Member Since: 22 Jun 2011
Location: West Midlands
Posts: 1223
Towing electrics help need
Good afternoon all I have a 2024 Adria Mississippi caravan, when towing the fridge doesn’t work on 12 volt battery is charging and volt meter is reading 14.7 at battery and 10.1 at fridge turn fridge off and it reads 14.7 turn fridge off and once under load it reads 10.1 volts again, we tried the dealership owners Volvo xc60 hybrid and all worked well , have done a little research and it says that euro 5/6 certain cars are not compatible due to smart alternator , so I am hoping that someone may be able to assist me with a solution, regards Steve
21st Oct 2024 2:07 pm
karsteb
Member Since: 10 Aug 2014
Location: Oslo
Posts: 14
Could be a zener-diode in your fridge has popped and is short-circuited. Happend to my Engel fridge. The zener was rated a 15V and acts as a overvoltage protection circuit for the fridge. The voltage from the D4 alternator can sometimes exceed 15V and hence it broke and short-circuited. Always broke the car-fuse afterwards.
My brother who is an electrical engineer said "nah - no problem, you don´t need the zener. Good engineering, but a little over-protective" and just snipped off the zener - did not even replace it, and it has never bothered me again.
Could maybe be be something else since you do not see a persistent short-circuit (since it works with another car) - if there is a zener, it will be broken once you exceed the breakdown voltage and will be short-circuited forever. Maybe there is a smarter protection mechanism. But if it is a zener, your local TV repair guy will recognise it by looking at it without any schematics.
31st Dec 2024 1:30 am
Sylvester19
Member Since: 17 Jul 2020
Location: Central Scotland
Posts: 138
Have you checked the earth point in the rear boot passenger side access panel along with the trailer wiring loom connectors & the socket connections? As a minimum you should get battery voltage or whatever the alternator is putting out at the time. Measure the voltage at the car earth point and power wire when the fridge is connected, unfortunately I don't know the wire colour in the connectors for pin 10.
31st Dec 2024 10:57 pm
stephenw46
Member Since: 22 Jun 2011
Location: West Midlands
Posts: 1223
Thank you for the replies, but the caravan dealership as fitted a sterling wild-side relay and I will be picking up the caravan on Friday and will find out if the problem as gone, everything worked fine on my previous caravan but as my friend as the same car and caravan, I have looked into the issue and found out that anything car with a smart alternator will not operate the new thetford fridge, I will update on Friday when I pick up caravan
1st Jan 2025 11:16 am
Sylvester19
Member Since: 17 Jul 2020
Location: Central Scotland
Posts: 138
What model of Thetford and battery type fitted? Hopefully the dealership can do some basic checks on the wiring when the car is connected and running, did they do a volt check using a voltmeter at the input side of the sterling unit, fridge on, fridge off & compare voltages on pin 9 & 10 input to unit? 10.4v is the cut off voltage for the Thetford I've fitted, needs 11.7v to cut in, and max running voltage 16v at the fridge, 10.1 is too low.
1st Jan 2025 3:07 pm
stephenw46
Member Since: 22 Jun 2011
Location: West Midlands
Posts: 1223
The dealership as checked the caravan and it is fine the problem is not just with landrovers it is apparently all towing vehicles with Stuart alternators and thes new fridge freezers the fridge is drawing more then the car gives but hopefully all will work okay when I pick it up Friday
1st Jan 2025 3:40 pm
Sylvester19
Member Since: 17 Jul 2020
Location: Central Scotland
Posts: 138
I'd appreciate if you'd post the input side voltage of 9 & 10 the dealer gets when the car is running and fridge switched on.
1st Jan 2025 10:56 pm
stephenw46
Member Since: 22 Jun 2011
Location: West Midlands
Posts: 1223
Okay guys this problem as not gone away with the sterling wildside relay fitted , voltage from pins 9/10 with engine running was 14.7 volts and at caravan battery, but when I turn the caravan fridge on to 12 volt the relay kicks in then out and lights flash indicating no power, the fridge requires 204watts / 17amps surely the car should cope, any assistance with this will be appreciated
3rd Jan 2025 4:44 pm
Sylvester19
Member Since: 17 Jul 2020
Location: Central Scotland
Posts: 138
That unit is setup as default battery bias by default, are you giving it enough time to allow it to switch to fridge, seen 15 mins mentioned, could switch it to fridge bias mode, should power fridge right away. What model of Wildside?
Going back to what I've asked, what is the voltage at pin 10 when the fridge is on or makes an attempt to switch on with the car running, if that voltage is lower than that on pin 9 the fault lies between that point and the car fuse box. Have to be careful to ensure that both earths are connected and work as they should.
Possibly as a workaround, cool the fridge via mains power power, once it's chilled the power required to run may be around 4amps, I'm asssuming this is a compressor fridge?
3rd Jan 2025 7:39 pm
stephenw46
Member Since: 22 Jun 2011
Location: West Midlands
Posts: 1223
Click image to enlarge
Okay this is the sterling wildside that as been fitted, as for solving my problem, I plugged another caravan in with a 140 watt fridge and all worked fine, we then tried a VW transporter to my caravan and the fridge didn’t work through the wildside but worked fine without it , so my D4 as the required voltage but only 15amp supply and the fridge is drawing 17amp and the pcb is seeing this and closing the relay, so it looks like I need to run a 2.5or2.8 wire from the battery down to the back of the car through a bigger relay to pin 10, or find a wiring diagram and see if I can use any wires that are not being used, as for the voltage at pin 9 & 10 it’s 14.4 but when the fridge is on the amp load is insufficient
4th Jan 2025 10:58 am
Sylvester19
Member Since: 17 Jul 2020
Location: Central Scotland
Posts: 138
Did you connect the fridge to terminal 10 direct with the transporter or put the wildside to fridge bias mode? The car switched supply is protected by a 15a fuse, the fridge is 17a, in theory that should blow the fuse, it doesn't and it possibly wouldn't blow at 17a for a period of time, that cable if it was shorted against the vehicle body would blow the fuse instantly, current in the cable would be more than 17a! Don't try this at home.
The wiring if I'm correct is already 2.5mm to the rear of the car, minimum would be 4mm you would run and then you are restricted to 2.5mm for the 13pin and cables. You will be surprised how long the actual cable run is from battery to fridge and you have to count the -ve side as well, adds to the volt drop. If you have access to a clamp ammeter to check current flow to the battery and then fridge, would've been ideal when the transporter was connected for reference.
Looking at the wildside specifications, would seem to indicate the larger one should've been fitted with regards fridge current draw.
Question everyone's thinking, how did the xc60 manage, maybe the voltage it was supplying was slightly higher, which means lower current load within spec through the wildside at the time. Be interesting to know what the fuse ratings are for the xc60.
Might be that a separate switched supply of 20a to the rear of the car is required, but would check volt drop, current values and if correct wildside is fitted 1st. Apologies if it's a little difficult to follow, a photo of the wiring at the wildside would help, I'm sure others are interested in the outcome.
4th Jan 2025 5:05 pm
stephenw46
Member Since: 22 Jun 2011
Location: West Midlands
Posts: 1223
It’s the fridge that’s shutting as it’s not seeing the required load , this is why the fuse doesn’t blow on the D4 , secondly sterling are saying the wild side won’t do what we require so tomorrow if weather permits I’ll be out with the multimeter and see if I can use any of the heavier wires not being used, would be easier with a nice warm garage
4th Jan 2025 5:56 pm
Sylvester19
Member Since: 17 Jul 2020
Location: Central Scotland
Posts: 138
Interesting what sterling says, what's their reason for saying that? I'd still check connections.
There is a possible wire that can be used if my diagram is correct 2014 one, which is wire NU, 4.0D,5765, connector C0839S-4 it's the motor wire for the rear aircon, 4mm brown/blue, it's in a connector with 2, 4mm black wires beside the rear connectors for the trailer loom, this wire appears to go to the engine fuse box and would use fuse 22E and relay 10e mini if it was populated, thats assuming you don't already have rear air con!
The above info would have to be double checked, possibly other threads where forum members have taken power to the rear.
The way the media portrays the weather, it's as if we've never had snow before!
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