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PaulRandell

2002 Petrol Mondeo - Faulty Alternator? - Battery Drain

53 posts in this topic

Hi,

I have a 2002 Mondeo 2.0 Petrol.

My car has an intermittent battery drain.

I replaced the battery - No change

I have completed a battery drain test with an AMP meter, but without much luck as the battery drain can be as high as 3.0amps (everything off), or as low as 0.10 amps (also everything off). It is so intermittent that it is hard to get any consistent readings when removing fuses etc.

If I leave the car overnight, sometimes the battery is fine next day, and sometimes completely drained.

My local garage has identified this as an alternator problem, and whilst it charges the battery Ok, if it stops rotating at a specific point it drains the battery.

My question is in 4 parts.

1. Does this sound likely ?

2. The quote to replace the alternator is £225.00 +vat, does this seem like a fair price ?

3. I like to do as much work on my cars as possible (brakes / plugs / oil filters etc etc) but never an alternator, is it a potential DIY job ?

4. Are there any alternatives to replacing the alternator ?

Any advice would be welcomed

Kind Regards,

Paul

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think your clue is in the 3a with every thing off...can you give a bit more detail about that..

is this just an initial amp drain then settles to 0.1 within a minute or two, or is it an occasional constant drain?

carry out the test with everything off and all doors closed etc...allow a couple of minutes for anything to power down (such as any alarm etc) then take your reading

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Hi, thanks for the reply,

I wait for everything to be off doors closed etc and the vast majority of the readings I get are 0.08 and 0.09a

The 3a figure seems to be so intermittent (no more than 20/30 seconds at a time) that it is almost impossible to get a consistent reading, and not long enough for me to be able to complete an accurate drain test.

I guess overnight it is at 3.0a long enough to drain the battery completely

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if you can see no reason for a 3a drain suddenly coming on, then that might be a problem...that will drain a new battery in about 3 days, so an old one could very well drain overnight.

have you noticed any kind of electrical issues at all

can see that would be tough to pin down if its that intermittent...but may pay to pull the fuse on the interior lights as well as any light that might be in the glove box/boot etc...it could be one of those switches that operate the lights playing up...if you pull the fuse and just see if you still get battery issues..if not then you know where to focus

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Does the big (3 Amps) current consumption go away if you disconnect the alternator?

I've been trying to think of whether the alternator stopping at a particular point could cause a problem, and I don't think it could. You could blow one of the diodes in the rectifier bridge, and that would stop it charging at some point, but I think it would either discharge the battery, or it wouldn't (although, I could be wrong; I haven't drawn out a circuit diagram).

4. Are there any alternatives to replacing the alternator ?


Well, if it is the diode bridge (and, that seems most likely; the regulator could be a problem, too, but that doesn't seem to have any relevance to the 'only one point in the rotation', unless its just an intermittent and they are mistaken about the correlation to rotation part), you could replace the bridge...but you'd have to take the alternator out to do it, and why you wouldn't then just get an exchange alternator, I don't know.

3. I like to do as much work on my cars as possible (brakes / plugs / oil filters etc etc) but never an alternator, is it a potential DIY job ?

Probably.

2. The quote to replace the alternator is £225.00 +vat, does this seem like a fair price ?

No. Well, not to me and using an exchange/re-con alternator or a pattern one, as opposed to a brand new Ford one (at which point it might be vaguely reasonable...but would you do that on a 2002 Mondy, rather than go for a cheaper alternative, which might only last 10 years???).

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...continued...

There ought to be some kind of 'bodge' 'solution' (temporary work around, maybe better) to finding where the current is going where you connect a series diode from the alternator charging circuit to the battery, but

  • You'll never charge the battery fully, this way (voltage drop in the diode)
  • It'll have to be a pretty high current diode, and be able to stand the high current pretty much continuously, which implies a heat sink, and you'll need to insulate the diode electrically
  • And you'd have to look carefully to see whether you can insert this diode without interfering with the alternator start up, because at this point the battery is powering the alternator. Depending on how the vehicle wiring is, exactly, you may be able to get at just the 'charge' wire, and then it isn't that difficult. In any case, the alternator will probably start up, from remanent magnetism, just at higher rpm than is usual.

Anyway, as a means of testing whether the current is going back into the alternator, and not for something you'd use, long-term, it might be worth a go, provided the diode is not too expensive.

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im just going on the fact he has detected a 3 amp draw with everything off, even though it is intermittent.

plus the battery appears to be draining overnight rather than just after a journey...to me that would eliminate the alternator, which the diagnosis doesnt really make sense to me either, anyway...i wouldnt dismiss this but at the least wouldnt think it worth pursuing till this 3 amp draw has been confirmed and traced.

but one way it can be confirmed is remove the belt, carry out the amp test whilst turning the alternator by hand, if diagnosis is true it will register on the reading

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Thank you for the responses.

I am pretty sure the alternator is charging the battery with no issues. (Green charge light on battery always on - I see it every 8 hours or so) All I am currently doing is disconnecting the battery every night and while I am at work each day. The battery remains fully charged (I have a 40 minute drive to and from work)

The breakdown of the price is £150.00 Alternator & £75.00 labour, I like to think that I am pretty smart, but I didn't think of buying a recon/2nd hand alternator as an alternative. Could I ask the garage to fit it for me? I have seen them on ebay for circa £30.00 is it worth this as an option?

I only paid £850 for the car, 2002 2.0 petrol 90,000miles it drives really well and apart form being a bit untidy on the bodywork it seems like a great car. I have had 3 Mondeos now all between 8 & 10 years old and they have all been really good cars, my wife has a 2006 1.8 petrol 115,000miles, which is like the perfect car!

The biggest issue would be if it is not actually the alternator.

I will remove the alternator fuse first and see if I can still get the 3.0amp reading. As if I do I guess that eliminates that as the fault. I could do a full drain test this way rather than connecting the amp meter first, but I'm not sure that the intermittent nature of the fault will allow this.

Sadly the other tests/suggestions I think are over and above my skill sets.

Thank you for your advice, I will come back to you.

Paul

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i wouldnt purchase an alternator at all, at this stage...you have nothing to prove that its faulty beyond a bit of a wild card diagnosis given to you by a garage...not saying its impossible, but highly improbable...not something i have ever seen or heard of before...save your money, you have the tools and skills to prove them right/wrong

the fact is you have confirmed something is draining the battery, as disconnecting overnight eliminates the flat battery problem...it will be easy enough to eliminate the alternator with what you suggested..

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im just going on the fact he has detected a 3 amp draw with everything off, even though it is intermittent.

plus the battery appears to be draining overnight rather than just after a journey...to me that would eliminate the alternator, which the diagnosis doesnt really make sense to me

Yes, but the question is, is it in to the alternator, as seems to be suggested by the Garage, who has looked at it, or is it somewhere else. Now, the problem is that the garage's description of their diagnosis seems a bit implausible, so we really don't know.

Now, if it is going somewhere else, there is no case for doing anything with the alternator. You could take the belt off the alternator and slowly rotate the alternator and look for a point at which you get the current drain, that would be a way of testing whether the garage's diagnosis, as stated, is correct (but I suspect that they've just 'dumbed down' their diagnosis for you and they've really mis-described or oversimplified it, but that's just my suspicion).

(I would say, don't try to spin it fast and look for the charge - we know that it is charging some of the time, anyway, and you'd have to get the alternator up to 1500 - 2000 rpm to really get it working, and for that you need a drill and a pulley, and, unless you can look at the current waveform you'll probably not learn what you want to know.)

The breakdown of the price is £150.00 Alternator & £75.00 labour, I like to think that I am pretty smart, but I didn't think of buying a recon/2nd hand alternator as an alternative. Could I ask the garage to fit it for me? I have seen them on ebay for circa £30.00 is it worth this as an option?

Personally, I'm not a big enthusiast for the 'Bay of Fleas', but a more co-operative Garage might have mentioned the possibility of getting a remanufactured alternator, for which yours is usually taken in exchange, and there may be a deposit to be paid until they have yours. From a scrappie is probably cheaper, but with less of a Warranty. A Motor Factor ought to be cheaper than a Ford-branded one, by some way. The Garage hasn't really, as I understand it, said that you'd be getting a Ford-branded one, anyway, so at least check what you are getting for the money, which seems on the high side.

My preferences, assuming that some test does conclusively point the finger at the alternator, would be Motor Factor or Remanufactured/Reconditioned, but if a scrappie is way cheaper, that could persuade me. YMMV.

The £75 labour doesn't sound too unreasonable (a bit high, but not excessively so), but the garage hasn't helped you much towards the economical options, and you might have expected them to query what you wanted, on an older motor. And what if it isn't the alternator? Do they take responsibility if they've got the diagnosis wrong (ie, you don't have to pay, or only pay once and they fix it, whatever the cause actually turns out to be)?

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Yes, but the question is, is it in to the alternator, as seems to be

suggested by the Garage, who has looked at it, or is it somewhere else.

Now, the problem is that the garage's description of their diagnosis

seems a bit implausible, so we really don't know.

i agree with you, think the simplest way to test this would be to remove the bat+ connection on the alternator and carry out the drain test...if no longer getting the 3a drain then reconnect the bat+ and go again

not saying its impossible, but definitly wouldnt purchase an alternator on the strength of info given by the garage when he is in a position to double check the diagnosis himself...i'd be suprised if the garage was correct

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Hi,

I have checked the alternator and found the connectors, I'll disconnect it tomorrow morning and then re-do the drain test, I'll let you know how i get on.

Thank you for your help

Paul

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Ok, I am not the most scientific person but here goes!

Battery Volts Battery Amps

9.15am Start Car (move 10ft to garage) Test 9.17am 11.71 0.09 10 seconds then 0.02

9.18am Start Car (move alternator?) Test 9.19am 11.68 0.09 (1minute)

9.21am Start Car (& Drive 5.0 miles) Test 9.31am 11.86 0.09 then 3.56 for approx 1 sec then 0.02

9.33am Leave car battery connected until Test 9.45am 12.06 0.09 10 seconds then 0.02

I am assuming that every time I start the car the alternator rotates and then should stop rotating in a slightly different position?

How many possible different positions are there?

I have seen the exact same 3.56a reading in a previous test and it lasted more like 20 seconds at a time.

Not sure how I can test the alternator when the drain test is so unpredictable?

I am also assuming that I should ignore the 0.02a reading as insignificant?

Any ideas would be appreciated.

Paul

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I am assuming that every time I start the car the alternator rotates and then should stop rotating in a slightly different position?

How many possible different positions are there?

every time that the engine stops, it will (tend to) stop in one of 2 (4, but that's not really relevant) positions. If the 'gearing' (gear ratio of the belt drive to the alternator) is a nice integral number (which it usually isn't) then the alternator will probably stop in one of very few positions.

If the gearing is something more like 1.26:1 (effectively random numbers!), then the stopping positions for the alternator are effectively infinite.

I have seen the exact same 3.56a reading in a previous test and it lasted more like 20 seconds at a time.

That may irrelevant to the problem. If it only lasts ~20 seconds, and doesn't happen often, it probably isn't discharging the battery quickly. On the other hand, if it does happen often (or, if it waits for you to go away and then happens continuously, which it might if it has something to do with the anti-theft system) then we are close to being able to shout bingo!

Battery capacities are ~ 70 ampere-hours. Each time this happens, it is more like 70 ampere seconds, so would have to happen, very roughly, 60 x 60 times (3600) to discharge the battery. Well, it depends how often it happens, I suppose, but I got the impression that it happened once and then didn't happen again for a fair time - if that is wrong and it happens again quite soon, then it probably is the cause.

So, here is a suggestion for you (just floating a theory, here, that may or may not turn out to be true):

  • the problem is nothing to do with the alternator
  • there is something in the car that switches on intermittently even after the ignition has been turned off
  • the current that takes, summed up, is enough to flatten the battery over a time period
  • (WAG) this is a relay that is normally switching something on and off, but now, due to a near short is taking a lot more current than it normally would (or, alternatively, is coming on for a lot more time than it normally would)

I've got to ask - has anything been modified, or has anything started behaving oddly, in the vehicle electrics recently, however unrelated to the alternator it seems?

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Nothing modified as far as I know.

I do know the car had a new (recon) gearbox just before I purchased the car.

I have checked and double checked the earths.

Also someone has done the mod where you turn off the seatbelt warning light/noise, but I cant seem to reset that.

I am now also pretty sure that the alarm isn't working, it seems to set ok with a double click of the key fob, but I cant set the alarm off? Is there a test to see if the alarm is working ok? (The horn works ok)

Paul

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great answer from BOF

should also be noted your battery voltage is very low, bordering on flat

most common reason i have found with intermittent drains over the years have been, cigar lighters shorting, courtesy light switches and alarms...these would be the areas to check first...mondeo bonnet alarm switch was a very common problem, wondering if alarm is triggering overnight but your unaware as its not setting off the horn

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Ok, I am now sure the alarm is working, I set the alarm, waited 20 seconds and then tried to open the bonnet. Alarm went off Ok.

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do you have access to anything that can communicate with the ECU's beyond engine...

when you previously said you couldnt seem to set the alarm off, what/how were you doing.

there is a data you can access via the ecu, which will give you not only faults within the alarm, but reasons for the last 5 triggerings..

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The only other thing that has been changed is the stereo it is currently a 5000rds tape stereo. Which means the steering column control stalk doesn't work.

Pretty sure its not this however as I have already disconnected the stereo completely and the battery still drained overnight.

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was the battery connected last night, as that voltage is very low

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Sadly I don't have access or the kit for the ECU.

My other issue would be that I cant replicate the drain. Is it practical to just remove the fuses for Interior lights / Cigar Lighter / Alarm and see what happens over a longer period?

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no the battery was not connected last night.

I have a trickle charger which I a can put on now, what should the battery voltage be? Is it possible that the alternator is just no charging the battery enough, and the 0.09 drain is enough to stop the car starting?

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12v or below is classed as bordering on flat...a fully charged battery should read at least 12.5v

may not seem a lot of difference, but if the voltage is low then it can play havoc with electrics..

if the alternator is giving the correct charge, all battery leads/connections are good, then it could just be a case of a faulty battery.

you will need a charged battery in order to get an accurate reading on drain test, the downside of trickle chargers are that they will never fully charge a calcium battery unless you have a specific calcium battery charger.

would ignore your readings for now, till you get battery charged

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should add that a low amp drain will still flatten an already low/flat battery quite quickly

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My other issue would be that I cant replicate the drain. Is it practical to just remove the fuses for Interior lights / Cigar Lighter / Alarm and see what happens over a longer period?

In principle, yes. In practice the difficulty is that whatever documentation you've got on which fuse does what is probably wrong and incomplete. It still might be worth a go, though...

At least, pulling out all the fuses that it seems safe to pull out and seeing if the drain goes away might be useful (oh: tip - take a photo of the fuse box(es) before you start, just in case you get confused about which fuse goes where later on; and of course, you'll need the radio code, but you must already have that).

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