Accessory Outlet problem

(13-11-2011 12:44am)PhilSkill Wrote:  It takes 240W to blow a 20amp car fuse, if you up the fuse rating beyond design you are relying on the loom wiring being overspecced, you'll probably get away with it, but not getting away with it means burning out your loom! the device blowing the fuse must be faulty or cheap and nasty and personally i'd bin it rather than run a risk... fuses have a purpose... ignore at your peril!

I whole heartedly concur and if it were for just a single device plugged in, I'd gladly toss the device and stick with the recommended fuse, however, I've tried 4 different devices, including the power cable to a new $500 radar detector, which is by no means a cheap device, and each snapped the fuse.

At this point I'm stumped. If I could just place the 20 amp fuse back in and be on my merry way, charging my cell phone with even a brand name charger, I'd be delighted, but I don't have any confidence that I'll be able to. I have both a motorola and blackberry charger I will try with the 20 amp but am doubtful at best

The fuse is there for a reason and, as Phil says, is there to protect the wiring loom. Simply replacing the fuse with a higher fuse rating is crass ignorance. Why not use a paper clip, that will do it and you'll be able to enjoy the acrid smell of burning PVC?

Seems likely the device is either momentarily shorting out the supply when inserted or has a very high inrush current when first powered up. Throw it away and buy a better quality one. I bet it came from Wall-mart, right?

As for your friend, have you discussed with him who is going to pay for the burned out wiring loom now that you have voided the warranty?

Edit: since you have tried 4 devices, have you tried a different power outlet? Are the plugs a tight fit in the power outlets or can they move around which could cause a short circuit? I assume there is one fuse for all the outlets which limits the total current. Are there other devices in the car running off the same fuse. 20A is a huge current and the fuse should be enough. Have you had any after-market accessories added by an auto-electrician which may have been spliced into the same circuit?

(13-11-2011 07:19am)mark_n Wrote:  The fuse is there for a reason and, as Phil says, is there to protect the wiring loom. Simply replacing the fuse with a higher fuse rating is crass ignorance. Why not use a paper clip, that will do it and you'll be able to enjoy the acrid smell of burning PVC?

Seems likely the device is either momentarily shorting out the supply when inserted or has a very high inrush current when first powered up. Throw it away and buy a better quality one. I bet it came from Wall-mart, right?

As for your friend, have you discussed with him who is going to pay for the burned out wiring loom now that you have voided the warranty?

Edit: since you have tried 4 devices, have you tried a different power outlet? Are the plugs a tight fit in the power outlets or can they move around which could cause a short circuit? I assume there is one fuse for all the outlets which limits the total current. Are there other devices in the car running off the same fuse. 20A is a huge current and the fuse should be enough. Have you had any after-market accessories added by an auto-electrician which may have been spliced into the same circuit?

The car is now a day old so there have been no modifications. I guess it would be informative to state that there are 3 accessory outlets in my vehilce. I'll use the port names from the manual for reference.

I am only having the fuse issue with the Cigar outlet (in cup-holder compartment). I used the Rear outlet as well as the Cubby outlet without issue. My devices operate as expected from both of the other outlets. The Cigar outlet also has no other devices on its circuit, so I didn't believe it should be detrimental to any other devices.

...and while I appreciate the input, I really don't quite understand the negative tone and condescending manor of your tone. Phrases like "crass ignorance" and "it came from Wall-mart, right" has an air of pomposity that I don't quite understand. I raised the thread based on my personal frustration and lack of solution. So far, I haven't really read anything that's even come close to offering a proposed solution, and seem to be chastised for my decision-making. Not exactly what I had in mind when posting.

Don't take Mark's comments as an insult, Mark can come across very negative.

You need to find out what is causing the fuse to blow, you just should not be able to blow a 20A fuse with a phone charger, at least upping the rating to 25A and then it's ok means you have less than 300W going through the loom (think of the heat a 1 Bar electric fire, that draws 1000W, so a quarter of that is how much energy is passing through that fuse!), does every device you plug in do this? if so you must have a wiring fault. I would pursue this with your dealer, see if they have something that you can plug in to blow the fuse, as the dealer will of course assume it's your device, you need to prove to them you have a fault there.

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Have you tried going back to a new 20Am fuse? As you may have had a bit of swarf (old speck of wire from assembly) in the connector and the higher current drawn through the 25A fuse will have burnt it out.

Since there is no problem with the other two outlets, I would try obtaining a plug from a parts accessory store to see whether simply plugging in the plug (with nothing connected) is enough to cause the fuse to blow by disturbing the wiring in which case there is certainly something wrong with the socket or the wiring to it.

It may be the loop resistance of the wiring is such that the short circuit current will not reach the current required to blow a 25A fuse - these fuses do not blow instantly at the design current - they require a significant over-current for a period of time to cause the heating required to blow the fuse. If the loop resistance was just 0.5 ohms - which isn't much - the current would never be enough to blow the fuse but the wiring would then be dissipating over 300W as Phil says which is definitely not good news.

My guess is the socket or the wiring to it or the insulation of the connectors is faulty. Whichever it is, you should not assume all is fine just because a 25A fuse doesn't blow. I'm sorry if you didn't like my tone, however, arbitrarily changing the fuse to 25A when you do not apparently understand what you are doing is foolhardy.

(13-11-2011 07:45pm)mark_n Wrote:  Since there is no problem with the other two outlets, I would try obtaining a plug from a parts accessory store to see whether simply plugging in the plug (with nothing connected) is enough to cause the fuse to blow by disturbing the wiring in which case there is certainly something wrong with the socket or the wiring to it.

It may be the loop resistance of the wiring is such that the short circuit current will not reach the current required to blow a 25A fuse - these fuses do not blow instantly at the design current - they require a significant over-current for a period of time to cause the heating required to blow the fuse. If the loop resistance was just 0.5 ohms - which isn't much - the current would never be enough to blow the fuse but the wiring would then be dissipating over 300W as Phil says which is definitely not good news.

My guess is the socket or the wiring to it or the insulation of the connectors is faulty. Whichever it is, you should not assume all is fine just because a 25A fuse doesn't blow. I'm sorry if you didn't like my tone, however, arbitrarily changing the fuse to 25A when you do not apparently understand what you are doing is foolhardy.

That's a much more sound and resolute response, and I appreciate it. I intend on bringing it to the dealership this week and have them take a look at it, however, in the meantime, I'm going to replace the 25 amp with a 20 amp fuse again and try plugging in a plug that has nothing attached, so there is no draw. My belief is that there is either a short at the plug-end of the socket, or with the wiring itself. The two other outlets (rear and Cubby) are both fine, but are separate circuits with their own 20 amp fuses, and each of them are fine.

So - my reasoning is this - with 2 of the 3 plugs working without issue, and using the myriad of devices I've tried until now, its reasonable to deduce that the Cigar Accessory outlet has a defect. I can replicate this with several of my own devices, but you're right, it would probably be best to show the service folks using one of their own adapters. I'm just frustrated that I need to have service take a look at a vehicle with less than 200 miles on it.

For what it's worth, I highly doubt that any of the adapters have a short in them considering they each have their own in-line glass fuse. Specifically, the fuse for my Monster iPod charger comes with a 2.5 amp integrated fuse. I'd think that would definitively refute it being device specific or application specific, but I have to cover all the bases before I can impress upon them that there is a defect with the vehicle itself.

Take it back with a 20A fuse in! Save you from any dodgy get out clause for an unscrupulous dealer...