Maybe I reversed the positive and negative 12volt supply to my camping fridge?

[FairweatherDave]

I have a Dometic CDF36 camping fridge and a small project has been to change the power lead from cigar lighter plug to a more reliable connection (I went for Wago in-line connectors.) So I cut off the cigar plug and used the Wagos to connect to the battery (and connected an in-line fuse on the positive side). However I failed at the final hurdle, nothing happened when I pressed the on switch on the fridge. I stuck my voltmeter onto the plug and have 12 volts there. But I failed to consider, until I got home, that I might have reversed the polarity - ie at the new connection put the fridge positive onto the battery negative and fridge negative onto the battery positive.
Question 1. Can I simply swap them over to test the fridge?
Question 2. Can I damage the fridge doing this, if in fact I had got the polarity correct originally?
(The twin cable wire on the original lead has a very fine ridge along one of the wires which I assumed to be identifying the positive, like you get on stereo speaker wire).
Would really appreciate some electrical knowledge,thanks

 

[Alex_Blackwood]

I have a Dometic CDF36 camping fridge and a small project has been to change the power lead from cigar lighter plug to a more reliable connection (I went for Wago in-line connectors.) So I cut off the cigar plug and used the Wagos to connect to the battery (and connected an in-line fuse on the positive side). However I failed at the final hurdle, nothing happened when I pressed the on switch on the fridge. I stuck my voltmeter onto the plug and have 12 volts there. But I failed to consider, until I got home, that I might have reversed the polarity - ie at the new connection put the fridge positive onto the battery negative and fridge negative onto the battery positive.
Question 1. Can I simply swap them over to test the fridge?
Question 2. Can I damage the fridge doing this, if in fact I had got the polarity correct originally?
(The twin cable wire on the original lead has a very fine ridge along one of the wires which I assumed to be identifying the positive, like you get on stereo speaker wire).
Would really appreciate some electrical knowledge,thanks

Yes, you should be able to swap them to get correct polarity. When using your multimeter if you go across the POS and NEG and you get -12 showing it is the wrong polarity if correct it will be 12 with no - (that is negative sign!). Hope that is clear. There always is a possibility that you may have "blown" a component such as an electrolytic capacitor. You won't know before you try. Make sure that your polarity is correct before switching on!

 

[FairweatherDave]

Thanks for the reply Alex, I tried to compose a reply which became thinking aloud and I have worked out my next steps - it is all so elementary - I can retest the fridge by reinstalling the cigar plug on the wagos. If the fridge works then I can just switch over the wires on the new set up as clearly I reversed the polarity. (And I can use the multimeter for continuity tests etc) . At the end of the day the fridge socket doesn't label the positive and negatives, it just has one orientation to receive the plug. My fear is I damaged the fridge moving it in and out of position and the polarity has been correct all the time. Fingers crossed for next visit to the boat.

 

[RupertW]

Thanks for the reply Alex, I tried to compose a reply which became thinking aloud and I have worked out my next steps - it is all so elementary - I can retest the fridge by reinstalling the cigar plug on the wagos. If the fridge works then I can just switch over the wires on the new set up as clearly I reversed the polarity. (And I can use the multimeter for continuity tests etc) . At the end of the day the fridge socket doesn't label the positive and negatives, it just has one orientation to receive the plug. My fear is I damaged the fridge moving it in and out of position and the polarity has been correct all the time. Fingers crossed for next visit to the boat.

As long as you know which wire was attached to the cigar plug end and which to the cigar plug sides there is no need to reconnect it. Just ensure the end wire is connected to positive and the side wire to negativ.

 

[FairweatherDave]

As long as you know which wire was attached to the cigar plug end and which to the cigar plug sides there is no need to reconnect it. Just ensure the end wire is connected to positive and the side wire to negativ.

That's true, but I am anticipating the cigar plug might not want to be dismantled, and the wago 221 connectors are so easy to connect and disconnect.

 

[Refueler]

When I remove a 'Cigar plug' .... I always only cut one wire - then test plug / cable to see which it is ... + or -. Then I stick a bit of black or red tape on it so I know which it is. Too many cables are unmarked for polarity.

OP - you say a ridge running along one ... only ridge I have ever seen is when pulling the two apart - a ridge of the joint gets left behind on one ... which does not indicate which is +ve. Usually twin flex has one with a narrow feint white line running along it - thats +ve.

 

[davidej]

Many battery driven devices are fitted with a diode so that reverse polarity does no harm.

 

[penfold]

I have a Dometic CDF36 camping fridge and a small project has been to change the power lead from cigar lighter plug to a more reliable connection (I went for Wago in-line connectors.) So I cut off the cigar plug and used the Wagos to connect to the battery (and connected an in-line fuse on the positive side). However I failed at the final hurdle, nothing happened when I pressed the on switch on the fridge. I stuck my voltmeter onto the plug and have 12 volts there. But I failed to consider, until I got home, that I might have reversed the polarity - ie at the new connection put the fridge positive onto the battery negative and fridge negative onto the battery positive.
Question 1. Can I simply swap them over to test the fridge?
Question 2. Can I damage the fridge doing this, if in fact I had got the polarity correct originally?
(The twin cable wire on the original lead has a very fine ridge along one of the wires which I assumed to be identifying the positive, like you get on stereo speaker wire).
Would really appreciate some electrical knowledge,thanks

The Secop/Danfoss compressors most of these are fitted with are protected against reverse voltages.

 

[FairweatherDave]

When I remove a 'Cigar plug' .... I always only cut one wire - then test plug / cable to see which it is ... + or -. Then I stick a bit of black or red tape on it so I know which it is. Too many cables are unmarked for polarity.

OP - you say a ridge running along one ... only ridge I have ever seen is when pulling the two apart - a ridge of the joint gets left behind on one ... which does not indicate which is +ve. Usually twin flex has one with a narrow feint white line running along it - thats +ve.

Unfortunately I don't have the cable in front of me but I did look hard at it and was fairly certain I could see a ridge along the outside of one of the wires that made up the twin flex, not the ridge you can see from separating the two cables. All will be revealed on my return trip.

 

[FairweatherDave]

And thanks to those posters reassuring me about damage and reverse voltage. Although it bothers me that I could be sufficiently inept to wire it up backwards I will be really happy if it works. The alternative is that I have damaged the fridge manoeuvring it a bit clumsily. It had a bit of a heavy landing as I lowered it into a small space.....slight bonk. However my hearing aids seem to amplify those sort of things, so I can't judge. You would think a portable camping fridge should be quite robust. Fingers crossed.

 

[Alex_Blackwood]

And thanks to those posters reassuring me about damage and reverse voltage. Although it bothers me that I could be sufficiently inept to wire it up backwards I will be really happy if it works. The alternative is that I have damaged the fridge manoeuvring it a bit clumsily. It had a bit of a heavy landing as I lowered it into a small space.....slight bonk. However my hearing aids seem to amplify those sort of things, so I can't judge. You would think a portable camping fridge should be quite robust. Fingers crossed.

Further to my last. You really want to get to the fridge terminals and determine which wire is connected to which terminal and work your polarity check back from there. If necessary, use your ohms scale (with your input from the battery disconnected) and identify which wire goes where. Once you have confirmed your + & - from the fridge at the Wago connectors you can then connect to the correct battery polarity.

 

[FairweatherDave]

Well it's all sorted. Polarity was reversed. Rookie error, I had assumed the ridge down the outside of the twin flex cable sheath indicated that was the positive. Should have tested it. There was also some printed Information running along the other wire of the pair which might have suggested that that was the positive ,to a more experienced eye. Next time, no assumptions, do a continuity test.
As a complete aside, I discovered that the internal fridge light comes on when the lid is open, even when the fridge is switched off at the panel. So if I want to leave the lid open (don't need the fridge on tonight) and the fridge off I need to introduce another switch...

 

[jamie N]

Does the light 'thing' mean that there's a separate light battery, being that you've isolated the fridge at the panel?
That seems slightly 'unusual' to me.
When the fridge is isolated, and the light is on, does it stay on for a 'long' time, or is it a consequence of capacitance in the line, and the compressor power supply, and only on for a few seconds?

 

[Alex_Blackwood]

Well it's all sorted. Polarity was reversed. Rookie error, I had assumed the ridge down the outside of the twin flex cable sheath indicated that was the positive. Should have tested it. There was also some printed Information running along the other wire of the pair which might have suggested that that was the positive ,to a more experienced eye. Next time, no assumptions, do a continuity test.
As a complete aside, I discovered that the internal fridge light comes on when the lid is open, even when the fridge is switched off at the panel. So if I want to leave the lid open (don't need the fridge on tonight) and the fridge off I need to introduce another switch...

Glad you are sorted, sort off! I would be doing double checks on my wiring. Can't see how the light would be on if isolated at the panel. Check your connections either at the fridge or your WAGO connectors and see if you have power, with the panel switch off! Or even just try switching the fridge on with the panel off.

 

[PaulRainbow]

I suspect Dave means "switched of at the fridge control panel" ?

 

[Alex_Blackwood]

I suspect Dave means "switched of at the fridge control panel" ?

Could be??? Perhaps he will elucidate!

 

[VicS]

Could be??? Perhaps he will elucidate!

There is only one power supply connection. The fused cigarette lighter type plug. He must therefore mean the unit's own control panel.
If the fridge remains connected by a plug and socket as intended the solution to the "problem" is obvious but could be overcome by removing the light bulb altogether. Surely it's not necessary on a portable camping fridge.

The instruction manual is here.
https://www.dometic.com/assets/48/6...46_opm_4445102393_emea16_14_2019-06_74862.pdf

Section 7.10 for details of removing/ replacing the light bulb

 

[Alex_Blackwood]

There is only one power supply connection. The fused cigarette lighter type plug. He must therefore mean the unit's own control panel.
If the fridge remains connected by a plug and socket as intended the solution to the "problem" is obvious but could be overcome by removing the light bulb altogether. Surely it's not necessary on a portable camping fridge.

The instruction manual is here.
https://www.dometic.com/assets/48/6...46_opm_4445102393_emea16_14_2019-06_74862.pdf

Section 7.10 for details of removing/ replacing the light bulb

Have had a look at the original post. He has removed the "Cigar plug" and if I read correctly has wired via the WAGOs straight to the battery via a fuse!?
So yes he is referring to the fridge panel. Personally I would rethink that and wire via a switch into that circuit. He may not have room or spare ways on his main panel but there must be room somewhere for a switch and fuse or a small circuit breaker. Do away with the WAGOs.

 

[QBhoy]

Hi. I have the cf11. Should be similar. In the off chance that you find the wiring effort was in fact ok…is there perhaps a possibility that (if it’s similar to mine) maybe the battery is a little less potent than it might be…and the built in (adjustable) battery protection setting on the unit is set to medium or high. Meaning anything less than early to mid 12’s from the battery..and it won’t fire up and/or shutdown. Low setting allows a weaker battery to have a go, within reason.
Thought I’d mention, just in case. Presumably the fuse is msn enough too ? Hadn’t blown ?

 

[FairweatherDave]

I can report back that fridge is fully functioning and the internal light is functioning as intended by the manufacturer, its just that we always used to pull the cigar plug out to switch the the fridge off, so never knew about the fridge internal light working as soon as power gets to the fridge (if the lid is open). Obviously there are a number of elegant solutions but closing the lid will do for now, or disconncting one wago...both of those are much easier than disconnecting the power lead where it plugs into the fridge . No aaccess. Obviously the reason we like to leave the fridge open is to keep it fragrant when not in use.