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  1. #1
    JBN
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    Default Find the Bitron

    The Bitron switch is mentioned a lot in relation to aircon and radiator fans, but where the bloody hell is it?

    Below are two photos of a Series 1 Xantia automatic's engine compartment with the battery removed.

    I would be obliged if some Citroen sleuth was able to indicate if the Bitron switch is visible in these photos.

    John

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    Attached Thumbnails Attached Thumbnails Find the Bitron-bitron-1.jpg   Find the Bitron-bitron-2.jpg  

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    1000+ Posts Ken W's Avatar
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    Hi,

    From what I remember, it is a brown temperature sensor mounted on the thermostat housing.

    Cheers,

    Ken W

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    1000+ Posts FIVEDOOR's Avatar
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    Default

    Perhaps this may be helpful

    Is this Xantia overheating?

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    JBN
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    Quote Originally Posted by FIVEDOOR View Post
    Perhaps this may be helpful

    Is this Xantia overheating?
    One of the last posts in that article mentioned a "Bitron unit" which was placed behind the passengers headlamp. That is what I am interested in identifying in the photos.

    Also, another of the latter posts in that thread mention that people were unable to identify any sensors near to the thermostat housing, I problem I also have.

    I have noticed the red light on the temperature guage coming on when starting the car with the temperature guage is below 80 degrees, and then going off after a few minutes.

    I think my love affair with French built things stopped with Brigitte Bardot. Certainly the Xantia's electrics are pushing my patience.

    John

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    JBN
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    The warm weather is keeping me focussed on my Xantia's cooling fan problem and lack of aircon or heater blower motor.

    I think that the Bitron control unit is the same as 8010 Water Temp Control Unit.

    I think that the Bitron sensor is the same as 8008 Refrigeration Water Thermal Sensor.

    Below is a photo of the engine bay (with battery removed) and fuse cover removed. I believe the Bitron control unit is located behind the two 40Amp fuses (BMT1, Bmt2).

    The Bitron sensor (along with two other water temp sensors) is located in an inaccessable area below the distributor cap and behind the thermostat housing. If there was a hole through the firewall, it would be easy to access through the glovebox.

    The other two diagrams show the location of items and the detailed wiring.

    Cooling Fans

    Although ONLY the passengers side cooling fan comes on ONLY at full speed, I do not believe that the fans are at fault. Removing the relays and bridging the 30 and 87 slots on the passengers side relay operates both fans at slow speed. Therefore, I think that a broken wire between the passengers side relay and the Bitron control is the primary problem. Easily said, bloody awful to get to.

    John
    Attached Thumbnails Attached Thumbnails Find the Bitron-engine-bay-1.jpg   Find the Bitron-bitron-location.jpg   Find the Bitron-xantia-cooling-fan-harness.jpg  

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    You also want the third diagram in the series to see what the circuit is. I assume you must have the factory wiring diagram book handy. It will show you how the three relays interact.

    Have you figured out how to read these diagrams? Pretty easy, if you look at which way each wire points into the harness and look at the wire numbers at each soecket pin. Earths are often common.

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    Unplug the Bitron (8010) connector, taking care not to lose the very springy spring clip.
    Measure between pins 7 and 14, they go to the water temperature sensor.
    With cold engine, it measures 1900 Ohms and 3700 when warm.
    If you get readings like that, the sensor and wires are good and you then have a dodgy crimp in the connector going through the inner guard near the battery.

    Back tomorrow.

    Last edited by Clogzz; 24th January 2012 at 01:03 AM. Reason: Trying to insert a thumbnail :(
    2003 C5 2.0i AL4 205,000 km 76372389

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    JBN
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    Finally unscrewed the Bitron controller, coaxed off the connector without losing the spring or breaking anything. This is no mean feat when you have no room in which to manoevre and a limited length of wires which further constrains you.

    Tested the resistence across pins 7 and 14 (as in the photo above) with a cold motor. With the multimeter set at 2000K the reading was 2; on 2000 or 200 it was 2.15. I don't know what that means in white mans language but I suspect that the Bitron Sensor is stuffed.

    I guess the quick way is to remove the engine. The second quickest is to cut through the back of the glovebox and the firewall, whereas the frustrating way is to remove all the bits and pieces obscuring it and practice ones French. I realise that French is the language of love, and all French cars have always left me rooted, so its option 3 for me.

    John

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    Fellow Frogger! Clogzz's Avatar
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    Thatís a good reading, itís 2.15 where mine was 1.9 when measured as you did.
    Your 2150 is close to my 1900, and depends on the engineís temperature, so the sensor is good.
    2003 C5 2.0i AL4 205,000 km 76372389

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    JBN
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    Damn. That's not the answer I was looking for. This is where I am at:
    • Bitron sensor supposedly good
    • Every wire from the IC08 connector (between the Bitron Controller and the relays) is good. I removed the 3 relays, unplugged the IC08 connector and using the ohm meter tested each of the 5 pins to there respective pin on their respective relay. I also (from the same IC08 pin) tested every other pin on all 3 relays and noted the results
    • With the engine switched off, I tested the pin 3 (Input Live +) to pin 5 (output to fan motor) of both the R/H Fan relay and the L/H Fan relay. Initially I used an LED light with two wires; then a volt meter (12 volts) and finally plugged in a wire with two spade connectors
    • When the R/H Fan relay was thus shorted out, both fans ran at half speed
    • When the L/H Fan relay was thus shorted out, the left (passengers) fan ran at full speed
    What am I missing here? I have ignored the Aircon switch as it doesn't seem to work. When the engine coolant gets hot (above 90 degrees), only the left hand passengers fan comes on at full speed. Seems like the Bitron Controller is the cause.

    I have the Bitron Controller removed from the car and will drive the car until it gets to about 90 degrees and test the pins 7 & 14 for resistence.

    I am glad the 2CV cooling fan is bolted directly onto the crankshaft - sure cuts out the middleman. The VW Beetle stuffed things up by running the fan off the generator - good until the rubber band between the crankshaft and generator broke and then you had a seized motor. Citroen have excelled themselves with the Xantia.

    John

    The self taught auto electrician - trying to commit suicide by electrocution, 12 volts at a time.

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    Fellow Frogger! Clogzz's Avatar
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    Hi John,

    The Bitron and sensor are good because they spin the passenger’s side fan when too hot.
    Since both fans go to low speed when shorting pins 30 & 87 of the top right relay, the fans and the wiring are good.
    Even with the key out, there has to be 12 Volts on pin 85 or 86, don’t remember which one, that’s the voltage to energise the relay.
    If not, there’s a blown 5 Amp fuse in the box under the bonnet, don’t know which one and haven’t got the Xantia anymore.

    I’ll be back tomorrow and answer your PM.

    Last edited by Clogzz; 2nd February 2012 at 02:03 AM. Reason: Trying to post a picture :(
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    JBN
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    I left the Bitron off today as I drove the car. When I returned home, the temperature guage was showing 90 degrees. I checked the resistence between pins 7 & 14. With the OHM meter set to 2000K, the readings ranged between 100 and 165, occilating wildly around 125/130 give or take. Five minutes later, still occillating, the range had dropped below 100 down to 65, I presume because the coolant temperature was getting cooler.

    I have reinstalled the Bitron. It was marginally easier to clip on the plug, compared to removing it, but only marginally.

    I can see why the French make such good lovers. They have the patience to frig around for an hour on what should be a 3 minute job.

    The photo shows the Bitron sitting on the LHM reservoir and the multiplug below the passengers front sphere. The fuse cover has been removed.

    Both the F3 30A fuse and the F5 5A fuse are intact (checked by an Ohm meter)

    John
    Attached Thumbnails Attached Thumbnails Find the Bitron-bitron-location.jpg  
    Last edited by JBN; 2nd February 2012 at 02:38 PM. Reason: missing text

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    1000+ Posts robmac's Avatar
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    Quote Originally Posted by JBN View Post
    I left the Bitron off today as I drove the car. When I returned home, the temperature guage was showing 90 degrees. I checked the resistence between pins 7 & 14. With the OHM meter set to 2000K, the readings ranged between 100 and 165, occilating wildly around 125/130 give or take. Five minutes later, still occillating, the range had dropped below 100 down to 65, I presume because the coolant temperature was getting cooler.

    I have reinstalled the Bitron. It was marginally easier to clip on the plug, compared to removing it, but only marginally.

    I can see why the French make such good lovers. They have the patience to frig around for an hour on what should be a 3 minute job.

    The photo shows the Bitron sitting on the LHM reservoir and the multiplug below the passengers front sphere. The fuse cover has been removed.

    Both the F3 30A fuse and the F5 5A fuse are intact (checked by an Ohm meter)

    John
    Looking at the circuit above they like get their jollies on a net hammock whilst standing up!

    Only a french engineer could come up with such a convoluted arrangement of the series and parallel relay arrangement of selecting the appropriate fan and fan speed.

    They should have just pulse width modulated (speed controlled) each fan individually.
    They could have used transistor switching and got rid of all the relays. Heaven knows they were halfway there with the bitron control module.

    If I had one I would have Arduino micro, about 20 lines of "code" and some switching transistors in it like a flash...

    If the relay that controls the first fan or (lhs in the image) fails none of the fans will run. Poor design and bad execution of a concept

  14. #14
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    Did you try swapping the relay positions? The parts diagram and component location diagrams show the green fan relays in one of the top and the bottom positions. The two top positions may be confused though. In the photo you'd sent me, you had both the greens in the top positions. Unless, you've moved the sockets around, you need to ensure you have green relays in the 4 wire sockets and the switching relay located in the 5 wire brown socket. I can't see how it will work if one of the fan relays is swapped for the switching relay. That's the contribution I can make here.
    Attached Thumbnails Attached Thumbnails Find the Bitron-xa_fan.jpg  

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    JBN
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    This is a diagram that I have made of of the 3 relays in my car. The top two relays are 4 pin ones plugging into green connectors. The bottom control relay is 5 pin plugging into a black connector.

    In actual fact, all the relays I use are 5 pin. The unused middle pin (Bosch 84/Cartier 4) just plugs into a plastic hole on the green connectors and does nothing. It is cheaper buying $10 relays from the auto electrician next door rather than mauve or green coloured Cartier relays from Citroen.

    The diagram is oriented the way it looks when you take off the front cover and remove the relays. I use the term "Right Fan Relay" to denote the relay that operates the Right Hand Fan on the right hand (drivers) side of the car. Both the top two relays operate the fan diagonally opposite, NOT the fan directly below the relay (its a French car, mon ami).

    The Pin numbers are the Cartier pin numbers which correspond to the Citroen Workshop harness diagrams. Note that the diagram has the 1 and 2 pins reversed compared to the relay as it shows the slots in the connector into which the relay plugs. Each of the 3 relays is oriented in a different way with the Pin 3 (input) at the top, the bottom and the side (Double Dutch but in French?).

    The reason for this diagram was to check (using an Ohm meter) the relationship between the IC08 connector and the relay connectors to both see which connects to which and to check that the wire is not broken. The colour of the wires is as they leave the the IC08 connector and the 1510 wire is orange, NOT green as the harness states.

    So, the picture is great, neatly drawn, appropriate use of colour, etc, etc. Now all I need is some animation.....of the fans.

    John
    Attached Thumbnails Attached Thumbnails Find the Bitron-xantia-relay-pins.jpg   Find the Bitron-xantia-relays.jpg  

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    The switching relay is different though, which is why there is a different part number given. The fan relays can be 5 pin relays with 87 and 87b being switched on/off together, even if 87b goes nowhere. However, if you use that same relay for the switching relay, I don't think it's going to work, because the circuit diagram shows that relay switches one on and the other off and vise-versa.

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    JBN
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    Thanks David. I will get a switching relay tomorrow and check it. The two 4 pin relays were old black Cartiers and I just replaced them unconditionally hoping that a buggered relay was the problem. Didn't think of changing the newish looking Bosch relay that is the changeover relay.

    I have seen some Citroen diagrams that imply that the changeover relay is not neccessarily at the bottom, but I work on the colour of the connector as that is referred to by its colour and the number of pins in the harness diagram.

    My relay setup looked identical to the photo, except for the black bypass wire and the intact black plastic post. My post broke of when I unscrewed it. Fortunatly the Shelleys two part plastic glue is holding it together now.

    John
    Attached Thumbnails Attached Thumbnails Find the Bitron-fan_relay_bypass.jpg  

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    The parts diagram tells you there are two different types of relay, so I would expect it not to work if you inadvertently ended up with three of the same sort, which is what I assumed from your earlier comments. The positions may have been altered, but it seems that whichever socket takes the switching relay has to have 5 wires in it according to the wiring diagram.

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    Hi John,

    Irrespective of its place, the change-over relay is the only one that has a socket with five contacts. (Sorry David, hadn’t seen your post by then)
    While the Bitron plug is dangling out, you could measure for continuity from its pin 1 to the top right relay socket’s contact 85 or 86 … that’s the wire to energise the relay from the Bitron.
    The opposite contact must have 12V from the 5A fuse.

    If the switch still works, switching on the air conditioning must start both fans almost immediately and you should hear the top right relay click on.
    That’s even if the aircon doesn’t work for compressor or pressure faults.

    Back later.

    Last edited by Clogzz; 3rd February 2012 at 12:02 AM. Reason: Adding to story :)
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    JBN
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    Unfortunately the Bitron plug is not longer removed, but the same effect could be achieved by testing Pin 3 of the ICO8 connector on the half that is connected to the Bitron. It connects wire 809 from the ICO8 to Pin 1 of the Bitron.

    I have tested ICO8 Pin 3 on the half nearest the relays and the wire 809 is good to Pin 2 of the Right Fan Relay.

    Since the Right Fan is the one that won't work, I guess the answer would be wire 809 into Pin 2 (85) or wire BM05 from Pin 1 (86).

    Unfortunately, the Aircon switch is not working, nor is the blower. I have decided to concentrate on the cooling fans first as I don't want a cooked engine. Cooked passengers I can cope with. I have a very good PNG recipe for "long pig".

    John

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    Fellow Frogger! Clogzz's Avatar
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    If you can reach 809 behind a known good relay in place, shorting it to earth must close the relay and start the fans.
    If not, BM05 has no voltage.

    Don’t tell us about the long pig recipe !
    Last edited by Clogzz; 3rd February 2012 at 01:56 AM.
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  22. #22
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    Quote Originally Posted by Clogzz View Post
    If you can reach 809 behind a known good relay in place, shorting it to earth must close the relay and start the fans.
    If not, BM05 has no voltage.

    Donít tell us about the long pig recipe !
    I presume the long pig recipe would work on the designers of this system. I'm reading this with a sort of horrified fascination, hoping my Xantia never behaves like it!!

    Thanks to all for the post and responses!

    Good luck with the problem John.
    JohnW

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    1000+ Posts robmac's Avatar
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    Quote Originally Posted by David S View Post
    The switching relay is different though, which is why there is a different part number given. The fan relays can be 5 pin relays with 87 and 87b being switched on/off together, even if 87b goes nowhere. However, if you use that same relay for the switching relay, I don't think it's going to work, because the circuit diagram shows that relay switches one on and the other off and vise-versa.
    The other thing to note is that are two standards for relay pins outs.

    The older bosch relays in the steel case with the mounting tab are different to Bosch relays in the all plastic case , ie current Holden type relays.

    So if you are buying a replacement, compare the pin outs on the case of both or meter both out to confirm they are the same.

    Personally I use 5 pin (c/o contacts) all plastic relays for all purposes. So you can't mix them up. Just ignore the N/C contact if not required.

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    JBN
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    Bought a new changeover relay from the auto electrician next door. This switches between pins 4(87a) and 5(87). So all the relays are new, but the problam is still the same. Full speed on the passengers fan or nothing. Same as it was on all the old relays.

    I'll test out wires 809 and BM05 on the right fan relay tomorrow.

    Today I'll take the dog for a walk. Its a French poodle. Everytime I approach a pole, I ask "Do you want a Citroen?". He usually answers by peeing on the pole. I am envious. I know if I do it, I'll probably be hauled off for exposing myself in public. Mondo cane.

    John

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    JBN
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    Checked out the Bitron socket today.
    • Wire 809 Bitron Pin 1 to IC08 Pin 3 is good
    • Wire BM05A Bitron Pin 4 to IC08 Pin 5 is good
    • Wire 8091 Bitron Pin 10 to IC08 Pin 4 is good
    • Wire C03C Bitron Pin 15 to IC08 Pin 1 is good
    • Bitron Pin 1 to earth ran both fans on slow speed
    • Bitron Pin 10 to earth with ignition key at ACC ran one fan on high
    • Bitron Pin 4 has permanent 12V
    • Bitron Pin 15 has switched 12V
    Tomorrow is forecast as a sunny day, first for a very long time. It is a Sunday and probably an inappropriate time to spend the day swearing. My wife also needs the car with the backseat down to cart a whole heap of rubbish to a market to sell to people who want a whole heap of rubbish. I will await with baited breath to see if she returns in an empty car OR returns by cab with a whole heap of old clothes.

    Merde Monday is my next scheduled joust with the Xantia and those sick minds that designed it.

    John

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