I know this will probably have been covered here,but here's my experience. 

About four months ago I put my van into our local dealership to investigate a battery drain,they replaced the battery through the warranty,five weeks ago we put into the same dealership for it's first service,the heath report from them said that the fig lights and horn weren't working and would need further investigation,dropped it off yesterday and they phoned late afternoon to say that the fog lights had been disconnected under the dash,I told them there was no reason anyone would go behind the dash to disconnect them,she quickly deflected saying that the "technician "has opened a case with Ford about the horn,in other words he's not a clue what's wrong with it.

I have read on line about Transit fog lights draining batteries.

I find it highly suspicious that they replaced my battery and now they find the fog lights disconnected, trust me the fog lights worked before they replaced the battery.

I'll hopefully pick the van up this afternoon. 

We are going away in the van next week for three months and need to know the battery is going to keep the charge.

Your thoughts please.

Make sure you have good breakdown /repatriation cover, and a jump starter (invaluable anyway?)
Get them to show you that there is the correct (i..e tiny 30mA?) current drain once all the modules have gone to sleep (they'll need to latch bonnet and doors and have it set up ready for you)
Check the fog lamps and everything else works after that, of course.
Otherwise leave fog lamps off until you get back?

As caravanners, we like to be independent and try to cover all eventualities...

Thanks for that but I have never had the fog lights on.

The garage in question seem to think someone has taken the dashboard out and disconnected them because thats what you need to do to get to the disconnected cables,they tried to charge me £140 for an hours labour,which means,their mechanic or technician or whatever they're called today manage to find out what the fault was take out the dash,reconnect the lights, refit the dash and check it worked all in one hour.

As I said previously it all seam very suspicious to me,in my opinion they knew exactly why the lights didn't work because they unplugged them when they changed the battery to save it draining again.

Even wondering if they DID change the battery or just charge the one that draining.

Edited June 14, 2025Jun 14 by Big Alan
Typo

I don't quite understand, I thought the fog lights had been disconnected by someone (if it's a conversion, that might have happened during that work) but I now think you believe that they found that the fog lights were causing the drain so disconnected them?

What is the current (pun!) problem, what do you want advice on  as there is much suspicion about battery, disconnection, charging for work not done etc etc?

Again, I'd want to see everything working, then use an Amp clamp on the main battery terminal (or an ammeter in series), wait until the vehicle goes to sleep (20 min) then observe the current drain and confirm it is within limits.
If outside that and the battery is still losing charge, there would need to be an investigation based on measuring the draw at the battery then tracking back to the specific fuse box then identifying the circuit(s)  responsible  and fixing that.

There are loads of You Tube videos showing how to do that, including:
https://www.youtube.com/watch?v=GML80iq-hC4

Unless I'm missing the point?