Heater Won't Provide Heat...!

[citrophile]

Hi

When I started my C5 this morning my heater wouldn't work, it flatly refused to provide any heat whatever setting I put it on. I have the dual climate controls and even when set to high it still only provided a nice blast of cold air. I have checked coolant levels and fuses and connected it up to the lexia but nothing showed as a problem. It was fine yesterday!

Any thoughts? Is there a thermostat or temperature sensor somewhere which might have failed?

Rob

 

[paul.h]

When you alter the temperature setting can you hear the flaps in the heater air con unit moving - if not could be the motors that move them or the flaps may be broken, or the software may need a reset, or the temp sensor (wherever that is) is faulty. You could look in the passenger footwell and see if the coolant pipes to the heater are hot - as far as I know the only temp control is by moving the flaps so no  heater valves to look for.

[citrophile]

Thanks Paul, will try all of that when I get some time on the weekend

[MikeLane]

"When I started my C5 this morning my heater wouldn't work, it flatly refused to provide any heat whatever setting I put it on. I have the dual climate controls and even when set to high it still only provided a nice blast of cold air."

 

This has happened on my C5 (2005 1.6 HDi). Neither side provides hot air either from  outside or when recycling cabin air (blower works fine). With ignition on but engine not running, I hear a click when I increase or reduce the temp settings (on both sides).

Is there a "Master Flap" which controls ALL air flow through the heater matrix.

Is it likely that both driver and passenger flap control motors have failed at the same time?

Will I have to drop the dash to get at the driver and passenger flaps?

(Could I have stopped it working when I changed my driver's window switch, without doing a full S/W reset??)

[citrophile]

Hi Mike

The driver and passenger flaps are independent of each other so it is unlikely that they will both have failed at the same time. I would think it more likely to be an electrical fault so a full BSI reset is probably a good starting point as would be a check of the connectors to the motors and any fuses. You could also check to make sure the heater matrix is getting hot. You can get at the pipes if you partially remove the trim cover underneath the glove box. Make sure the engine has warmed up and then check if the pipes are hot. Be careful though as there is no regulator valve so the pipes will have engine coolant temperature water in them around 120 degrees C as it is a pressurised system.

If after the above there's no change then you will need to start checking individual motors. Firstly, with engine running and on one side only adjust the temperature to Hi and then down to Lo, you should hear the motor whirring a little as it moves the flap. Do this a couple of times each side.

Failing that then you may need to think about a more disruptive investigation involving glovebox removal and motor removals. Dash removal is really a last resort and really only when you're absolutely sure nothing else can fix it, although it's not as bad as you think.

Cheers

Rob

[MikeLane]

Thanks Rob - I checked the pipe through a gap on the passenger side and it was rather hot (ouch!) so the matrix is being fed.

I'll try a BSI reset tomorrow and hope for the best. 

Mike

[MikeLane]

Hi there - whilst waiting for the rain to stop (still hasn't) I started to wonder whether my cabin temp sensor might have failed. Tried Haynes but no mention of where it is housed. Does anybody know please?

[MikeLane]

BSI reset done but still no heat! (Also the driver's front and rear windows control is playing up AGAIN!) However, I (think I) heard a whining noise when I pushed the Demist button on the A/C control and Cold air is blown  only to the windscreen and then out of all orifices when Auto is pressed. I still can't locate the cabin temp sensor. I have a sunroof and, next to the control, there is a small grill. Is this where the sensor is housed? Oh! Just discovered  how to take the sunroof control out (Haynes Manual 12.5 para 9) so I'll have a gander tomorrow.

[citrophile]

Temperature sensor is behind the small grille on the dash just above and to the right of the passenger glovebox. Although there are independent left and right hand temperature controls there is only one sensor!!

[MikeLane]

Hi Rob - thanks for the replies and advice.

My C5 has a sunroof and there is a small grill on the control, next to the switch so I thought the sensor might be inside the unit. The Haynes manual tells me to prise out the lamp (easy - for a change) and undo the single screw which isn't apparent! However, there is a sort of plastic stud with a hole through the centre. I tried a small screwdriver but couldn't find a slot (perhaps there's a small torx or Allen key slot?). Now I'll look at the top of the dash to see if the sensor's there before I have another look at the sunroof. As you say, taking the dash out is a bit daunting, especially as my garage is full of junk and it keeps raining!

(Just discovered that the passenger side side lamp is blown and, of course, there isn't room to take the bulb holder out without removing the battery AGAIN!!!)

(I don't think those clever guys at Citroen want cars more than 10 years old on the road! There's a very smart looking BLACK Cactus in my local dealer's showroom........)

[paul.h]

If you test the Cactus, try it on a few bends with passengers inside, just to check the high up seating position does not make you feel seasick - based on a comment I overheard requiring some design changes but I have not tried the car. If you do test one, please give a report for other potential owners.

[MikeLane]

Found the grill Rob so thanks. Now just the problem of taking out the glove box, trim etc. to get at the sensor.

Incidentally, in the sunroof control/map reading lights "box" I found a twisted pair which ended with an unattached connector bound with sticky sponge rubber, located just above the grill. Any ideas......?

Edited January 11, 2015 by MikeLane

[paul.h]

In the mark 3 C5 there is a microphone located in the overhead bit, so maybe it could be for that.

[MikeLane]

If you test the Cactus, try it on a few bends with passengers inside, just to check the high up seating position does not make you feel seasick - based on a comment I overheard requiring some design changes but I have not tried the car. If you do test one, please give a report for other potential owners.

I believe it's based on the C4 chassis. I had to drive a C4 Picasso for a couple of days and neither I nor my partner were impressed with the ride!

(Looking for a vehicle in 1982 to cart us and a dog and half-a-dozen kids, she suggested I tried a CX Familiale and I was sold! Since then 2 BXs (1.6TRS and 1.9D) a Xantia 1.9D SX and now my (usually) trusty C5 1.6HDi VTR, I've got so used to "proper" Citroen suspension!)

[paul.h]

We have a 2011 C4 and that is one of the better cars we have owned. It handles well enough and is comfy for long motorway trips. I think the C4 chassis is also used for the DS5. It could be the ride quality is not related to the base chassis but what they then do to it for the various models.

[MikeLane]

In the mark 3 C5 there is a microphone located in the overhead bit, so maybe it could be for that.

Thanks Paul (and for your comments on the C4). I've now spotted the corrct grill! Do you happen to know whether the cabin temp. sensor is checked by a Lexia - i.e. if it's faulty or appears to be "sending" a high temperature reading? (I'd rather have this checked before looking at motors/spindles.)

[MikeLane]

Just spotted this on "French Car Forum" :

 

The humidity sensor problem was traced to the sensor behind the three slots on the fascia, just next to the glovebox (it's a C5 II). This unit is a combined temp and humidity sensor. It was gunked up pretty badly and its circuit board was corroded. A new part was £41.12+VAT but at least the climate control now works perfectly.

 

Mine's booked in for a Lexia check at my Indie (Citroen Care at Rake, near Petersfield - Peter Boxall) to see whether this sensor is working on Wednesday. Might take a look at the Black Cactus tomorrow!

[MikeLane]

If you test the Cactus, try it on a few bends with passengers inside, just to check the high up seating position does not make you feel seasick - based on a comment I overheard requiring some design changes but I have not tried the car. If you do test one, please give a report for other potential owners.

Hi Paul - I saw the "Black" Cactus but was not impressed enough to take a test drive. Depending on the model chosen (Touch, Feel, Flair) one then has to go through the "configurator" (available on the Citroen web-site) to see what is and what isn't included.

On the Flair (top of range) I still needed to specify 7 additional items (including black paint at £495, Glass roof  at £495, spare wheel at £75 and CD player at £139.63) as well as engine, wheel type etc. For the Feel I would need to specify a dozen items to get a similar spec. The car is "alright" but doesn't compare with my lovely C5! (except for excellent lower consumption and CO2 figures).

[MikeLane]

"Mine's booked in for a Lexia check at my Indie (Citroen Care at Rake, near Petersfield - Peter Boxall) to see whether this sensor is working on Wednesday."

 

Sure enough the temperature and humidity sensor has failed but (thank goodness) everything else is OK. New sensor c. £35 and about £50 to fit it so...... (Peter Boxall also fixed my recalcitrant window control!)

[paul.h]

In the parts diagrams for the 2004 to 2008 C5, it has the humidity sensor as part no. 6445VC Sensor Hygrom, but does not mention temperature. This part is not shown for the earlier C5 model. The procedures do not say how to replace it - if you get chance, ask the garage how to do this.

 

To help others, the following is the complete relevant bit from the other forum topic from Nov 2012:

2. Code 0702 - 'Passenger humidity sensor not defined' - I presume this means the air con humidity sensor is dead. I checked the reading (using Lexia) and it thinks the interior humidity is 32768%. Does anybody know where it is located? I presume this is different to the temperature sensor, situated next to the glovebox behind the small fascia vents.
 

The humidity sensor problem was traced to the sensor behind the three slots on the fascia, just next to the glovebox (it's a C5 II). This unit is a combined temp and humidity sensor. It was gunked up pretty badly and its circuit board was corroded. A new part was £41.12+VAT but at least the climate control now works perfectly. The humidity, when tested, was around 28%, compared to the 32,678% recorded by the old one. (part number 6445.VC)
 

[MikeLane]

In the parts diagrams for the 2004 to 2008 C5, it has the humidity sensor as part no. 6445VC Sensor Hygrom, but does not mention temperature. This part is not shown for the earlier C5 model. The procedures do not say how to replace it - if you get chance, ask the garage how to do this.

 

To help others, the following is the complete relevant bit from the other forum topic from Nov 2012:

2. Code 0702 - 'Passenger humidity sensor not defined' - I presume this means the air con humidity sensor is dead. I checked the reading (using Lexia) and it thinks the interior humidity is 32768%. Does anybody know where it is located? I presume this is different to the temperature sensor, situated next to the glovebox behind the small fascia vents.

 

The humidity sensor problem was traced to the sensor behind the three slots on the fascia, just next to the glovebox (it's a C5 II). This unit is a combined temp and humidity sensor. It was gunked up pretty badly and its circuit board was corroded. A new part was £41.12+VAT but at least the climate control now works perfectly. The humidity, when tested, was around 28%, compared to the 32,678% recorded by the old one. (part number 6445.VC)

 

 

Peter reckons he can replace the part after removing the (passenger) glove box, hence about 3/4 - 1 hour to do the job. I'll try to watch what he does and confirm or otherwise.

[MikeLane]

"This part is not shown for the earlier C5 model. The procedures do not say how to replace it - if you get chance, ask the garage how to do this."

Hi Paul - (thought I'd posted this reply yesterday but it appears not!)

Peter (Boxall) reckons this part can be accessed and replaced simply by removing the (passenger) glove box, in abround 3/4 - 1 hour. Hence the c.£50 labour estimate.

I'll watch what he does and let you know.

[MikeLane]

"To help others, the following is the complete relevant bit from the other forum topic from Nov 2012:

2. Code 0702 - 'Passenger humidity sensor not defined' "

 

On mine the message was "Permanent Fault"

[MikeLane]

"This part is not shown for the earlier C5 model. The procedures do not say how to replace it - if you get chance, ask the garage how to do this."

 

I watched Peter Boxall (who'd never done the job before). He removed the passenger glove box and felt behind the grill on the dashboard. After a bit of fiddling he removed the connector and then unclipped the sensor. It's about 3cm square and 5.5cm long with a small tube at the front end. The new sensor was then clipped in and the connector replaced. He tested the AC/Heater and it worked! Then replaced the glove box and used his Lexia to clear all recorded faults.

Total labour charged 3/4 hour + diagnostic (Lexia) charge of £25. Total bill including part and VAT £129.60.  (I have a feeling he didn't charge for the time he took (about 1/2 hour) to diagnose the fault before ordering the part.)