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WOODGREENMAN

Tow bar live feed fuse blows

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After near 10,000 miles of towing around UK and France the permanent live from the fusebox  is blowing the 15 amp fuse .

I went to Glossop to pick up my caravan  after a small repair  and when I connected the caravan to the car everything was dead .

The mechanic on site checked the caravan with his box of tricks and said the fault must be in the car . 

I found that the main fuse feeding the tow bar electrics had blown.

I replaced the fuse and everything seemed ok ,alko ,lights etc

After driving 30 miles to home I checked my lights and the fuse had blown again.

I can't see anything obvious any help would be welcome  .

Car Land Rover Freelander 2 , Coachman Pastiche 520

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I assume you are 13 pin socket and fully populated electric/charging.

I assume you mean the permanent live feed to the van (and not the road light "box".)

I am also assuming your road lights are all completely operational.

 

Could the minor repair be connected? Even if the repair was non electrical.

Did you have the battery connected in the van? If not, could the battery connectors touch? As the charging power comes from the permanent 12v supply, this could short and blow the fuse.

 

Otherwise I would check the towing socket and plug for any loose wires or moisture floating around inside.

 

 

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Check that the lead through the A frame to the 13 pin plug  hasn't  been pinched by the jockey wheel  assembly.

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9 minutes ago, AlwynMike said:

I assume you are 13 pin socket and fully populated electric/charging.

I assume you mean the permanent live feed to the van (and not the road light "box".)

I am also assuming your road lights are all completely operational.

 

Could the minor repair be connected? Even if the repair was non electrical.

Did you have the battery connected in the van? If not, could the battery connectors touch? As the charging power comes from the permanent 12v supply, this could short and blow the fuse.

 

Otherwise I would check the towing socket and plug for any loose wires or moisture floating around inside.

 

 

 

Thanks for your reply , I am on 13 pin socket .

The fuse blown is in the car fuse box  and feeds the tow bar electrics .

The battery is connected .

I will check the socket and plug for loose wires or moisture as you suggested .

I am going to replace the fuse in the car again and see if it blows when I'm not towing .

14 minutes ago, Stevan said:

Check that the lead through the A frame to the 13 pin plug  hasn't  been pinched by the jockey wheel  assembly.

Thanks that's something I never thought of I'll check that in the morning . 

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You need to work out what that fuse feeds though as the road light has to be separate from the road lighting.

First thing, when the fuse has blown does the road lighting work if so, you need to work through the power feeds to see if a cable had been chaffed through somewhere and shorting . Next thing do the same on the van and check the battery as above. 

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If you have a volt meter, put it on resistance and with the fuse still removed, connect the fuse outlet side through the meter to an earth point on the car. If a resistance/continuity is shown then it indicates a possible short to earth in the wire between the fuse and tow bar electrics. If there is a relay at the tow bar end then disconnect the fused wire to it, just to check it is a problem with the wire and not the electrics.

 

Just a comment on the size of the fuse, I have always had a 15 amp fuse for the lighting and a 20 amp fuse for the permanent live.

Edited by Paul1957

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Has the caravan ATC, as this requires the use of a higher rated fuse than 15 Amps. Clearly if the wiring can stand uprating it for this short term over current.

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So as I understand it the fuse that has failed is the one supplying power to the smart relay in the car that drives the caravan road lighting. Not the permanent live that goes directly to the 13 pin socket? 

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1 minute ago, Tuningdrew said:

So as I understand it the fuse that has failed is the one supplying power to the smart relay in the car that drives the caravan road lighting. Not the permanent live that goes directly to the 13 pin socket? 

 

That may be the only power connection to the smart relay which allows the unswitched supply straight through plus voltage-senses a switchb supply for the fridge - if that's what the OP is using, the fuse and cabling  need to be 30A to cope with the combined current.

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33 minutes ago, JTQ said:

Has the caravan ATC, as this requires the use of a higher rated fuse than 15 Amps. Clearly if the wiring can stand uprating it for this short term over current.

 

As said a higher rating fuse ? I thought 20 a was required .

 

 

Dave

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What was the small repair? 

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The pin 9 supply to the pin 13 return on my car has a 25amp fuse.

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10 hours ago, Artleknock said:

The pin 9 supply to the pin 13 return on my car has a 25amp fuse.

 

Hopefully Ford or an after market installer put adequately sized wiring in to take it, rather than somebody simply put in a  25 fuse?

 

 

Edited by JTQ

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3 hours ago, JTQ said:

 

Hopefully Ford or an after market installer put adequately sized wiring in to take it, rather than somebody simply put in a  25 fuse?

 

 

The OP said that he had towed for 10,000 miles before the problem, this suggests that the wiring was OK before the fault happened!

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1 hour ago, Stevan said:

The OP said that he had towed for 10,000 miles before the problem, this suggests that the wiring was OK before the fault happened!

 

But the OP did not say they had a 25 Amp fuse fitted, "AK" did.

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If it was ok for 10000 miles it would suggest that a fault has developed. 

Could be a chafed cable, bad connection or a faulty component drawing excess current.

If the fuse blows immediately it would suggest a short circuit to earth somewhere.

Always worth checking earth points for cleanliness and security. My experience of old cars is that earth issues can cause problems.

First check to see what rating fuse should be fitted, if an incorrect rating has been fitted that could be the issue.

 

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33 minutes ago, 664DaveS said:

If it was ok for 10000 miles it would suggest that a fault has developed. 

Could be a chafed cable, bad connection or a faulty component drawing excess current.

If the fuse blows immediately it would suggest a short circuit to earth somewhere.

Always worth checking earth points for cleanliness and security. My experience of old cars is that earth issues can cause problems.

First check to see what rating fuse should be fitted, if an incorrect rating has been fitted that could be the issue.

 

Earth faults seldom cause blown fuses. Chafed cables or overheated connections, with carbonised plastic and/or melted insulation are more likely causes of blown fuses. 

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1 hour ago, Stevan said:

Earth faults seldom cause blown fuses. Chafed cables or overheated connections, with carbonised plastic and/or melted insulation are more likely causes of blown fuses. 

Any short to earth will cause a blown fuse. 

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20 minutes ago, Durbanite said:

Any short to earth will cause a blown fuse. 

I was using the term "earth fault" to refer to a fault in the earth connection. A "short to earth" only happens if there is chafing etc. 

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Never connect up with the engine running, I've not had a problem since I followed this rule.

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18 hours ago, Stevan said:

I was using the term "earth fault" to refer to a fault in the earth connection. A "short to earth" only happens if there is chafing etc. 

BTW a poor connection can also blow a fuse. 

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The fuse I have fitted is a 15 Amp ,which I now know should be a 20Amp because of the Alko .

The confusing part is when I changed the fuse (to another 15 Amp) everything was OK , Alko on ,all lights working.

by the time I reached home 30 miles I checked and the fuse was blown again the ALKO light was out and the brake and indicator lights were not working.

As I have said I had done approx 10,000 miles with the 15 Amp fuse in with no problems .

The small repair I had done was on the side where I caught a gatepost not near any electrical connections. 

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17 minutes ago, WOODGREENMAN said:

The fuse I have fitted is a 15 Amp ,which I now know should be a 20Amp because of the Alko .

The confusing part is when I changed the fuse (to another 15 Amp) everything was OK , Alko on ,all lights working.

by the time I reached home 30 miles I checked and the fuse was blown again the ALKO light was out and the brake and indicator lights were not working.

As I have said I had done approx 10,000 miles with the 15 Amp fuse in with no problems .

The small repair I had done was on the side where I caught a gatepost not near any electrical connections. 

 

Very odd wiring arrangement surely if the permanent feed fuse to the ATC also supplies the brake and indicator lights?

That lot is well able to blow a 15 Amp fuse if all coming on together.

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4 hours ago, WOODGREENMAN said:

The fuse I have fitted is a 15 Amp ,which I now know should be a 20Amp because of the Alko .

The confusing part is when I changed the fuse (to another 15 Amp) everything was OK , Alko on ,all lights working.

by the time I reached home 30 miles I checked and the fuse was blown again the ALKO light was out and the brake and indicator lights were not working.

As I have said I had done approx 10,000 miles with the 15 Amp fuse in with no problems .

The small repair I had done was on the side where I caught a gatepost not near any electrical connections. 

It can't be something simple then.

Pin 1 powers the L/H indicator

Pin 4 Powers the R/H indicator

Pin 6 powers the Brake lights

They are earthed through pin 3

The Alko is powered through Pin 9 and earthed through pin 13.

 

Just check that there is no earth wire anywhere near the repairs that you did that could have been affected.

I know that in olden days I have had wierd symptoms in cars electrics because of a faulty earth, indicators earthing through brake lights, that sort of thing.

 

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My money is on an earth fault

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