Heater speed control
Q Can you advise me on a problem with the heater fan speed control in my wife’s 54-plate Peugeot Partner Escapade 2.0 HDI with aircon. We recently experienced the infamous Peugeot heater problem, where the fan constantly operates on full blast. I examined all the visible electrical plugs both to the speed control module in the fan housing, along with those at the rear of the speed control and direction switch on the fascia. None appeared to show signs of overheating or burning, so I replaced the speed control resistance module.
Not wanting to experience the same problems that Vauxhall Zafira owners have had, I bought this item from a well-known UK distributor, albeit at three times the price being offered on the internet. I also went to great lengths to ensure the part numbers and the colour of the PCB (white) was a match, as I believe different colours denote different models within the same part number range.
I installed the unit and tested the fan assembly while it was secured in the passenger footwell. All appeared well, with four or five distinct differences in speed. However, it did not appear to switch off completely, in that it runs continuously at the slowest speed regardless if the switch is in the ‘Off’ position or either ‘Slow’ direction. I returned the unit to the supplier, who exchanged it for another from a different manufacturer, but it performed in exactly the same way.
Having read on various online forums about problems with speed controllers and heat-sink temperature, I checked the temperature of the resistor heat-sink. After running for about 10-15 minutes and while rising rapidly when in the ‘Off’ position, it then stabilised to about 25-30°C above ambient. I was not overly concerned with this, as the resistor is consuming the best part of 40 amps when running slowly and this test was conducted in free stationary air outside the confines of the heater housing.
My initial thought was that the speed control switch might be faulty and possibly be the cause of the initial failure, but then I wondered if the unit is designed to run constantly at this slow speed when the engine is running, in order to cool the heatsink and resistor. I have now fitted the whole fan unit into the heater system and the slow running of the fan when in the ‘Off’ position is undetectable, either by noise or anything exiting from the vents.
I noted that the speed and direction (fresh air or recirc) switch mechanically changes the direction paddle within the heater trunking when moved from ‘Stop’ to either of the ‘Slow’ settings, which seemed to confirm that it should run continuously. I might also add the symptoms do not change when the aircon is either on or off. Andy Blakemore
A According to my data, you have the correct electronic speed control module fitted in your Peugeot. This can be distinguished by the two diodes on the face of the speed control unit. Unlike the standard resistance units fitted to many heater motors to control speed, these do allow a bypass of current to enable a slow steady movement of the fan. This is normal and, as you say, undetectable in normal use when the fan is fitted in place.