Hello, split charge relay issues

[Rustywesty]

Hi Everyone,

We’ve got our first MOT due on our shiny new L reg t4 westie California.
The battery light is on all the time (started flickering to start with). I’m getting 14.2v at the engine battery when the engine is running, 12.7 when not. The 14.2 goes all the way to the split charge relay. It doesn’t now register at the over head control panel.
Like wise when I hook up. It charges all the way to the leisure battery side of the split charge relay and does register on the over head control panel. I’ve replaced the split charge relay and the relay beside it that controls the split charge relay and comes off the battery light (I think). I’m on the verge of delving deeper but currently feeling out of my depth. Can anyone help, many thanks

 

[Loz]

Why are you messing with the split charge?
I’ve not seen the T4 circuit diagrams, however;
Traditional alternators control(extinguish) the red charge light by adding 12v to one side as the other side already has power from the ignition. As the voltage on the wire increases the light dims. Check the control wire going down to the alternator has not chafed and gone to ground.

Or are you saying that when you remove the control relay the light extinguishes?

 

[Rustywesty]

I will check the alternator/light cable tomorrow, good shout Thank you
There’s a digital display control panel in the westfalia conversions just above the map light. Normally when the alternator is charging the leisure battery’s the control panel shows this ie voltage goes up from about 12.7ish to 14ish. Currently not doing that, although it does when the hook up is plugged in and the inverter is charging.

 

[Loz]

Is it possible that the alternator is indeed failed and you are seeing current flow from your leisure batteries being charged by the ehu?
It sounds like you need to isolate the 2 systems and test the alternator is charging.

 

[sidepod]

This makes no sense. You’re 99% certain it’s not the split charge relays as you’ve replaced them.
The wiring should be intact as it’s behaving correctly when on hook up.

What I would do is mimic the alternator signal to the split charge relay.

Engine off. Hook up in place. Take a 12v supply to the relay coil and trigger it to simulate engine running. See if you get the correct voltage at the panel.

I’m with Loz on the theory.

Let us know, we do love a sparky fault.

New Westy? My old one was on an L plate. Pics/details?

P

 

[Rustywesty]

She’s a ‘93 plate with over 200,000 (about 340,000 in German), new to me ;-)
Will get some pics up when I get home.

The artificial signal is a great idea (first thing I’m going to try) and with Loz on a possible corroded signal cable off alternator.
Have found a wiring diagram on a previous thread (will try and link it)

 

[Rustywesty]

 

[sidepod]

That’s mine

 

[Rustywesty]

Haha, that’ll be a thank you again then

 

[Padraic]

You mentioned in your first post that you have replaced the split charge relay and the relay beside it. Are there two relays there? If so what is the second one for?
If there are two relays there, are both of them being triggered by the signal from the alternator? If they are this could be your problem, there is not enough current to drive the two relays and it may put the battery light on.

 

[sidepod]

There are two, if you look at the diagram, the first one switches the alternator signal to the split charge relay.

 

[Loz]

In the OP you mentioned the battery light and MOT.
So just to clarify the "Battery light" you mention; is this referring to the camper electrics or the alternator warning light in the instrument cluster?

I ask as the latter is an MOT failure but the former not..

 

[Rustywesty]

Unfortunately it’s the alternator light. Here’s some photos to show you which bits I’m playing with

 

[Rustywesty]

That black and red cable coming off the alternator could be the issue.
The Alternator is running just over 14volts which I’m happy with. The reading at the alternator on the above mentioned cable is about 7volts.
This carry’s through to the small brown 30A relay (turning up as one of the blue cables) also reading 7 volts. I’ve got a feeling this should be at least 12 volts to kill the potential difference across the alternator light (mentioned by Loz).

 

[Loz]

So have they tapped into this to trigger the split charge? Does the light extinguish if you disconnect the blue wire? Or pull the brown relay out?

I am just thinking that the relay fed by the tap into the alternator light is too low a resistance and dragging the voltage down.

 

[sidepod]

So have they tapped into this to trigger the split charge?

That is the stock method of wiring a split charge system.

 

[Loz]

That is the stock method of wiring a split charge system.

Thanks I needed that clarification.
Okay, in that case, I have a theory.
The brown relay looks new? If the battery light goes out when the relay is removed, then I think it is the wrong impedance and needs to changed out for one with a much higher impedance so it draws less current.
So my suggestion is to unplug the brown relay and get the mot out of the way, then find the correct relay for this application or better still swap out both relays for a VSR (voltage switched relay) that will not need this trigger or additional relay.

 

[Padraic]

Can I ask what the second brown relay is for?
Does the stock setup, not just have one relay? Are both of those relays being triggered by the D+ signal from the alternator?

 

[Rustywesty]

Sorry about the delay, hectic weekend!
The brown relay is rated 30a same as the original.
I’m guessing the brown relay is mainly a step up relay. I’m pretty sure it’s all original westfalia gear.
It likes like the d+ sets off the brown relay which in turn sets off the black main 75a relay.

Thanks I needed that clarification.
Okay, in that case, I have a theory.
The brown relay looks new? If the battery light goes out when the relay is removed, then I think it is the wrong impedance and needs to changed out for one with a much higher impedance so it draws less current.
So my suggestion is to unplug the brown relay and get the mot out of the way, then find the correct relay for this application or better still swap out both relays for a VSR (voltage switched relay) that will not need this trigger or additional relay.

I will bear this in mind, unfortunately it’s MOT day to day so I’ve said take and I’ll sort things out after failure.
It’s also part of the test that all warning lights switch on then off after start up
Also I don’t think removing the relay would switch the light off due to the voltage required from the relay to cancel out the potential difference across the alternator light.

 

[Rustywesty]

The one that has me puzzled is why the 7volts off the b+ terminal, both at the alternator and reaching the brown relay (so not a volt drop issue)

 

[Loz]

Sorry about the delay, hectic weekend!
The brown relay is rated 30a same as the original.

30a is the switching current not the impedance of the relay coil.
If you pull out the brown relay the light might go out and you can pass your MOT?