Dometic fridge problem

[Roy2]

Dometic 75 series fridge fitted to a spectrum 540 2004 model.

When switched to 12 volt for towing the relay drops in and out behind the fridge,and the habitation relay at the front of the van also drops in/out.

Have had the fridge checked out ok by dometic,all supply's ok on 12s socket including earth ok on pin 7.Advised by swift to switch car/van switch to van,no different.

Any Idea's?

works ok on gas/240 volt.

 

[rayc]

Richie, this sounds like a high resistance ( poor connection) in the car on the supply on pin 6 (fridge +) or pin 7 (fridge -). Can you monitor at the car 12s socket with meter (or test lamp) on pin 6 and 7 ( with the van connected and engine running). To get a monitor point you may have to make a testlead using spare plug and socket wired pin 6 to 6 and 7 to 7 through the lead.

I think you will find that the supply on pin 6 is pulsing from 12v to 0v ( with respect to pin 7). What happens is the voltage is present but when the caravan circuit tries to draw current a high resistance (poor connection) in the car causes the volts drop.

In my particular case when I had a the fault it was the operating voltage connection of the car relay (which senses when the volts rise due to the engine running) being a poor connection. hope this helps. Let me know what you find, Ray

 

[rayc]

Ricie, I have re read your posting and you say the supply on pins 6 & 7 is ok. Can you confirm it was checked with the van connected and was steady not pulsing? mIf it is steady then the poor connection must be in either (or both) connections from pin 6 & 7 to the relay in the van.

 

[Roy2]

I suspect an hr earth connection at the car end.Both relays have been changed and the 12v heating element in the fridge.When I checked the supply at the socket,it was with a multi meter not taking any current.I will make up a test bulb cct (spare headlight 55w) and connect it to pins 6-7 to make sure it will take the current.The wiring dissapears into the car someware.(jeep cherokee) so will poss have to take it back to the dealer who charged mega bucks for the bar/electrics!!

 

[rayc]

Richie, a simple test you can do is to connect a battery directly to pins 6 & 7 of ther caravan 12s plug ( via a spare socket). Best to put a 20A fuse in the + supply to pin 6.

If the habitation relay pulls in and stays in then the fault must be in the car. Ray

 

[Roy2]

I have a spare battery and can do that no problem,the vans in storage at a caravan club site locally,will pop up thursday am (on nights since wed) and try it and update forum.

Richie

 

[Surfer]

In addition, don't forget your van is under warranty so besides the obvious don't start messing around with anything. Get the dealer to sort it.

 

[Roy2]

Thanks for you reply.I have reciently moved some miles from the dealer from which the van was purchased.

Would like to prove if its the car or van first,the dometic engineer was a nice bloke,but not very up on caravans,in fact it was service force who do all the waranty work,manly domestic appliances.He changed the 12v element and it seemed to work for a while before he went.(typical).

Thanks for your suggestion I suspect it will end up back at the dealer,in fact the problem seemed to happen shortly after the 1st service!!

Richie

 

[Roy2]

Nearly have the problem sorted.

Applied a 12 volt supply to pin6 as suggested and the relay operated ok and the fridge element was drawing 13 amps ok.So it looks like a car problem.

Eurobar not very helpfull initally,no fitters available to check electrics due to holidays.

Eventually a fitter contacted me 30/08 and advised that it sounds like a relay problem,and advised me where it was fitted,suggested I take a look first,and check wiring etc.

After removing car trim in boot,found relay and also found pin 6 wiring terminal on relay board melted.Called Eurobar who suggested I obtain a new one from a local stockest!!

Obtained a new relay and have fitted it,just going to van storage to test,fingers crossed.

Also checked relay manufacture's web site.A note was added in 2004 that says new large fridges being installed from 2004 ie dometic 7000 series need an updated ryder relay 30 amp working.

Checked melted relay,rated 20 amps,new one rated 30 amps,could be usefull info for anybody having the 7000 series fridge fitted?

 

[Roy2]

Final update

Yes its works now,these RYDER voltage sensing devices are very sensitive.

Changed relay and still had problems.contacted ryder help line.

advised by tech wiz kid to adjust setting for cutin/cutout voltage by adjusting componet on board.

Now works fine.He said all cars are slightly different with reguard to charging voltages and a test board should be applied to 12s plug with appropriate loads applied to pins 2&6,then adjust relay as above.I presume this was not done when mine was fitted,wiz kid said they are adjusted in the factory for average load and average car.

When other devices are switched on ie headlights/air con etc,and when car is stationary due to increased load the relay does drop out,but returns when the car is moving again,this is normal.

Good idea these relays, but harder to set up than the old type activated by an ignition switched supply.They never dropped out until the car was switched off.

THATS PROGRESS FOR YOU!!!!!

Hope this info may help others with same problem.