I wonder if any auto-electricians out there have any ideas on this irritating problem I have had pretty well throughout the four-year life of my Fiesta ?
I have had a succession of battery failures, going either almost or completely flat, usually overnight for no obvious reason. Each time they checked, the AA proved there was a good output from the alternator and there was no current drain. The Ford dealer subsequently changed first the alternator and then the battery under warranty (although I am not convinced that the battery they fitted was a new one).
I eventually put the problem down to the frequent very short journeys I do and fitted an LED voltmeter plugged in to the power socket to monitor the battery voltage.
Usually, the voltmeter shows about 12.2 volts static and after start up and sometimes goes up to 14 v settling down to around 13.0 - 13.2 whilst driving. I have taken to putting it on trickle charge every few weeks which I think should not be necessary.
The battery failed again only last week which was quite inconvenient.
What has prompted this particular post is that while out yesterday, I noticed that the voltage dropped to only 11 volts with no lights or heated screen on which quite concerned me. To see how low it would drop with a load, I switched on both heated screens, half expecting the engine to cut out but to my surprise it actually rose to 13.2 and stayed there after I switched the screens off.
When I got home I kept the engine running and double checked the reading across the battery with my Fluke testmeter and it showed a normal 13.2 - 13,5v, confirming the LED reading inside the car.
The car has only done 17,000 miles in four years.
Anyone have any ideas ?