My alternator on my campervan appears to be struggling:
The voltage at the starter battery appears low, with the engine running is around 13.8v, but after driving a short while I can see the voltage starts dropping towards 13v. Engine stopped the starter is around 12.8v I think.
Could a poorly starter battery drag down the 14.4v from the alternator or should this stay roughly the same at the terminals regardless. And I should expect the alternator voltage to remain roughly the same when headlights and other loads are turned on? If the voltage at the starter battery drops as loads are applied, whilst the engine is running, is this a sure sign that the alternator is poorly?
The van is starting OK and from the readings the alternator appears to be having a half-hearted go at charging things, but the voltage is no longer high enough to activate my voltage sensing split charge system and so my leisure batteries are only charging intermittently.
Once its stopped raining I'm going out for another spanner session...but is there any way to test the alternator properly?
460 mile round trip to Twentyfour12 on Friday so I need to accurately diagnose the problem and fix it asap!
bump!
There is a voltage regulator usually mounted in the back of the alternator or integral to it, that should maintain the voltage at 14.4 volts ish constantly regardless of load. A faulty battery wouldn't pull the voltage down like that, so it may well be the alternator on its way out, or the diodes within which rectify the ac to dc might be giving up.
Afaik the alternator diodes can fail, an easy fix.
Just been out for another look...starter battery at 12.75, (that'll be fully charged then) running is 13.9. If I hold the engine at 2000rpm the voltage drops by 0.2v when turning on headlights etc.
Typically, the fault must be intermittent as my leisure batteries were charging well at 18 amps at 13.5v. Hopefully its an issue with the split charge as I can bodge a fix to that to get me through next weekend relatively easily.
On a camper, heavily discharged batteries could pull the battery voltage down, but before I start typing various theories, what kind of split charge system are you running?
Where are you? I can recommend an autoelectrician in Haverfordwest, as I had to get mine sorted whilst on holiday last week.
