Air con electrics

[Nuffield]

Hi Everyone,
I have an "R" reg 406 estate with climate control air con.All the system functions except the comp and rad fans. The rad fans are ok when controlled by the " Bitron" sensor, and also run when the comp is powered up with a link direct to the battery. There are no fault codes stored.I suspect the cooling ventilator control module as the feeds for the comp come from this, what I dont know however is what it looks like or where it is, can anyone point me in the right direction, and perhaps confirm (or not) my thoughts?
Regards,
Nuffield

[mjb]

Checked your fuse?

[Nuffield]

Hi,
Yes, all fuses were removed and checked.
Regards,
Nuffield

[Busman]

Hi.

Now I no mine is a D9 HDI, but a very similar thing happened to me. It turned out to be 2 thermistors which are located on the near side of the cooling fan behind the rad grill in front of the condensor. Yours may well be different but it may help to point youy in the right direction.

Richard.

[Nuffield]

Hi,
Thanks Richard, I will have a look for these.
Regards,
Nuffield

[Nuffield]

Hi Everyone.
This may be a "red herring" but I have noticed that my control panel is almost impossable to read on the extreme left , could this be tied in with the aircon problem? Next, does this car have a "BSI"? If not I believe it would be a straightforward job to change the panel, but what would a panel change entail if a "BSI" is fitted?
Regards,
Nuffield

[mjb]

Hi Everyone.
This may be a "red herring" but I have noticed that my control panel is almost impossable to read on the extreme left , could this be tied in with the aircon problem?

Just a blown bulb

Next, does this car have a "BSI"?

No

[Nuffield]

Hi Everyone,
Thanks MJB, from the display, it seemed that the panel display was LCD! I can now look for the dead bulb. How ever I am no nearer sorting out the air con problem. This is of some imortance as my partner suffers with breathing problems, and needs the steady air temp this system should provide. I can run the system with a supply taken from the battery, but as this would bypass the pressure switch, is not a "fix" I am keen on! If you can think of anything that could cause this problem, please let me know, and thanks again for your reply
Regards,
Nuffield

[mjb]

It may be worth a trip to your dealers for diagnostics, or if you put your location in your profile some kind member with working equipment may be able to do the job for petrol money.... See, if you just used a cheap EOBD scanner, you're only speaking to the engine ECU and then in an extremely limited capacity. The dealers diagnostics (PP2000) will be able to query the climate control ECU and see if that has any faults recorded, or if it's registering some wrong values from any of the many sensors (temperature, humidity, sunlight...) it uses.

I strongly suspect a diag session with PP2000 *WILL* show faults.

[Nuffield]

Hi MJB
Thankyou again for your help. My location is 6 miles from Bath, on the Weston S Mare rd.I have tried to put it on my profile but cant work out how! ( To be honest, I am much more at home with a half inch whitworth spanner, than a pc!) I will try to find out the type of reader which was used but I do remember there were mutterings that it would not operate as asked!This was however a proff piece of kit, not a acc shop "will do" unit. On the wiring info I have, a diagnostic socket is listed on the ac wiring, is this seperate to the one in the fuse box cover, if so where is it situated? I dont feel it would be fair for someone to have to travel to me in order to help, but I will do the traveling if anyone can.
Regards,
Nuffield

[Nuffield]

Hi Everyone,
The plot, unlike my hair, thickens! Had to take other half to hospital today and so had to run comp direct from battery for about half an hour, system worked fine. Now however it is still working,without the feed from the battery although the comp is "cycling" running for around 30 sec, off for around 10! Can anyone shed any light on this?
Regards,
Nuffield

[mjb]

Sounds about right for certain conditions. The climate control adjusts everything to maintain a comfortable environment, and once the desired temperature and humidity level has been reached, the a/c will be turned on andn off periodically to maintain it. The 406 climate control is VERY good

[Welly]

The compressor 'cycles' are linked to system pressure rather than cabin temps i.e. it cycles on and off to maintain a set pressure required to serve the evaporator in the car.

This system seems to be working correctly but something is failing to 'call' for the compressor to run. Something in the Climate ECU I would say?

Might be worth disconnecting the battery for 30mins and trying again??

[mjb]

The compressor 'cycles' are linked to system pressure rather than cabin temps i.e. it cycles on and off to maintain a set pressure required to serve the evaporator in the car.

Learn something new every day... although on a cold day it runs the compressor a lot less than on a hot one

This system seems to be working correctly but something is failing to 'call' for the compressor to run. Something in the Climate ECU I would say?

The thing that gets me is that hooking "it" (presumably the compressor clutch solenoid?) up to the battery jump-started it into working as normal, without the lead to the battery.

My guesses (based on experience with the 406s electrical systems) are:
1) The clutch solenoid connection was dodgy
2) The solenoid was 'sticking' and the climate ecu (which is the display unit) figured something was wrong then decided to not activate it to prevent the possibility of braking something further

In the second case, I suspect everything will be fine now as long as the CC is kept on auto, as with it working properly it's regularly hitting that solenoid which'll loosen any gunk inside it. If it's the first, it could go again

[Welly]

The compressor 'cycles' are linked to system pressure rather than cabin temps i.e. it cycles on and off to maintain a set pressure required to serve the evaporator in the car.

Learn something new every day... although on a cold day it runs the compressor a lot less than on a hot one

That's only because on a cold day the refrigerant is not absorbing as much heat from the cabin so the whole cycle slows down - a bit like your fridge at home (flat out in the summer and quiet in the winter).