HDi Additional Heating - is it working?

[Welly]

All HDi's have an additional heating programme which uses electrical resistors in the heater matrix to help heat the cabin in cold conditions.

The HDi's combustion is so efficient that it struggles to get up to temperature quickly and therefore the cabin will be cold for ages.

I had an 'Additional Heating' fault on my recent code read and I am also slightly aware that my cabin heating appears to be slow to get going.

I wonder if it's not really cold enough yet outside or whether something is wrong?

I have found on the internet where this additional heating fault comes up alot on our pugs and mostly comes straight back up on the fault-log after clearing and also the fault will be seen even without any heating-related complaints from the car owner.

I understand there is a couple of big fuses/relays behind the N/S headlight and I have seen a small black box here with big wires but couldn't liberate it from it's mounting.

Anyone know if I can test/check it's operation?

[steve_earwig]

All HDi's have an additional heating programme which uses electrical resistors in the heater matrix to help heat the cabin in cold conditions.

Sorry, first I've heard of it!!!
I thought it was quick getting the frost off the windscreen this morning! Probably much better than the stinky stove my dad had on his Flealander too.

[jameslxdt]

the only real way to test it would be to trigger it through the fault code reader, and see if its working, im sure they only fail as a result of a matrix leak shorting out the wiring, it should come up on the display something like 'additional heating' when it starts working

[Welly]

Well I can safely say it does work

This morning the temperature at the face vents was -2degC and after 7 mins of engine idleing the temp went up to 47degC I felt the heater matrix pipes going through the bukhead and they were only luke warm! so the engine's coolant wasn't doing the heating - the electrical resister pack in the matrix was.

After another 6 mins the temp was at 60degC. Interestingly the temp from the floor well vents on the transmission tunnel was some 30 degrees less at the same time. Somehow the max heating is only from the face vents during the warm up period. The floor level vents do stabilise after a few minutes of driving where I surmise the engines coolant heating takes more effect.

Cleverly, once you begin driving, the engine's coolant no longer has to 'give up' it's heat into the cabin as it is aready hot so it can concentrate on heating up the engine for efficient combustion as soon as possible.

I have also determined that the additional heating does not appear to be enabled when the ambient temp is above 10degC which coincides with the way the a/c switches to cycling on/off mode below 10degC.

Damn clever system I say!

[mbell666]

All HDi's have an additional heating programme which uses electrical resistors in the heater matrix to help heat the cabin in cold conditions.

Bugger me, learn something new every day. kind of explains why i need the engine to run for about 30 to 60s before the fast clear system starts to work, even thou the engine is still stone cold!

[mjb]

I foresee a visit to a breakers yard and the application of duct tape and twist joints...

[jameslxdt]

it would be easier to fit the 306 HDi version as this its simply and inline unit on one of the bulkhead heater pipes

[mjb]

it would be easier to fit the 306 HDi version as this its simply and inline unit on one of the bulkhead heater pipes

Sounds pretty ineffective to me! Most of the heat from that would be dissipated into the freezing cold engine block once the heater matrix gets a few degrees over ambient...

[Welly]

it would be easier to fit the 306 HDi version as this its simply and inline unit on one of the bulkhead heater pipes

Sounds pretty ineffective to me! Most of the heat from that would be dissipated into the freezing cold engine block once the heater matrix gets a few degrees over ambient...

The resister pack will preheat the water going into the heater matrix whereupon the the heat energy is exchanged into the cold cabin air, this results in a cooled return from the heater matrix back to the engine.

The electrical heater unit inputs far more heat than the engine's coolant during the first 10 mins.

I am convinced that the numerous 'additional heating' faults that HDi owners see on a diagnostics check is the result of a software glitch where the additional heating is called for by one sensor only to be defeated by another, say around the 10 deg C set point, flagging up a fault. I wonder if Pug did an upgrade for this?

[mjb]

it would be easier to fit the 306 HDi version as this its simply and inline unit on one of the bulkhead heater pipes

Sounds pretty ineffective to me! Most of the heat from that would be dissipated into the freezing cold engine block once the heater matrix gets a few degrees over ambient...

The resister pack will preheat the water going into the heater matrix whereupon the the heat energy is exchanged into the cold cabin air, this results in a cooled return from the heater matrix back to the engine.

The electrical heater unit inputs far more heat than the engine's coolant during the first 10 mins.

What I'm talking about is after 30-60 seconds or so the heated coolant goes into the heater matrix hot and leaves it warm - the matrix is nowhere near efficient enough to dissipate all the heat once the matrix has warmed up (feel how hot the egress pipe is on a radiator at home). So an increasing amount of energy from the heater ends up being piped into the engine.

On the other hand with a heater in the cabin heating the air not a liquid, ALL the heat it generates ends up where you want it... coming out the vents.

[Welly]

Yes that's correct once the heater matrix is upto temp but the electrical heater for the water inlet pipe is vital for that high load warm up period for the cabins cold air. The HDi just cannot generate any heat quick enough. Once the engine is above 70deg the climate control ramps up the fans and the water heater is switched off leaving the engine's coolant to take over.

I suppose an electrical *air* heater could be unreliable, dangerous, high amperage?

[mjb]

I suppose an electrical *air* heater could be unreliable, dangerous, high amperage?

Didn't you just say the 406 has an air heater? Or do you mean this additional heating works by heating the heater matrix directly (as opposed to the 306 heating the coolant via the pipework)?

As for high current, any kind of electric heater needs high current. In any heating system, amount of heat produced is directly related to the amount of energy used to do the heating... The difference is one of efficiency; how much of that energy ends up as heat where you want it (inside) as opposed to where you don't (the engine block)

[Welly]

Sorry if I was unclear the in-line heater device is fitted close to the matrix on the 406 rather than in the bulkhead/engine bay.

The electrical heater is not 'part of' the matrix as such.