Waeco Won't Go

[KT66]

Hi. I have a 2009 Swift Mondial PVC fitted with a 12 volt / Mains Waeco Fridge. This seems to work fine when on mains hookup, where it gets its 12 volts from the companion quaintly named "Rectifier". However when not hooked up it runs spasmodiacally for a few seconds at a time, and the internal red LED flashes once every few seconds. Both the Leisure and the Vehicle battery are charged and OK for voltage at the battery terminals. Running the engine doesn't change this behaviour.

 

I suspect I have a bad joint somewhere in the 12V wiring, giving excess voltage drop. I am no stranger to working on electronics and electrics, but to save me time before I pull it all apart, has anyone else had this problem ? Is the original installation up to scratch ? There is a rocker switch in the wardrobe which the previous owner told me was to turn the fridge off at night when not hooked up, presumably to save battery drain. This looks like a CBE MCD1N. I wonder if its contacts are man enough for the job. There's no mention of it in the van handbook but it looks factory fitted.

 

The Swift wiring diagram I have from 2009 shows the Fridge running from the Vehicle battery, via Fuse 6 (15A). However i am suspicious that this is in error and that it actually runs from the leisure battery. Does anyone know for sure ?

[Derek Uzzell]

I note from one of your earlier postings that you obtained your Mondial at the beginning of 2015. Has your fridge always behaved as you’ve described, or is this something that’s shown up recently?

 

This 2014 MotorHomeFacts discussion may be of interest

 

http://www.motorhomefacts.com/forum-printtopic-1-198169-0-0-asc-viewresult-1.html

 

(although in your case you’ve said that running your vehicle’s motor does not help).

 

I agree that it should be expected that your compressor fridge would be powered by the leisure-battery, as powering it from the vehicle’s starter-battery would be asking for trouble. Disconnect the leisure-battery temporarily and if the fridge stops working that should confirm your suspicions.

 

The average power consumption of a Waeco CoolMatic CR-80 fridge is quoted as approximately 48 watts, so a CBE MCD1N switch should be man enough for the job. (I assume you’ve done the obvious and confirmed that the switch can actually be used to stop the fridge operating.) If you think that the switch might be contributing to your fridge’s LED-flashing behaviour, you could ‘wire around’ the switch to see if that does any good.

 

It sounds like the voltage at the fridge is insufficient when the vehicle is off 230V hook-up (though I would have thought that starting the motorhome’s engine would address this) so you really need to check at the fridge itself what voltage it is receiving, rather than checking at the battery terminals. This should indicate whether on not there’s a serious voltage drop between the battery and the fridge and, if that proves to be the case, you’ll know that the fridge itself is OK (probably!) and it’s the power-supply to it that you’ll need to look at. (You might also experiment by connecting your well-charged leisure-battery ‘point blank’ to the fridge with short, thick cables so that voltage drop will be virtually nil.)

 

If I were in your position I’d also ask about this on SwiftTalk

 

https://www.swift-talk.co.uk/

 

as that’s where owners of Swift Mondials like yours are most likely to be conversing.

[Charles]

You could run a piece of 2.5 mil flex direct from battery to the fridge temporarily, to see if it cures the fault.

[polo]

I had a similar problem with my Alto.Having spent a lot of time and money checking the fridge and wiring, including new leisure batteries. Finaly just wired the fridge to the leisure batteries with large cables sorted problem.

[Geoff Cole]

Hi,

I have the same fridge and fitted a MPS35 rectifier unit so that on hook up it runs on the mains supply. when not on hook up the rectifier unit switches the fridge to the leisure leisure battery.

The red light flashes when the voltage drops below 10.4 volts and switches on at 11.7volts, so it would appear that your battery is either not charging or is duff. If you put your meter across the battery to see what the voltage drop is when the fridge is running and compare the reading at the fridge connection this will determine if you have a supply problem.

Your supply cable to the fridge needs to be at least 6mm to avoid voltage drop the current consumption is around 5.7amps.

I have fitted a separate battery for my fridge and a relay switches the fridge to the cab battery when running so that I get a full charge from the vehicle alternator to the my leisure and fridge battery, so when stopped without hook up I have fully charged batteries. If your batteries are in good condition 12.8v at full charge, the fridge will drop this to around 12.5v-12.6v under load and will recover to 12.7v - 12.8v quickly when fridge is switched off.

I find mine works very well and to get the best out of it, I turn the thermostat to 5 when running and just under 2 when on site without hook up,

I also keep a couple of freezer packs in the ice box these help prolong the periods between the the thermostat operating.

Incidentally these fridges are dual voltage 12/24v and have a danfoss compressor powered by a dc brushless motor Tthe rectifier unit when fitted provides 24V to the dual voltage input f so the current draw from the rectifier is only about 3amps so voltage drop is not a problem. When not on hook up the the supply is switched to your onboard 12volt supply.

It does sound like your problem lies in the 12volt supply.

Geoff C

[Barry38]

 

I have read many forum letters including the latest edition of the MMM magazine whereby a correspondent has queried the same issue. Countless ideas have been put forward by 'experts' including additional batteries, solar panels, and battery to battery chargers etc.. Whilst a combination of these suggestions might marginally improve the situation it is not the most cost effective or simplest answer.

Both Swift and Autocruise are very guilty of supplying the fridge with cables of insufficient capacity to prevent voltage drop. The fridge electronic control will sense a low voltage, shutting off at 10.4and below. The start up voltage must be higher than11.7 and it is important to remember that the compressor uses considerably more amps on start up decreasing the supply voltage dramatically.

If the voltage drops below the minimum figure the unit will 'cycle' without cooling properly and run the battery down even further.

Both Autocruise and Swift have regularly used 2.5 mm cables which are only suitable for a run of approx. 2.5 metres from the supply. They steadfastly argue that this is adequate but they clearly do not consider customer complaints or listen to Waeco!

My Autocruise Rhythm has a supply run of approx. 4.5 metres and has a Waeco compressor fridge fitted. In this scenario the demand from the fridge requires a cable size of 8 mm min. I chose 10mm cables ( suitable for a 6m. cable run) wired directly to the leisure battery (note the Autocruise wiring diagram shows connection to the vehicle battery!) . I use two 75ah Gel batteries mounted on their side under the front seats and alternate between the two if desired, by a simple manual changeover switch.

I have run this system for 4 years now and it has been ultra reliable allowing us at least 4 days ( I haven't tested it for longer) without hook up or the need for solar panels. huge battery banks or battery to battery charging systems.

 

[aandncaravan]

It isn't just the cabling that is often undersized, connections and fuse holders are too.

 

I would start by looking at the wiring/connections behind the switch that 'turns it off at night'?

The switch itself might be Man enough, but are the cabling and connections fit for purpose?

 

It would also be a good place to start taking voltage readings, as it might be easier and safer than getting in behind the Fridge? I would hope that the switch has been installed near the Fridge end of the 12v circuit, so potentially a good place to take readings?

 

 

If it was me, I would consider replacing the switch with a bigger one, not because it isn't up to the current, but because the terminals may not be up to taking the cable size that should be used.

 

The ideal is really chunky connectors on cable where zero voltage drop is important.

 

Also think about uprating any 'Mini' fuse holders to the physically bigger, but same current rating, Maxi type.

 

With a 12v Fridge, we would suggest you 'go over the top' when sizing everything, as even the smallest voltage drop reduces efficiency and that means, using more precious current.

 

 

Suggest you do voltage readings 'under load' as an 'unloaded 12v' can quickly drop to 8v when the Fridge is turned on.

 

 

[KT66]

Many thanks for those who replied with suggestions. I have spent a good part of today investigating, and now have a working fridge.

 

Despite Swift's 2009 circuit diagram, the fridge does as suspected run from the unswitched side of the leisure battery.

 

I measured the difference between the leisure battery voltage (directly across its terminals) and the voltage right at the input to the Fridge PCB, which is downstream of the Rectifier unit. Initially the total voltage drop was 1.8 volts, i.e. 12.5 volts at the battery (not on charge) and only 10.7 volts at the fridge.

 

A quick clean of the 15 Amp blade fuse and its holder contacts and the voltage drop reduced to a more reasonable 1.1 volts, giving a more healthy 11.4 volts at the fridge. This was the basic cause of the problem. However, this still seemed rather a big drop so I carried on.....

 

Looking at the wiring, Swift have used mostly fairly reasonable 3 square mm cross-section, with some 4 square mm to the On/Off switch in the wardrobe. This looks like a factory modification. However the wires and switch were joined using a total of 5 blade connectors. As a precaution, I replaced the 10 Amp rated switch with a heavy duty one, and replaced the blade connectors with soldered joints. This reduced the total voltage drop by 0.1 volts to 1.0 volts. Modest improvement, but worth having.

 

I noticed that the 12V input to the Rectifier is via a 0.8 metre length of black twin flex with 2.5 square mm cross section. However I couldn't shorten this as you need some slack to pull the fridge out. The DC output from the rectifier was via 1.2 metres of surprisingly thin red and black wires with only 1.2 square mm cross-section. Most of this was coiled up in a bundle, so I shortened both legs to the minimum that would reach (0.25 metres) and replaced another two blade connectors with soldered joints. This reduced the total voltage drop by a further 0.2 volts to 0.8 volts. Both these cables are captive to the Waeco rectifier unit, and are presumably supplied with it, so it's Waeco who are the weedy cable people rather than Swift !

 

One could go further in beefing up cables and connections, and a better fuseholder might help. However I have now got to the point where the fridge ought to carry on working until the leisure battery is practically flat, and the energy wastage is only about 6%.

 

Just for the record, the current drain when the fridge switches on is about 6 amps, which rises over several seconds to 7 amps. I didn't notice any switch-on surge, more of a soft start. The rectifier output when the mains is connected rises to 28 volts.

[aandncaravan]

KT66, good result.

 

Sorry, I should have elaborated yesterday. Bear in mind that a Fuse is a small resistor. The more current it passes the hotter it gets until it eventually melts. Any resistance is obviously going to cause voltage drop.

 

You might find that if you 'uprate' the fuse to 20amps (the more usual rating for a Fridge and still adequate protection for you Waeco) that it might have a lower resistance and you might notice a little bit less voltage drop?

Just trying a different manufacturers quality 15a fuse might also give a better result, we have seen 0.5v difference between a quality and 'budget' fuse.

 

Cheap fuses tend to have a more varied resistance, as well as falling apart.

 

Generally, the physically bigger Maxi fuses and holders, offer a lower overall resistance.

 

 

You also talk about running the battery till it is 'practically flat'?

Do you realise that discharging a battery right down to 90% discharge will usually result in a battery that lasts just a handful of cycles, versus around 1,000 cycles (for a G80) if you only shallow discharge to 30%?

See chart below supplied by Exide.

[Charles]

Is it a compressor fridge? My Mobicool compressor fridge runs at 2.25 amps on 12v

[aandncaravan]

KT66, another way of 'gaining an additional 0.4volts' might be to start with a higher voltage battery?

 

Not all '12v' batteries have the same resting voltage, VRLA (such as the Gel Exide G80) generally rest at 13v as opposed to Lead Antimony batteries at just 12.6v.

We are not a fan of Gel batteries but might not be bad compromise here?

 

 

See chart. below from Yuasa.

 

Note that higher voltage batteries, also have a corresponding 'fully discharged' voltage, so a 50% discharge battery will be a surprisingly 'high' 12.5v. If you drop one of these batteries down to 'conventional' batteries 12.1v, the battery is likely to suffer damage?

[Brian Kirby]

For what it's worth, two things.

First, don't forget that the fuse rating should be dictated by the gauge of the wiring, as its sole function is to protect the circuit. If you have beefed up the wiring between the battery and the fridge, you might wish to consider increasing the fuse ratings accordingly. Should lower resistance a bit more.

Second, having beefed up the wiring from the battery to the fridge, have you considered investigating the wiring from the charger/alternator to the battery? It seems quite a few converters use rather light gauge wire in this area as well, and beefing that up may result in a better charge getting into the battery, so you start off with more "ammo" in place.

[Geoff Cole]

Hi Barney, well done you seem to be on top of the problem.

As I stated on my earlier post the compressors fitted to these fridges are powered by a brushless DC motor and they are soft start so as not to drop the battery voltage to low when starting. Once started the current rises to around 7amps then settles down to around 5.7Amps.

When using the mains unit the current consumption is around 3 Amps on the 24 volt output from the rectifier unit. 6mm-8mm cables and decent fuses are essential. hope you have no further problems

 

Geoff C