BMW E30 Heater Matrix Hoses Configuration - Right and Wrong way round + how to bleed matrix / remove air-lock

My E30 had little or no hot air from the blower inside the cabin. I have heard it is common for the two hoses running to the heater matrix to be fitted back to front, so the flow of coolant through the core is reversed. This causes air locks and severely reduces the amount of coolant flowing through the heater matrix, thus no hot air. 

The reason these hoses so often get fitted incorrectly is due to their location and the way they look when fitted. It appears obvious that the upper hose (back of cyl.-head to heater) goes to the upper stub on the heater-matrix and the lower hose (side of block to heater) goes to the lower stub on the matrix. The hoses look happier this way round, but the matrix and heater-valve are designed in such a way that flow is interrupted and causes the air-lock. 

The correct way round is actually with the upper hose connected to the lower stub and the lower hose to the upper stub, which does of course appear to be back to front, but is essential for correct flow of coolant round the whole engine, not just the heater-core. The correct and incorrect hose configurations are shown in the pictures below.

RIGHT:

WRONG:

How to Bleed system and remove air-lock from Heater-Matrix:

** This is not the normal air-bleeding process when refilling an empty system with coolant, this process is to bleed a system with the air-lock at the back of the head and / or the heater-matrix full of air. **

1. Ensure heater-matrix hoses are fitted the correct way round, if not swap them over. [You should notice if there is an air-lock that no coolant comes out of the hoses when removed from the matrix and the stubs appear dry].

2. Fully tighten the lower [inlet] hose.

3. Leave the upper hose disconnected from the matrix. 

4. Remove the radiator bottle cap. Assuming the coolant level is up to the halfway / max. mark, there should be some gulps of air and the coolant level should drop slightly in the rad. bottle.

5. Cut the bottom off a 2-litre drinks bottle and fill it with water, holding your hand over the lid.

6. Dump the water from the drinks bottle into the radiator bottle, allowing the weight of water to push the remaining air though the system. Water should start to come out of the upper heater-matrix hose from the head. Block this hose with a finger.

7. Continue to top up the radiator bottle with water until water begins to flow out of the upper stub on the heater matrix and quickly refit the upper hose, which can now be fully tightened.

8. Drain the radiator bottle back down the halfway /max. / fill line.

** You should be good to go, but can now bleed / top-up the system using the usual bleeding procedure if necessary. **

E60 Driver's Door: No power to windows, mirrors, remote-lock, etc. - Door Module fuse.

Symptoms:

• Driver's window switch-panel doesn't operate or illuminate buttons.
• Remote door-lock doesn't operate, but all doors operate when key is turned.
• Driver's door courtesy light does not illuminate.
• Mirror control and other door switches do not operate or illuminate.
• Speaker still works.

Cause:

FUSE 10 - 30A - [Driver's Seat Adjustment] It's the first green fuse from the left in the glove compartment fuse-box.

The fuse is labelled Driver's Seat Adjustment, but is really just power from Terminal 30, which also supplies the Driver's Door Module. This module is located inside the driver's door and metes out power to the different door components so that all operations are communicated back to the CAS [Comfort Access System]. This means that when the fuse to the door module blows, power is lost to the window, mirror, etc. switch panel, the remote door lock, basically everything except the speaker. This causes a lot of confusion as to the root of the problem, as it would be very hard to guess that the fuse for the driver's seat adjustment motors would also power a hidden module in the door that controls everything. Oh well, that's modern cars. 

There is a lot of conflicting information on forums about this. It appears that most people have the symptoms described above and not one reply mentions this fuse! Owner's have even shelled out for new door modules which have had no effect and perhaps their lack of further contribution to the thread suggest the same sheepish frustration I felt when I found the fuse. Quite a few people have foxed indy auto-electricians with this problem, who have probably been testing wires, as I did, while not knowing about the fuse.

I eventually discovered the fuse by tracing the wiring diagrams on bmw-planet.com. This is a brilliant place to access the TIS wiring-diagrams and navigate them easily. I have condensed the layout of the door module wiring in the pic below.