go to [url]http://.ebaman.com[/url]
then Register
go to Files Area (tab at top)
Motor
Citroen
XM
Workshop Manual
Series 2
Mechanical part (download parts 1 to 8 separately, or whole work in one large file).

Or http://ebaman.com/index.php/remository/ ... op-manual/
- but you'll need to register (on the homepage) first.

Each section of the Manual begins with a list of models/engines/RP numbers applicable/etc.
Not all pages are present, but it's pretty good for S2 2.5, although not completely.

For 2.5 Cooling, look at pages:
230-00/4 - DK5 Cooling Circuit (sensors, fan cut-in temperatures, etc)
644-2/10c - Electrical circuit diagram for engine cooling and AC for RHD 2.5

Hope helpful. Could keep your printer busy!

Where is the fuse located for the cooling fans?

They are 40 amp fuses in individual holders clipped to the front of the under-bonnet fuse box. One does the RH fan at high speed and both fans at low speed, the other does the LH fan at high speed, so either fuse blowing does not totally prevent cooling.

Useful. So now the joys of finding out first access, then solution?