Xantia coolant fans

[atr]

Hi
Its the Xantia again! I've noticed that the temp gauge needle is rising above the horizontal - 90deg - to about the 100deg mark. when I turn on the A/C, it stays on the 90deg mark. my assumption is that since in A/C on mode both radiator fans are working it causes the temp to stay on it's normal point. I guess that when the A/C is off, the second fan doesn't kicks in or kicks in too late. my question is - is it possible that the heat sensor that operates the second fan is faulty? if so, please let me know where it's located. one more thing, if I will jump/short
the sensor terminals, would that cause the fan to work constantly? let me make it clear - the other fan (the "low temp" fan is working fine).
Thanx.

[xantia_v6]

On a Xantia with a/c, both fans should always run together, both off, both slow or both fast. If only one is running, then either a fan motor, fuse, relay or wiring are faulty.

Having said that, 100 degrees is probably correct in warm weather with a/c off. With the a/c on the radiator is typically over-cooled in the UK climate.

[atr]

Hi
Maybe I didn't explained myself good enough. when the A/C is on - both motors are running, so there is no doubt that both motors are in working order. the problem is that without A/C on - only one motor is running (after the coolant had reached a certain temperature)/ when I turn on the vehicle at morning, no one of the fans is working, whet the temperature rises - one motor (I guess it's the low temp fan motor) is starting to run while the other one is still. when the coolant temp rises more - the other (the high temp) should start running and it doesn't, at least not always. so, my guess is that the problem might be a lack of command from the temp sensor because I think that if the problem would've been in the motor/fuse/relay, it wouldn't run at all.

[xantia_v6]

There is no low temperature fan and no high temperature fan. Both fans always run at the same time.

You must have a fault in the wiring or relays, or it could still be a stiff bearing in a fan motor.

[white exec]

There will be a group of three relays, up front in the engine bay.
These control the two fan motors, putting them in series (slow speed) or parallel (full speed).
The three relays are inter-connected, and receive two supplies: go slow speed, or go fast speed.
If any of the external or internal contacts for these relays are oxidised/dirty, the system will work erratically.

Remove the three relays, and clean them up - preferably internally as well.

Beyond that, an engine (coolant) temperature sensor (there are 2 or 3 of these, one of which controls the cooling fans), which may have become faulty, and need replacing.

As Mike says, the fans always work as a pair - never singly - unless thee is a fan/relay/wiring fault.

[atr]

Hi
Thanx for your replies. I guess that I was misinformed. I will check the relays.

[xantia_v6]

BTW, you should read this: https://www.frenchcarforum.co.uk/forum/ ... 22&t=31403

[atr]

Xantia V6 - Thanx. the content of the link is awesome!

[atr]

Hi
Looking into the wiring diagram (courtesy of Xantia V6) I've seen that there is a "cooling fan control unit".
anyone remembers where it is located?
Thanx for your help & tolerance.

[xantia_v6]

It is commonly called the "Bitron" on a Xantia and is located under the LH headlight, and rather difficult to access. You should be able to see the connector between the headlight and radiator.

Search this site for Bitron to get more information.

[atr]

Is there a way to determine whether it functions right? from what I've seen on the wiring diagram, I guess that my problem is that the low speed doesn't work at all and when the coolant reaches the point that the system has to change from low speed (series connection of the fan motors) to the high speed state (motors connected in parallel) only one (the left motor, according to the picture) works at full speed. now, since I know that the right motor works as well when the A/C is on, I guess that the problem might be with the relays or the bitron, as you call it.

[Clogzz]

From what I remember that’s a faulty top right relay or socket.

Fan_relay.jpg (16.44 KiB) Viewed 368 times

[white exec]

To start with, just pull all three relays (one at a time, just in case they're not identical*) and inspect the base contacts for dirt, damage or corrosion, as well as the relay sockets. Are those pix above of atr's car?
The relays are handling considerable current, and a poor contact can cause burning of the contact and/or melting of insulation etc. All three relays must function properly for the two fans to work correctly at the two speeds.

* Usually all are the same: 5-pin, with the same numbered pins. Standard automotive type, 12v 30/40A, single pole changeover (SPCO). Obtainable from any motor factor or electronics supplier.

[Clogzz]

Are those pix above of atr's car ?

No, they're from my bucket ... photobucket.com/Clogzz ... over 10 years old.

Swapping the top left relay to the right should indicate where the fault is.
The top right relay does the low speed for both fans, and a missing top left relay will only cause one fan to stay still when the other one spins at high speed.
So … the low speed should work even with the top left relay taken out.
Only the lower centre relay needs 5 pins, the two top ones get by with 4 pins.

[white exec]

It's common for all three of these relays to have all five pins, although for this application - as you say - only one of the relays has a 'changeover' function, so using all five pins. (The relay sockets/loom will be wired 4-pin/5-pin as necessary.) This normally allows the same type of relay (SPCO 5-pin) to be used in all three locations.

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On an different tack, an identical triple-relay (series-parallel) arrangement can be used - on a DIY basis - to create a Dim Dip headlight system, putting the two dip beam (halogen filament) bulbs in series for Dim, and in parallel for normal Bright. This sidesteps the need for voltage droppers or hot-running series resistances.