anyone got any ideas what could be up with my alternator / battery

car is a 2.5 tdi ranger (06)

its charging at 12.5v at tickover and about 12.8v at 3k RPM with nothing electrical on

with everything on it drops to 11.5 regardless of RPM

it has not had enough power to start a few times but has no pattern to it , i can be driving short journeys at night with everything on and not have a problem but 1 in 100 times it wont have enough power in battery

if i leave sidelights on for just 5 min without engine running it wont have enough to start

i have replaced the battery and just fitted another alternator from a known working truck but its still the same

is the voltage regulator separate or built in to the alternator like most ?

any other ideas ?????????????????

 

a bad earth some where
the alternator should be chargeing around 13-14 volts

 

I'd be checking all the wiring connections personally, quick check for a good earth to engine is to put a decent jump lead between engine and batt - and try it.
But go thru all the wiring connections and check for any poor ones.

 

forgot to say in my original post , ive checked all the connections and all are good , also have taken a voltage reading at the battery and straight from the alternator and they read the same

 

put the volt meter between the + lead and the+ terminal on the batt and see what it reads with every thing off should be around .3 volts or amps cant remember which but should be .3 any thing higher you have something drawing power

it could be the ignition switch playing up the black switch on the end of the ignition barrel

 

Anyone know if the regulator is separate from the alternator as this would explain why 2 alternators behave the same way too

 

2 pin oval plug one is warning light one is battery +, internally regulated [ie not seperate regulator]that charging voltage is too low fella ,should be 14 volts ish .drop test battery dead cell would be my guess

 

My brother's Vauxhall Astra 1.4 is doing exactly the same thing. When running it's showing 13v and not charging enough for short journeys. I assumed it was alternator not charging enough, but haven't been able to do any checks. Car was fine before winter?

 

The alternator is not working, it could well be electronically controlled in this case so this is where the problem could lie else I suspect a problem in the charging circuit, clearly it's not the alternator as you have replaced it with a known working unit. In the case of a Ford this is known as the "Smart Charge system". It should be charging higher than the open circuit voltage that does not neccessarily mean 14V so long as it has enough power to overcome the internal resistance of the battery, I.E 13V +.

Even if it was something draining the battery the alternator should still charge!

FletchCossie that does seem a bit low I am assuming this is with no load? If so under load you will probably find this drops further, I suspect the alt itself has gone, in winter the electrical system is under far higher demand (I suspect it was weak before) and as such this has probably taken it's toll on the alternator and finished it off.

Martin

 

That's what I was thinking Martin and yep not under load when the weather is not so cold the car does seem to charge enough (Not tested voltage tho)

 

have you checked the tension on the belt or belt condition, may be too slack or slipping but gripping just enough to keep battery light out... happened with me few weeks back, belt loose and light was out and showing 11.8v on the gauge

 

i think it wont have the smart charge system as its basically a mazda with a ford badge stuck on

the alternator came from a ranger that was "running fine before the head went" so it is possible it also knackered , might drop my old unit off to be bench tested

AWOL- belt tension is fine but it does have a constant little squeak as though its under plenty of load , not a slipping squeal / squeak

 

LOL no it won't have a smart charge system, I was just using that as an example, but it may have a similar system. Tbh it's more likely to be a wiring problem, the alternator in itself is usually pretty reliable.

Martin

 

i know what it is its the main lead to the starter motor if lose will give make it seem like flat batt or not charging

 

If your battery will hold a charge on it's own, but goes dead a while after you start and run your vehicle, it is probably your alternator.
Or, if you can get it running, it should have an alternator light that will come on when there is a problem. I would almost bet your car has one... my 1970 ford does.



_______________________________________________

2009 Ford Ranger Parts Alternator - MOTORCRAFT ALTERNATOR,
REMANUFACTURED -- 110 amp; Features new OE voltage
regulators, new OE brushes,