Fridge on 12V

[relgate]

Hi guys
Just a quick question.
We are heading off for the official shakedown trip this weekend and I was wondering if there is any easy way to tell if the fridge is working on 12V?
We will assume the tug wiring is all good, I'm using a 12 pin. I can check there is voltage at that end, but how do I actually see if the fridge is functioning?

 

[bigman0510]

if you have a multimeter or DC voltage tester (always good to have for travelling) you can remove the bottom vent and you should be able to see the 12v connector there.

 

[relgate]

Thanks Bigman! That was too easy, and very clearly labelled!
On another note of interest, I read 14V at the 12 pin plug on the car side (unplugged), but at the fridge itself I only read 10.8V max. The fridge had been on 240V and was cold.
This seems like a significant voltage drop, or is it just not drawing because fridge is already cold?

 

[relgate]

Another quick Q.
Does it matter what temp setting you have when on 12V? I seem to remember it just runs full time and doesn't matter what you set it too. Is this correct?

 

[Burnsy]

10.8v....that does sound low! Maybe it is voltage drop? As far as I know there is no thermostat on 12v. Hope you have a great weekend mate and all goes well!

Cheers!

 

[ROnEM]

Relgate,

Much like yourself, i am getting ready for our shakedown trip.

Picked up a multi-meter the other day that also has a temp sensor, so you could get the fridge cool, put the sensor in and close the door, leaving the connectors to the multi-meter out and then check the fridge temp is being maintained if you can run it on a 12v source for 24 hours.

I did the voltage readings last night too. Getting 10.6v at rear of fridge, 13.8v at car 12 pin plug. Clearly the 6mm wiring Jayco use down the drawbar and over to the fridge is an issue. Could be more 6B&S will be run when time permits, but as the 12v function an the fridge is not designed to "cool" but rather maintain temperature, this is not a priority.

Also checked the Anderson plug - 13.8v at rear of car, 0v in the van. :frusty:

Warranty list is growing....

 

[cruza driver]

Hey RonEm, I had the same problem just make sure that the fuse is in the inline fuse holder located near the battery. Lucky you checked though as you may never never noticed till you really needed the battery charging between trips.

Mine was missing and once I fitted one it was all sorted.:happy:

 

[Tuco]

On another note of interest, I read 14V at the 12 pin plug on the car side (unplugged), but at the fridge itself I only read 10.8V max. .....This seems like a significant voltage drop...

Hi relgate - given the number of different battery arrangements that may be present in our rig combinations there is a need to establish just where the voltage loss is occuring.

1. Is your tow vehicle fitted with an AUX battery?
2. If so - what type of isolation is used between the main (cranker) and the AUX battery?

The process of ilimination is easy if you have a digital multimeter. You need to establish if there is a voltage loss between the Main and aux OR is the loss between the tug supply battery and the 12 Pin or Anderson plug. Or is the loss happening within the 12 Pin (poor contacts) OR is it happening between the 12 Pin and the fridge.

I note that you have already measured 14V at the 12 pin and i assume that this measurement is taken with the engine running - but as you say, unplugged. With no load 14V would be typical. You need to open the van 12 pin and get access so you can take any measurements with the full fridge load. ie - the plug needs to be connected and the fridge running, then take measurements at the 12 pin plug/socket and also at the fridge.
From these measurements you should be able to establish exactly where the loss is occuring.
Good heavy wiring, good extra earth. and good wiring within the van should give you no less that 0.5V loss between the tug battery and the van battery or fridge.
On a 3 way fridge the performance difference will be amazing.

Sometimes achieving only 0.5V total loss (under load) requires really heavy cable - AND good earths at every join. Extra earths everywhere never go astray either. On a couple of our vehicles I have resorted to using welding cable and ended up with virtually no measurable loss under load. Of course this means using a 50A Anderson plug as very large cable won't physically fit into a 7 or 12 pin.

 

[ROnEM]

Thanks Cruza Driver - did not check that very obvious point - The Fuse!

Not to worry as I have taken it back to the dealers this morning to have six things fixed unde warranty:
- RUST & pitting of the drawbar underneath where the cables come out and go up through the floors. Gal dip has all come off there.
- Water tap screws sneered off (happens on almost all vans)
- Water level on one tank not working (reads full even after all tanks were emptied)
- Pop-Top latch screws come out
- Drawer handles/locking buttons broken
- 12v fridge cooling fan on all time (thermal switch not fitted in factory)

Once I get the Anderson plug voltage sorted and the CTEK 250S installed, I was thinking of running a new wire directly from the van's dual 100Ah batteries to the fridge (with fuse and low voltage cut out switch), while disconnecting and leaving original factory wiring there. This would minimize any voltage drop from the 12 pin plug and also allow the 200w solar panel to keep the batteries topped up while the fridge draws 12v and the car is off.

Cheers,

Ro

 

[Peter D]

As far as I can tell I've improved the voltage at the fridge by 0.5v by changing to a short run (2 metres) of 8b&s wire instead of the long run (~8 metres) of 6mm wire. At the fridge it still drops from 14.2v to 13.2v when you turn the fridge on, but I've got mine plugged into the setec as well, so I think the missing volt might have something to do with the setec. (It occurred to me that it might be the setec's 0.8v trickle charge coming into play??)

 

[ElectricGuru]

As far as I can tell I've improved the voltage at the fridge by 0.5v by changing to a short run (2 metres) of 8b&s wire instead of the long run (~8 metres) of 6mm wire. At the fridge it still drops from 14.2v to 13.2v when you turn the fridge on, but I've got mine plugged into the setec as well, so I think the missing volt might have something to do with the setec. (It occurred to me that it might be the setec's 0.8v trickle charge coming into play??)

Hey Pete

Good to hear all is ok. The 0.8 V drop is the blocking diode that we spoke of in the SETEC Auxilary input to prevent the SETEC supply going back out to the rig. That will always be there unless you go direct to the fridge from the battery.

13.2 V is still very good but anything less than 11 V is a worry and may need some looking into...

Cheers.

 

[Peter D]

Hey Pete

Good to hear all is ok. The 0.8 V drop is the blocking diode that we spoke of in the SETEC Auxilary input to prevent the SETEC supply going back out to the rig. That will always be there unless you go direct to the fridge from the battery.

13.2 V is still very good but anything less than 11 V is a worry and may need some looking into...

Cheers.

The old blocking diode - that must have gone in one ear and out the other! I took the whole rig out for a drive today and the fridge was showing good signs of cooling after a bit over an hour, so I'm pretty happy with that.

Speaking of diodes, and back to the OP, if I owned a Toyota I'd be beefing up and shortening the run of the wiring and giving one of the Toyota voltage boosting diodes a try. That might improve things by close to a volt which would mean close to 12v at the fridge if you're starting at 10.8v. Always bearing in mind I don't really know what I'm talking about. I figure you'd never regret upgrading the wiring, and the boosting diode is a fraction of the price of any other option.

Edit to add: Myswag has a few threads debating the pros and cons of dc-dc chargers versus booster diodes - e.g.