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Heater Sticks On Hot


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#1 bravocars1

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Posted 28 August 2012 - 07:13 AM

Have a xsara Picasso 2003 exclusive. Sometimes the heater sticks on to hot setting, even though we turn it down to 14'c. Now I know air con don't work because rad/condensor leaks, this is one of my jobs to do next. But need to look at heater sticking. Anybody else had this problem?

#2 stimulator

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Posted 28 August 2012 - 04:14 PM

Ok a small explanation of how the system works. As you have an Exclusive you will have auto climate.

In the box under the dash there is an evaporator (aircon heat exchanger) and a heater matrix. The air enters the car and then goes thru the evaporator, from there it arrives at a modulating flap. This flap bypasses the air either through the heater matrix or around it. If the system demands more cold then the flap will modulate to a position to bypass the heater matrix. If it demands more heat then it will put the air thru the heater matrix.
The flap is driven by a stepper motor which is controlled by the cars brain. These motors are known to shed a tooth or two so that the flap is in the wrong position.
You say your aircon doesn't work which should not make any difference to the operation it just won't get as cold as it should.
Also there is small sampler fan and a thermistor in the small grill on the centre dash, either the the left or right. The fan draws air into the grill across the thermistor to regulate the desired dialled in temp. Also the OAT from the mirror sensor is added into the equation.

I'd suspect stepper motor.
62 Reg C3 Picasso VTR+ 1.6 HDi 92BHP
Previous Xsara Picasso 20HDi, C3 SX 1.4HDi, C3 SX 1.6HDI, C4 Picasso 1.6HDi VTR+ EGS

#3 bravocars1

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Posted 28 August 2012 - 11:12 PM

Thank you for that. Where is the stepper motor situated and if removed would I be able to see damage? By the way it does not always stick on to hot. It's intermittent.

#4 stimulator

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Posted 29 August 2012 - 08:18 AM

It's in the heater box under the dash.
62 Reg C3 Picasso VTR+ 1.6 HDi 92BHP
Previous Xsara Picasso 20HDi, C3 SX 1.4HDi, C3 SX 1.6HDI, C4 Picasso 1.6HDi VTR+ EGS

#5 bravocars1

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Posted 29 August 2012 - 08:28 AM

Ok, will have a look. Is it easy to get at and inspect?

#6 stimulator

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Posted 29 August 2012 - 08:38 AM

Simply put not easy. Suggest you purchase a Haynes manual or look at one in the library
62 Reg C3 Picasso VTR+ 1.6 HDi 92BHP
Previous Xsara Picasso 20HDi, C3 SX 1.4HDi, C3 SX 1.6HDI, C4 Picasso 1.6HDi VTR+ EGS

#7 yragdraw

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Posted 03 June 2013 - 11:16 AM

Hi

 

Apologies for hijacking this thread but I have the same problem.  Hot air coming through the car when the temp set to 16c.  Occasionally the cold air will come in and be fine for several weeks.  However it now seems stuck on hot and I am in S Sapin- not ideal when its 30c outside.  Is it a relatively easy replacement?  I know access probably involves removing all the trim around the footwells but what else would need taking out?  Not many English manuals here so any help appreciated.  Is it the flap that breaks down or the motor.  What is the flap attached to in order this it rotates.  Happy to do the work but need to do it fairly soon before it gets really hot!  Any advice apart from the Citroen garage would be great.  Sorry this is a 2.0hdi with climate control.  Thanks



#8 anthony38

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Posted 19 July 2013 - 08:09 PM

Thank god. I am not the only one who has the problem above. I had he same intermittent issue for three years lol. It has not got any worse but it's so annoying. Will have a look.



#9 JRLawton

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Posted 02 October 2013 - 01:00 PM

Hi, sorry to drag this topic back up again but I've been having the exact same problem with my Exclusive Picasso for a while now. I've taken it to several garages including citroen and no one has managed to diagnose the fault.

 

If you managed to locate the stepper motor it would be good to know what you found and if you managed to get it sorted!