Thanks. When you say needs to be checked probably with a multimeter inline do you mean the blade fuse reader would not indicate the correct fuse pulling the power? When I checked them all with the blade fuse reader it was the one I noted in my first post that was pulling the power. I am not an expert in any of this so just asking - will the multi meter show me better information/indication of the issue. To be honest I though it gives the same as the blade meter with the only difference being that you don't have to go back and forth every time to check the meter when taking out a fuse.
Hello Ray,
Auto-mobile doesn’t actually mean what you are suggesting, what he is referring to here (quite correctly by the way) is that all the parasitic/quiescent drain needs to be measured as a
“global” figure, rather than a single isolated component figure, and that can only be done by one of two methods using an ammeter. Firstly, by disconnecting the vehicles negative battery lead and inserting an ammeter in series so
“all” the current is measured when
“all” the vehicles modules are in
“sleep” mode, and secondly, you could use a clamp-on ammeter, not quite as accurate as the former but simpler to use without breaking in to or interrupting the electrical integrity of the circuit. There is actually another way in the absence of an ammeter, but you would need to place a fixed 1 ohm x 10 watt resistor in the circuit and then measure the voltage dropped over the resistance and then calculate the current draw from the figures obtained, that’s not as difficult as it sounds, its really very easy and a method some people prefer to use anyway.
By the way, 0.047 amps (47 milliamps) is the maximum permissible parasitic/quiescent current draw on a CL, calculated on and from the engineering data given for each modules parasitic limits - times those limits by the number of modules on the car and its easy to see where the maximum threshold limit should be. Yours being the CL65, further and slightly complicates matters here with the integration of several supporting systems. I would imagine that it does have everything on it, so anything in excess of that figure of 0.047 amps should be considered as being “suspect”. The figure of 1.26 amps obtained from that particular circuit alone that you refer to be excluding any other parasitic drains within the remainder of the electrical system does seem to be relatively high and does need investigating. There could very well be some other underlying issues here and the vehicles systems need to be checked out properly – speculation and guessing on these cars could prove to be very costly.
The AAC or ACC systems, like most electronic control systems on a modern motor car, have sub-systems and often a component in the sub-system can give rise to a fault with does in fact affect the main or primary system. The climate control system on your car is slightly different to some of those, in fact, fuse number 82 is considered as the main input supply voltage, however, the sub systems on the CL’s are powered up primarily from the head unit and it could very well be that there may be an issue here. Before you start to look for any issues elsewhere, it might be advisable at this state to interrogate the AAC control module and extract any fault codes that may be stored in there. Follow this procedure Ray and then come back to me with the fault codes, if any, and we can look at those first.
- Start the vehicle and then switch on the AAC system by pressing the button marked as “O” on the right hand side panel at the bottom, now hold down the switch for the activated charcoal filter at the bottom left hand side of the left hand panel and at the same time hold down the switch marked as “REST” at the top in the right hand side panel. Hold both of these switches down simultaneously for between 5 and 10 seconds until you see the word “searching” appear in the panel display in the centre of the AAC screen.
- When the diagnostic procedure has finished, you will see the letters marked as “DIAGN. ERROR” and the symbols marked as “- - - -“ appear, this means that there are no fault codes actually logged and we can assume from this that your area of concern is somewhere else and not down to any specific component in the AAC system. If any fault codes are logged, then write them down so we can look them up to identify the component/s. It will only show one logged fault at a time, so you can scroll up or down with the temperate control toggle switch on the right hand side of the middle paneluntil you have identified all the fault codes logged.
- If you want to clear any fault codes, then just press the centre button in on the left hand side panel marked as “AUTO” first and then do the same on the right hand side panel marked as “AUTO”. The codes will now be erased. If there is a “hard” fault within the system, then when you come to do another diagnostic check, the fault code should come back
- To come out of the diagnostic mode sequence, then just press the “REST” button on its own to display the normal window in the centre panel display. Turn the car off, wait several minutes and start the car again if you wish to go through the procedure again to confirm if any codes are now stored.
In answer to the specific question you raised above
“Does anyone know what the two items in the points above are/control and what in them could be causing the issue.” From the head unit itself, which you have identified as N22, then the power is supplied from this unit to the stepper motor electronics control module; centre ventilation electronics control module, the sun sensor and the multifunction sensor, to name just a few. There are quite a lot more units involved other than these here Ray that are in fact networked over the data bus (CAN) to various other modules, so all in all, a very very complex networked system.
The other item that you have identified as being A31, well, this unit is actually the heater supply unit, which houses the two duo valves, left/right and the coolant circulation pump for the heater. If you need to know of its location, then it’s just to the right and slightly rear of the brake servo unit under the plastic scuttle panel. To be honest with you Ray, from my own personal experience, most people are frightened to death of going anywhere near a W215 for obvious reasons, and those that are brave enough to do so have to tread very carefully as it is so very easy to cause additional damage. Noting from the lack of input to this thread says it all really; it’s probably why no one on here has offered to help you other than to guess at what it might be. If you do get someone skilled enough with a STAR machine, then it’s very easy for them to go in to the system and then check the entire individual sensing/active components.
I’m off work now until Tuesday, but I will come on to the forum sometime over the holiday period to see if you have resolved the issue, if you haven’t, then I’ll explain what to do and how to go about it. Its not difficult, but you will have to be able to navigate where to go and what to check, some of these modules require a considerable amount of interior trim to be removed to gain access, we can also assess them in isolation so you will get a better chance of finding the right culprit. As laborious and time consuming as it may be, (without the aid of diagnostic equipment) it’s the only way to do it properly. Some modules actually do go to sleep and then have a tendency to awaken again, but that’s another matter and way beyond the scope of this thread, so you will have to be patient and monitor the meter readings for quite some time.
My wife’s old CLK 500 (A209) model, well I say old but it was actually a 2005 model when I bought it for her in 2006 as a used vehicle from MB, what a stunning car that was, but it was an absolute electrical nightmare when it came to parasitic drains; lots of issues and module faults with that car and it was never away from the dealers whilst it was under warranty, even my old CL has had some issues in this area. Sometimes they can be relatively inexpensive repairs (hopefully yours is a minor issue) and the worst-case scenario they could cost you several hundreds if not thousands of pounds. No point as I said earlier though in speculating at this juncture as to what it may or may not be – you don’t guess at what things it may be on a Mercedes Benz CL, its far too costly, so do it properly and diagnose the issue and then decide where you want go from there.
The in-line fuse ammeter you have just bought, what is the threshold limit, is it 20 amps, if it is 20 amps, then you can use that in series with the battery although you may have to make a couple of small fly leads to connect to the battery and the battery leads. These are not the most accurate meter on the market to use but it will give you a rough ball park figure as to what current is actually being drawn, alternatively, get yourself a relatively inexpensive digital multimeter (always handy to have one anyway) that goes up to the 10 amp range. As a general rule of thumb anyway, most digital multimeters these days only go up to 10 amps and it is often the case that the fuse in the meter will blow if this threshold is exceeded, but you can initially overcome that by inserting a small switched (by-pass) jump lead first in to the system before you connect the ammeter.
If you haven’t yet resolved the issue, then just post up on the thread what information you have and done to date and don’t touch anything else, not unless that is someone else on here wishes to volunteer and guide you through the process, anyway, speak to you sometime over the next few days to see how you are getting on. I have just read your PM’s Ray, I will reply to them when I have a little bit more time. If you haven’t got a proper fuse chart for the CL, then let me know and I will let you have a copy of my own version that I made many years ago, it still applies to the CL65 as all the W215’s are all the same electrical architecture anyway.
Best Regards.
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