Key Fob Not Working

[over_the_hill]

I had a bit of an unfortunate incident yesterday.

Got the car out of the garage - it fired up fine - but I do leave an Accumate plugged in - and set off out.
I pulled in for petrol just up the road and returned to the car only for it to not start - very embarrassing on a busy forecourt on a Bank Hol.

The fuel pump seemed to be priming but turning the key did nothing at all.
I have a hot start kit fitted and hadn't gone that far for it to get very hot anyway.

Repeated tries of keys out, keys in, prime pump, turn key gave varied results of nothing or about half a feeble crank of the starter motor.

Tried other electrics and lights were very dim, wipers wouldn't work and the windows wouldn't open so suspected a flat battery.

Just to be sure I went back into the shop and got new batteries for the fob - did nothing.
Got down in the foot well and checked all connections were pushed home well.
Quick look under bonnet for anything loose - nothing obvious.
Unplugged ECU and reconnected it in case anything scrambled and needed a reset.

Anyway a kind soul in a Volvo helped me push it out of the way of the pumps and gave me a jump start.
Fired up fine and all went well. Drove off to where going - reasonable distance so should have put charge in battery.

Got to the other end of the journey and the car would not lock - there was no response from the fob at all.
(No big deal as safe enough to leave unlocked where it was)
Came to leave and got back in car - had to use the plastic tag to unset the alarm/immobiliser but all fine and fired up first time.

Drove back home again and put car safely in garage.
The fob was still not working so couldn't actually lock it.

The plastic tag seems to deactivate the alarm/immobiliser so I don't think it's that.
Put new batteries in the fob so don't think it's that
Tried spare fob and no luck there either.

I intend to get a new battery as the current one has been on a good while (will read up on the battery threads) but does anyone have any ideas on the fob ? I'm hoping that disconnecting the battery when I change it might do some sort of reset but am stumped after that

thanks

[Goaty Bill]

Disconnecting the battery for about 5 minutes will reset the alarm, assuming you have the original fitted.

But I don't recall ever having a problem with the fob not working (dead batteries excepted of course), even when the alarm is in that 'confused state'.

Might be it though. Disconnect, wait 10, reconnect.
Only takes 12 minutes to find out I suppose.

[over_the_hill]

Quick Update.

Before shelling out for a new battery I decided to run a few tests on the old one.

I wedged the probes of my voltmeter under the battery connectors and went to start up so I could see how much the voltage dropped while cranking. Unfortunately the negative probe had fallen out so I went back to stick it in again and the negative battery connector just fell off !! It had obviously come loose and was just sitting on the battery post.

Went inside to get spanners to refit it but unfortunately the door swang shut !! In the words of James May "Oh Cock".
Battery disconnected and now locked out. Used an alternative entry method so no real drama.

Refitted the negative connector to the battery.

The key fob then worked fine locking, setting and unsetting the alarm etc.

Furthermore 5-6 starts then stops of the car caused no problem at all and the voltage only dropped to 9v when cranking.

I left it for 10 mins and came back and repeated another couple of times. Again no issues at all and it fired up just fine.

So it looks as if all of this was down to a loose connector on the negative battery post.