Hi WMF. Sorry to bump your thread, I was going to post a separate thread, but yours seems to follow the ilk of mine, so it made sense to put mine with yours.
I've posted to help and ask in the past couple of years, and now it's time to ask again!
I have had a similar experience. I took my daughter to A&E last Monday, the night of the snow, and it struggled to start ( two turns to catch) though I thought nothing of it as it was minus 4. We got to the hospital no probs, heater full blast, all lights usual for conditions.
I set off from the hospital, went over a speed bump and BEEEP! Alternator fault and EBD System failure contact garage (SH*T!) I knew that if I stopped the engine, I would be doomed in the car park, so carried on home. After not long, the fan motor stopped working, the lights went dim and odd things like when I put the indicators on, they ticked really slowly, and the dash lights flashed in time with this. When I cancelled the indicator, the dash lights carried on reacting in the same way. By the end of the short journey, the dash display kept stating Check in Progress, then going blank, and repeating this, over and over.
Now, just after I got the car two years ago, I had to have a new alternator fitted, so although not likely, I cannot rule it out, however, when it went then, I got the same warning, but also the battery symbol on the dash came on too, yet it didn't this time. Also the car ran fine with no alternator for a good while on the battery alone, yet this time it clearly wasn't the case.
I don't know how old the battery is, but had the battery gone with the cold weather, the car run still run fine on the alternator, so unless I've been really unlucky and both the alternator and battery have gone, OR I have a bad earth, or positive connection somewhere, which has fractured with the bump from the destructively evil lump of tarmac called a speed bump.
With a multi meter I've checked and the voltage at the battery terminals is 8v, and when turning the key on the ignition, I get the repetitive click of the various relays, as it still flickers from off to Check in Progress, and off and so on. I think that the fan on full has drained the battery quickly and that it'll be fine once I fix the fault.
I have tried to check continuity along the earth cables, but am I correct in thinking that my cheap multimeter, would be unable to check continuity along something as thick as the earth cable?
I've had the air box off to check the physical condition of the cables, and they seem okay, but I know that they fracture internally.
Any suggestions, experiences etc would be welcome seeing as though you've been through something similar.
I am in the RAC and am considering towing more than 1/4 mile from home and phoning them for the diagnostic check if nothing else, but it would be great if I could fix it without doing so.
Heres hoping...