Peugeot 806 HDI - Peugeot 806 heater blowing luke warm air

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Tue 28 Dec 2010 20:39
Peugeot 806 HDI - Peugeot 806 heater blowing luke warm air - Oldskoolskater

Hi

My 806 has started only blowing luke warm air from the vents, not hot like it used to.

I've had a look around and it looks like I need to check the temp at the heater matrix to see it both pipes are hot as this is where the heat is generated. Could anybody tell me where this matrix is? Is it in the dash somewhere or in the engine bay??

The car runs at normal temp on the dash gauge and the coolant level warning light did blip on temporarily the other week, but I topped the levels up and have not had the warning light back on since.

I guess once I have checked the matrix incoming/outgoing temp I need to look at the thermostat?

Thanks in advance for any suggestions

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Tue 28 Dec 2010 21:06
Peugeot 806 HDI - Peugeot 806 heater blowing luke warm air - Railroad.

Many people just don't understand where the heat inside the car comes from.

Edited by Railroad. on 28/12/2010 at 21:17

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Tue 28 Dec 2010 21:16
Peugeot 806 HDI - Peugeot 806 heater blowing luke warm air - Railroad.

Many people just don't understand where the heat inside the car comes from. A petrol engine is only about 30% efficient at best. Diesels are slightly better at about 35%. This means only around a third of the heat generated from burning your fuel actually goes to driving the piston down the cylinder. The rest is wasted and carried away by the cooling system. It's impossible to achieve 100% efficiency, but let's just suppose we could. The engine would be making use of every last scrap of heat. There would be no need for a cooling system or even a gearbox, except for providing a means of driving in reverse.

It doesn't end there though as some of this wasted heat is channelled to the car's interior, and this is how you have a heater. The second law of thermodynamics states that heat always seeks out cold areas, and we have had some very cold weather recently. Your engine will be dissipating heat in every direction during this cold spell, and the law of physics says there's nothing you can do about it.....

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Tue 28 Dec 2010 22:32
Peugeot 806 HDI - Peugeot 806 heater blowing luke warm air - Peter.N.

Canyou actually vary the temperature with the controls? if not it could be that the air mixer flap motor is not working.

You will probably find the heater pipes coming through the bulkhead into the engine compartment just behind the top of the engine, they should both be hot, one slightly less so, if they are both hot the fault is in the heater, if not the matrix could be blocked.

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Wed 29 Dec 2010 16:58
Peugeot 806 HDI - Peugeot 806 heater blowing luke warm air - Oldskoolskater

It doesn't seem to vary but then its only luke warm at best at the moment. I'll try setting it to cold and work my way up from there to see if it does increase in temp.

If it is the mixer this will be an electric affair on this car as all controls are electronic - no manual dials, etc

Cheers for the reply

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Wed 29 Dec 2010 19:30
Peugeot 806 HDI - Peugeot 806 heater blowing luke warm air - Cymrogwyllt

Given the weather we have just had I'm not surprised in the least to see a long warm up time. I've ran diesels for many years and in a normal winter I've seen most of them needing ten miles plus to show the gauge at 'normal'. I recently ran 15 miles only to see the temp gauge between cold and normal. Diesel = more mpg but less wasted energy to get the heater hot

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Wed 29 Dec 2010 20:06
Peugeot 806 HDI - Peugeot 806 heater blowing luke warm air - Peter.N.

If you have electronic controls the flap is operated by a motor, these do have a habit of packing up. Set your heater to cold and then see if you still have any heat coming from it, if so its highly likely to be the motor. If the temperature gauge is reaching normal you should have a good heat output.

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Thu 30 Dec 2010 00:10
Peugeot 806 HDI - Peugeot 806 heater blowing luke warm air - Oldskoolskater

Thanks Folks

The air was only tepid after a 2 hour motorway which is definitely not right : (

I'll set the temp to 14 degrees after warming the car up and see if I get warmish air, as this would suggest the flap is stuck.

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