Xantia (Mk1) Fan Relay Modification

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The heater blower (and the heated rear window) become intermittent – usually, they can be persuaded to work if the key is jiggled slightly. When the fault first appears, the HRW may sometimes work when the blower is off. The key diagnostic for this problem is that the blower and HRW switch (light) simultaneously show the fault.


In S1 Xantias (with or without A/C), the heater blower motor (no relay) and the Heated Rear Window switch are supplied through a dedicated set of contacts in the ignition switch. These contacts aren’t really man-enough for the start surge of the blower motor (the HRW is powered via a relay with the ignition switch contacts only providing the power to switch on the relay) and eventually burn out. As this set of contacts are on only when the key is in the ‘run’ position, every time the engine is started with the blower switched on, the contacts have to handle two current surges: On, Off in Start position, then back On as soon as the key is released.


The solution is to substitute a relay for the burnt ignition switch contacts and for the relay to be switched by an alternative source. It has to be switched On only when the ignition is in the ‘Run’ (and ‘Aux’) key positions. One suggestion is to 'T' off the white wire that comes from the next set of ignition switch contacts. The trouble is that this is a big fat 50A cable and crimping a 'Scotchlock' splice onto this will seriously damage it. It is much better to take the relay's small operating current from the fuse panel, and Citroen conveniently provide a test socket on the same circuit (the white wire) which takes a standard ¼” spade connector.

  • Torx T20: hex bit with a dumpy driver and an extension. It helps if the bit is magnetised. The one pictured get into lots of awkward spots, lives in the car and cost less than a fiver. A magnetised T20 x100mm makes life easier.
  • A decent ratchet crimper.
  • Wire cutters.
  • Wire stripper.
  • Inspection lamp/torch.


  • 1 x 30A relay with (4 or 5) spade terminals.
  • 2 foot or so each of black (earth) and coloured 5A or 10A automotive cable.
  • 1 x ring crimp terminal (6mm internal diameter) to fit the black wire.
  • 2 x Yellow (30A) crimp receptacles to fit the load terminals on the relay.
  • 2 x crimp receptacles to fit this wire and the switch terminals on the relay.
  • 1x spade terminal to fit the coloured wire - shown crimped on.
  • A couple of small cable ties.
  • Use good quality, shielded, crimp terminals; cheap ones are made of thin brass instead of thicker plated copper and don't crimp reliably nor do the receptacles grip the spades properly. Cheap and nasty (left) and quality one (right).


Disconnect the battery: the negative terminal first and park it where it can't possibly touch the terminal by accident. Then disconnect the positive terminal and isolate that too.

1. Remove the lower trim panel

There is a total of 8 Torx self tappers holding the lower trim in place. 4 inside the fuse panel access flap, 2 on the left side of the steering column, one lurking behind the wash/wipe stalk and finally one holding the floppy felt to the side of the centre console. There is no need to fight with the plastic 'buttons' that attach the floppy felt to the rigid plastic - just remove it all as a single piece:-

  • Start with the difficult two just above the hinge of the fuse panel access flap,
  • The two on the other side of the steering column,
  • One holding the felt to the centre console,
  • One hidden behind the wash/wipe stalk. and finally
  • The top two under the flap.

Then just let the trim flop into the footwell and park the whole thing out of the way in the passenger footwell.

Three high current connectors are now revealed , Brown (nearest camera), Black and Grey – we're only interested in the Brown.

If the battery were still connected, all three connectors would still be 'live'!

2. Cut out the ignition switch

Unplug the inner half ( connected to the ignition switch) of the brown connector

Cut its wires (that go to the ignition switch) as near the ignition switch as possible and at least 3” away from the connector,

DO NOT cut where the side-cutters are pictured.

3. Relay terminals

It's essential to correctly identify the relay terminals. Most relays have a little diagram moulded into, or printed on, the casing. In the diagram at right, 1 is usually from a switch, 2 is earth; 3 is common (usually power in), power out is either 4 or 5. With no voltage on 1, 3 is connected to 4 and 5 is isolated. When the relay is energised by 12V on 1, 3 is connected to 5 and 4 is isolated. A relay with only four terminals has no equivalent to 4, it simply switches ON (3 to 5) and OFF. Other relays will have the terminals numbered differently. Work out and note which connections are 'load' and 'switch' (two for each).

Crimp the pair of yellow receptacles onto the cut wires on the connector plug. Push this pair of connectors onto the load terminals of the relay and put this little assembly (half=connector plus relay) to one side.

4. Coloured 'switch' wire

Crimp the spade terminal to one end as in this photo.


Push the spade connector into the central test point below Fuses 15 and 30.

Feed the other end of the wire wire up beside the fuse panel and behind its brackets to emerge behind and above the bonnet release handle, close to the stud indicated in the photo below.

5. Earth wire.

There's a handy M6 stud (arrowed) between the fuse panel and the steering column – shown at right with the earth wire already fitted (2 lengths of wire to provide a spare).

Crimp the ring terminal onto one end of the black wire and fit it under this (10mm) nut. Decide where the relay is going to go and cut the black (earth) wire to length, but leave some slack. Crimp a receptacle (to fit the relay) onto the other end of the earth wire and push this onto the corresponding relay terminal.

As an alternative, the relay earth wire can be connected to the starter solenoid wire, instead of directly to earth. This then allows the relay to mimic the behaviour of the original switch contacts, removing the load of the the blower and HRW while the engine is cranking.

6. Test the relay.
  • Reconnect the battery.
  • Strip a few mm of the free end of the coloured wire; it should NOT be live – check it with a meter or spare bulb.
  • Turn the ignition switch to the first (Aux) position, the battery light on the instrument panel should light and the coloured cable should now be live – check again.
  • With the relay in your hand, hold the bare end of the coloured wire to its terminal on the relay (there might be a slight spark) and you should feel the relay click On. When you remove the wire from the terminal, the relay should click Off.
  • Turn the ignition switch off and remove the key.
  • Cut the other end of the coloured switch wire to reach its terminal on the relay when the relay is in position,
  • Crimp a receptacle onto the newly cut end of the coloured wire and fit it to the relay.

Now, when the ignition switch is turned to Aux, the relay should be heard/felt to click ON and stay ON in the next (Run) position. Switch off and remove the key.

7. Fit the Relay

Once you have pushed the two halves of the brown connector together, the relay will probably stay in place held by the power wires. Use a couple of cable ties to hold the coloured wire to the black one – one tie (see opposite) close to the earth terminal, the other mid-way to the relay. Set the blower slider to OFF. Turn the ignition to Aux, the blower should now work in all positions and the HRW switch should light when pressed for On. Turn everything off and remove the key. In the unlikely event that the blower and HRW are not now working properly, check back for mistakes or look for a further fault.

8. Refit the lower trim panel

Don't forget the screw behind the ignition switch.