xantia cooling fan

[Clogzz]

Strange indeed to have aircon and radiator switch at the same time.
Looking at Haynes ‘turbo diesel cooling system’.
With the ignition on, pins 1 of all 3 relays must have 12 Volts on them, lighting the lamp bright and strong.
If it’s missing from the so-called ‘low speed’ relay, you’ve got DaveW’s fault.

[f00lzz]

Once I had managed to remove both the fans, It was relatively easy to access the necessary wiring and I also found the elusive Bitron Unit

[suzie]

once again guys thanks for all your help,and here is today's update!yes,i can confirm that the car has aircon and a radiator switch just below the top hose,haven't had the car long so i don't know if anyone's modified it.on the thermostat housing there are two sensors,both blue.the l/h one (looking from front of car)has two wires,one brown and one green.the r/h one has one wire,it's green.i can confirm that with the ignition on pins one on all relays are live.when a temporary earth cable is touched on pin two of the r/h relay,both fans start on slow speed!so maybe we're getting somewhere!but the fans stay on even if i remove the key so that's no good.what does this mean?help!!!

[DaveW]

Suzie.

Have you checked the earth connections on the plate attached to the inner wing by the battery. You will have to take the battery out (check you have the radio code) to get to them. The earth for the fans is on the right (as you look at the plate) above the two at the bottom right. If any look even slightly corroded unscrew and clean.

I have just checked back and it seems I gave you some dud information.
For some reason I typed in that pin 3 of the radiator switch socket should be earth. That is incorrect. Pin 1 is the earth and I think that is what you found. Apologies for that I must have been thinking about bridging pins 1 & 3 and suffered temporary brain paralysis.

So with everything back as it was at the start, with the ignition off, socket pin 1 should be earth and pin 3 should show 12V.
With the ignition on , pin 2 should also show 12V.

Dave.

[Clogzz]

f00lzz,

Hope this is a joke. Or did you have a stack ?




Suzie,

It looks like you have a faulty radiator switch, that doesn’t earth pin 3 of the switch at about 90ºC to turn on the fans at the low speed.
Your temporary earth wire does what the switch should do.
Pin 2 of the switch earths when the temperature reaches about 100ºC, but since pin 3 isn’t working, only the other fan comes on at the high speed.
For both fans to work at the high speed, both pins 2 and 3 have to be put to earth.
The post by Tom in this BX thread explains it:

http://www.bxclub.co.uk/forum/viewtopic.php?p=6857

Once you have determined that the switch is faulty, get a new one from a parts merchant.
It’s no use getting an old one from a wreck.
As per Tom’s post, they deteriorate over time, and pack up at the sight of a spanner.

[suzie]

hello everyone,think we may have found a possible cause.on the rad switch socket hole 1 is earth,hole 2 becomes live with ignition on,but there is no live on hole 3.am i right in thinking that this should be live?is there any way of livening hole3 up by running a new cable?would we run the new live cable into one of the relay sockets or directly into the fan switch socket?we'll replace the rad switch as well later.thanks.

[f00lzz]

f00lzz,

Hope this is a joke. Or did you have a stack ?

Sorry couldn't resist it... it was prompted by your pic of the Xantia with the front off displaying the Bitron unit.

[suzie]

hello everybody.we replaced the rad switch this afternoon,unfortunately it didn't work.we also removed the battery and cleaned all the earth connections on the plate.still no luck.we suspect strongly that the fault must be in not having a live to pin 3 on the radiator socket.how can we make this live?all the fuses and relays are okay so what supplies it?it seems like we may never get to the bottom of this problem,if i drive the car with just one fan working will i do any damage,or will one fan cool it down enough?your help so far has been great,thanks.

[DaveW]

Suzie,

You are in exactly the same position I was.
If you go back to my second post, you will see that I suggested you try running a wire from the battery + to pin 1 of the right hand relay (viewed from front of car).

Did you try that ?
You can spread the the strands flat and slip them into the socket and then gently push the relay in.

If you then short the rad socket (1 & 3) - with the ignition off - both fans should run at slow speed if your problem is only no volts (or low volts) to that relay's coil.

[Clogzz]

Sorry couldn't resist it...

Very good joke, nothing to be sorry about.
From seeing your avatar, I thought it could be your silvery car.
But enlarging your avatar shows that it is the mythical Xantia 2-door coupé.

I can confirm that with the ignition on pins one on all relays are live.
When a temporary earth cable is touched on pin two of the r/h relay, both fans start on slow speed!
So maybe we're getting somewhere!

It seems like we may never get to the bottom of this problem, if I drive the car with just one fan working will I do any damage, or will one fan cool it down enough?

Suzie,

You’ve nearly made it, it’s not the moment to give up.
Since you're certain that the r/h relay pin 1 is live with the ignition off, and that earthing pin 2 of the relay starts the low speed, then the fault is in the wire from pin 2 of the relay to pin 3 of the radiator switch.
Earthing at the relay works, but not at the other end of the wire, so the wire does nothing and is open.
With the temporary earth wire on pin 2 of the relay the fans were spinning at the low speed, even with the key out.
If the other end of that wire had been poked into pin 3 of the switch, they would have been stopped with the key out, only to come back on when the switch sensed that the engine got to about 90ºC, when it shorts pin 3 to earth.
As an experiment, poke a wire between pin 2 of the relay and pin 3 of the switch.
That will bypass the faulty wire, and will turn on the fans at the low speed when required.
It only has to be a thin wire, because relay coil current is low.
Another test for that would be to also short pin 2 of the switch to earth with the ignition on, and then all 3 relays are energised, and both fans will go to the high speed.

If you drive it as it is, only one cooling fan comes on only when you’re close to overheating, and over time it will harm the engine.
With a replacement fan, new relays and switch, there’s only the wire to blame.
It’s either corroded or the crimping at the relay socket terminal, or at the switch socket has let go.
Just a little bit more fiddling, and you will have made it.

Best wishes !

[suzie]

hello everyone....success!!!!fiddling about today we found out that pin3 of the rad switch becomes earth when the rad switch reaches about 90degrees,so knowing that we needed an earth on pin2 of the r/h relay we spliced a cable between pin3 of rad switch and pin2 r/h relay and this has done it!they both come on slowly at about 90degrees and then fast at 95.clogzz,just came in and read your post and it was spot on!many many thanks to everyone that's replied to my posts,much appreciated.thanks,suzie.

[Clogzz]

Hi Suzie,

And congratulations, it's very nice to read about another good outcome.
I could see from this distance that you were going to make it.



I got plenty of benefit from this too, because by now I know the diagram, and won't have to explore when my turn comes.

Regards,
Terry.