Mondeo, sometimes car is dead when I turn key

wpd

ongoing intermittent issue sometimes car is dead when i turn key (1 in 20 times), totally dead no dash lights or anything. open bonnet and barely touch fuse box and it comes back to life. i tried replacing main relay but still same issue

any idea could it be the earth or live feed to fuse box??

thanks

extra-ordinary_

wpd wrote: »

ongoing intermittent issue sometimes car is dead when i turn key (1 in 20 times), totally dead no dash lights or anything. open bonnet and barely touch fuse box and it comes back to life. i tried replacing main relay but still same issue

any idea could it be the earth or live feed to fuse box??

thanks

...think you'd be on the right track...:)

wpd

Thanks extra-ordinary for reply

would you have any idea where earth for fuse box comes in would it be on the underneath??

extra-ordinary_

wpd wrote: »

Thanks extra-ordinary for reply

would you have any idea where earth for fuse box comes in would it be on the underneath??

I'm not familiar with the layout of your car in particular but if the issue is resolved every time you fiddle with the fusebox then it must point to either a bad/loose connection somewhere or a damaged cable. Get a manual for the car and check the wiring diagram so you can troubleshoot next time you have the issue which wire should be live and isn't. Sounds like the main fuse circuit has a problem.

wpd

thanks for reply will give that a try

zg3409

You don't mention year, engine type nor size or specific engine model. What mileage? Try battery connection, earth and live from battery to chassis and starter. Try swapping all big relays in the area. Does for example the radio come on when you turn key? Does interior light come on?

wpd

sorry I havent updated recently

So i had a good delve into fuse box and made sure all fuses looked okay and were fully pushed home

I then replace the R1 relay which i think is starter relay, I thought this had solved problem however same problem
couple of days later
then put new relay into R2 PCM relay = since then no issues and my cruise control which was very hit and miss
seems to be working 100%
Finger crossed but good so far

Redauto

I had the same trouble as you with a Mk 4. Turned out it was the negative lead where it bolts onto the shell at the nearside top shock. The bolt had a bit of rust on it and this was causing the issue. Very frustrating...

wpd

thanks i did clean that up as well when replacing relay so maybe that helped