The fuel flap actuator on my ML55 does not function when I unlock/lock the car with the remote FOB.
So I removed the actuator to test it on the bench - when I apply 12V across the terminals it functions immediately - it opens fully and when I reverse the polarity it closes.
So I tested the voltage in the harness connector when I unlock/lock the car and is shows about +0.3V and -0.3V respectively. I have a digital volt meter so its possible that the voltage is much higher (i.e. 12V) but only momentary (so the volt meter doesn't get a chance to display the max voltage achieved). I can't tell.
Given the above, I think the actuator is in good order but that somewhere in the system there is a relay which applies the voltage to the actuator harness for a few seconds so that there is enough "juice" to open or close the fuel flap. The central locking system works fine.
Any ideas where to look next? Seems to me the actuator is good. Thanks.
So I removed the actuator to test it on the bench - when I apply 12V across the terminals it functions immediately - it opens fully and when I reverse the polarity it closes.
So I tested the voltage in the harness connector when I unlock/lock the car and is shows about +0.3V and -0.3V respectively. I have a digital volt meter so its possible that the voltage is much higher (i.e. 12V) but only momentary (so the volt meter doesn't get a chance to display the max voltage achieved). I can't tell.
Given the above, I think the actuator is in good order but that somewhere in the system there is a relay which applies the voltage to the actuator harness for a few seconds so that there is enough "juice" to open or close the fuel flap. The central locking system works fine.
Any ideas where to look next? Seems to me the actuator is good. Thanks.