Please can anyone tell me what the resistance in a 12v element be?

[ambulancekidd]

Please can anyone tell me what the resistance in a 12v element for a Dometic RM4 series 3 way fridge be?

I'm installing a replacement second hand fridge which is long overdue, some DIY fiend had rewired the old fridge (another RM4 series) & made a proper ladies makewater out of it.
It has always worked fine on gas, but the 12v & 230v side was like a butchers shop despite me fitting a new 230v element last year it was a no go.
I've tested the Ohms of the new 230v element & it shows around 200Ohms which strikes me as probably healthy?
The 12v element shows no resistance on the meter at all, I suspect I need a new one.
I'm aiming to make a perfect one out of the two, then rewire the one which I choose not to use, my gut instinct is to stick with the one I have as I know that it cools well on gas,

Thoughts with huge thanks in advance...Robert.

 

[thebriars]

Depends how good your multimeter is. If the element was broken it would show a high resistance. At a guess its probably just one or 2 ohms. Can your multimeter read that low a resistance?

 

[Sandancers]

For 240v one, you need to know the wattage of the element, might be marked on somewhere ?

Look at it this way, if it's a 1000W element on 240v then more or less it's taking 4A. Which gives a resistance of about 60 ohms.

If it's a 2000W element then it'll be about 30 ohm.

For 200 ohms you'd be in the range of 300W. So if the label says that then your OK.


For the 12v one, is there any markings or labels which give any info about it, or a manufactures name where you can maybe look it up ?

 

[Eddystone]

Very low.
As far as I remember, the element is rated at 125w which draws about 10 amps.
Ohms Law I=V/R transposed gives R=V/I so R= 12/10 so that gives 1.2 Ohms.

 

[Eddystone]

You will need to be very careful of the material you use to create a workable element.

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[PeteH]

There are so many RM series fridges it would be hard to be specific but I suspect that it is generic?. They cover much of the range. Have a look online? As for the resistance, if it is showing zero it is likely to be beyond redemption?. From memory, I don't think they are that expensive? But can be pigs to fit!!.

 

[ambulancekidd]

Depends how good your multimeter is. If the element was broken it would show a high resistance. At a guess its probably just one or 2 ohms. Can your multimeter read that low a resistance?

My multimeter was playing silly beggars, so my mate is bringing his professional job to test what we have but I take your point on board & I'm really grateful for your assistance.

Look at it this way, if it's a 1000W element on 240v then more or less it's taking 4A. Which gives a resistance of about 60 ohms.

If it's a 2000W element then it'll be about 30 ohm.

For 200 ohms you'd be in the range of 300W. So if the label says that then your OK.


For the 12v one, is there any markings or labels which give any info about it, or a manufactures name where you can maybe look it up ?

I'll check the wattage of the elements tomorrow, its sounding like I might need to splash out to buy new elements which isn't a hardship. Thank you for your advice.

Very low.
As far as I remember, the element is rated at 125w which draws about 10 amps.
Ohms Law I=V/R transposed gives R=V/I so R= 12/10 so that gives 1.2 Ohms.

125w rings a bell mate, I'm looking forward to getting stuck back into it tomorrow.

From memory, I don't think they are that expensive? But can be pigs to fit!!.

The fitting bit is easy, I've done quite a few in the past, I've already got both elements out from the existing fridge, why are these wee jobs never as easy as they sound lol???

Thanks to everyone who has helped me here, I am still a bit out of my depth & on a steep learning curve.

 

[autorouter]

There's two equations:
watts = volts x amps (P = VI)
volts = amps x ohms (V = IR)

They can be combined in various ways, for example.
watts = volts x volts / ohms (P = VxV/R) so a 200 ohm element at 230V uses 230x230/200 = 265 watts.

If you think the 12V element is about the same power, say 200 watts, then the amps is 200/12 = 16.7A.
The resistance will be volts/amps = 12/16.7 = 0.72 ohms.

Inexpensive meters will struggle to measure this with any accuracy, but you should be able to see if it is open circuit (very high resistance), short circuit (very low resistance) or about right. If the meter has no 'Ohms Zero' function, touch the test leads together to measure their resistance, and take that as your zero point.

 

[ambulancekidd]

I have to apologise to the kind forum members for the delay in working out the answers that they had asked me.

So to bring you all up to speed, I finally used the 230v element from my original fridge which I suspected was working perfectly as I'd fitted it only last year but, never managed to get that fridge running properly other than on gas.
So I've serviced & fitted the replacement fridge along with my original new element, powered everything up & its working perfectly.
I've rewired my original fridge to put right the bodges carried out by the previous DIY fiend., I followed the wiring from the new fridge & now all is well albeit that it needs a new 230v & 12v element. All switches tested up perfectly.

TheBig1 last year suggested that the wiring had been butchered due to the 230v element failing, then they'd wired the 12v element to work off the caravans 12v charger which had also resulted in the charger being burnt out & the charger is knackered, which supports the theory that TheBig1 suggested, nice one.

Advice/Help required, please can anyone tell me what this is?

Renewed the 230v element on our Kon-Tiki fridge, a job which I've done may times on caravan fridges but, alas never on a motorhome. The first thing I noticed was this small black box titled "Volton Combi" & its not something I'm familiar with. I strongly suspect that its an auto changeover relay...

www.motorhomefun.co.uk

My thanks go to all who've offered advice & assistance with the issue's the fridge situation had thrown up, this forum comes into its own when we need help.