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Just over a week ago I came back to my car (Fiesta mk7 2009 1.4 tdci ~50k miles) to find the remote fob not working to unlock the car. Assumed the fob battery had died, so unlocked manually via the key. Got in the car, realised there was absolutely no electrical power, completely dead, no dashboard/interior lights, turning key in ignition did nothing.

Assumed the battery had randomly died. Checked under bonnet for connections etc., all seemed fine. Was about to call break down, then suddenly all power came back and I was able to start the car. Assumed it was some electrical glitch, didn't think much of it.

All fine been driving as usual all of last week until today - came back to car, unlocked fine, all power fine and then electrics go completely dead just as I'm turning key to start engine. Thought I was scuppered this time, but then suddenly, again about 5 minutes later, all power came back and I was able to start engine and drive home fine.

I noticed both times the clock had lost about 5 mins of time, so I assume somehow using the key fob in the first instance was what caused the power cut? I can't think what the problem is, the battery should be perfectly healthy as it was replaced only a couple of years ago. I don't know much about these things, but perhaps an issue with the alternator? Or just battery connections/terminals?

In any case, it probably needs a trip to the garage but I thought I'd ask here if anyone has any idea what the problem might be and if there is a simple fix that could be tried?

In the meantime I assume I am ok to drive the car until it goes into garage (if it comes to that) - I'm worried now that the electrics could go dead while driving which I don't think would be a pleasant situation to be in!

Thank you in advance for your help.

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  • The first thing I'd check before doing anything is your battery terminal connections, it's a possibility one of them is a bit loose. If there's any play then tighten them up.
    – GdD
    Commented Jun 13, 2017 at 8:35
  • just to add similar data points - had a car good battery, no electrical power at all situation that turned out to be a battery ground wire (the short negative terminal-to-chassis wire) that was shorting positive because of enough build-up on an uncovered battery. wiggling it would bring power to the car. in another case, it was a bad ignition switch. electrical cut out for just a second while stopping at a light, then started right up again. hint was that once before car wouldn't lock because it thought key was still in ignition after everything turned off. These things are tricky.
    – Nick J
    Commented Mar 14, 2022 at 16:59

4 Answers 4

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Start by checking your ground wires, they run from the battery to the frame, and the engine. look for corrosion in the wires, and at terminal points. Make sure terminal points are not loose.

Then also check the positive line to the starter and to the fuse/relay box. again looking for corrosion and loose connections.

if everything is out intermittently, you have an intermittent open somewhere in the main return/supply lines to/from the battery.

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  • open in this case would be a higher then desirable resistance, not necessarily in the meg-ohm range.
    – Jrican
    Commented Jun 13, 2017 at 3:27
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It is also possible that you have a broken link inside the battery, rare but possible - had a car battery with that fault once very difficult to find...

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Was your car been sitting idle for long? If yes Chances are that battery terminals would have corroded which breaks contact. You can rub it off with sand paper and apply some grease or petroleum jelly. Other issue could be loose connection to battery terminals (check for the nut which tightens the bolt if that is tight enough that the wire connector does not become loose)

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the most likely was due to your remote key out of battery.replace the batt then things will be normal again.your car's security immobiliser was activated when the signal was faded.

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    Even if the fob battery is dead, the immobilizer won't keep the dome/courtesy lights from coming on. The immobilizer will only keep the vehicle from starting.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Aug 20, 2018 at 17:25

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