driving light fuses melting

Four wheel driving. Vehicle modifications. Off road driving and recovery techniques. Towing and miscellaneous vehicle topics.

driving light fuses melting

Post by Jon79 » 27 May 2018, 1:20 am

thought I'd see if anyone has any ideas on why suddenly my driving light fuses are melting?

I had them wired up by an auto electrician over 12 months ago and have never had an issue and haven't changed anything, (I have 2 lightforce 240's and a light bar), then about 3 nights ago on the way home the driving lights went out and I pulled over and checked the fuse and it was completely melted.....the next day I pulled it all out of the fuse holder and wacked a new one in (20amp like was previously in there with no issue)


went out for a shot tonight and flicked the driving lights on when I was heading out & within 5 mins the fuse was stuffed and when checked had started to melt... I pulled it out when I got to the property and stuck another one in and on the way home same thing except only lasted maybe 1-2 mins
Jon79
Corporal
Corporal
 
Posts: 135
New South Wales

Re: driving light fuses melting

Post by darwindingo » 27 May 2018, 2:01 am

Considering it is not blowing as it would in a short circuit situation. I expect it is occurring due to something causing poor contact between the fuse blades and the terminals. The poor contact causes resistance resulting in the generation of heat. Ive seen this on more than one occasion, if its a stand alone fuse holder I would change it for a different type of fuse/holder. Perhaps a reset style one like this soldered in place would be a good option.

https://www.jaycar.com.au/standard-blad ... t/p/SF2335

Personally I would also remove and directly solder any other blade or bullet type connections within the circuit, as you can't get a better connection than that.

:drinks:
“Accidental Discharges” DO NOT OCCUR !!

An "Unintended Discharge" is nothing more than the lack of appropriate safety procedures or the failure to follow them..!

I love my country, but fear my government.
User avatar
darwindingo
Second Lieutenant
Second Lieutenant
 
Posts: 814
-

Re: driving light fuses melting

Post by Rod_outbak » 27 May 2018, 6:12 am

How big is the light bar?
The 240's would be drawing ~8 amps each, so you only really have 4 amps 'spare' in that fuse, to run the light bar.

A separate circuit (switch & relay) for the light bar, might be necessary.
---------------------
Sharing the extreme love with cats in Outback QLD
Rod_outbak
Staff Sergeant
Staff Sergeant
 
Posts: 589
Queensland

Re: driving light fuses melting

Post by Chronos » 27 May 2018, 8:29 am

Run a seperate circuit for the light bar as Rod_outback said above. A normal short circuit that blows fuse is normally a massive current but running just on or above a fuses capacity for long periods will see it slowly heat just enough to melt the plastic housing.

Chronos
.177 pellets through to .416 Ruger
User avatar
Chronos
Brigadier
Brigadier
 
Posts: 2286
New South Wales

Re: driving light fuses melting

Post by straightshooter » 27 May 2018, 10:40 am

What Chronos says is basicly correct.
A rough rule of thumb is for the fuse to have double the current rating of the maximum expected current.
Another consideration is the temperature where the fuse is located. If the temperature at that location is elevated then the rating of the fuse becomes less than it's nominal rating.
So in the the case of the example an earlier post a 240 watt lightbar can be expected to draw 20 amps at a nominal 12 volts so it should have a 40 amp fuse or at the very least a 30 amp fuse as a LED lightbar won't have the high inrush current that an incandescent lighting system of the same power will have.
"There is no expedient to which a man will not resort to avoid the real labor of thinking." Sir Joshua Reynolds
straightshooter
Sergeant
Sergeant
 
Posts: 359
New South Wales

Re: driving light fuses melting

Post by Lifesaride » 27 May 2018, 11:28 am

Don’t forget a fuse is to protect the cable, so it’s definitely not a good idea to replace it with a higher amperage fuse in place.

Did the auto sparkie install a relay? Melting fuses could be caused by multiple things, high resistance joint, damaged wiring, bad earth. It’s pretty hard to give good advice without going through it all with a multimeter.
Cheers
Lifesaride
Lance Corporal
Lance Corporal
 
Posts: 54
Queensland

Re: driving light fuses melting

Post by Die Judicii » 27 May 2018, 12:45 pm

Darwin Dingo got it first up.

Some of the other causes mentioned are also possible, but the fuse pins not making proper contact is the main cause.
Without seeing what you've got, I'd bet that it/they are the inline fuses with the bayonet type pins.
Piss it off and get different type as someone else suggested.

If you have to use the inline type,,,, scrub the pins with steel wool before inserting them, and as an added measure put em in and out 6 or 7 times and really wriggle them into place against the female receptors.
I do not fear death itself... Only its inopportune timing!
User avatar
Die Judicii
Colonel
Colonel
 
Posts: 2200
Queensland

Re: driving light fuses melting

Post by darwindingo » 27 May 2018, 3:33 pm

The setup had previously functioned without reported issue for 12 months, so although it may be running close to the limit it appears it was capable of doing the job up until now. I can only assume the auto sparky had some idea what he was doing, so on that basis I would simply install a better fuse type and see how it goes.

:drinks:
“Accidental Discharges” DO NOT OCCUR !!

An "Unintended Discharge" is nothing more than the lack of appropriate safety procedures or the failure to follow them..!

I love my country, but fear my government.
User avatar
darwindingo
Second Lieutenant
Second Lieutenant
 
Posts: 814
-

Re: driving light fuses melting

Post by Jon79 » 27 May 2018, 5:57 pm

darwindingo wrote:The setup had previously functioned without reported issue for 12 months, so although it may be running close to the limit it appears it was capable of doing the job up until now. I can only assume the auto sparky had some idea what he was doing, so on that basis I would simply install a better fuse type and see how it goes.

:drinks:


cheers mate, all makes sense :thumbsup:

this is the light bar I have
https://www.korrlighting.com.au/product ... light-bar/

and these are the spotties
https://www.lightforce.com/products/bli ... -halogen-0
Jon79
Corporal
Corporal
 
Posts: 135
New South Wales

Re: driving light fuses melting

Post by Rod_outbak » 28 May 2018, 6:08 am

Jon79,

If those 3 lights are on the same relay/circuit, they are drawing just under 27 amps.

Firstly, the 20 amp fuse as installed by your auto-sparkey is way too light.
Each of the Lightfoce 240 Halogens are drawing around 8 amps apiece (16 amps in total).
The Lightbar looks to be drawing nearly 11 amps.

Secondly, as others have mentioned, the cable(s) need to be up to the load required. Given the sparkey seems to have installed a fuse way too light for the job, is there any chance the wiring is also under-spec?

Any ideas why the sparkey made such an error in his install?
Were the Lightforce lights installed first, and the light bar some time later?
The 20 amp fuse sounds about right for the pair of Lightforce lights alone(or the light-bar).
Are you certain there isnt a second relay somewhere for the light-bar, and he has just run both relays off the one switch?

Seriously; you seem to have a problem with the install that goes way beyond the wrong size of fuse. As others have suggested, the size of wiring needs to be assessed, the light-bar really should be on it's own circuit, and maybe look into a different type of fuse mount.
A melted fuse might end up being the least-painfull outcome for you.

All these questions and more.

Cheers,

Rod.
---------------------
Sharing the extreme love with cats in Outback QLD
Rod_outbak
Staff Sergeant
Staff Sergeant
 
Posts: 589
Queensland

Re: driving light fuses melting

Post by Jon79 » 28 May 2018, 4:04 pm

Ok just the one relay

The light bar was on first and shortly after the pair of lightforce sportiest went on ( all done by same auto sparky)

Wire used is about 6mm

Have replaced the inline fuse holder and so far no melting although the fuse is bloody hot to touch and the wire near the fuse holder is fairly warm?

All this had previously been hooked up without a single issue for around the last 12-18 months
Jon79
Corporal
Corporal
 
Posts: 135
New South Wales

Re: driving light fuses melting

Post by Jon79 » 28 May 2018, 6:11 pm

Ok I take that back still melting the f#@king things
Attachments
263B5025-0C14-4CC3-B948-38C6E601C898.jpeg
263B5025-0C14-4CC3-B948-38C6E601C898.jpeg (1017.24 KiB) Viewed 1474 times
Jon79
Corporal
Corporal
 
Posts: 135
New South Wales

Re: driving light fuses melting

Post by Daddybang » 28 May 2018, 6:32 pm

I'm not any sort of sparkiie but is there any chance something has happened to the lights themselves if ya been rattling around off road?? :unknown: :unknown: :drinks:
This hard living ain't as easy as it used to be!!!
Daddybang
Major General
Major General
 
Posts: 2797
Queensland

Re: driving light fuses melting

Post by darwindingo » 28 May 2018, 7:20 pm

Been a while but 6mm cable if I'm not mistaken can handle up to about 50 amps. Does that sound about right to you Rod ?
& Jon how certain are you that the original fuse was indeed a (yellow) 20 amp ? Did you read it or colour match it, just wondering if there is any possibility it may have been mixed up with an orange 40 amp in poor lighting or something ?

:drinks:
“Accidental Discharges” DO NOT OCCUR !!

An "Unintended Discharge" is nothing more than the lack of appropriate safety procedures or the failure to follow them..!

I love my country, but fear my government.
User avatar
darwindingo
Second Lieutenant
Second Lieutenant
 
Posts: 814
-

Re: driving light fuses melting

Post by Tiger650 » 28 May 2018, 7:24 pm

Deterioration after a period in service [originally worked OK] could be high resistance via bad earths ?

Pretty easy to run cables from the lights back to battery negative ?.
Tiger650
Sergeant
Sergeant
 
Posts: 260
Victoria

Re: driving light fuses melting

Post by darwindingo » 28 May 2018, 7:36 pm

Jon, just out of curiosity whats the relay rated at ?
“Accidental Discharges” DO NOT OCCUR !!

An "Unintended Discharge" is nothing more than the lack of appropriate safety procedures or the failure to follow them..!

I love my country, but fear my government.
User avatar
darwindingo
Second Lieutenant
Second Lieutenant
 
Posts: 814
-

Re: driving light fuses melting

Post by Jon79 » 28 May 2018, 7:36 pm

darwindingo wrote:Just out of curiosity whats the relay rated at ?


30amps
Jon79
Corporal
Corporal
 
Posts: 135
New South Wales

Re: driving light fuses melting

Post by darwindingo » 28 May 2018, 9:32 pm

Hmm

The 20 amp fuse is heating up like a toaster with that much continuous load on it. If my recollection of the 6mm cable is correct and that is indeed what you have and considering the 30 amp relay along with the approximate 27 amps that Rod indicated the lights are drawing you may be able to fuse it with a (green) 30 amp fuse (possibly 40 amp if the relay was upgraded) ? ... But don't do it based on my post, It would be better to seek advice from a reputable auto sparky regarding your specific setup. After properly assessing everything with his own eyes, he would be in the best position to advise you of the most appropriate course of action (possibly splitting the circuit) probably without any charge. :unknown:

Let us know how you go :friends:

:drinks:

Jeff
“Accidental Discharges” DO NOT OCCUR !!

An "Unintended Discharge" is nothing more than the lack of appropriate safety procedures or the failure to follow them..!

I love my country, but fear my government.
User avatar
darwindingo
Second Lieutenant
Second Lieutenant
 
Posts: 814
-

Next

Back to top
 
Return to Four wheel driving and off road travel