Cab Light - Enough Voltage but Dim

[digitalgypsy]

Hello Bongos, seeking your advice again

I've got a problem with my cab light not working properly. When you turn it on, it shows full brightness for a split second but then goes dim. I'm no techie but I have tried to determine the issue or fix. I measured the voltage coming through and that seems fine, around 10.5. I also cleaned the connectors the best I could. The rear left smaller light works fine and so does the AFT light.

So to be clear, when switching on, the cab light shows full brightness for half a second and then goes dim. I did push the tube down a little which temporarily solved the problem but now back to normal. Any ideas what's happening here?? I'm tempted to just replace it with an LED setup since someone posted that good video guide recently!

Thanks as always
Steve

P.S. The tube is also fairly new.

[g8dhe]

If the voltage is around 10.5 then that is way low, you should expect to see no less than 11 volts even with the engine off if the battery is in reasonable condition, unless your drawing any other significant load from the same battery ?

[digitalgypsy]

Bugger That's without anything running. So maybe I can assume there is enough voltage getting through to the other 2 lights? i.e. rear small light and AFT light.

One thing that I have wondered is something to do with my Zig power unit, which may or not be related to this issue. I don't think the Battery Selector switch is doing what it's meant to do. Reason being is that the fridge and lights work even when it's in OFF position. Does that sound normal? I thought the appliances such as fridge should only run off the leisure battery? Of course I may be wrong here. The fridge and lights run regardless of whatever position that switch is in.

[digitalgypsy]

Correction for the voltage! I measured it again and got a steady 13.8, so voltage isn't a problem after all. I also carefully put the bulb back in place and appears to be a bit better, I'll test in the evening. Perhaps I simply didn't have it in place properly It does seem to come and go...

I'm more concerned about the battery selector switch but perhaps that is for another post!

[francophile1947]

This gets more confusing 13.8V is far higher than the battery should give, as a fully charged battery is only about 12.7-12.8V Did you have the engine running when you measured the voltage?
What sort of fridge are we talking about - compressor or 3 way?

[digitalgypsy]

I did think that 13.8 is high, BUT! I do have a 80w solar panel constantly feeding the leisure battery and it's been a very clear sunny day today. Only measured with engine off and nothing else running. The fridge is a compressor, Vitrifrigo C39l to be exact.

The plot thickens with this...

The water tap and ADDED extra light from converters don't work in the OFF position which is what I would expect. So just leaves the question of fridge and interior lights running on any position i.e. VAN, CAR and OFF. So I suspect the interior lights have nothing to do with the Zig unit...just a bit puzzled about the fridge.

Am sure I'm worrying about nothing here just like to know everything is as it should be

[francophile1947]

Solar panel would explain the high voltage
I have a compressor fridge, connected to the leisure battery, and that has it's own switch, independent of the Zig panel controls - turning off at the Zig still leaves the fridge on.
It sounds like your standard lights are still wired through the car battery and not through the Zig/leisure battery.

[digitalgypsy]

Thanks Franco, that sounds right

Kind of amiss as to why the converters didn't wire up the interior to LB, if that's the case. Know of any easy way that I can determine if the lights are running off the car battery? Guess I could disconnect the car battery and see if they still work? Sounds a little drastic to me however, being very non technical!

[Simon Jones]

One thing to mindful of if you have an alarm fitted is that it will be wired to the main battery & typically monitors for a voltage drop caused by a door being opened & the interior light coming on. By moving interior lights to leisure battery, you will mess up the voltage sensing such that it may not work at all or may produce strange results.

Unless you specified the lights to be changed over, there's a fair chance it would not have been done. Most convertors would fit additional lighting in & wire it direct to the LB so as not to interfere with the standard vehicle wiring.

[g8dhe]

The easiest way to find out what is connected to which battery is just that, turn on the devices and then disconnect the earth strap to the -ve post on each battery in turn and check to see what is and isn't running. The only other way is to follow wires around which is a lot more fiddly! 10 minutes work, one spanner and its done. Just make sure you note down for a permanent record rather than try to remember what was connected to where.

[digitalgypsy]

I have since found out that the lights are running off the LB, along with existing 12v socket and radio. Someone else from here kindly helped me a while ago and confirmed we switched it all over to LB, I couldn't remember. The fridge isn't controlled by the Zig unit, like Francophile said, has it's own switch. I'd be extremely surprised if converters wired the fridge to SB.

I'll assume everything is alright until otherwise! Original problem of dim cab light will most likely be cleared by upgrading to LED, going to follow the guide that was recently posted on here https://www.youtube.com/watch?v=L_digIxwxV4

Thanks all!!!

Oh and thanks for alarm info Simon, having a CAT1 installed was the first thing I ever did. Had quite a few things done to the van since but alarm never shown any problems, still works!

[Dodgey]

It's quite good practice to have the fridge wired directly to the LB and not through a power management unit in my opinion - the PMUs usually have a live bus that is far too thin for the cable needs of a fridge.

Also - 13.8v is normal when a battery is on charge - that's the voltage a charger will take it up to when topping-off at a very low current. When the charging stops the battery will immediately fall to 12.6 again.

[digitalgypsy]

Dodgey is said person who helped me previously Nice to know my battery is fully topped up!

[mikexgough]

yeah...my LB is sitting on 12.8v tonight and the SB is also topped up.. cold cider in the fridge... Happy Days and free charge from daylight... - Like Dodgey says... Wire the Fridge direct to the LB and fuse protect it...

[digitalgypsy]

Me again...

Have since found out that there ISN'T enough voltage getting through the cab light. As noted before, the roof and rear light are working fine. I'm going to run a wire straight from the positive of the leisure battery to the cab light. Does anyone know easiest route to get the wire from the leisure battery to the cab light??

Many thanks again