The two fuses from the battery lead were blown but when I replaced them they just blew again.
Before blowing the voltmeter pulls to the left suggesting a negative supply but I know for sure that the battery is now connected correctly.
Could the initial mistake have damaged another component? Everything works fine on mains.
I thank you in advance for your reply.
Response
Thanks for your e-mail, not a good situation as there's a few things that could be suspect in such circumstances.
You mentioned that 2 fuses were blown - I take it you are referring to the 20 amp and the 5 amp - the 20 amp directly off the battery and the 5 amp that feeds the radio, fridge control circuit and alarm system.
Try this in the first instance:
Remove all the 12 volt fuses from the control panel and the 5 amp & 20 amp near to the battery.
Connect the battery leads to the battery.
Replace the 20 amp fuse only. If it blows come back to me. If it holds replace one by one the fuses on the control panel trying out each appliance before replacing the next fuse.
If all is well with this I suspect your fridge control panel is damaged.
You can check this by disconnecting the 12volt supply to the fridge and replace the 5 amp fuse, obviously if it holds you know what's failed.
Let me know how you get on, what works and what doesn't. It might take a few goes to get to the root cause.
Feedback
Thanks for your speedy reply, when you say remove all the 12 volt fuses I am guessing you mean all of the fuses on the BONUS PDU3 box.
Feedback
I did what you suggested and removed all of the fuses from the Bonus PDU3 unit, I then replaced the 20 amp fuse straight from the battery but not the 5 amp, I then replaced each fuse and bit by bit I got all of my 12 volt system working again apart from the water pump.
Now the only fuse I had not re-fitted was a 7.5 amp that was marked "fridge" on the PDU3 and I wondered whether this would energize the water pump, I replaced it but sadly the pump is still not working.
I am certain that if I re-fitted the separate 5 amp fuse it would blow but could it be that this fuse covers the pump as there is no alarm fitted?
If I could disconnect the 12 volts to the fridge I could replace this fuse and see if it cures the pump. So how do I get to the fridge (Dometic RMS 8401) 12 volt supply?
I am really grateful for your time and help and look forward to your reply.
Update
Apologies I now have the pump working (forgot to open water valve) so the only question is how to get to the fridge PCB and how can I tell if it has blown?
Response
It looks as if you are making some progress. All fused appliances working on the 12 volt side via the PDU3 unit.
Let's look at the fridge then - if you have the installation/operation manual take a look at pages 20/21/22.
We are concerned with the 12 volt side, section 4.9.3 terminal block page 21.
Connections A&B are for the heating element which is ignition controlled, this draws a large current, I assume your car was NOT connected when the incident happened, and your fridge was TURNED OFF, so this circuit shouldn't have been affected, let me know if it was connected before you go any further.
So we are looking at connections B&C - with the 5 amp fuse removed disconnect these on the caravan side - I think the wire colours are brown/red tracer & black, brown & black on the fridge side. Make sure these are insulated before you replace the 5 amp fuse. Remember the radio is still connected.
The terminal block on the fridge you'll find through removing the vent cover on the outside of the caravan, from memory it's the lower cover. Proceed with caution as sometimes the spring plastic clips can become brittle over time and break.
When you have released the clips again be careful in removing the cover itself as there are two locating plastic pegs on the other end of the cover. Release the cover to just clear its frame and wiggle it up and down to loosen from the other end.
For what it's worth at this point I think I'd isolate the radio before replacing the 5 amp fuse. Remove the plug from the rear.
If all is OK replace the radio connection, operate the radio, take the fuse out reconnect the fridge and see what you get.
Let me know how you get on.
Feedback
I think I may be OK, unfortunately I did not have the installation manual for this fridge (RMS 8401) but I managed to download a copy. The page numbers and diagrams differ from what you must have but no matter.
I removed the lower vent panel and found a large amount of black cable pushed down the back of the fridge.
After extracting it I found a push connector each side of which was marked 12 volts, the colours are 1 purple 1 black and 1 red & 1 white. Both cables run up the back of the fridge and disappear inside a gap at the fridge top.
I unplugged these cables and connected the battery. I then gingerly inserted the 5 amp fuse -it did not blow. I re-connected the radio and it played, so I now have EVERYTHING working apart from the fridge.
The only thing left to do was re-connect the push connector, expecting the fuse to have blown I entered the van and to my delight everything was fine. I turned on the gas and selected this mode on the fridge and the piezo sparked and presumably lit.
What I can’t understand is why both the 20 and 5 amp fuse blew repeatedly immediately after I first discovered the polarity mistake. Could something have happened to the PDU3?
I have not tried the system on mains yet.
I hope that this is the end but would like to thank you for your help and time.
Response
OK think you need to make sure that the 12v charger is operational and available to charge your battery in the caravan.
With the mains connected and the charger switched on you should have 13.5 volts at least at the battery terminals
Feedback
So far the electrics have been OK, although we have not been able to get away in order to test them on site. We are hoping to get a few days away soon when I will be able to give them a good workout. I will let you know how this goes.
In the meantime I would like to thank Allan again for the help he gave me.
