Battery drained after long ride

[FarWare12]

I've been experiencing some electrical issues. I drove about 5 hours with the van and the next morning, the van would not start. The voltage on the battery was 9,4V, so I recharged it and this time the van started and drove without any issues.

During the 5 hour drive I experienced some electrical issues. The radio kept resetting. What I noticed previously, is that the radio would sometimes reset when switching the lights on. Also, the windshield wipers were returning very slowly to their starter position when turning them off. The drive must have taken a lot out of the battery because I had the lights on, the radio on some of the time and the heater on. Two weeks ago the blinkers were also not working, but I replaced fuse 21 and they have been working ever since.

I don't know if I have alternator issues or there is something wrong with my electrical setup. I drove quite a bit with the van in the past weeks and stayed mostly in campsites. I have two leisure batteries which I charge with a battery charger at campsites. The leisure batteries are also wired to a Cyrix CT which is wired to the starter battery. However, I've noticed the Cyrix never seems to charge the leisure batteries during the drive. I am not sure however if charging the other way is possible, in other words if the starter battery is also being charged when the leisure batteries are charged at the campsite. I also wonder if it's the Cyrix that's emptying my starter battery somehow.

After recharging my starter battery, I noticed the voltage is around 13,1V. After starting the van, the voltage is 12,86/12,9V. I believe this is too low?

How do I test what the problem is here?

[colinthefox]

What engine?

[FarWare12]

What engine?

WBX 1.9 petrol

[Aidan]

alternator voltage regulator has probably failed/brushes worn out, so the engine and everything else has been draining the battery, easy to check with multimeter, if you don't see 14v ish at the battery with engine running then you are not charging the battery from the alternator
worth carying a spare with these old vans unless you know it has been replaced fairly recently, febi ones aren't expensive and are decent quality

[Oldiebut goodie]

If your starter has been down to 9.4v you have almost certainly fooked it!

[colinthefox]

What engine?

WBX 1.9 petrol

The reason I asked was because I had a similar problem due to glow plug relay malfunction. That won't apply to a 1.9wbx!
Best to include engine type in your signature to avoid confusion.

[ZsZ]

It seems like your alternator is not charging. With a fully charged battery running on idle measuring at the battery voltage should be around 13.8V on a petrol van.

Check voltage at the alternator stud, at the starter stud, and at the battery. Check the ground strap at the nose of the tranny. Clean all the contacts, ground paths.
The alternator might charge OK, but the voltage cannot reach the battery.

Check the blue wire of the alternator.
The aternator might not excite - although then the dash light should illuminate.

[FarWare12]

alternator voltage regulator has probably failed/brushes worn out, so the engine and everything else has been draining the battery, easy to check with multimeter, if you don't see 14v ish at the battery with engine running then you are not charging the battery from the alternator
worth carying a spare with these old vans unless you know it has been replaced fairly recently, febi ones aren't expensive and are decent quality

Right now I'm seeing 12,9V with the battery off, 13,1V with the engine running. But this goes down to 12,7/12,8V if I put radio/lights/heater on. So it seems the alternator is charging somewhat but now fully.

I haven't checked the alternator itself yet. Will do so this weekend.