12 volt power issues

[Alpaca]

Intermitantly (more often than not), when I plug a 12 volt appliance in, the power indicator drops down to around 4 volts. The battery is new and holds over 13.5 volts.
It occurred when I plugged in the Camframo fan so I thought that I had a problem with the fan but this morning, I plugged in a new 12 volt TV and the same thing occurred. Strangely, it appears to rectify it's self and at the moment, both the Fan and TV are working.
Even when it happens, The battery is still showing 13.5 volts.
I checked the 30 amp fuse and it shows full power on both sides and also checked the (not sure if it is a fuse or relay fitted adjacent the draw bar.
I'm thinking it's an earth issue but I can't see where the battery is earthed to the Tvan. 
The Tvan is a 2006 Mk11
Any assistance would be greatly appreciated.
Cheers
Alpaca

[Cruiser 105Tvan]

Hi,
Have a look on the underside of the van.
On the inside of the A frame, near the front of the Van, on the drivers  side.
On mine there's a wire  pop riveted.  Can I suggest you drill out the pop rivet and insert, fit a fine threaded self drilling screw.  Make sure the crimp fitting on the wire isn't loose too.
Mine needed fixing.  From memory, I think there's one or two under the back as well.
In behind the pivot of the floor (Red Bit), on the sides of the chassis.

[Alpaca]

Thanks Cruiser, I'll check it out in the cool of the morning.
Alpaca

[The Hueys]

There was no battery earth on a 2006 model, it was introduced later. Either way all Tvans run dual core wire to all lights, sockets and the volt gauge. Could be a faulty gauge or loose connections at the back of the gauge causing it to give a false reading.

The reading of the battery voltage, is that done on the battery posts, the terminals or the wire? There could possibly be a bad connection somewhere there causing the voltage to drop. If the reading is at one of the power sockets then getting a low reading due to dirty battery terminals is unlikely.

[Alpaca]

Thanks for your reply Craig.
I did have a scratch around under the Tvan this morning and there is an earth wire connected directly at the chassis. As it is a bolted connection, and in light of your comments, I would suggest that the previous owner may have fitted it.
I took the voltage readings directly on the post.
The gauge inside the Tvan was also reading over 13.5 volts and when I plugged the fan in, it dropped to about 4-5 volts. When I unplugged the fan some minutes later, the gauge jumped back to 13,5 volts again.
The gauge did the same thing when I plugged in a 12 volt TV.
Now everything seems fine when I plug in either the fan or the TV.
Will have to keep an eye on it and if it still occurs, I will remove the cover panel of the internal board and check the earth wire in there.
Thanks again to you both for your assistance.

Regards

Alpaca

[Harry Lissimore]

I don't know if this has anything to do with it but I had a serious 240V issue last year and while I was inside the yellow electrical box, I noticed that the red wire connected to the voltmeter was loose, the problem being that the screw in the voltmeter that held the red wire was tightened as far as it could be but it wasn't enough.  I had to put a washer as a spacer.  The screw was a fraction too long for the voltmeter connection.

I also have a similar problem in that I run my Engel from the 12V merit plug on the yellow box and every time the thermostat turns on the voltage drops by about 0.4V at the merit plugs.  If the battery voltage at the merit plugs is 12.8, then when the fridge turns on that voltage goes to 12.4 or 12.4V.  I don't know if this is normal or not.  When I measure the voltage at the battery, it doesn't change at all and when I use a fairly heavy duty cable to connect my fridge up directly to the battery via the anderson plug at the front, the voltage at the merit plugs at the yellow box does not change at all when the thermostat turns on.  I can only think that either the wiring from the Tvan battery (located on the front draw bar) to the merit plugs at the yellow box has too much resistance because it is too small a gauge or there are some bad connections in-between.  I recently plugged  an inverter into the merit plug to charge and run a laptop and it kept erroring because the voltage dropped to below 11.5, whereas if I plugged the inverter into the battery via my heavy duty cable via the front anderson plug, the voltage did not drop at all.

As my Tvan is a 2002 model, I wonder if I either have to rewire with heavier duty wire or go through every connection and reseat/clean them.  Any help would be much appreciated and I would like to hear if anyone has similar problems.

[Phil G]

I had to rewire most of my 2003 TVan because or corrosion in the wires.  I rewired with tinned marine wire.

[The Hueys]

I'd start by cleaning all the connections. Fridges are usually OK from the power box sockets. Bigger wire would always be better but you can start to run into size/packaging restraints once you go bigger than what is there.

How big is the inverter? Due to the length of the wire it is really too small to run anything much bigger than 100-150W from the standard wiring.

[Alpaca]

Craig, not sure if your reply was directed to me but my fridge lives in the car and only time I use an inverter is to run the lap top occasionally.
Fridge is too heavy to lug around in the Tvan

All appears good ATM but if further problems occur, I'll check the magic yellow box then Phil's idea with the wiring.
Heading down to Lower Glenelg River next week so I'm sure it will test everything out.

Cheers


Alpaca

[Mal.W]

You could try connecting a jumper lead from the Batt-ve to the chassis, and a multimeter plugged into another 12volt socket.
Does your fan or TV operate correctly with your abnormal readings?

Mal

[Alpaca]

G'day Mal, When the voltmeter shows only 4.5 volts not even the ceiling LED lights will work. then after I unplug the fan or TV the system returns to normal. It seems OK ATM though

[Cruiser 105Tvan]

Alpaca,

When you have this problem of Voltage drop.
Is it just at the one socket or all of them?
Have you tried using your appliances, and not involving the Tvan?
By hooking them onto a Transformer (power supply), or the battery charger, and measuring the voltage?
There could be a resistive problem in the back of a socket that doesn't blow a fuse?
Did the wiring let some smoke out at some stage in the past maybe?

Rule one: Electricity runs on Smoke.
Rule two: If you let the smoke out, it will never run again.
Rule three: You can't re-insert the smoke to get it going again.
Rule Four: Smoke is always expensive.

Robert.