2013 Ford Focus Dynamo Question

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gizmo1990

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Our Focus wouldn't start before Xmas with the breakdown service suggesting it might be the starter. The garage has just rung and said that the dynamo seems to be running at a high voltage so they suspect that possibly in conjunction with the starter? They then also mentioned the battery might have sulphur damage? That peaked my interest since the battery is only a year old and should be fine. The breakdown guy said it's readings were fine too. I guess this dynamo issue could have damaged it but, it just seemed that at that point in the conversation, I was getting an extra thing added onto another..

Could anyone give me some advice on what a faulty dynamo repair might the entail? For example does a faulty dynamo always lead to a damaged starter? I find speaking to mechanics extremely uncomfortable as I know so little about engines.

Any advice much appreciated.
 
More diagnostics needed for this one, I'm afraid......the battery (voltage) reading (engine running, lights on) should be in the region of 14.4v.
The alternator has a rectifier (changes AC to DC) and a voltage regulator (keeps the voltage within required limits) and these parts are internal.
A voltage reading which is too high may goose the battery, but it's unlikely to affect the starter motor.
John :)
 
@Burnerman Thanks a lot for the reply. Apparently the garage thinks the starter is obviously gone since the dynamo is running at a higher voltage. Does that seem to chime right with you? The alternator in this case is the dynamo right?
 
Yes. the alternator is the dynamo. If it's the garage calling it the wrong name, I suggest you go to another garage
 
Alternators replaced dynamos many years ago......their output is much higher, even at low rpm.
I think you need to get the alternator and battery sorted first - as I said, too high a voltage could wreck the battery but there wouldn’t be any visible damage.
Starters on the other hand are much tougher and can stand more abuse.....it’s pretty easy for an auto electrician to check all of these things though.
John
 
The alternator on a 2013 focus is controlled by the car electronics. It can vary it's voltage depending on the state of charge and the temperature of the battery, it is designed to charge the battery to 80% of it's capacity and then stop charging to save a microscopic amount of fuel that is required to drive it.

When the battery was changed was a new one of exactly the same specification as the old one fitted? If the battery capacity or type has changed and the car has not been re-programmed with the new battery details then the electronic control could be over charging or under charging the battery.

Was the Battery Monitoring System reset when the battery was changed? If not the electronics could be providing a charge suited to an old battery rather than a new one.

The sequence of repair/replacement would be: Test the battery, replace with the correct one if necessary (batteries are cheaper than alternators). Test the alternator, replace with the correct one if necessary (a faulty alternator can damage a battery). Then move on to considering the starter motor if the car still wont start. This all needs doing by someone who understands how the Ford smart charging system works.
 
The alternator is controlled by a tiny 1 amp fuse in the fuse box. Unlike alternators of old, modern ones do not need a 12v feed to excite the coils. Without that, they will charge at maximum output. The thin wire going to the alternator is to regulate the maximum voltage so check that fuse first. Don’t ask me how I know this!
 
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