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Hi Everyone, iam new to the forum and have done a bit of searching but unable to find a related post so apologies if this has alredy been covered in another thread,

My Problem :

Car : SX4 2008

New Battery (1 week old) and 3 new alternators swapped out.

so my car lost power a fortnight ago whilst on the motorway, i didnt cut out but lost all my power steering, abs, radio etc, so managed to limp back to house, tested the battery with multi meter and was getting less than 9v, so got a new battery and car started first time and everything seemed ok with a reading of 11.6v from the new battery (just assuming this is ok because i havnt driven it and hasnt had a proper charge as have only driven it to shops and back)) everything seemed to be working so i then tested the alternator so switched on the engine again and tested it and still getting output of 11.6v, no change, so i took it to my mechanic to check the alternator wasnt faulty as it was still under warranty having just been replaced july last year so he replaced it with a new one and still no output just the same 11.6v, so he then got an auto electrican to look at it and he said it was the alternator, so again my mechanic got ANOTHER new alternator and STILL it wasnt charging the battery with the same output of 11.6v, so now i have the car back, £210 lighter and still in the same position, i do not want to drive it because i will just run out of battery again and be back to square one, does anyone have any idea what this problem can be or had anything similar, the electrician has said wiring all ok from alternator to battery hence we swapped it out for another alternator again, but clearly the alternator isnt charging the battery as it should read over 14v when switched on, my mechanic is at a loss now and reckons it could be the ECU so i have called suzuki up also and they said it would be pretty rare that the ECU go but not impossible as they are pretty robust cars , is there anything else i can check that they may have missed

Thanks

Mark
 

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OBviously the alternator does not receive "excitation" voltage. UNless a battery is 5-6-7 year old, it is rarely a culprit and batteries are changed regularly..at a price.. for irrelevant reasons. So...ir seems the same here for alternators....
There a two main connectors on an alternator: excitation voltage (that normally comes as soon as ignition key is turned to ON..C194) and output voltage C192, that cannot raise to 14 volt if there is no excitation. NOw...on some cars there is a fusible link between the alternator OUT and the battery....because if someone connects a battery in reverse polarity, an excessive reverse current would flow through the alternator and ruin it. ON this one it is a 80A physical fuse right on the + battery connector. See picture on page 3. HOwever you would not start the car if it was blown. THis is why I suspect excitation....you should test this one with KEY ON.
. I have also seen corroded connectors....and even rupture in the black wire (alternator to battery) between C192 and C283...weird but possible.
www.avigex.ca/sx4/PowerSupply.pdf
www.avigex.ca/sx4/chargingstarting.pdf
And as you can see from the diagram the ECM has NO relation AT ALL to this circuit...so DO NOT go to that expense for nothing. COme back with results and more questions when needed.
NOw....PLEASE fill up your profile with LOCATION, and all details about car: model, mileage, engine type, transmission, AWD?, etc. Obviously you seem from GB and the circuit I show are for 1.5 and 2.0 petrol engines....so there might be differences and we will ask for these details EACH TIME if they are not in your profile or signature. GO to USER CP . THere are members in GB and they can at times provide more relevant replies if THEY KNOW you are from GB.
 

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I was under the impression the ECM controls the IC regulator which controls the field windings and therefore the output, is this just the models with this load current sensor. This may only govern ampage and not voltage anyway.
I'll be honest I don't really understand why they are now connected to the ECM.

 

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Yes..these connections are also visible on my diagrams....they are there to protect BCM and ECM from overvoltage..above 16 volts....so they should have no impact below that voltage. Too bad we do not see clearly the internals of the regulator circuit....
ANd...this weld splice C312...seems to be there as a fusible link on the exciter circuit....not sure where it is but failure would kill voltage at C194 and inhibit the development of voltage .
 

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I was under the impression the ECM controls the IC regulator which controls the field windings and therefore the output, is this just the models with this load current sensor. This may only govern ampage and not voltage anyway.
I'll be honest I don't really understand why they are now connected to the ECM.
The ECU controls the voltage regulator, which controls the excitation current in the "field" windings, and thereby controls the output amperage, which actually determines the system voltage.

Thoroughly confused now??

The battery acts as a load on the charge system and as you charge it, by supplying a charge current (measured in amps), the voltage rises to what is known as a "nominal 12V", which can actually be anywhere between about 11~14V - as the battery nears full charge, the voltage rises and the charge system compensates by reducing the charge current and when the battery is fully charged, the charge system will be putting out just enough current to supply the demand of running the engine, lights, etc..

The reason for having the ECU control the alternator is to improve fuel efficiency - it reduces the load the charge system puts on the engine so that more of the power produced by the engine can go toward moving the car, so for example, when you're accelerating it might not be charging the battery, but when you've gotten up to speed and you're cruising along, the battery will charge - it's actually quite interesting to watch - and very easy to do - all you need is one of the digital voltmeters that plugs into the cigarette lighter
 

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For all we know, mice chewed up one of the three small wires that go to the alternator.

It is a relatively simple test to see if there is continuity between the connector on the alternator and the ECU.
 
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