Rad Fans not working

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

User avatar
windysurferuk
Posts: 76
Joined: 10 Oct 2005, 17:39

Rad Fans not working

Post by windysurferuk » 04 May 2010, 20:29

I know this has been done to death as I've just spent the last hour reading old posts but I'm still not quite sure where to start.

My car is a Xantia 2.1 td with Aircon.

The fans do not come on when the aircon is switched on.
They do come on when the engine gets to around 100 degrees at high speed I think.

I've had a quick fiddle and cleaned the 3 relay contacts and given the fans motors a sharp tap with a hammer, which has worked in the past but can't get the fans on so I guess I need to get the voltmeter.
I just need to know where to stick it and what reading I should be getting!!

Is there an idiots guide to fixing this problem or can anyone suggest where to start

cheers

MikeT
Posts: 4838
Joined: 11 Jun 2007, 16:17
x 185

Post by MikeT » 04 May 2010, 21:54

You might some titbits of info in my blog though my fans were not working at all.
http://www.frenchcarforum.co.uk/forum/v ... &start=120

I've got a memory like a seive but Toby seemed to be very efficient with the wiring and showed a better understanding of it than I did so perhaps he might be able to suggest a few pointers for you. Otherwise, Clogzz is very au fait with this particular circuit if you'd like to search for some his posts - all the info is here on this forum if you can find it.

To get an idea of the state of play, the easisest test is to remove the brown plug connector off the thermostat housing with the engine running. As a safeguard, the fans should start at half speed then spin up to full speed within a second or two.

This will tells us if you've got half speed working as they're too quiet to hear over ambient noise.

IOW, I'm guessing there's nothing wrong with the fans nor the feed to them, it's just not being switched properly.
Last edited by MikeT on 07 May 2010, 19:50, edited 1 time in total.

citroenxm
Posts: 7812
Joined: 31 Dec 2004, 00:10
x 27

Post by citroenxm » 04 May 2010, 22:22

Sounds like to me the "Slow Running Fan" relay is not getting power to switch the slow speed on...

This is a common problem and is associated with the 3 relays between the Fans behind the black cover, slightly triangular..

IF all contacts behind the relays are good in here, then its likely to be a typical "French Wire" breakdown, were the copper inside certain wires corrode away and break contact!

I think, IIRC, the controlling wiring goes up to the Passenger side inner wing, in the battery compartment, and the Bitron Box is located under the passenger headlight.. You may very well benefit from removing the battery and battery tray to see it, and have a clearer view to follow wires ..

Ive delt with a good few Xantias now with fan problems.. and is more so VERY likely to be broken wires, after a corroded pin on one of the relays..

The Sensors in thethermostat house dont often cause a problem - though , yes they can!

Regards
Paul

User avatar
windysurferuk
Posts: 76
Joined: 10 Oct 2005, 17:39

Post by windysurferuk » 04 May 2010, 22:31

I've just been reading a few more old posts and it looks like my first job is disconnecting the brown temp sensor to check both fans are running at high speed (fans are coming on when engine is hot but I'm only guessing its both)


Also found a post from Cloggz that had some good info.
I'll work though them and let you know how I get on

User avatar
windysurferuk
Posts: 76
Joined: 10 Oct 2005, 17:39

Post by windysurferuk » 05 May 2010, 17:18

Right just pulled the brown temp sensor off and only have one fan running a high speed.

I've swapped the two green relays over but no difference still only one fan at high speed.

I've put a voltmeter on the green relay terminal and have 14v to both 1 and 2 (or was it 1 and 3?) terminal on both relays.
An I right in thinking that one of the fan motor is not working or is there something else I should check before coming to this conclusion.

If it the fan motor is there a way to just have the one working fan come on instead of two fans at low speed?
Not bother about my aircon working.

I really don't want to have to change the faulty motor as it look to be a right pain and I only need the car to get me though the next 4 months before I'm planning to scrap it and get something else.


Any suggestions

cheers

Windy

User avatar
hirsty
Donor 2016
Posts: 216
Joined: 14 Sep 2008, 11:05
x 8

Post by hirsty » 05 May 2010, 17:22

I had the same problem on mine and got a fan motor from the scrapyard. If you file some flats on to a short socket, you can get to the mounting bolts easily without removing any thing other than the slam panel. Mine took about 30 minutes from start to finish. :D

Keith

User avatar
windysurferuk
Posts: 76
Joined: 10 Oct 2005, 17:39

Post by windysurferuk » 05 May 2010, 17:49

just sat in the car with the laptop reading some old post and have connected a wire directly from the battery to terminal 5 on the nearside relay and both fans spin at low speed so looks like the faulty fan is not faulty after all??

Not sure exactly what to try next but will keep sticking bits of wire in random holes :lol:



just tried from battery to offside terminal 5 and only get the nearside fan at full speed :roll:

MikeT
Posts: 4838
Joined: 11 Jun 2007, 16:17
x 185

Post by MikeT » 05 May 2010, 18:42

Get the wiring diagram, that'll show you which wire you need to chase.

I think one of the relays are triggered by an earth - possibly from the Bitron.

User avatar
windysurferuk
Posts: 76
Joined: 10 Oct 2005, 17:39

Post by windysurferuk » 05 May 2010, 19:36

I've had a look at the diagram but it doesn't make any sense to me :oops:

User avatar
windysurferuk
Posts: 76
Joined: 10 Oct 2005, 17:39

Post by windysurferuk » 06 May 2010, 07:45

How do you test to see if an earth is good or not?

I'm pretty sure the two green relays are OK but haven't tested the 5 pin black relay.
How do I remove this and hard wire this to check if its working or not?

thanks

User avatar
Clogzz
Posts: 2072
Joined: 15 May 2005, 18:04
x 16

Post by Clogzz » 06 May 2010, 13:03

Hi all, and thanks for the endorsements. :D

Windy, since both fans spin at the low speed when you feed 12 volts to nearside pin 5, then it means that the centre relay, the fans and the earths are good.
The fault is that the nearside relay isn’t feeding the fans.

With a piece of wire, short pins 3 & 5 of the nearside relay, as shown in the picture.
If the fans don’t spin with that, it’s caused by lack of 12 volts on pin 3, because of a blown 40 Amp fuse in the fuse box under the bonnet, fuse E or F.
If they do spin, then it’s caused by the nearside relay not clicking.
The usual culprit is a 5 Amp fuse under the bonnet not feeding pin 1.
Don’t test this pin by trying to feed the fans from it, because the 5 Amp fuse will certainly blow.

These tests can be done with the key out, because the low speed must work with the engine stopped.
The offside relay is for the nearside high speed only, and can be left out for low speed testing.

Enjoy a good fiddle, and as usual … we will overcome ! :lol:

Image Image Image

MikeT
Posts: 4838
Joined: 11 Jun 2007, 16:17
x 185

Post by MikeT » 06 May 2010, 15:55

Thanks for stepping in Clogzz, my memory hasn't retained any of those finer technical details and am unable to offer further advice whereas you appear to have it well ingrained with perfect recall. :notworthy:
Last edited by MikeT on 07 May 2010, 19:49, edited 1 time in total.

User avatar
windysurferuk
Posts: 76
Joined: 10 Oct 2005, 17:39

Post by windysurferuk » 06 May 2010, 17:36

Just had another play.

If I short terminals 3 and 5 on the nearside with ignition off thn both fans spin at low speed. Checked pin 1 and have 12 volts, 5 amp fuse under bonnet is fine.

If I then run a wire from pin 2 on the right hand relay to earth with the relay in place this also puts both fans on low speed.

If I then start the engine, remove the temp sensor and earth pin 1 on the right hand relay with the relay in place the both fans spin at full speed.

Confused, you bet I am!!

User avatar
Clogzz
Posts: 2072
Joined: 15 May 2005, 18:04
x 16

Post by Clogzz » 07 May 2010, 13:50

You’re welcome Mike ! :D

I actually saw this topic on Wednesday afternoon GMT time, but I’m getting complacent when I see other people in the know chipping in.
I’ve had to work out the cooling fan electrics about 5 years ago because the fans were coming on intermittently and unnecessarily.
It was caused by the intermittency of a brown sensor wire crimp connection in the plug/socket that passes through the inner wing near the battery.
I plumbed a wire around it, :twisted: and that's fixed it for good.


Windy, the fault is in the thin low speed wire from the Bitron’s pin 1 to pin 2 of the nearside relay … it’s probably corroded at the relay end.

When you remove the brown sensor plug, the fans first go to low speed for a second or two, then next to high speed.
If you have a short delay to go to high speed when disconnecting the sensor, that’s where the low speed must fit in.
The Bitron is very unlikely to be faulty, and getting to it needs at least the removal of the headlight.

Keep enjoying all that fiddling ! :lol:

Image Image
Image Image

User avatar
windysurferuk
Posts: 76
Joined: 10 Oct 2005, 17:39

Post by windysurferuk » 07 May 2010, 17:04

More fiddling tomorrow then.

Hopefully it is at the relay end

I'll check it out and report back

Cheers for the replies so far

Windy