The instrument cluster has it's own built in voltage regulator to maintain a steady voltage so as gauges remain steady. They can tolerate quite a wide input voltage before they are unable to provide a steady output. My thoughts are this is an earthing problem, maybe a loose earth strap between the engine and the chassis.
Ford Mondeo - 2008 Mondeo - 'Low Battery' AGAIN! - Lancelot2 : My 08 1.8 tdi threw up the message of low battery last night for the first time. I am so pleased I logged on tonight. Over the past 2 weekend I have driven about 250-300mls each time so I was surprised to see the message.
Reminding of a coupe of pitfalls when buying secondhand: 1) Make sure the tachometer is right for your engine. For diesel, the scale should go to 6k rpm. If the scale goes up to 7k rpm or 8k rpm, it's meant for petrol engines. 2) When buying from sellers outside the UK, make sure the speedo scale shows MPH, rather than KM/H.
I have a 58 S-Max with a Convers+ instrument cluster that's suddenly started resetting intermittently. Sometimes it's continuous, sometimes it's every few minutes, I think the longest it's gone without resetting is about 10 minutes. I've got it booked in at the local Ford dealer, but I'm worried they'll just charge me £85 for the diagnostics
oslmap.