406AC suddenly stop working

[asanka]

The RPO is 08829 (the 89 means it was built at Sochaux, like the majority of 406s), Thu 11 Jan 2001 so definitely a semi-mux. I forgot there are 4 1.8 engines but the diagrams all appear to be the same. I'll add the descriptions in a minute...

Thanks very much for the detailed info Steve. ill check with this . i hope this diagram will be helpful for many people in the future .i spent hours to searched and find this ac diagram for 406 last week ,but i end up with nothing even Haynes manual doesn't cover the ac wiring .so thanks again for the great help .ill be back with the update

[asanka]

Update
found that the MFD it show up -- at the temperature display position all the time . i guess out side temperature is about 25c .

can this be a cause to compressor not to engage?

i remember it was worked fine before this AC problem occurs .

[steve_earwig]

Ah yes, I seem to recall the a/c won't cut in below freezing as there' a risk to the condenser. Good call!

There's a bit of a how to here, sadly the pictures seem to have died. viewtopic.php?f=3&t=4616&p=62121&hilit= ... jpg#p62121

[asanka]

thanks steve how do i check the sensor whether its working or not .
i just dissemble the wing mirror and found the sensor which leads 2 black wires .

which voltage does the wires supply to the sensor .i have a multi meter so i can check the sensor wires have power at the connector in the door .

[asanka]

thanks steve how do i check the sensor whether its working or not .
i just dissemble the wing mirror and found the sensor which leads 2 black wires .

which voltage does the wires supply to the sensor .i have a multi meter so i can check the sensor wires have power at the connector in the door .

[steve_earwig]

Ah, now that I have no idea about (anyone?), I'd just test it anyway, hoping for something meaningful.

Is it always zero? Never below?

[8Jb9]

I think it's most likely a thermistor. If it's reading 00 it might be the computer's way of saying open circuit, as otherwise I would expect it to say -255*C for NTC or +255*C for PTC.

Since you have a multimeter there anyway hook it up as a voltmeter across the connection, that should give you the supply voltage (or alternatively it would give you an indication of a wire issue, although a thermistor issue is perhaps more likely).

[asanka]

Ah, now that I have no idea about (anyone?), I'd just test it anyway, hoping for something meaningful.

Is it always zero? Never below?

sory it was not 00 its only -- . no any numbers

(this photo is not mine .but my MFD show temprature as same as this )

[steve_earwig]

Ah, the sensor is (almost certainly) toast. I'm not sure if that qualifies to be low enough to stop the a/c working but the ecu is probably programmed to assume the worst.

[8Jb9]

That suggests that the sensor is not connected properly (e.g. sensor faulty, wiring faulty, connector faulty, or - less likely - BSI faulty)

PP2000 might throw an error to let you know what's going on, and if you measure the sensor you'll have an idea if it's an open circuit. There's a slight chance the sensor is amplified, but a 2-pin connector strongly suggests that it's just a dumb thermistor.

You can perhaps trick it into working by connecting traditional resistors in place of the sensor and see what temperature read-out you get. Try biggest resistors first then work your way down until you see a realistic tempreature. Maybe AC will turn on then (and of course replace the sensor with a new one as soon as you know if that's the fault)

[asanka]

That suggests that the sensor is not connected properly (e.g. sensor faulty, wiring faulty, connector faulty, or - less likely - BSI faulty)

PP2000 might throw an error to let you know what's going on, and if you measure the sensor you'll have an idea if it's an open circuit. There's a slight chance the sensor is amplified, but a 2-pin connector strongly suggests that it's just a dumb thermistor.

You can perhaps trick it into working by connecting traditional resistors in place of the sensor and see what temperature read-out you get. Try biggest resistors first then work your way down until you see a realistic tempreature. Maybe AC will turn on then (and of course replace the sensor with a new one as soon as you know if that's the fault)

that's a good idea i will connect a resister between the sensor wires will try with a 15k resister first .have to wait some time to do that .i will post updates as soon as possible

[8Jb9]

http://www.pug306.net/forum/archive/ind ... 49069.html

Relevant...

[Malc]

Fyi I fitted a new passenger side (RH) wing mirror from fleabay UK to my French LHD 406 not realising it would come minus the outside temparature sensor. Now outside temp indication on the display is a blank but A/C works fine...

[asanka]

http://www.pug306.net/forum/archive/ind ... 49069.html

Relevant...

i just checked the voltage between the wires of the sensor .it shows only 0.5v .also i check the wire continuity all good .and the outside temperature sensor show 535 ohm reading .and when i move the soldering iron to the sensor tip the resistance keep reducing bit by bit .i checked till it reduse to 440 ohm .
also i connected a 10k resister between the wires an nothing changed.
i think the voltage to the sensor is very low .may be due to a BSI problem ...
today ordered a pp2000 tool kit and need more help from you guys for doing scanning things .
will continue the diagnosis after it arrives ..

another problem here

also found this part (picture) fitted to ventilation box near the evaporator sensor .it has 2 green wires and wire cover almost peeled off in both wires.


what is this thing ?

[asanka]

Fyi I fitted a new passenger side (RH) wing mirror from fleabay UK to my French LHD 406 not realising it would come minus the outside temparature sensor. Now outside temp indication on the display is a blank but A/C works fine...

thanks malc .i don't know what pugs are doing when wiring problem occurs ,different from each other