Fans not kicking- overheating - a Bitron Snensor problem?

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mezuk04
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Post by mezuk04 »

Out of my own curiousty, this 'second radiator' that has been mentioned - are you lot referring to the intercooler?
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Post by Johnno »

F00lzz, you're right - the brown plug, referred to by Haynes, incorrectly, as the Bitron unit, forms part of the overall temperature control circuit. Bizarrely, this item is actually easy to get at on the TDs and unplugging it causes the fans to both go to high speed - i.e, an emergency default.

I can only comment on the experience I have with my own car and part of that experience suggests that Citroen, in common with most manufacturers, change/modify/leave out items during production runs. The Haynes manuals have, of late, been less and less inclined to consider anything out of the ordinary - partly due, I'm sure, to the number of minor mods made. My radiator has a three pin relay or switch which feeds into the same loom that serves the Bitron - so I am making a big assumption abouts its function, I freely admit.
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Post by Clogzz »

A radiator switch!!
It does look like early Xantiae :mrgreen: with air conditioning can have a 3-pin radiator temperature switch to operate the fans.
This 1994 TD does:

http://www.frenchcarforum.co.uk/forum/v ... hp?t=19090

this 'second radiator' that has been mentioned - are you lot referring to the intercooler?
No, it’s the air conditioning condenser.
It’s a radiator that lives in front of the coolant radiator, and serves to cool the refrigerant that’s being compressed, and hence heated, before it can be evaporated in the evaporator inside the dash. :mrgreen:

Citroen, in common with most manufacturers, change/modify/leave out items during production runs.
Just made that finding too when fiddling with the fan fuses yesterday.
I removed one of the 40 Amp fuses, and it caused the nearside fan not to run at the high speed, but the low speed was still normal.
According to the map, that fuse is for the ‘right fan’, offside, starboard. :?
It also looks like relay positions vary. :x
The map shows the change-over relay in the centre, which is logical, then we have this:

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Last edited by Clogzz on 03 Aug 2006, 15:01, edited 2 times in total.
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Post by DaveW »

Clogzz wrote:
No, it’s the air conditioning condenser.
:
Mostly !

My 1.9 TD (non-aircon) has a radiator in front of the coolant one and this is the intercooler for the turbo. ........:-)

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Post by mezuk04 »

So on a car with A/C, where is the intercooler ??? :-s
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Post by Clogzz »

Oops, Dave ! :oops: Wasn’t thinking of the intercooler in this context of air conditioning. :?
If you have both intercooler and air conditioning, do you then have 3 radiators at the front ? :shock:
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Post by DIR »

I have also now checked the 10 amp fuse in the box under the dash, and looked at the fuses behind the battery. I can't get the 40 amps out (nervous about using force - there must be a trick) but they all LOOK intact. However, this box has an amazing array of coloured goodies, especially the 'relay' on the LHS with the word BITRON emblazoned on it. Could this be the famous control, or is this hidden in the depths of the engine.

My next stage is to attempt Dave's suggestion and remove at least one fan. Once I have done this I will put 12V across it and see if there is life.

BTW, in Haynes ( which I now know is referred to as BOL) it has notes like 2V, 5V, 13V, next to the connectors. This is calls ' number of connector channels (- see p13.29 'How to read the wiring diagrams..). However, these numbers seem more like voltages- any comments/ideas
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Post by Johnno »

If you have both intercooler and air conditioning, do you then have 3 radiators at the front ?
I seem to recall that there were three radiators on my car - an AC/Turbo model. Of course, that raises interesting questions about which you place where, to minimise the effect of the temperature gradient across the three.
I can't get the 40 amps out (nervous about using force - there must be a trick) but they all LOOK intact. However, this box has an amazing array of coloured goodies, especially the 'relay' on the LHS with the word BITRON emblazoned on it. Could this be the famous control, or is this hidden in the depths of the engine.
There should be a small plastic removal tool inside the fuse box. If not, a pair of pliers with firm but steady force will do it. The term "Bitron" is a trade name and can refer to relays, amongst other things. The Bitron control unit is generally under the n/s headlight, buried under the plastic cover that runs across the front of the car. You should be able to see it by removing the battery and dislocating your neck. It is mounted using two 10mm nuts. You can just reach one but not the other. You can try, as I did, to drill a large hole where you think the other nut is. I missed...
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Post by DaveW »

DIR wrote:I can't get the 40 amps out (nervous about using force - there must be a trick) but they all LOOK intact.
You can do a rough check on those big jobs in situ. You will see that there are two small metal 'blips' on the top at either end, put a meter (or bulb) onto each one in turn (with the other probe/wire to earth) and check for 12V.
If you see 12V. (or the bulb lights) at both ends it will be OK. If there is 12V on one end only then it's dud or may have corrosion on one of the terminals.

Sometimes fuses can look OK but are not. The only sure way to check is with a meter, either passively (fuse out, check for continuity) or included in a live circuit - (or with a bulb).

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Post by AndersDK »

You can get blade fuses with a buil-in LED fault indicator. This will be lit on a blown fuse. Worth considering on stocking up.

I have seen large blade fuses secured with a small center rod thru all fuses. Must be pulled out to remove fuses.
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Post by mezuk04 »

:shock:

So intercooler, air con condensor and the radiator are all shoved in at the front.

By heck, Citroen dont half like wedging things in :cry:

Wilkobob has his intercooler bolted on the top of the engine on his Mondeo P-Reg 1.8TD and it seems a much more easier place to have it.

Simply unbolt and flush with petrol, I dont like the sound of having to do the same job on a Citroen intercooler.
Volkswagen Golf 59' 1.6TD S :(
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Post by Johnno »

DIR: I don't know if you've had any luck with your investigations, but I thought it worth asking if, when doing your checks on the fast settings, you have had the ignition on. This is because the relay that controls the first (slow) setting is permanently connected to the positive side of the battery. The relays that allow the high speed setting are only fully connected when the ignition is on. Remember that, as the slow setting is obtained by linking the fans in series to create a voltage drop, if either fan is u/s, neither will work. In the fast condition, then assuming all else is correct then either one may work as they are in parallel.

Another test you can consider is: Ignition on, engage air-con, disconnect the Brown plug. After a few seconds, the air-con should disengage, as this is part of the emergency default action, even if the fans don't operate as they should. This may go some way to indicating that the Bitron control unit is at least receiving and acting on a signal.

But I believe the brown sensor is a swine to get at on petrol models?
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Post by alan s »

I found a way to get to it, but it ain't easy I can tell you. From memory it entails taking the air duct off that runs from the front of the car where it passes the thermostat housing, but that's not why I'm sticking my beak in here.
One of my sons recently purchased a 94 Xantia 2.0i petrol with air.
It seems this car has had a whack at some time in its life and as a result, there were a few issues associated with a couple of things on it, one of which was the fan(s) running consistently which turned out to be the brown plug off the engine temperature sensor. WE found the reason there was a fan operating and not 2 and the reason it was running at a speed halfway between fast and slow was that the brushes in both fans were worn out, so when we'd overhauled them, they both spun at full bore....whoopee!! :lol: :lol:
Next came a drama that required the car to be inspected by a Government Inspector (250 klms away - don't ask; long story) :roll: and I had noticed that the ABS was constantly showing, so in my wisdom, I grabbed the owners handbook and proceeded to remove fuse #5 under the dash, shown as the ABS. This caused the ABS light to not operate...clever me I thought.
When he has travelled the 500klms round trip, his response on his return was that the fans weren't working and the temp needle had gone right past 100 with no response from the fans. Don't ask me why, but I replaced the fuse #5 and bingo, fans back in action.

Thought I'd mention it as although it may not make any sense or it may be coincidental and something else is at fault, but that's what happened in that case. 8-[ 8-[


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Post by f00lzz »

mezuk04 wrote::shock:

So intercooler, air con condensor and the radiator are all shoved in at the front.

By heck, Citroen dont half like wedging things in :cry:

Wilkobob has his intercooler bolted on the top of the engine on his Mondeo P-Reg 1.8TD and it seems a much more easier place to have it.

Simply unbolt and flush with petrol, I dont like the sound of having to do the same job on a Citroen intercooler.
Quite simple when you think of it really.... Heat Soak The intercooler when mounted on top of the engine defeats the object of a 'cooler' because the heat from the engine rises into the Intercooler and prevents it from carrying out it's proper function.... much better to put it where you can get a flow of air :wink:
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Post by mezuk04 »

Ah, interesting information.

I only pretend to be a bit 'fick :wink:
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