12v auxilary coolant heater from a BMW

[fearone]

Im playing with the idea of fitting a oem coolant heater off a diesel bmw into my car.

It has 4 wires, a thick positive and negative pus two thin wires which usually go to the heater control unit in the bmw.

The thing I'm not sure about is how to wire a switch up to it?

Will add more details later. Any advice welcome as I'm not too good with auto electronics.

[Daox]

Why a 12V heater? If its for efficiency, its probably not the best idea to be honest. Running a 100W (which isn't a ton of heat) heater will cost you about 300W of engine power which is almost a half of a horsepower.

To answer your question though, the best idea is to use a relay to activate the heater, because it probably pulls a good amount of current. You need to find out how much power it pulls and find a relay that will handle that amount of current. You'll also want to add a fuse to it for safety and you'll need to know how big of a fuse to use.

[oil pan 4]

I really don't think a 12v coolant heater is worth the beating it give your battery and charging system.

I like the idea of warming the engine with free waste heat:
http://ecomodder.com/forum/showthrea...ler-29085.html

Problem with a 300w heater is thats not much power, about 2000 BTUs per hour. A normal block heater that plugs in uses 500 to 1000 watts. I like them a little bigger.

This is a real block heater:
http://ecomodder.com/forum/showthrea...mer-23893.html
4700w total, works pretty fast.

[fearone]

Only 12v because mains is not practical for me, it will only be switched on for a few mins after starting and on over run when cold. I want it both for eco and heating/defrosting in the winter.

From what iv read its 400w and is fitted to 2l to 3l, 4 and 6 cylinder engines, mine is only 1.7l. BMW owners have reported increased warm up time when it fails so it sounds like it could be ideal for my needs/wants.

[fearone]

This is the one, the thick cables go direct to battery and earth but the other two on the plug i'm not sure of, at least one will be going to the heater control but i need to work out how to rig a switch up to it.

[fearone]

Taken from another forum..

Electric Auxiliary Heater DDE 4.0 (E46 only)

The electric auxiliary heater heats the coolant with electric heating elements to compensate for the slight heat loss at high degrees of engine efficiency. Depending on the vehicle equipment, the heating request is sent either from the air conditioning system (IHKA) or from the heating control to the DDE control unit.

The heating elements only cut in when there are sufficient electrical power reserves. To determine the available power reserves, the alternator sends a pulse duty factor signal corresponding to the current alternator load to the DDE control unit. Depending on the permitted additional alternator load, the DDE control unit activates the auxiliary heater with a square-wave signal with pulse duty factors (= variable pulse widths) between 5 and 95%, thus controlling various heating power stages.

The idle speed is increased to 850 rpm when the auxiliary heater is activated.


Cutout conditions

The auxiliary heater is switched off under the following operating conditions:
•Battery voltage < 12 V (ON hysteresis 12.8 V)

•Engine speed < 710 rpm (ON hysteresis 730 rpm)

•Time after engine start < 10 s


•Coolant temperature
The coolant temperature threshold that must be exceeded for the auxiliary heater to cut out is determined with the measured ambient temperature from a characteristic curve. Characteristic curve data:






Ambient temperature [°C]

Coolant temperature threshold [°C]


-10.0

86.0


-5.0

86.0


10.0

50.0


20.0

17.0


Important: A fixed coolant temperature threshold of 86°C applies if no outside temperature sensor is fitted.

The outside temperature sensor is fitted in the following E46 models:
•On all models with 6-cylinder engines

•On models with 4-cylinder engines only with on-board computer or air conditioning.



The auxiliary heater is also switched off when one of the following fault codes is stored:
•0115, ”Coolant temperature sensor”

•1A04, ”Electric auxiliary heater”

•1A0E, ”Alternator load signal”


Troubleshooting

The activation function is monitored for short-circuit and open circuit.

As from DDE software version B1 (phase-in 07/2000) the auxiliary heater will be monitored for overheating.

Fault code 1A04 ”electric auxiliary heater” is stored if a defect occurs.

Consequence: Poor heating capacity at low temperatures

If the alternator indicates a load signal of 0 %, fault code 1A0E ”Alternator load signal” is stored.

Consequence: Auxiliary heater is switched off

[cptsideways]

I have several of the Webasto diesel ones, they are brilliant things. Standard on e39 diesels here in Europe. Can be rigged up to come on remotely too with 1 wire. I have previously fitted one to my Landcruiser too.

Will get the big diesel up to operating temp from freezing in about 15mins, they use about .2 - .4 L of diesel per hour.

[fearone]

Originally Posted by cptsideways

I have several of the Webasto diesel ones, they are brilliant things. Standard on e39 diesels here in Europe. Can be rigged up to come on remotely too with 1 wire. I have previously fitted one to my Landcruiser too.

Will get the big diesel up to operating temp from freezing in about 15mins, they use about .2 - .4 L of diesel per hour.

I would love to have a Webastro but think it will be too difficult to fit on my car, too many wires.

[oil pan 4]

Just make sure your battery and charging system can handle it.

The small wires going to the plug look like they could be a temperature switch.

Something that much power really needs to be ran off a relay or contactor.

[oil pan 4]

Another starting option might be to install something like this:

DIY: Teaching an old J-code new tricks - Diesel Place : Chevrolet and GMC Diesel Truck Forums

Diesels really don't like cold air when you cold start them.