Battery v Alternator Fault?

[Neil-yaj396]

Unfortunately the Coupe broke down on the LMC Great Northern Weekend when trying to re-start after a rest break. Turn the key - nothing, not even lights on the dash. Although there was no phone signal I was able to call the AA via WiFi from the pub/hotel we had stopped at.

However, before they arrived I did that 'turn the key in frustration' thing and the car spluttered into life. Having a running engine I decided to head back to our hotel and cancel the AA. On the drive back the engine etc. ran fine with the only noticeable issue being the volt meter sat on zero and the indicators being highly ineffective. The charging warning light went out at the start and stayed off, nor was it 'glimmering' in any way. On switch off at the hotel it was back to nothing when turning the key.

The car was left overnight and in the morning gave one clunk on the solenoid before back to nothing, but we were able to jump start the car with a helpful fellow member's power pack. We then drove 70 miles home. The volt meter sat at normal for 10 minutes then dropped to just above the red. After an hour it dropped to zero and everything was dead again once I switched off back in my garage.

I'll add at this point that the volt meter has been dropping after 10 minutes driving for quite some time, but I just ignored it under the 'Beta gauges are pretty hopeless' theory.

So, sorry for the long description but do we think this is just a duff battery or something more serious, such as a faulty alternator or something nasty in the ancient wiring? And if it is the battery what should I replace it with? It's currently a Varta 52ah and to my dismay Tayna batteries, who supplied an excellent battery for my Ypsilon, are recommending a Varta 40ah for all Betas, even ie and Volumex! I've had one of those before and it didn't see out 2 winter lay ups.

While I

[WestonE]

Hi Neil you need to test with a multimeter the alternator output and also after re-charging run the standard battery tests. These tests are described in the The Haynes Manual on Electrical and Electronic Systems. £30 on Amazon. Add a £50 multimeter and some reading time and you will be able to tell if you need a new alternator and or a new battery. Do check for obvious loose connections as well.

It is easier than you think.

Eric

[Nigel]

Hi Neil,
Your ' something nasty in the ancient wiring' comment sounds more likely than
a component. It sounds like there's one dodgy connector causing it.

I would check the black/white wires that run from either side of the fuse
box to battery and alternator respectively. Corrosion and/or failed crimping being likely.
Also check the 4 block connectors and their numerous terminals under the fuse box.
Also check the heavy green cables from batt/earth to starter and ground at gearbox.

Eric's suggestions are of course good, the above is in tandem with this.

Good luck.

[Neil-yaj396]

Thanks both, I'm not confident with electrics and unfortunately the auto electrician next door to my garage packed up and retired at the end of last year. I'll swap the battery with the MG and see if my ex electronics engineer mate is up for a visit.

As a cautionary tale around battery warranties The Battery Group who sold me the battery have presented a labyrinthine process to claim under the warranty, including a £20 fee only refundable if they agree the battery is shot......

[JohnFol]

I have a 65Ah battery so higher capacity are available.

Easy option is to see if you get ~14v on battery while engine running to confirm alternator is at least trying to charge.


However easiest option is Halfords do free battery health checks, without any obligation.

[smithymc]

I/m no electrical expert but my experience of Varta has, happily, been better than Neil's- all 3 of our cars have them.

The Beta has a C6 Silver Dynamic 52AH and has been on for about 5 years.

Mark

[Neil-yaj396]

I/m no electrical expert but my experience of Varta has, happily, been better than Neil's- all 3 of our cars have them.

The Beta has a C6 Silver Dynamic 52AH and has been on for about 5 years.

Mark

It was the 40ah one that was useless Mark. I bought a 52ah last time on your recommendation and to be fair it's lasted just short of 5 years and some early digging in the engine bay indicates it might not be the battery's fault as Eric and Nigel suspected. Amazingly it had a 5 year warranty that the seller is trying to dodge.

[Neil-yaj396]

Bit of an update to this. Since getting back from GNW I've found that after the car is left for a couple of days all is good on starting; charging light on, then off, volt meter at normal. However, after driving for 5 minutes or so (this used to be around 30 minutes) the volt meter drops, and after switch off the charging light does not come back on, ie it is dead.

So, found my multimeter and put in a new 9 volt battery (£5!). 12 volts across the battery then 13.8 on start up, BUT, after that 5 minute drop on the voltmeter it's down to 11.2 and moving to the alternator itself I found pretty much the same reading. So, my bet now is on the voltage regulator on the alternator, or some other alternator fault.

I take back what I said about Varta batteries!

As for the breakdown, well, the earth lead from the battery was only finger tight, which must have really exacerbated the drain off of power. Lucky I got home at all........

[Neil-yaj396]

Just to (hopefully) finish this off and for future reference I sourced a voltage regulator from Lithuania via ebay. It arrived in about 3 days and as I seem to be busy at the moment, and I had the deadline to get to Northampton on the 21st, I took the car to Classic Car Lab and they fitted it for me.

All working 100% on the drive home. I shouldn't have ignored the voltmeter for so long! Who says old car instruments can't be relied upon.....