Heh... 1 hour in a traffic jam -> overheating engine

prm · Post by **prm** » Wed Jul 01, 2009 2:31 am

Not only are we going round the houses!! But also have knickers and wires crossed!!!!!.

You definitely need to investigate the connections on the rad temp switch first, and establish if circuits on cooling and air con systems are as per OE, as Mat and Jaba mentioned. Also, if the twin fan system, is controlled by relays, or resistors, Any fan run-on direct feeds installed??

I’m afraid the DIY guide maybe wrong/ misleading, with testing, and operational status.

This is where the confusion has arisen with the bl—dy temp switch operation and connections. Seen quite a few alternatives, not so good (crap) set ups. The temp switch contacts not designed to continually handle the amperage of both fans at high speed, (parallel)

I presume the single green and two blue wires you mentioned refer to the temp switch connection.

With air con off, ignition on, engine cold and stationary.
If you bridge the green wire to chassis/earth, nothing should happen, as this wire is the earth point return for both low and high temp circuits. If any fans operate, I would presume your wiring is incorrect. But,??? You never know with Citroen. Could be different looms fitted.

Bridge blue wires in turn to earth, to establish which one runs both fans at slow speed. This wire connects to the right of the horizontal tag when placed at 6 o-clock. Low temp.
Presuming a relay controlled set up installed.
Bridge the other blue wire to earth. Both relays should energise, and one fan at high speed should run. This wire connects to the left of the horizontal tag. High temp.
The rad temp switch is a progressive 3 pole type. When the low temp range is activated both fans should be at slow speed, (fans in series). When the higher temp is switched on, the low temp connection is still maintained, along with the high temp connection.
Both relays are activated at high temp, separating the fans circuits to operate both fans at high speed(fans in parallel) Sending one fan negative, direct to earth, and the second fan negative to earth, via the temp switch.

I hope I’ve got all this right. Makes you think twice when you’ve actually got to write it down. ………………To be continued :-

With ignition on. The AC switch activates the main relay, normally, fans at slow speed, regardless of engine temp and AC pressure.
In circumstances where the refrigerant pressure exceeds approx 19bar due to system temp changes, dryer pressure switch disengages the compressor clutch; both fans will operate at high speed, then, return to normal –slow speed, when the high pressure/temp has been reduced.

Hope this makes your trouble shooting slightly?? easier Best of luck

Regards

Post by **mat_fenwick** » Wed Jul 01, 2009 10:46 am

prm wrote:I could never easily spot the small yellow/orange dash warning light as TZD,s

What is really useful is a gauge- so much more useful as you can detect trends and sort out problems before they become serious. One of the first mods I did (searchs for 'smug git' smiley!)

During my recent fan problems (caused by poor fan switch connections*) I dug out a hand drawn schematic of the fan circuits, with different scenarios showing the current paths. I could post these up in addition to Pete's comprehensive reply if they help?
*Although the connections were bright and clean, covered with silicone grease one of the female spades had opened up slightly so I was getting relay chatter when the temperature rose.

prm · Post by **prm** » Wed Jul 01, 2009 8:24 pm

Mat

I wonder how many BX’s have been lost, or had expensive repairs, due to just a faulty temp switch and connectors?? Especially diesels.

Post your schematic drawings up.

Any BX electrical information is always welcomed.

Did you manage to get your AC working, or identify the fault??

Regards

TB2 · Post by **TB2** » Wed Jul 01, 2009 9:06 pm

BX electrical information? I found this in my car:

(Beware, I uploaded the full size images I made, so they're quite huge in size)

Full wiring diagram of the whole car. Though honestly, I don't understand much of it.

Bummer, I didn't have a chance to to the rear arm bearings today either, the geezer from the garage doesn't have time until friday so our trip will be postponed again.

Thanks for all the info though, I'll try figuring out the wiring on my temp sensor on friday or saturday!

prm · Post by **prm** » Wed Jul 01, 2009 11:48 pm

Carl.

I can now see why you’re struggling with your wiring if your working from the schematic drawings posted!!!!!

If you could let us know how your cooling system is wired up, with any small drawing of relays, any resistors and wire colours etc
I’m sure, between us we can hopefully get your system working correctly.

Regards

Post by **mat_fenwick** » Thu Jul 02, 2009 10:22 am

Here are the diagrams I drew up...not the neatest but hopefully understandable!

Engine Hot

Engine Very Hot

The problem with the AC turned out to be that the sliding potentiometer had failed (open circuit). I couldn't find a match from RS, Farnell and the like, at least from their websites and the nearest Maplins is about 100 mile round trip so I have temporarily attached a 100k rotary pot (all I had!) in place of the 10k slide. Docchevron is very kindly sending me one which should be here today, which will be very welcome - the current method of control is very sensitive to say the least...

Jaba · Post by **Jaba** » Thu Jul 02, 2009 10:45 am

Carl
This si the wiring diagram that your car will (probably) have........