Mercedes Benz C240 (W203) 2002 - Cooling fan runs continuously at full speed #
Posted by Shaun Dale on September 21, 2012, 4:44 pm
Year of Manufacture *: 2002 (Approx, on private plate) ( Optional ) Engine Code or CC: 2.6l
Cooling fan runs continuously at full speed when ignition is on. One code in engine system: P2073 electric fan for engine and airconditioning fault. Front SAM has several faults: B1047 B12/2 refrigerant pressure/temp sensor short or open circuit. B1044 S41 coolant level and S42 wash level open circuit (I may have introduced this one when checking level sensor). B1051 No description. B1029 No description. B1046 As B1047 Instruments: B110D CAN fault with N22 (AAC) C-AAC: B15D0 N2/7 Right blend flap stiff or blocked. B1205 Refrigerant pressure low. Previous diagnostic work at MB main dealer involved replacement of refrigerant pressure sensor/regassing system and (they claim) replacement of the cooling fan which was subsequently removed. Customer lost confidence when they claimed to have fixed the "coolant visit workshop" message and they obviously hadn't, so now I've got it! This car has about 22,000 miles only on it and spends a lot of time in "secure" storage as the owner works abroad for long periods of time. I found a large rodent nest by the battery which I cleaned away, obviously "secure" mice. Some of this nest was trapped under the battery so somebody who removed the battery knew it was there but did nothing about it.There was slight evidence of white salts on the loom in this area so it was unwrapped and checked for nibbles and corrosion. I checked continuity and earth isolation tests on the signal wires to the fan. Supply and earth to the fan module are obviously good as the draw is about 50A. There are two signal wires, the Black/White is NBV at ignition on, which it should be. The Green/Blue is at approx 3.6V with the fan module disconnected but goes up to 10.8V with the fan module reconnected. There is no sign of any activity when 'scoped, steady state voltages. Can anyone shed any light on what signal to expect? Is it an analogue voltage, a PWM pulse or is it a data stream of some sort. I am thinking that there is a fan module fault that is pulling the signal high thus equalling full fan speed. But as MB say they tried one with no success either I'm barking up the wrong tree or they failed to clear codes etc. and the fan was running in default mode. Shaun
Re: Mercedes C240 (W203)
Posted by andyhyoung on September 21, 2012, 5:15 pm, in reply to "Mercedes C240 (W203)" Andrew Young
Most of this faults relate to the front sam.I would think this is where the problem is.Has the car suffered any damage n/s/f?The fault logged with heater blend flap is unrelated.hth
Hi Andy, Thanks for the reply. I usually post all logged codes whether they appear relevant or not. Although the front SAM is reporting faults it is giving ignition 12v To the fan module. What concerns me is the change in signal voltage with the module plugged or unplugged. Will power up the fan module independantly of the car tomorrow and see what voltage I get on the command pin. I talked to the customer after my post and he said the MB tech remarked on the lost of sound deadening from the bonnet, but there were no remarks about the nest which was about the size of a small melon. Shaun