rad fans and aircon

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Robbie
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rad fans and aircon

Post by Robbie »

Hi,
Can anyone explain my rad fan / aircon problem, to start with I put the aircon on and found the fans weren’t coming on as they should when you press the aircon button. I assumed that the fans weren’t working at all and as I was about to go on a journey involving the M25 I thought this was bad news if I got stuck in traffic and the car overheated, so I put the car into the local non Citroen garage to ask them to look at it. An hour later they rang me and said they could not find anything wrong with it and that they had run the temperature up to 110 and the fans had come on as normal. I said what about the aircon but they were very busy and asked if I could I bring it back later now that they knew the fans were working and I wouldn’t overheat. I drove home and out of interest put the aircon on and then the fans came on as they should, great I thought until the next day when they didn’t again. The car is a Xantia 1.9TD 1998 (new shape). Thanks Robbie.
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Kowalski
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Post by Kowalski »

Sounds like a Bitron unit problem or a dodgy connection somewhere in the system.
Robbie
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Post by Robbie »

Is there anything simple that I can do to test it? where is the bitron unit?
Robbie.
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Kowalski
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Post by Kowalski »

The Bitron unit is a complex box of tricks and it lives somewhere around the under bonnet fuse box, or behind the LHS headlight, its not in the same place on all models, in fact I'm not sure of the exact location of the one on my car.
A simple test, would be to disconnect the brown plug on the thermostat housing and see if the fans run at full speed or not. The fans should come on at low speed initially when the car reaches about 90C and high speed at 110C. You could have one fan dead or a dodgy connection so make sure that when your fans run both fans run, they should always run in tandem.
Richard Gallagher
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Post by Richard Gallagher »

Take a look on www.peugeotlogic.com website and you will find a very detailed descriptionof how the fans work. It uses a Pug 306 as the model, but Xantia fans work the same way.
The Bitron unit is normally found right under the N/S headlight, well hidden away.
mcfarlmx
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Post by mcfarlmx »

Sound like the same problem I'm having only the dreaded red stop light come on with me. Think it could be the bitron unit near the fuse box under the bonnet, dont know if there cheap to replace but they're easy enough to change out.
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Post by Niek »

I read of a guy not too long ago (maybe even on here?) who had opened the biton box very carefully, resoldered it and closed it back with lots of resin to get it watertight. I suppose it should be the last resort sort of thing because chances are quite good to get it all wrong and not working anymore at all (I would try it though if you're swapping it anyway :) )
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Post by Richard Gallagher »

If you want a Bitron ecu then give me a shout, I've got a known good one off a Xantia I broke earlier in the year.
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Post by ghostrider »

Do your fans run at half speed?, if the engine gets hot enough to run them flat out a relay cuts off the aircon to reduce the load on the engine
Pete
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Last edited by ghostrider on 22 Feb 2011, 06:02, edited 1 time in total.
Robbie
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Post by Robbie »

Update on Aircon and rads.
I found the brown wires that I think are coming from the bitron unit and sprayed them with wd40 (of course I could be spraying something else) but nothing happened until I slammed the bonnet down then one fan came on, the right hand one as you look at the front of the car, but then it went off again and then it came on again for about ten seconds and off again and keeps doing this, only the one fan though. The aircon button is on by the way and the temp on the gauge was at about 70degrees. I seem to remember when I switched the aircon on before both fans came on regardless off temperature. I know it needs to be regassed but don’t want to do that until I know it’s working as it should. Am I right that both fans should be on all the time? The brown wires I sprayed were right in front as I looked in the engine, the throttle cable runs just above them, I couldn’t find any more.
alan s
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Post by alan s »

The symptoms are the same as mine when the carbon brushes wore out in one of my fans; the other had already been replaced!!
Have a read FYI:-
http://www.andyspares.com/discussionfor ... C_ID=10752
Alan S[;)]
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oscarloco
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Post by oscarloco »

You should check the relays that control the fans. In the ZX they are located in a triangular box between the fans. I had a similar problem and only one came on. It turned out to be a bad relay plus a fan on its way out. Replaced both. No problems to date.
jochem
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Post by jochem »

I have a similar problem with my Xsara hdi....citroen fault diagnosis said that it was the coolant temerature sensor, so i replaced that, but it didn't solve the problem (red STOP light sill comes on), and in addition, the yellow engine management symbol light now comes on too. I don't know what step to take next! The temperature meter still reads fine in spite of all of these problems!
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Post by alan s »

Mine was s simple case of overheating without warning.
I found the problem by firstly driving (on a day about 38C) at around 100kph over a few klms and noticed that the temp dropped. I then turned on the air/con and it rose slightly and when I slowed tight down, the temp rose sharply.
When I stopped with the air/con on, it was only one fan that was operating. Disconnecting and attaching power individually showed I had one fan going and one inoperative. I had an invoice from the previous owner who had a second hand fan fitted at enormous expense including A$265 for a second hand fan which is why I did the other one myself for only a few dollars and it's been fine since, but allow a whole day just to remove and replace; it's a dog of a job. Easiest part is fixing the motors when you get them out. Hardest is pulling the front off the car for the first time.[B)][:(]
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oscarloco
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Post by oscarloco »

I replaced a fan motor without removing the front of the car. This had been repaired by the local Citroen Dealer a few years ago so it was not riveted, instead it was held in place by three screws. I just unclipped the rad from the small hooks on top, unhooked the top hose, lifted it from the pins on the sides, pulled the aircon rad a little and then I had enough space to insert a socket in which I had drilled a small hole to insert a pin to get enough grip, and with a extension in the ratchet, undo the screws. The bottom one was a real pain to remove since I scraped my knuckles with the aircon rad. But it can be done.
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