Club 80-90 Forums

Have been through the forum and wiki to find a solution but nothing has come up.

Van battery did not to have enough power to start engine, had driven 50 miles day before. Voltage measured at around ~11/12v with engine off. When failing to start engine, I measured a drop in voltage to around 5v, so my initial thoughts were that the battery was on its last legs.

I then used a battery charger to charge the battery indoors, took it to ~13v. Reinstalled in van, starts ok drove a few miles, battery now 12.7v with engine off. Test with lights and blower (engine running) pulls down to ~11/12v. So, thinking that the alternator is not putting out enough charge, I test the alternator with the engine running, however it is reading 14v.

So: the alternator measures 14v, but when under load, the reading on the battery is not increasing, i.e. it appears that charge is not going back to the battery. Could it still be a duff battery, able to hold charge for a bit?

I'm stumped, any thoughts greatly appreciated.

How old is the battery?

Ralf85 wrote:How old is the battery?

It came with the van when I purchased it, it's a Yuasa, there's an indicator light suggesting the battery is 'ok' but I suspect that this relates to the level of charge rather than overall condition.

Any chance the belt that turns on the alternator might be loose especially under load.?

AlandAnn wrote:Any chance the belt that turns on the alternator might be loose especially under load.?

Thanks AlandAnn. Belt is super tight, no issues there.

Might be worth changing the regulator on the alternator, mine would generate enough voltage to put the warning light out but wouldn't charge the battery.

The fat cable that goes from the alternator either to the starter, or the terminal block (whichever version you have) is a candidate for corrosion, but they are in a sheath so you can't see much of them. They get hot, and react with melted PVC and water (Hydrochloric acid!), so can be rotted inside even though they look OK. Measure the volt drop along that cable. If that's where your volt drop is occurring that's your problem and the cable can be doubled up as an upgrade.

If you have a known to be good battery, try it. Always worth ruling out the battery of possible. I learned this the hard way a couple of weeks ago!
Likewise as Colinthefox mentioned, the cable from the alternator can be badly corroded. Mine was alarmingly bad, it is easy to replace though. A cable from the alternator directly to the starter should do the trick. If you have a bolt rather than plug connector on the back of the alternator it is easier still! You could test this connection with a jumper cable?

Thank you for all the useful pointers.

Today I set to, and wirebrushed the terminals / made good the connections at:
– Crown of earths
– Battery terminals
– –ve strap from battery terminal to body.
– Gearbox to body strap.
– Alternator to starter cable.

This has seen the reading of ~13.6v at the alternator now present at the battery at idle. So a whopping extra 1v back to the battery, which I'm hoping will make all the difference, and made all todays' hours worthwhile.

Given that the voltage regulator should be able to provide 14v, next I'll look at the regulator brushes and the starter motor to alternator cable to see if the voltage can be improved, but I'm pleased with the progress, and means the van is useable again. The headlights are brighter and the van seems to have a bit more vim and vigour (probably unrelated to the earthing!).

Despite all the frustrations, a great way to get to know your van better

It is not just the pieces that you can see - you can have corrosion under insulation and inside any crimped terminals. I lost 1v in the 1ft of cable from the alternator to the battery solely due to crimped terminals with corrosion inside. This is why a couple of us advocate soldered terminals in exposed areas.
You may well find that the regulator that you have is a 13.8v one. Worth replacing it with a 14.5v one - I see 14.3v from mine which is better for modern batteries according to the battery gurus.

Spot on. I posted a whole page or two on uprating these cables in the WIKI and I too recommend soldering as it helps keep out the water. If your main cables have never been replaced, after 30 years they certainly need it now.

https://club8090.co.uk/wiki/VW ... ain_cables" onclick="window.open(this.href);return false;

and

https://club8090.co.uk/wiki/VW ... ry_to_dash" onclick="window.open(this.href);return false;