pms 3v

[ninjasmith]

Hi I've read other posts on this and my problem seems to be slightly different.

Symptoms
1) leisure battery doesn't charge when driving. Plugging into 240v does charge it.

I've check the voltage on both batteries when engine is running and I get 14ish on car batt but leisure batt does not change when engine running. i've unscrewed the pms and both batts appear to be wired in correctly from -ve to the respective dc inputs label car+ and van+ when I start the engine the voltage on these jumps on the car+ from 12 ish to 14 ish but the van+ reading does not change. All consistent with a fault so far.

When plugging in the 240v I get a change in voltage on EITHER the car + or the van+ so consistent with the hookup charging the batteries.

Can anyone who knows how these work shed any light on what's going on. For what its worth its an elite conversion and the guy who wired up the internal 240v plug wired it wrong which I fixed in a previous thread so he's proved himself to be incompetent.

There is a big obvious 20v fuse on back of pms that is intact

[g8dhe]

I don't have an actual circuit of the PMS 3 available but I don't think the PMS3 includes the vehicle leisure battery charging relay, but there will be a relay in the vehicle that is operated when the vehicle has its engine running, it is this relay that connects the Starter battery and Alternator to the Leisure battery for charging. The fact that you see correct voltages at the PMS3 either when the vehicle is running or from its built in charger from the mains suggest that the connections to the batteries are OK. I would look towards the relay in the first instance either the relay is faulty or the signal from the ignition is faulty.

Or just maybe the converters never did fit a relay to allow charging from the vehicle, merely the mains battery charger ?

[ninjasmith]

Yes that sounds feasible. However the pms is con strutted of steel and rivets so no way to get inside that I can see.

Anyway way I can verify the fault externally?

The signal from the ignition is a separate cable or just the relay picking up in the change in voltage?

if the fault is not fixable without breaking into the pms and pot entially knackering it fitting an external relay would be possible? I'm thinking that wiring it from the car+ to the van+ would work. Or failing that an isolation switch to connect the car+ and van+ then when we are parked we can try and remember to flip the switch and isolate the leisure battery so we can run fridge from it.

EDIT. Just noticed u suggesting the convertors might never have fitted a relay? Surely the relay in the pms is internal and standard. Other people seems to have the same unit and it charges both.

[madmile]

Im with g8dhe.
The PMS units have no in built 12v relay or even a basic switch like a zig. The readings you are getting suggest that the PMS is correctly wired, but if you have a split charging relay, then its not working.
If you have one, then it should be a small box(about the size of a matchbox) and will have a wire running to it from the main + terminal and then onto the leisure battery +. There should be some inline fuses as well, and these would be my first thought to check.

PS - I wouldnt even think about taking the PMS apart.

[Dan T]

Wasn't sure what I was going to see when I opened the post about 'pms' - half expected a long rant from someone with some tummy pains

[Cloughy]

Just to confirm, I have an Elite conversion and I had to fit my own Willington relay to get the LB to charge from the alternator. Without adding the extra relay, the LB only charges when hooked up.

Cloughy

[g8dhe]

The charging relay is normally kept under the bonnet, as you don't really want long wires going between the batteries. Take a look under the bonnet, and see if you can locate a cable going from each battery (it will have a fuse close to the battery) to a small unit as Madmile describes, the unit will have these two cables plus an earth connection as a minimum, it may also have a separate control wire (but not if its what is called a Voltage Sensitive Relay VSR). If you don't have this then there is no way for the alternator to charge the L/B, it an only be charged from the mains. If that's the case but you do want to be able to charge the L/B when driving (the normal requirement ) then get your self off to the EBAY and the Willinton split charging kit.

[Cloughy]

There is a small relay under my bonnet connected to the PMS, but I think it is for switching between LB power supply and car battery power supply. Annoying that this system doesn't charge when driving as I was expecting, after a couple of dark nights I realised I needed the Willington kit.

Cloughy

[Colin H F]

Mines an Elite conversion with a PMS 3 system and mine is wired so that the LB charges when running