C5 X7 heating resistance not working?

[Xantippa]

According to service.citroen.com my car´s heater has this heating resistance, but it´s not clearly working. In cold days there´s no heat until engine gets warmer.

How can I check whether heating resistance is enabled with Diagbox? Pic attached.

Thank you!

[GiveMeABreak]

Don't forget it won't be as quick and as hot as a Dyson Blade

It's basically a BEHR unit, nominal voltage is 13.5 Volts and nominal power at 0 °C is 1000W.

There are 3 Control connections (Pins 1-3) and the earth on Pin 4. So I suspect that there are 3 positive temp. coefficient resistance units that are combined to produce the heat.

Essentially if it isn't working - replace it as the specific unit isn't shown in any detail on the wiring diagrams.

[Xantippa]

I think I´ve seen sometimes a pic of diagbox (or in my own session) a setting to enable/disable this, but I´m not sure. I just thought maybe it´s not enabled to save battery (car has been sold new in Austria so not so cold there as here north).

[GiveMeABreak]

That option you are talking about is for the 'Additional Heating' Marko, that was an option in some countries. There is no option for the normal air heating resistance to be turned on or off.

[white exec]

There may be certain conditions for the PTC heater elements (look as if there are three) to operate
- engine running, maybe above a specified number of rpm
- coolant below a certain temp (could be 10°C or thereabouts)
Note: This could make non-diagnostic testing less easy in warmer conditions.
- cabin temp selected as near maximum

The three heater units will be controlled by a relay for each, and each will have its own fuse.
They will cut in sequentially, and cut out likewise as coolant temp climbs.

1000W for the three sounds about right: that's 330W each, or 24A apiece, 72A total.
As the unit warms up, its resistance also rises (PTC), limiting and tapering off the current consumed.
Because of this very high electrical load, the operating conditions (above) are carefully limited.

My figures/detail based on knowledge of our similar heater on RAV4, which is 3 x 30A max, 3 x 50A fuses, and 3 relays.
Circuit details should confirm the X7 arrangement.

[GiveMeABreak]

There's no circuit showing this component Chris and nothing to specify conditions - except that the module will operate to assist in rapidly meeting the interior temperature set by the driver.

[Xantippa]

That option you are talking about is for the 'Additional Heating' Marko, that was an option in some countries. There is no option for the normal air heating resistance to be turned on or off.

I think there wouldn't be need for this electrical heater if car is equipped with fuel heater, thus it may be possible to disable it?

[white exec]

There's no circuit showing this component Chris and nothing to specify conditions - except that the module will operate to assist in rapidly meeting the interior temperature set by the driver.

There was a thread from 2016 discussing this, wrt C4 1.6HDi -
viewtopic.php?p=514688#p514688
including wiring diagrams.

The C5X7 PTC heater (Air reheating resistance, diesel grade) is 6436 91.
Also fitted to C6.

There was some suggestion that the switching relays might be part of the resistance unit itself, and controlled by BSI.

Quite surprised this unit doesn't appear on wiring diagrams.

[GiveMeABreak]

That option you are talking about is for the 'Additional Heating' Marko, that was an option in some countries. There is no option for the normal air heating resistance to be turned on or off.

I think there wouldn't be need for this electrical heater if car is equipped with fuel heater, thus it may be possible to disable it?

Yes, for the additional heating configuration - it has to be one option or the other, so not a separate option for the internal heating resistance:

There are 3 options in the same parameter, so it can only be one of the three settings:

Absent - for Petrol Engines
Heating Elements - For a diesel engine without additional heating
Autonomous Burner - For a diesel engine with additional heating

So selecting the option for a petrol option would say it is not there - but what impact (if any) this would have on other systems is unknown - but I don't see the point of incorrectly setting this parameter to the wrong option. It would be easier to just not replace it?

[Xantippa]

Any quide how to find that setting in Diagbox?

[GiveMeABreak]

Yes, it is under the BSI configuration Marko. Probably in the Customer Options and 'Air conditioning – Cabin heating' section.