Leisure battety not charging while driving

[Juzzy]

Hi,

We have a 1999 Elldis firestorm and are now having an issue with the leisure battery not charging whilst driving.
Charges on EHU
Battery status will show its in the green until I plug the car in and running, then the needle suddenly drops to red.
The fridge 12v light is on when car is running.
Have checked both 25amp fuses near the leisure battery and they are fine.
Whilst on our roadtrip the 7pin S plug on the caravan was acting up (seriously corroded) and you had to have it sitting just right for the 12v fridge light to be on. So I cut it off and fitted a new one following the wiring guide and also cheching the number/colour coding to the existing plug. Unfortunately I didn't think at the time to disconnect the leisure battery when cutting the old plug off. 5 days later with no EHU the leisure battery is flat. 1 night on hook up and its charged again.
Have I possibly fried the recharge box in the caravan?
Or is there another fuse in the caravan I am missing somewhere?
I double checked my wiring with the plug and everything seems to be in order.

We are currently still on the road so don't have access to a volt meter to check anything.
TIA

 

[borderbilly]

Dont think it charges when you are driving, only on EHU.

 

[Mr Plodd]

What are you towing it with? (Mke model and year)

 

[woodsieboy]

With a caravan of that year do you have a switch inside that needs to be set to car, it will probably be a rocker switch that toggles between car and mains hook up, probably naer to door and control panel

 

[Dustydog]

1. If the plug was corroded so will the socket. Spray it with electrical contact spray. Then check the outputs on the car with a multi meter, engine running.

2. Check the master fuse on the battery. Whilst hooked to the mains EHU, test the voltage across the battery. Should be 13.4 v or close
Let us know

 

[Sam Vimes]

I'm assuming that the battery charged correctly before you rewired the plug.

Wiring of caravans varies. If you have no physical switch to select between car or caravan for the 12v, then there maybe a habitation relay inside the caravan that will switch the leisure battery over to the car supply when the ignition is turned on. I think the supply from car to the relay comes from pin 6, so might be worth checking those pins.

 

[Juzzy]

What are you towing it with? (Mke model and year)

2009 Mercedes C class wagon

 

[Juzzy]

With a caravan of that year do you have a switch inside that needs to be set to car, it will probably be a rocker switch that toggles between car and mains hook up, probably naer to door and control panel

No, no switch on this one. Charged fine for the last 3k Miles we have done with it