Our family car, a 2010 Ford galaxy wa6 (pre-facelift), is equipped with a diesel warmer / park heater. It serves to bring the engine coolant up to operating temperature quicker and can also be programmed to pre-heat the engine and cabin of the car. Our car had developed an issue where the park heater would only operate in warm weather – and not respond at all if the weather was cold, leaving the heater practically useless. Unlike with my older Porsche, this car is not very well documented online. There are a few forums, and for most issues someone out there has a solution. However, the fuel fired booster heater option is quite rare, and I could not manage to get in touch with anyone who had been down this road before. The factory service manual also fell short.
This is a description of my findings – not a repair guide. If you follow this step-by-step, you will be making all the same mistakes that I did. I will include all dead ends and mistakes, as some of it may be relevant for solving other problems with this type of heater.
Gaining access to the circuit board
The heater (Webasto Thermo Top V Diesel) is located in the right side (passengers side in most countries) front wheelwell. Since this is a roadside repair, I want to avoid disconnecting the coolant hoses. I found that while access is tight, it’s possible do get the circuit board off the unit for inspection/repair without disconnecting the coolant lines.
First remove the wheel and the plastic liner. Beware, there are more bolts than you may expect holding the wheel liner near the front of the car.
Next, remove the 4 or 5 screws securing the webasto heater bracket and exhaust to the car. Since I’m doing this at the side of the road with basic tools, I want to avoid disconnecting the coolant lines – avoiding spills, and also avoiding having to purge air pockets from the engine coolant system.
As soon as I had the bracket loose from the body of the car, I started disconnecting the electrical connectors (and even broke one off) – my advice at this point is to do them later. It turns out that the wiring harness is secured to the webasto bracket further up, so disconnecting these connectors does not help at this point. Access will be much easier with the heater detached from its bracket.
Remove the three T25 Torx screws holding the webasto unit to its bracket.
Then (using a T25 bit on your smallest ratchet) remove the bracket holding the air supply hose and filter. remove the air supply hose from the heater by twisting it anti-clockwise. At this point it should be possible to wiggle the heater out and get much better access. Disconnect the three electrical connectors. One of them is a bit counter intuitive. You disengage the safety clip by inserting a flat screwdriver and bending it towards the connector itself. The picture below shows how – on a different connector with the same mechanism.
Next we need to disconnect the diesel hose from the point where it enters the webasto unit. The hose clamp closest to the webasto must be destroyed to disconnect the fuel hose and you will have to replace it – this is a generic hose clamp. The hose diameter is around 11mm. I had no fuel spillage whatsoever upon disconnecting this hose.
With the fuel hose out of the way, pry the plastic cover off. Underneath the top cover, 3 connectors must be disconnected (see picture above).
Unscrew the 4 torx T20 screws, and the cover and circuit board slides out. At this point I was struck with a feeling that I won’t find anything wrong with this circuit board. Upon closer inspection, the circuit board was in very good condition. I found no faults. It seems that the problem most likely is somewhere else.
Wiring loom
At this point, the next logical step would be to figure out the wiring. There is a breakout cable between the wiring harness and the webasto heater. One end of the connector connects to the engine compartment wiring harness, the other splits out to 3 connectors, named X1, X2 and X4 in the webasto service manual (pictured below – connectors to the webasto out of focus, my apologies).
Looking at the car-side, it can be seen that only 8 pins are actually in use:
Studying the schematics in the Ford galaxy service manual, I found that the connector is named C1HF01-C, the Webasto heater circuit board is refered to as “Auxiliary Heater Control Module (AHCM)”, and also refered to as 1HF01. I found this to be the pinout of the 12pin connector:
C1HF01-C pinout:
1
2 W-bus
3 +12V Main supply (F27 30A)
4 GND
5
6 MS_CANLOW (CAN-)
7 Dosing pump (fuel pump)
8
9 Coolant pump -
10 Coolant pump +
11 MS_CANHIGH (CAN+)
12This correlates perfectly with the missing pins at the plug, so I believe the schematic is correct.
By studying the schematic in the Webasto Thermo Top V service manual, I found this to be the pinout of the three relevant connectors:
X1:
pin 1 - binary input from timer. 12V switch-on signal
pin 2 - W bus
pin 3 - optional exterior temp-switch
pin 4 CAN+
pin 5 - signal to or from the metering pump
pin 6 - summer/winter switch
pin 7 CAN-
pin 8 - signal to or from a solenid valve
X2:
pin 1: 12V power supply
pin 2: Ground
X4:
3 pin connector interfacing the coolant circulating pump. I believe pins 1+3 drive the pump, and pin2 is tach/RPM signal. The schematic is not clear on this, but I won't chase it down, since it's not relevant for my problem.I pieced this together – based on the two service manuals. I have not verified by measuring the actual connector:
Looking at this, I realized that the binary switch-on signal is not in use. Hence, the heater is controlled entirely either by W-bus or CAN-bus. However, the 12V switch-on signal may still work, and could be useful for testing purposes.
I have also found that the device connected to the webasto w-bus pin is the “Fuel Fired Booster Heater Control Unit” and that it grounds to LEFT A-POST 2 SIGNAL GROUND. I believe this is inside the cabin, by the drivers side footwell.
Take a step back
Up until this point I had been assuming that the reason for the Webasto issues would be cracked solder joints at the Webasto circuit board, or possibly a corroded connector at the unit itself. Now that this has been ruled out (more or less), I have a few main suspects:
Ground points: if the supply voltage dips below 11.5V the heater is programmed to not start. A corroded ground point or internal corrosion in mains wiring could cause this. It could also be caused by a poor connection at the fuse box, though less likely. According to the Ford service manual, the relevant ground point is: FRONT RIGHT WHEEL ARCH 2 POWER GROUND (ENGINE BAY) G1D132-A. I did not find it in the wheel arch, and will need to look further.
Corroded contacts in the fuse box or internal corrosion in wiring: the fuse box is easy – wiring will have to be diagnosed with a load on the webasto wiring.
CAN bus communication problem: I’m already having some issues with canbus communication in relation to the audio system. It could be that this also affects the diesel heater somehow.
W bus communication problem: I have found the “Fuel Fired Booster Heater Control Unit” in the ford schematic, however only 3 connections are drawn in: Ground, +12V and W bus connecting to the webasto circuit board. The schematic does not say how the instrument cluster communicates with this unit, and it does not mention where the unit is located. The only thing I know about it is which ground point it connects to and that it has a connector with 6 or more pins (pin6 is mentioned in the schematic). This module may be connected to canbus, or the instrument cluster may have a pin or two to pull high/low to tell the control unit to switch the heater on/off by the W bus.
W bus is essentially serial communication over K bus. I have ordered a K bus to TTL converter with the purpose of monitoring the K-bus and look for problems there.
TO BE CONTINUED….
