C5 2, 2007 reg. interior temperature sensing fan

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MJM
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C5 2, 2007 reg. interior temperature sensing fan

Post by MJM »

Good afternoon, all.
The C5 air con has been misbehaving. I've plucked up the courage to connect my Lexia to it(first time I've used it!) and it has thrown up a fault with the small fan that blows air to the sensing unit or the sensor itself. (The one behind the small grill by the glovebox). I've tested the rest of the system, distribution flaps etc and they are all reported as being ok. I could hear the Lexia cycling them with no untoward grinding type noises.
Can anyone tell me how to access this fan, please? Are replacements available, either new or used?
If the fan is ok, then where is the sensor and how do I tackle the access, repair etc of that?

The Lexia also recorded a suspension fault where the suspension ecu cannot obtain data from the steering angle sensor. I can't say that I've noticed anything untoward with the handling of the car so should I be worried about it or just ignore it?

Thanks for your time.

Malcolm

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Re: C5 2, 2007 reg. interior temperature sensing fan

Post by GiveMeABreak »

There is no fan there - that is the car interior air thermistor (Passenger compartment temperature and humidity information), which goes to the Climate Control ECU.

These are still available from Citroen Malcolm.

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Re: C5 2, 2007 reg. interior temperature sensing fan

Post by MJM »

Thanks for the reply. I've made a donation, pleased to do so. Any further advice on the part number and changing the thermistor would be welcome.
Some advice on the other reported fault would also be appreciated.
The VIN number is VIN No VF7**************[VIN obfuscated, can be read by forum staff].
It's a 2litre 16v HDI c5 exclusive hatchback first registered in december 2007.

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Re: C5 2, 2007 reg. interior temperature sensing fan

Post by GiveMeABreak »

Ok, thanks for that Malcolm.

Here is the sensor, (4) in the diagram.
MJM Hygrometry Sensor.PNG
It is part number: 6445VC and is the Temperature / Hygrometry Sensor. It is currently priced at £83.82 from Citroen inc. VAT.

There is no specific guide on replacing this Malcolm, but I believe if you remove the glovebox, you should be able to get your hand in there for access.

I'm almost embarrassed :oops: to say this, but if you have a Haynes BOL, for the MK II, then it's on Chapter 11:20 para 44 for the glovebox.

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Re: C5 2, 2007 reg. interior temperature sensing fan

Post by Estately »

For clarification if you have a handbook, do you mean whatever lies behind the three horizontal slots to the right of the glovebox, item 38?
Must say I thought it was a little fan, but maybe that was in the Xantia.
Anyway a possibility to save beer tokens may be worth your while, in that I noticed fluff inside those slots, don't ask me how, but feeling that said fluff was not conducive to the component's operation I blew and the fluff disappeared.
There had been no problem with the climate control at that point but it may be worth a puff of air to clear things.
Hope that helps.
Andy.

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Re: C5 2, 2007 reg. interior temperature sensing fan

Post by moizeau »

My Diag throws this fault. It thinks my car has 2 even though I'm sure and can only find 1. Diag says that 1 works and the other doesn't. I swapped it out for a known good one and still the same result. AC works, so I've ignored it ever since.

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Re: C5 2, 2007 reg. interior temperature sensing fan

Post by GiveMeABreak »

What car Pete? There's usually only 1 fitted regardless of dual or monozone systems.

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Re: C5 2, 2007 reg. interior temperature sensing fan

Post by MJM »

Thanks for the replies, gentlemen. I have the BOLs and will have a look at removing the glovebox. Looking at the cost of a new one, I'll definately check for fluff etc blocking the grill first. I don't think it is because the Lexia did highlight the sensor as being dead.
I suppose there may be a chance of finding a second hand one somewhere.

Malcolm.

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Re: C5 2, 2007 reg. interior temperature sensing fan

Post by GiveMeABreak »

Just Google:

Citroen "6445VC"

There's not many of these coming up as you'd expect, because of getting to the part in the first place. But beware! Some sellers on ebay are charging as much as, or more than Citroen and some have extortionate shipping charges.

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Re: C5 2, 2007 reg. interior temperature sensing fan

Post by Dommo »

I have previously replaced this sensor on my 2007 C5. I noted on Lexia that the temperature sensor was reading correctly, but the humidity sensor had failed showing a reading in the 1000's of % humidity - clearly incorrect.

There is a fan in there (see youtube link below), I remember the fan failing on my Xantia VSX which meant that it never knew a correct temperature in the car. As the journey got longer the car thought it was hotter (as no 'fresh' air was blowing over the thermistor) which meant that after half an hour or so the car would blow cold air on all temperature settings apart from full hot - I presume full hot and full cold ignore the sensor reading.

Anyway back to the C5, I replaced the sensor with a new OE part, I do recall it being around £60-80, which fixed the humidity reading. I don't actually remember there being any notable difference with the way the auto climate control worked with a fully functional sensor, and within a year the humidity part of the sensor failed again back to that huge humidty percentage being output from it. To access it you do ahve to remove the glovebox which is basically a series of torx screws around the door opening, and one underneath the dash towards the centre of the car, pointing forwards, weirdly. If I recall the sensor twists out, but it has been a while since I touched that sensor.

So in conclusion - if the temperature part of the sensor works correctly on lexia, and it is dust free, I would recommend against replacing it.



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Re: C5 2, 2007 reg. interior temperature sensing fan

Post by Dommo »

I had a feeling that I had posted something on the forum about this but can't seem to find it. The following forum post from many years ago mentions the same issue I had :

viewtopic.php?t=41870

The humidity read out was 32768% as mentioned in this post, I had forgotten what the value was but I knew it was many thousands of % apparently..

Incidentally, 16 bit computer components have a 'signed' number range between 0 and 65,535, and 'unsigned' numbers range from −32,768 to 32,767. So is it a 16 bit computer or sensor? Probably!

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Re: C5 2, 2007 reg. interior temperature sensing fan

Post by moizeau »

407 Marc, if this it the same part?
100_8123.JPG
It takes 30 seconds to liberate one from a 407.

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Re: C5 2, 2007 reg. interior temperature sensing fan

Post by GiveMeABreak »

Up to build dates of 2nd March 2008 on a 407, this was the same sensor as fitted to the C5 MK II 2007. From 3rd March 2008 the heater system was replaced on the 407 and this sensor was no longer fitted. On the new 407 system, they had 2 completely different internal temp probes, so that's probably where you are getting the 2 from - but again only on the later systems.

Here are the sensors on the later heating system (item 4):
later 407.PNG

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Re: C5 2, 2007 reg. interior temperature sensing fan

Post by MJM »

Quick update:
The glovebox came out as the BOLs says except for the L/H screw underneath. I spent about 10 minutes looking for it with a torch, mirror etc and couldn't find it. Took the rest of the screws out and the glovebox came out. I couldn't find a relevant hole for the missing screw to go through so I can't see how it would have been fitted in the first place. The sensor came out with a gentle-ish pull and went back in with a gentle-ish push. It was covered in debris so I gave it a good dose of compressed air. while the glovebox was out I changed the pollen filter, it seemed daft not to do so with much access to it.
When I tried the heating the fan on the sensor worked. The Lexia was still showing a fault so I have temporarily ignored it. Everything seems to be ok at the moment, I'll know more when the car is used again.

I also found the same obscure fault as triumphtoledo, "missing + on display" even though the display is working ok at the moment.

Malcolm

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Re: C5 2, 2007 reg. interior temperature sensing fan

Post by moizeau »

Mine shows a fault on the 'passenger side sensor' from what I recall which is why I changed it (5 euros from the tatter), then it clicked, 'passenger side' may be referring to the RHS with Diag English being a rough translation from French where they drive LHD cars. If everything works, ignore it. At least you took the opportunity to clean it and the change the pollen filter, so piece of mind there.