2003 Peugeot 206 1.4 Electric Cooling Fan not working
It's an intriguing thought that all over the world there will be Peugeot 206's experiencing this exact same fault. That's because no matter what the make of car, your model will share the same design weaknesses as it's brothers and sisters.
One such fault with my 2003 Peugeot 206 is the failure of the cooling fan to operate. It used to be that a cooling fan was controlled by a simple thermostatic switch. However, things have now moved on and I've learnt that that this is another function controlled by the ubiquitous ECU. That makes fault finding a little more involved than simply shorting a couple of wires!
Computer says STOP!
The problem became apparent when the car was idling and generally being driven slowly. The temperature gauge showed a rapid increase in temperature and the dashboard stop light activated.
Many years ago engine cooling was provided by a belt driven fan which worked all the time. For greater efficiency viscous couplings were then introduced but in the quest for more efficiency these were replaced by electric fans that would operate only when required and not all the time. There operation is usually a very obvious fan noise from just behind the grill so my first reaction on being alerted to a fault was to listen for the sound of the fan and check the coolant level. Silence and no coolant loss! Therefore, having let the engine cool, I drove the car home for investigation (because when the car is moving steadily the engine gets enough cooling from the forced air flow through the radiator).
First carry out research - Is it a common fault?
It could have been a more serious fault. At the very worst a failed head gasket but my golden rule is to look for the simple and obvious first. This it proved to be.Having carried out some basic research on internet forums I gathered some general information and one thing I did learn was that the cooling fan operation failure was a reasonably common occurrence and the cause was corroded cables. They corrode because they are in an exposed position behind the grill. Consequently I needed to start examining the wiring which required disassembling the grill components. Work such as this is an awkward task since it's not obvious how the various parts are held together so here's an attempt at highlighting the key lessons learnt.
Removal of grill components
Then there are two hexagon headed screws at either side which hold the second component which is the red trim panel that holds the badge and goes under the headlight to the wings.
Removing these screws provides enough movement to ease out the black grill which is located to the red trim panel with a row of tabs that can be disengaged with care.
When this is out of the way a star drive screw will be revealed behind the badge that has to be loosened. There is also two very innocuous tabs that have to be disengaged adjacent to inner corners of the headlights. Pressing down on these releases them and enables the trim panel to move forward. The picture below tries to identify what to look for.
This just leaves the fasteners at either end. The ones that hold the trim to the wing. These fasteners, two at either end, push into holes in the wing and should lever out. Three of the four broke in my attempts but it's not a show stopper. A trip to the dealer for the replacement can be made when convenient. The trim is a bit loose without them but not that it is noticeable. Here are some pictures that will hopefully help.
With this panel out of the way I also found it necessary to loosen the black grill below the bumper. Fortunately, this is easy since it is held in place by simple location tabs around it's perimeter. It wasn't removed completely due to the towing eye being in the way but once eased backwards it could be manoeuvred to give enough access to the wiring.
Gaining access to the wiring
Having removed the grills, the compartment that houses the two two relays and associated wiring that operate the fan can then be easily accessed. The compartment is to the left of the fan and the cover is held on by 3 fasteners of the type that require the centres easing out with a screwdriver. The picture below shows the compartment with cover removed and relays loose for inspection.
Corroded wiring confirmed
As indicated by my internet research from support forums the wiring was found to be corroded. In fact one wire was detached at the point where it connected to lower relay. It was obviously not possible to repair and this left two options; obtain another relay socket or remove the socket and put spade connectors onto the ends of the wire in order to connect these directly onto the relay unit itself. The latter was chosen since it was a simple and cheap solution requiring minimal tools.
Important to note that some of the cabling is quite heavy duty and the spade connectors I purchased from the local accessory shop wouldn't accept this size. Also since I don't have a crimping tool I decided to solder the connectors on but this wasn't as easy as I'd expected. It required a heavy duty soldering iron and the copper conductors needed a lot of cleaning to remove the black oxide often to be found in these situations.
Fan still not operational
It seemed in all probability that the fan would now work so I left the engine idling to cause the engine to heat and actuate the fan. The fan still didn't operate! This meant I now had to start thinking and investigate just how the control system worked.
The fan control system
After some investigation the role of the various relays and sensors was deduced. The first component to mention is the engine temperature sensor pictured below.
It's the green object in the picture on the right side of the engine. This is a component that alters it's resistance according to engine temperature. The ECU measures the resistance to determine the temperature and when too high it switches the fan on.
However, disconnecting the sensor makes the ECU think the engine is over temperature and avoids having to run the engine to create the over heating.
When the ECU thinks the engine is too hot it switches the fan on by actuating the relays described above. In fact there are two relays to achieve a low and high speed of fan operation.
The upper most relay in the compartment powers the fan at low speed. This has a resistance in it's feed to the fan which means the fan is supplied with a reduced voltage. This resistor which is a coil of wire, can be found at the bottom of the radiator housing
The lower relay has no resistance in it's feed and provides the fan with the full battery voltage.
Another important point to note when testing is that the engine must be running to check the fan operation. With the sensor disconnected the STOP light operates immediately the ignition switch is turned BUT it does not bring the fan on. This requires the engine to be running.
Fault rectified
With the cabling problems fixed the final problem was found to be with the low speed relay. It simply needed a gentle tap with the screwdriver to coax it into operation! It's repeatedly tested OK since then.
It has made me aware that there are two separate cabling types on a modern car. Those that are used by the ECU to sense and actuate and those that provide the power. These functions are often reflected in the two sizes of wire encountered. For example, the wires from the ECU that control the operation of the relay are of light duty whereas the power feeds to the fan that they are controlling are noticeably larger.
Importantly the voltages on these wires are different. The ECU controlled wires being 5V and the power often 12V so it's important not to get them mixed up.
To sum up
Well it didn't prove to be a very technical fault after all but was made more daunting by the discovery that it was controlled by the ECU.It has made me aware that there are two separate cabling types on a modern car. Those that are used by the ECU to sense and actuate and those that provide the power. These functions are often reflected in the two sizes of wire encountered. For example, the wires from the ECU that control the operation of the relay are of light duty whereas the power feeds to the fan that they are controlling are noticeably larger.
Importantly the voltages on these wires are different. The ECU controlled wires being 5V and the power often 12V so it's important not to get them mixed up.
