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      Posting in General Chat thread.   11/11/2017

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  1. Diagnosing Smart Charge

    Thanks. Good of you to offer! If your battery is the OEM silver calcium like ours and has the same charging strategy, then it would appear that you should never see more than 13.8V between the terminals when the engine is running If however, as I suspect we will find, you measure 14.4V (especially with a warm engine) then we can say that there's either an unaccountable difference between charge regimes (for the same type of battery) on petrol and diesel models... or that our PCM has a fault that flies beneath the Ford diagnostics radar.
  2. Hello,

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  3. Diagnosing Smart Charge

    Hi Fede, well, this is still unresolved for us. The last attempt was to take the car to another Ford garage and have them run an independent test. The stupid answer was "It passed all the tests". When asked how it could "pass all the tests" yet remain stuck permanently at 13.7V nobody had a clue. I finally used an OBDII tester to look up the PCM codes and sure enough the demand voltage is always the same so that explains what's seen on the PWM signals at the alternator. Like I concluded before, the PCM is making a seemingly odd decision to maintain a constant voltage at the battery. Maybe this was an engineering decision on this year of vehicle - the silver calcium battery is less reliant on equalising charge according to some, I found one instance of them being used in a large array (for power line backup) and fed from a constant 13.8V to avoid the need for step-down conversion before the voltage was transformed (which hints at a dopey kind of invertor being used) If so, it's a different stratedgy to that used with the same battery on a 2007 Diesel model I had my hands on. Not having a fleet of Fords to hand I turned to the next best thing (a Ford internet forum) but so far nobody seems to want to play.
  4. So, Ford has been using a so called "smart charge" system for quite a while now. This system can be a bit confusing for auto electricians (but a few seem to be catching on). The main thing that will be noticed is that, with the engine running, the battery may not have the "usual" (like it has been up until smart charge systems came in) 14.4V Instead, much of the time, a float/maintenance charge is applied at approx. 13.7V With Fords, the PCM decides what voltage the alternator should put out on the B+ terminal and varies the voltage according to conditions. This article provides a useful insight into the type of scheme but uses GM's system as an example. What I would dearly love to have is a similar description of Ford's scheme. By this I mean that there is a PCM parameter called GENVDSD (generator desired voltage) which is the target voltage the PCM requires from the battery/alternator. This ought to be reflected by the battery terminal voltage (you'd think) but I have a contradiction to this in our C-MAX. If it was like the GM system, GENVDSD would rise to 14~15V shortly after starting (to replenish the lost charge during cranking) then fall back to 13.7V to save wasting power cooking the battery. The article above shows two graphs that differ according to temperature. Various sources on the net describe similar allowances made for battery temperature in Fords, but nothing specific. In our C-MAX the 3yr old battery was replaced as it wouldn't hold charge. Suspecting the charging system I've been trying to diagnose the problem with very little success. I have all the right tools ('scope, OBDII scanner) but lack the information about the expected charge sequence that the PCM applies. In my tests it ALWAYS asks for 13.6 and never anything else. I am deeply suspicious about this but find it hard knowing how to approach the "trade" with such a technical concern. I've already been "sent away" by the garage we bought the car from (they say they've double checked it and it's all OK, but when I start talking technical, we just go round in loops until I run out of breath). Does anyone have a snippet of info that might reveal the correct sequence for GENVDSD? I can monitor batter voltage which matches GENVDSD with no electrical load, and GFS (generator field strength) which does go up and down according to load, but at the same time the battery voltage falls (e.g from 13.7 to 11.8) while GENVDSD stays put at 13.7 Here is a screenshot from the Torque app that shows the battery down at 12.1V with the engine running and heated screens/AC/Lights all on. Unfortunately GENFDC (the field command to the alternator) is highly intermittent and reads incorrectly but the other readings are good.
  5. Diagnosing Smart Charge

    Finally got the scope on the Alternator Load Request/feedback PWM signals on the back of the 3-way plug as per mintalkin's link. The request signal (PCM telling the alternator how strong the field should be) is virtually stuck at 43% positive duty cycle all the time. It doesn't make any difference if I apply all the heavy electrical loads or not - the PCM doesn't vary the request. The feedback from the alternator varies alot, 98% positive with all the loads on, and hunts widely around 50% with electrical loads off. No loads: Heavy loads: Yellow trace=feedback Blue=request Now I'm trying to understand what this means. The PCM seems content with one fixed, moderate, rate of current generation no matter what. So the battery is taken to a middling 13.6V Adding electrical loads depresses the battery voltage but the PCM doesn't request more juice. This suggests that the PCM is making bad decisions! I would still love to know what other people see when they monitor their battery voltage and progressively apply the big loads - something that can be done in under a minute while sitting behind the wheel ;)
  6. Diagnosing Smart Charge

    Still none the wiser. Correct Siver Calcium battery now fitted and garage assures us the charging system has passed every check. However, I still haven't seen more than 13.8V at the battery terminals under any conditions. Using a scope I can see that all three phases of the alternator are there (diodes OK) but even when I deliberately skim the charge off the battery using the generous number of electrical loads the car can provide, still nothing higher than 13.8V appears on the battery with the engine revving and all other loads off. What is the smart charge thinking? One other unhealthy looking thing is that even with the engine revving, switching on fogs, main beam, heated front/rear screens and full cabin fan - the alternator can't keep the battery voltage up above 12.2V Now I appreciate that there is a limit to the alternator output current (not sure what the C-MAX can manage - it looks pretty puny) but I can see the winter scenario where this may be an issue. Of course, the PCM will step in and cut the heavy loads when the "low voltage threshold" is met (rather than fit an alternator with adequate capacity?). Perhaps someone here could repeat this little experiment? Those who know how to get battery voltage up on the info display could do this quite easily. I managed to get my multimeter on the battery of another C-MAX and after a few seconds of starting it rose to a reassuring 14.5V To me, that's a tick in the box that I just can't give to our car yet - despite assurances to the contrary!
  7. Bearing Squeal - No A/c

    For a half minute or so after starting from cold there's a very noisy squealing sound like a bearing in distress coming from the auxilliary belt region. We just discovered that the A/C doesn't work but the squeal isn't when we try to turn it on, just when starting from cold. I'm wondering if these two things might be related. The battery isn't charging properly either (another thing that depends on the aux. belt) but that's another story Any "usual suspects" in this area?
  8. Diagnosing Smart Charge

    Thanks for that link mintalkin. That's slightly confusing - is 13.8V supposed to be seen with the 3-pin plug removed? I wouldn't think so because reverting to a conventional alternator should put 14.4V on the battery. So assuming that this test is done with the plug in, then yes there's approx 13.8V on mine. So, according to the author, the alternator is OK and it's the smart charge system that's under suspicion. I've measured the terminal voltage on the battery under a wide range of conditions now (e.g. fully charged, mostly discharged, hot, cold) and never seen over 13.7V so I'm still thinking that the smart charge system has gone into its own kind of "get you home mode". Given that I'm not going to attempt further diagnosis - as all I want to do is present the fault to the garage that sold me the car, this will have to do. With a convention charging system it would be much more black & white - the absence of 14.4V or more on the battery would indicate a duff alternator, or wiring defect.
  9. Diagnosing Smart Charge

    Hi all. We Just picked up a used C-MAX 08 with nice low mileage. However OEM Battery was flat when we went to drive away so garage swapped in a new battery. As might be expected it wasn't a Silver Calcium, but they assured us it was OK. Now I know it isn't really. But that can be sorted. What I am really concerned about is why the OEM battery was in such poor shape in the first place. It shows a high internal impedance so wont take or hold a decent charge. This leads me to suspect the charging system which is different to most other cars. I understand that the battery temperature is estimated and only when considered cold is a full charge applied. So far I have not seen anything higher than 13.6V - even when cold and after running down to 11.5V by putting on headlights before starting. I was hoping to see 14.4V or higher after starting the engine under these conditions but it generally holds at around 13.6V most of the time. As another test I switched on all the heavy electrical loads I could with the engine running and the battery voltage was around 12.5V and seemed to be falling slowly. I would have expected the alternator to do better than this. SO given that the charging voltage is variable, under what conditions should we be able to measure 14.4V or higher? To me it seems as though something has gone wrong and the alternator is just putting out a "safe" maintenance charge only. Wish I could see the back of the altenator to check the leads but it's pretty inaccessible. Is it necessary to get to it from below (i.e. drop the panel covering the underside of the engine bay)