A Peculiar Fridge Problem

Itchyfeet Pete · Member

A Peculiar Fridge Problem

Peter_n_Margaret · Guru

Where did you measure the voltages you quote?
How do you know the compressor was running and it is not just the condenser fan?
Cheers,
Peter

Itchyfeet Pete · Member

Peter, thanks for your quick response. As best I can see, without tracing the wiring through my dash, the aux battery voltage is measured at the battery terminals. There are a couple of thin wires terminated at the posts and it's displayed on a digital voltmeter mounted on top of my dash. All I know is that I could hear something running. Is there some way I can tell whether it's the compressor or just the condenser fan running?
Thanks,
Pete

DeBe · Guru

DANFOSS 101NO500 CONTROLER..3.JPG The only place to realy check voltage is here, if it has this controller on the compressor. With the 240V AC unplugged from the power point, just for safety reasons.

-- Edited by DeBe on Tuesday 1st of January 2019 04:42:08 PM

PeterD · Guru

There is a possibility that the 12 V wiring is too light and the sealed unit is not spinning at full speed.

oldtrack123 · Guru

PeterD wrote:
There is a possibility that the 12 V wiring is too light and the sealed unit is not spinning at full speed.

I go along with That .

Best check the voltage with the fridge running on 12V at the terminals as per DB's post

Warren-Pat_01 · Guru

A quick way to prove it Pete - run a long temporary pair of heavier wires (figure 8 HD) - put crimps on the fridge end & connect. Connect the other end to the battery & see if it works. If it does, then you'll have to due some permanent rewiring.

I had to run a separate earth wire as my Trailblazer wasn't working in our MQ years ago in Burketown (learnt that I couldn't rely on the body as a conductor).

Baz421 · Guru

oldtrack123 wrote:
PeterD wrote:
There is a possibility that the 12 V wiring is too light and the sealed unit is not spinning at full speed.
I go along with That .
Best check the voltage with the fridge running on 12V at the terminals as per DB's post

Agree

Baz421 · Guru

Warren-Pat_01 wrote:
A quick way to prove it Pete - run a long temporary pair of heavier wires (figure 8 HD) - put crimps on the fridge end & connect. Connect the other end to the battery & see if it works. If it does, then you'll have to due some permanent rewiring.

I had to run a separate earth wire as my Trailblazer wasn't working in our MQ years ago in Burketown (learnt that I couldn't rely on the body as a conductor).

Yep a good check. I fixed a blokes fridge In 2014 and he had same problem, crap wire (cheapo Chinese, very brittle) and too small diam/cross section.

Whenarewethere · Guru

Your fridge CR110 has a rated current of 5.9 amps. My tiny little CFX28 has a rated current of 6.5 amps.

I tested my fridge thoroughly over a few days in 35°C ambient temperature & fridge set at +2°C recording power consumption it uses about 3.8 amps while the compressor is running. Between cycles basically nothing. So about 0.0116kW/h or about 23AH for a 24 hour period at 35°C ambient temperature.

Back to the subject.

Lets round the 3.8 amps up to 4 amps. I cut one of the Waeco 12 volt power leads to put an Anderson plug on the end. They are using 1.31mm2 16AWG, it's a joke. It is only a short length & it's probably coiled up behind the fridge so you have enough length to pull the fridge out, so then you have to add this cable to the rest of the run, resistance here there & elsewhere adds up.

So lets say 6 metres from the battery to the fridge x 2 (for positive & negative), so 12 metres there & back. Lets say on average you only have cheapskate caravan wiring for the fridge of 14AWG & no other issues. You already have 0.4 volts drop. Thicker wiring: On average 12AWG 0.25 voltage drop. On average 10AWG 0.16 voltage drop. On average 8AWG 0.1 voltage drop. On average 6AWG 0.063 voltage drop. If you have 15 metres there & back add another 25% to the voltage drop.

Replacing the Waeco 12 volt 1.5 metre lead or cutting it as short as possible & connect it to heavier wire would be a bit of a start on fixing the problem. 4 amps 16AWG 1.5 metres lead (3 metres positive & negative) 0.16 voltage drop for the power lead alone.

Itchyfeet Pete · Member

Big thanks to everyone for the guidance on my fridge problem. I was on my friendly local auto electrician's doorstep at opening time on his first day back this morning. Wiring size and quality between the battery and the fridge 12v socket was all good but there was a bad connection in the Merit plug used for the final connection. Solution: a new Merit plug. Tested it when I got home and the freezer temperature dropped to -10C in 30 minutes running off the battery. I guess a partial air gap has a fairly high resistance biggrin

Thanks again, Pete

Whenarewethere · Guru

I have made the cable as short as possible so I can use my own proper thickness cable and stuck an Anderson plug on the end. This unscrews if I need to take this particular 12 volt connection out.

Itchyfeet Pete · Member

Wow, what a neat job. Unfortunately, with my built-in fridge design and the limited access available, it would be difficult for me to achieve an outcome like this. Having said that, if I do have further problems I'll certainly look for another similar alternative.
Thanks again for your help and advice.
Regards,
Pete

Whenarewethere · Guru

DeBe wrote:
The only place to realy check voltage is here, if it has this controller on the compressor. With the 240V AC unplugged from the power point, just for safety reasons.

-- Edited by DeBe on Tuesday 1st of January 2019 04:42:08 PM

I replaced the wires running from the 12 volt socket on the fridge to the fridge's circuit board & while at it added a 7amp panel circuit breaker to the back on the fridge. The wires inside the fridge were 55 cm each, so 1.1 metres positive & negative, & as measured they were a very thin 16AWG wire!

So now I have replaced 4.1 metres total length (internal & lead) of under sized wire with 10 AWG inside the fridge & 8AWG/6AWG to my controller & the battery (fairly short run) to keep voltage losses to a minimum.

When one is scrounging around for every last bit of voltage this is the easy stuff to fix.