[Watsey]

The diesel models have an auxilluary heater which is electrically-powered and draws a lot of current. It activates n the winter months when the ambient temperatures are low - there’s probably a coded threshold but I don’t know what it is.

It makes a significant hit on winter economy, reducing it by around 5 mpg.

Can this be coded out ? Can I just pull a fuse but not trigger a warning light ?

[Allworth]

I do not know answers to your questions, but I tend to have the heater off until car had ran for about 3-5 minutes.
I would assume there is no demand for electrical heater once an engine is warm.

[Eddamoo]

I seem to recall it being called a PTC heater and running upwards of 1.2KW - It would therefore need a ~75A+ fuse to be safe! I cant recall ever seeing one this big, but would assume it would be very close proximity to the blower (behind the glovebox) due to the gauge of wire needed!

I cant say i've ever noticed a change as cold running usually impacts economy anyway. I would argue that letting the aux heater work would allow the engine to warm up faster and reach its operating temperature more quickly - although not enough to offset the PTC's efficiency of course.

I would've thought EcoPro mode disables it?

Could you share how quickly your car blows warm? Mine takes ages and never use Auto or AC mode, i wonder if they also disable it?

[Watsey]

Originally Posted by Eddamoo

I seem to recall it being called a PTC heater and running upwards of 1.2KW - It would therefore need a ~75A+ fuse to be safe! I cant recall ever seeing one this big, but would assume it would be very close proximity to the blower (behind the glovebox) due to the gauge of wire needed!

I cant say i've ever noticed a change as cold running usually impacts economy anyway. I would argue that letting the aux heater work would allow the engine to warm up faster and reach its operating temperature more quickly - although not enough to offset the PTC's efficiency of course.

I would've thought EcoPro mode disables it?

Could you share how quickly your car blows warm? Mine takes ages and never use Auto or AC mode, i wonder if they also disable it?

Good point about EcoPro mode - I never (ever) use it, but I may try it while the engine warms and to see whether the electric heater is deactivated. My gut instinct is that the driving mode won't make a difference, but it'd be a lot less hassle than having to root around trying to find the aux heater / wiring / fuse.

The auxiliary heater generally kicks-in within a minute or two. Even in these modestly cold conditions, say around 5C, the engine oil doesn't reach 75C (the point at which I tend to drive the car normally, rather than deliberately light throttle inputs) for at least 15 minutes.

[Techno 9000]

My electric aux heater is putting out warm air within a mile of leaving home on a frosty morning. A great innovation IMHO.

I have Diesel aux heater (Webasto) in an Audi, and that takes a few minutes to get going and heat the water enough to get a stream of warm air from the vents. This will lower the fuel economy somewhat, but at the convenience of getting the interior warm quickly.

I can't see the electric heater impacting on the fuel economy in the same way, more like the cold mornings leading the engine to take far longer to warm up in itself and the engine management injecting more fuel in that phase.

[3-GT]

Hope this is of help to you.

[Barry330e]

Any idea where the fuse for the aux heater is in the f30 330e?

[xenon]

Originally Posted by Eddamoo

I seem to recall it being called a PTC heater and running upwards of 1.2KW - It would therefore need a ~75A+ fuse to be safe! I cant recall ever seeing one this big, but would assume it would be very close proximity to the blower (behind the glovebox) due to the gauge of wire needed!

I cant say i've ever noticed a change as cold running usually impacts economy anyway. I would argue that letting the aux heater work would allow the engine to warm up faster and reach its operating temperature more quickly - although not enough to offset the PTC's efficiency of course.

I would've thought EcoPro mode disables it?

Could you share how quickly your car blows warm? Mine takes ages and never use Auto or AC mode, i wonder if they also disable it?

Surely it's not that high? To get 1.2KW at 12v is exactly 100A and the vehicle cannot supply that level of current. I thought it was more like 350W but I can't remember where I read that.

[TurboWeasel]

Yeah I wouldn't feel comfortable with that much current passing through a plastic HVAC box. It has a pretty chunky wire on it though! I would put it at around 20-25 amps judging by how long it takes to heat up.

The aux heater in my MK6 Golf is blasting hot air after 1 mile. My 330d's takes a good 5 mins to blow tepid, and 10 mins + to blow hot. I set it at and leave it at 24 degrees all winter though, so maybe it's only heating enough to fulfil that demand. Might blow hotter sooner if I max out the temp.

The impact on mpg is negligible on mine. Normally sits on 50-52 spring to autumn and over winter it doesn't get any lower than 49.....but some of that could be down to the sheddier 'winter' diesel and maybe more regens.

[Stainy]

Originally Posted by xenon

Surely it's not that high? To get 1.2KW at 12v is exactly 100A and the vehicle cannot supply that level of current. I thought it was more like 350W but I can't remember where I read that.

Won't be the 12v battery, it'll be the alternator at around 14v (and rated for 180A?) that should be more like 90A draw for a 1250w element leaving some headroom

[Jolbex]

100A fuses are normal. European small cars (1.6 diesels) have 1500w heater cartridges next to cabin heater matrix, the fuses are nice yellow cubes in separate fuse boxes under the bonnet. The heaters are 3-stage (2 resistive windings - offering 500w (small wind), 100w (big wind) and 1500w (both windings))

[grey78]

I checked my F36 with Bimmerlink, the auxiliary heater is always active at 93% even with external temperature 25 C and engine 90 C. With engine OFF, it correctly deactivates at 5%. I have a friend with F36 and with hot temperatures and engine ON heater is rightly always at 5% What could be the problem? Heater to replace?

[Jolbex]

I dont know how the heater looks like on bmw but im almost sure heater is NOT the problem. Some relais, temp.sensor or climate logic error are more likely. For example, heater on a Peugeot is activated when outside temp is below some 5⁰C, or when cabin temp is set to max....

[grey78]

Originally Posted by Jolbex

I dont know how the heater looks like on bmw but im almost sure heater is NOT the problem. Some relais, temp.sensor or climate logic error are more likely. For example, heater on a Peugeot is activated when outside temp is below some 5⁰C, or when cabin temp is set to max....

This is what I expect from my F36. I think I'll blind my eyes and think it's okay.

[Tommo3]

Originally Posted by Watsey

The diesel models have an auxilluary heater which is electrically-powered and draws a lot of current. It activates n the winter months when the ambient temperatures are low - there’s probably a coded threshold but I don’t know what it is.

It makes a significant hit on winter economy, reducing it by around 5 mpg.

Can this be coded out ? Can I just pull a fuse but not trigger a warning light ?

If i had to worry about 5 mpg for 10 minutes while the car was warming up, then I would change the car for a Citroen C3 that is 20 mpg more economical in the first place.