Electric cabin heater

[ajsellors]

Thats my 1.4 petrol, the one im speaking of is fitted in my 2002 1.4 TDI and its no fan, ive had it all apart to fix the breakages and bodges its just next to the fan housing as such inbetween that and the cabin filter, hears a pic of the outside and you can see the wiring going into the top of it. the alloy heating fins are about 5 inches long and 3 inches square in shape at its base and go from the top of the casing down to near the bottom to heat the air as it passes through.


View attachment 21990

As to been retrofitted i doubt it but can not say 100% for sure.

Isn't that the speed control for the fan motor? It gets hot so the heat sink is in the airflow to cool it down.

http://www.ebay.co.uk/itm/Behr-Wide...724826?hash=item4aed5ab59a:g:wdEAAOSwTapV5dLP

regards

Andrew

 

[Birchall]

Hi Sco

firstly thank you for posting that detail it is extremely helpful and correct (of course)

two things though.

The section that mentions turning the rotary dial to "warm" is for cars without climate control (air conditioning) and i was not refering to the operation of that. But it is useful to let peopke know about how to trigger the extra heating, so tgat is great thanks.

I was pointing out that upping the temperature by a few degrees will have virtually no effect. As your extract indicates though that may be different if you set it to "high" (if that triggers the auxiliary heater)

So your post has clarified that nicely, and to be honest i was not 100% sure of what triggers the extra heater anyway.

Cheers
Steve B

 

[JIGSAW]

Isn't that the speed control for the fan motor? It gets hot so the heat sink is in the airflow to cool it down.

http://www.ebay.co.uk/itm/Behr-Wide...724826?hash=item4aed5ab59a:g:wdEAAOSwTapV5dLP

regards

Andrew

Thats the one, id of never of guessed its a speed controller thow, nice find andrew

I did find another electrical switch in the cooling system on the end of the cylinder head theres a plastic pipe that diverts the radiators top hose into smaller outlets that feed the oil cooler and heater matrix, hidden on the bottom of this plastic part theres also some kind of electrical thermal switch, item 21 on the parts list, This has some part to play in switching something on , off but no idea myself what its for or controls.




Gary

 

[Alan_uk]

If I've understood this thread correctly the cabin axillary heater is designed such that it will rarely be used: just how many A2 owners know the heat settings need to be set greater than 28 degrees?

There was me thinking that when the front windscreen was iced up (inside and out) I could press the front screen Defrosting button on the climate control panel (top left button) and that would switch on the axillary heater and clear the ice. Now that would be really useful. Could the CCU be reprogrammed or is that wishful thinking!

OK, just retrieved the manual from the depths of the glove compartment. Referring to the section on Air Conditioner [their words not mine ]:

page 98: Defrosting: the temperature is regulated automatically. The air output is increased to maximum and most of the air comes out of outlets 1 [centre front windscreen] and 2 [left and right front windscreen].

page 98: If a temperature above 29 C is selected, the display will show HI.

page 99: In the ECON (economy) mode the air cooling system is switched off, and the heating and ventilation system are regulated automatically. Fuel is saved by shutting off the compressor, which operates the air cooling system. On diesel vehicles the supplementary heater is switched off in ECON mode to save fuel.

So, the Defrost button gives no temperature increase. The button simply increases the fan to maximum and directs the air to the front windscreen. Also, ECON still gives some degree of automatic control. The manual quotes 29C not 28C.

Supplementary Heater section:

page 107: Models with turbo-diesel engine are equipped with a supplementary heater to help warm up the interior more quickly. At outside temperatures below about +5 C the supplementary heater is switched on (and off) automatically when the engine is running according to the coolant temperature.

Based on this thread, this seems only half of the story.

Some interesting tit-bits from page 95:

The humidity of the air is automatically reduced when the system cools the interior of the vehicle. This helps prevent condensation on the windows.

If the outside temperature is low, the blower normally only switches to a higher speed once the coolant has warmed up sufficiently (except when on defrost).

In order to achieve maximum engine power, the air conditioner compressor is temporarily switched off when pulling away from a standstill with full throttle.

The compressor also switches off if the coolant temperature is excessively high, to ensure adequate engine cooling under extreme loads.

 

[sco]

It is confusing isn't it - I had thought similar, that setting to defrost would also trigger the heater. I guess what would help would be a VagCom scan of heater switch / outside temp / rpm / and interior temp setting to see what triggers it on and off.

Simon.

 

[Birchall]

This is building up to be a very interesting and informative thread.

This area has always been a bit mysterious.

Thanks to everyone for adding extra info.

I may well add this to the "How to" index thread.
Entitled "how to figure out how the climate control and heating system operates".

Cheers
steve B

 

[sco]

Personally I don't think we are quite there yet! If I can't find the measurement blocks in Vag-Com then will need to be the voltmeter - does anybody know where the control unit for the heater resides?

Simon.

 

[steaman]

Found this:

t	The low heat output relay -J359- (for the additional electric PTC heater) is only fitted in vehicles with no auxiliary heater (fuel-burning additional heater).

t	A PTC heater with 1500 W is being phased in for model year 2003 onwards. Consequently the low heat output relay and the high heat output relay are not fitted.

t	You will find information on which vehicles are fitted with a PTC heater with either 900 Watt or 1500 Watt capacity in the workshop manual “Additional heater”. → Additional heater; Repair group 01

t	The PTC heater with 1500 W (electrical additional heater) is activated via the auxiliary air heater control unit -J604-. This control unit is located in the additional heater.

t	From model year 2003 onwards the auxiliary heater (fuel-burning additional heater) will be phased out gradually, there will be a PTC heater with 1500 Watt

Relay in 9-way relay carrier, dash panel on driver's side

1 -Low heat output relay -J359- --------------------------------------------------------------------------------------------------------------------------

Additional heater heating element -Z35 (with additional air heater control unit -J604)

A - Additional heater heating element -Z35
B - Additional air heater control unit -J604

The additional air heater control unit -J604 is available in different versions. Therefore, pay attention to precise assignment when replacing.
A Parts List
The additional air heater control unit -J604 is built into the additional heater heating element -Z35 (not replaceable separately). The additional heater heating element is built into the heater/air conditioner air distributor housing.
In vehicles with diesel engines and the auxiliary heater option, the additional air heater is not fitted in all vehicles (depending on equipment specification. If no additional air heater is fitted the additional heating function is performed by the auxiliary heater).

 

[sco]

That is interesting - that last sentence suggests there could be some cars that have both diesel and electric heaters.

Looks like there is a relay for the heater on the engine bulkhead and the control unit is part of the heating element - how easy is it to get to that lower part of the air-con unit in the passenger footwell?

Simon.

 

[Birchall]

Personally I don't think we are quite there yet! If I can't find the measurement blocks in Vag-Com then will need to be the voltmeter - does anybody know where the control unit for the heater resides?

Simon.

I agree, but this is as much info as I have seen about this so far, so when we have finished this should be a great thread that will help lots of people understand the options and the operation.

By the way I just tried putting the temperature up to "Hi" tonight (from cold) and could notice no difference in the time taken for warm air to start circulating.
Hardly a scientific test but it took several seconds of holding the up button down to get to "Hi" and then the same amount of time to drop it down to the normal setting (I use 23 degrees at this time of year) so I think I will just leave it on 23 degrees.

Steve B

 

[bretti_kivi]

the logic goes (without the aux heater taken into consideration):

- start air circulating when engine is started
- as the air warms, increase fan speed to distribute warm air according to desired temp

Setting to HI does not affect the speed of warmth - how can it? - but the fan speed can be set to 2-3 bars and that will increase the speed with which the windscreen is demisted, because if you leave it on Auto and 21, it won't push above one bar until the engine has started to seriously warm.

The Aux heater (webasto) will only kick in when it's cold and is turned off by the ECON switch.

Re the webasto and PTC heaters in the same car: no. Never seen, one replaced the other. The PTC has a 180A fuse IIRC...1500W / 12V is about right. So you'll drain the battery completely in around 20 minutes.

If flaps are playing up in any way, you will not get the correct distribution of heat or air.

Artur used the original PTC element in his Electric conversion. He reached 60C, I believe...

- Bret

 

[steaman]

Conditions for activation of the Auxiliary Heater:
Econ button is not operated, the outside temperature is below 6 ° C.
The engine speed is above 600 / min.
Coolant temperature is below 70 ° C (at very low outside temperatures below 80 ° C).
The load on the alternator is below 60% (for an electric auxiliary heaters with a rated output of 900 watts)

J248 = Control unit Diesel Injection System
J604 = Control unit for Auxiliary Heater
Z34 = Heating Element
T6i= Connector on Auxiliary Heater (PTC 1500W)

1= from Battery (150A fuse)
31= from J248
67= from Fuse SB31 (10A)power on with engine running

 

[sco]

the logic goes (without the aux heater taken into consideration):

Setting to HI does not affect the speed of warmth - how can it?
- Bret

Setting to Hi might well affect whether the electric heater is activated or not - most control systems will compare demand to actual - if the 'demand' is 16degrees cabin temp and the 'actual' temp outside is 5degrees you might expect the control system to consider it not worth turning on the heater. If the demand is 28degrees and the outside is 5degrees then the control system should turn on the heater as the demanded temperature would take ages to achieve without it.

Simon.

 

[sco]

Conditions for Auxiliary Heater:
Econ button is not operated, the outside temperature is below 6 ° C.
The engine speed is above 600 / min.
Coolant temperature is below 70 ° C (at very low outside temperatures below 80 ° C).
The load on the alternator is below 60% (for an electric auxiliary heaters with a rated output of 900 watts)

J248 = Control unit Diesel Injection System
J604 = Control unit for Auxiliary Heater
Z34 = Heating Element
T6i= Connector on Auxiliary Heater (PTC 1500W)

1= from Battery (150A fuse)
31= from J248
67= from Fuse SB31 (10A)power on with engine running

View attachment 22004

Steaman are you sure 31 is from J248? Looks like T6i/2 is the feed from the injection system to determine the engine speed, 67 is the heater control unit power supply and 31 is the trigger line from the ACU to turn on the heater?

Simon.

 

[bretti_kivi]

wait, let's differentiate here: HI is the setting for max warmth. On its own, without any additional heating, for example in a petrol, it doesn't and can't affect how fast the engine warms. There's no shut on the thermostat.
The only possible influence here is the PTC or Aux heater. The logic above says that without any aux heating, there's no difference.
With the aux heating, there's a massive difference if the Climate is set to 27.5 or HI.

The logic listed by Steaman agrees with the the logic you've posted. I suspect there's a really simple reason why it's not turned on sooner: you will empty the battery with it on, even with the engine running. 75A is a hefty load.
I suspect, too, that the webasto cost too much to plumb in, which is why it was discontinued.

- Bret

 

[steaman]

Yes, I am. It is the connection marked 117:

 

[bretti_kivi]

and for your information; I found it impossible for the climate to keep 21C at -20 outside temp and a constant 100km/h in an OSS car. Too many losses through the roof. The whole efficiency thing is why the PTC is required in the first place...

- Bret

 

[bretti_kivi]

... and putting cardboard in front of the radiator to help move the warming up process along doesn't seem to work unless it's seriously cold. At UK temperatures it won't help.

- Bret

 

[steaman]

An electric heater is an effective way to increase engine load (load on the generator) and shorten time to low emissions.

 

[sco]

wait, let's differentiate here: HI is the setting for max warmth. On its own, without any additional heating, for example in a petrol, it doesn't and can't affect how fast the engine warms. There's no shut on the thermostat.
The only possible influence here is the PTC or Aux heater. The logic above says that without any aux heating, there's no difference.
With the aux heating, there's a massive difference if the Climate is set to 27.5 or HI.

The logic listed by Steaman agrees with the the logic you've posted. I suspect there's a really simple reason why it's not turned on sooner: you will empty the battery with it on, even with the engine running. 75A is a hefty load.
I suspect, too, that the webasto cost too much to plumb in, which is why it was discontinued.

- Bret

Bret,

I'm not really following your reasoning - on a petrol (or diesel) the amount of heat you suck out of the coolant to heat the cabin directly affects the speed the engine heats up. The amount of heat taken from the coolant is set by the fan speed and air flaps that regulate the flow of air through the heat exchanger.

Steaman is right that the electric heater puts an extra electric load on the alternator that makes the engine work harder and thus heat up quicker.

Why would there be a massive difference if the Climate is set to 27.5 or Hi - do you mean at 27.5 the electric heater is not switched on and at Hi it is?

Simon.