# Blowing fuses on an Autotrail



## backaxle

HI,

I gave the MH a drive out today(Autotrail Mohican)and when I got back the control panel was showing no charge to the leisure batteries. I have had this problem 3-4 times before so I knew what to look for and sure enough a fuse was blown (one of the 3 near the chassis battery)as in the past, so I replaced it and all is fine. 
This will probably be ok now for a few months, then the fuse will blow again. I have tried putting a higher rated fuse in place, but it still blows eventually. If there is a short circuit somewhere I would have thought the new fuse would blow immediatley. 
Has anyone else had this problem? What causes it and how was it rectified?  

Thanks in anticipation. 

Backaxle.


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## tramp

hi backaxel,
NEVER :evil: put a higher rated fuse in place of a lower one as you will either burn the wiring loom out [if lucky] or at worse have your van go up in flames with no insurance cover.

on a lighter note have you had a look at the connectors to the back of the fuse in case of a bad contact or a over sensative rcd breaker. How about replacing the whole faulty fuse with a new holder and fuse ?

tramp


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## backaxle

I am quite aware of that Tramp,but the Autotrail handbook does not show the value of the fuse in the wiring diagrams.The fuses have been messed about by Brownhills in the past,so I don't know what amperage the fuse should be.There is a 20 amp fuse at the liesure battery connection,and there was a 5 amp at the alternator end,so I replaced it with a 15 amp.so long as it is lower than the 20amp I cannot see that it is a problem.


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## clodhopper2006

If your circuit is drawing slightly more current than the rating of the fuse it will eventualy blow. This is known as overload current as distinct from fault current. 
Do you have a multimeter? If you do then to measure current in a circuit you need to connect the meter in series with the circuit. To do that, disconect the wire from one side of the fuse and connect it to one lead of the meter. Put the other lead where you disconected the fuse to complete the circuit. Ensure that the leads are plugged into the right socjkets on hte meter ie com and current, select a DC current scale higher than the fuse rating. It doesnt mater for this test which way round the leads are.
If you do that it will tell you what the normal load current is and it should be lower than the value of the fuse. If it is lower then you probably have an intermitant short. If the current is higher than the fuse rating you need to have this checked. Before uprating the fuse somebody needs to be able to identify the cable size to determin its current carrying capacity.

Bob


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## safariboy

Was the battery very flat? If so the charging current could be too high and blow a fuse. The solution is to take out the battery and recharge away from the van.
Are you sure that the 20A and 5A fuse are in series? It seems a bit unusual. I would suggest that you try to contact Autotrail and find out the correct values.


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## bigbazza

I have an Autotrail wiring diagram for a few different models (Cheyenne,Apache,Frontier)
They all show a 20amp fuse near the leisure battery and a 20amp fuse (fuse 8 @ the EC200 Unit)
It also shows another 4 fuses in the circuit :-
1- Spare not fitted
2- Fridge 15amp
3- Leisure Battery 20amp
4- Vehicle Battery 20amp


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## peedee

Backaxle,
I have a Mohican and have also had similar problems but not for sometime. I suspected it was something to do with using a generator but I have never managed to pin the cause down and the problem has not reoccurred for some time now so I never did prove the cause. Not much help but you were not alone

peedee


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## sallytrafic

Hi 

It is normal and desirable that both ends of your split charge system are protected by a fuse to protect both batteries in the event that the joining wire shorts to earth somewhere in the middle.

(I am not sure however if we are talking about split charge but as you do mention the alternator end am assuming so for now.)

The alternator is capable of delivering far more that 20A to the leisure battery and all there is to stop it is the internal resistance of the leisure battery and the resistance of the split charging relay contacts, wire and fuses. Often the contacts will only be rated for 30A hence the 20A fuse. 

Under such circumstances it is inevitable that from time to time (especially if your leisure battery is well discharged) that the fuse will blow. I carry a few 30A fuses just in case the 25A one pops, (my wiring is rated at 33A).

Split charging as found in most vans is a cheap compromise to what can be arranged as for example in Clive Motts excellent article which I can't find at the moment as he has changed addresses.


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## backaxle

Thank you clodhopper for a really informative and constructive reply.I do have a multimeter and I will check it out as soon as possible,but after reading Bigbazza's reply it seems the fuse should be 20amp,there is a fridge fuse @15 amp,a vehicle battery [email protected], a spare and the one I am having trouble with, which was 5amp(put in by Brownhills) and looks like it should be 20amp.Thing is my wiring diagram does not show the values of these fuses for some reason.
Peedee,maybe you should read clodhopper's reply.It seems you have the same problem,and this could be the same remedy.
Sallytrafic,it is the splitcharger end I meant,and it seems as you rightly say it should have a 20amp fuse at each end.
Thank you all again for your replies.

Backaxle


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## Sargent

Hi Backaxle, the fuses are as bigbazza correctly identified and as Frank has pointed out, if the leisure battery is quite well discharged and the vehicle battery is well charged then a significant amount of the output of the alternator can be delivered to the leisure battery. We have to protect all of the electrical component, thus fuses are fitted as close to the vehicle battery as possible.

The fuses at both ends of the charging cable ie the ones near the vehicle battery should be 20A and the ones near the leisure battery should also be 20A

We on the newer systems control this quite differently limiting/modifying the current that is supplied to the leisure battery, but thats a different story?

I hope this is of help, but if you require any further assistance then please give our technical people a call 01482 678981

Best regards

Ian Sargent


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## backaxle

Sargent said:


> Hi Backaxle, the fuses are as bigbazza correctly identified and as Frank has pointed out, if the leisure battery is quite well discharged and the vehicle battery is well charged then a significant amount of the output of the alternator can be delivered to the leisure battery. We have to protect all of the electrical component, thus fuses are fitted as close to the vehicle battery as possible.
> 
> The fuses at both ends of the charging cable ie the ones near the vehicle battery should be 20A and the ones near the leisure battery should also be 20A
> 
> We on the newer systems control this quite differently limiting/modifying the current that is supplied to the leisure battery, but thats a different story?
> 
> I hope this is of help, but if you require any further assistance then please give our technical people a call 01482 678981
> 
> Best regards
> 
> Ian Sargent


Thank you very much.It does seem that the problem has been a 20amp fuse at the leisure battery and a 5amp fuse at the other end.I will correct this and do the checks with a multimeter as described by codhopper 2006.As you point out, the problem is worsened if the leisure battery is discharged,and this will be the case,because the fuse has been blown, the leisure battery has not been getting charged by the engine. I expect they will only have been charged when on Mains. 
Thanks once more.When I have done all checks I will keep everybody updated,as I expect this could be a problem others could experience.

Kind regards.
Backaxle


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## peedee

Thanks Frank and Sargent for the confirmation. That makes sense and ties in with it only occurring when I used a generator, i'e not on EHU and running the leisure battery down. Didn't know the alternator could push out over 20 amps though.

peedee


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## backaxle

Hi,Just to let you know,I have fitted a 20amp fuse at the vehicle battery as described ,and all seems well.I have not done the amperage checks yet because I can't find my multimeter(it will turn up when I don't need it).I am going to the NewarK show next weekend ,so I will see how things progress.I am sure that all is correct now.After reading all the information provided here,it has become obvious that a 5amp fuse fitted where a 20amp should be, is bound to keep blowing.  It is a pity that Brownhills didn't realise this 2 years ago. :!: :!: 

Thanks again.
Backaxle


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## 127050

*Autotrail (Cheyenne 2004) fridge fuse blowing*

Thanks to all.

I bought my MH used & without any briefing. I am fixing a few problems as I find them.

A quick browse though this discussion put me on to a blown 15 amp fuse located by the vehicle battery. My fridge now works on 12 volt & I have a step down alarm & auto retract that I didn't know about.

Cheers Tim


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