12V Outlet Receptacles Burnt out?

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This one is a bit strange.

Both of the 12V outlet recepticles on the Jeep burnt out this weekend.

There are two. One is (supposed to be) 20A and is always live. The other is 15A and is only on with the ignition. I often use an air compressor after offroading trips.

Because I don't want to catch the wiring on fire, I have put a 15A fuse in the 20A fuse location - to make sure I don't overheat the wiring; the fuse will burn out before anything else gives up.

This weekend, I was inflating my tires and the 20A rated one stopped working. I thought I blew the fuse.

Checked and the fuse was fine. I probed the fuse socket and it was getting 12V. I started tracing wiring through the dash ... still no problem there. Probed the multimeter into the outlet and it was fine.

I used the other one (15A) and it did the same thing.

Pulled it apart and it turns out the center section of both plugs (positive) burnt out.

Why would both of these burn out in the same day ... without blowing the 15A fuse? If the factory says they are good for 15/20A, they shouldn't burn out.

Anyway, I am going to be converting the compressor to connect directly to the battery.
 
Originally Posted By: Miller88
Why would both of these burn out in the same day ... without blowing the 15A fuse? If the factory says they are good for 15/20A, they shouldn't burn out.

Quite simple. There's enough resistance at that point in the socket to create heat, not so high resistance to get just warm, not so low as to blow the fuse. See Ohm's Law.
Originally Posted By: Miller88
Anyway, I am going to be converting the compressor to connect directly to the battery.

Sounds like a good plan.
 
Daimler Chrysler engineering at its best, I guess. I had mistakenly assumed that the outlets rated for 15A would be able to handle a constant 15A draw.

Especially the 20A outlet fused at 15A ...

I can't seem to set of leads that will clip on to a battery that are rated for 15A.
 
Originally Posted By: Miller88
Daimler Chrysler engineering at its best, I guess. I had mistakenly assumed that the outlets rated for 15A would be able to handle a constant 15A draw.

Especially the 20A outlet fused at 15A ...

I can't seem to set of leads that will clip on to a battery that are rated for 15A.


How about cutting off the lighter plug and crimping on clamps?

You can extend it with some 12gauge wire if needed.

http://www.amazon.com/Forney-54732-Batte...s=battery+clamp

or you could make your own with those clamps and your wiring of choice such as 10gauge speaker wire and some ring terminals.
 
Last edited:
Originally Posted By: Miller88
Daimler Chrysler engineering at its best, I guess. I had mistakenly assumed that the outlets rated for 15A would be able to handle a constant 15A draw.

Especially the 20A outlet fused at 15A ...

I can't seem to set of leads that will clip on to a battery that are rated for 15A.


Perhaps they can with the correct connector. The fault may be in the poor contact made with the connector for the compressor, these things are often shoddily made.

The direct connect method sounds a lot better for something with that kind of draw anyways. Good luck
thumbsup2.gif
 
Originally Posted By: Rand
Originally Posted By: Miller88
Daimler Chrysler engineering at its best, I guess. I had mistakenly assumed that the outlets rated for 15A would be able to handle a constant 15A draw.

Especially the 20A outlet fused at 15A ...

I can't seem to set of leads that will clip on to a battery that are rated for 15A.


How about cutting off the lighter plug and crimping on clamps?

You can extend it with some 12gauge wire if needed.

http://www.amazon.com/Forney-54732-Batte...s=battery+clamp

or you could make your own with those clamps and your wiring of choice such as 10gauge speaker wire and some ring terminals.


That's my plan. I just couldn't find a set of clips and wire attached that would be rated high enough. I'll probably end up buying those clips listed and throw some 8 gauge wire on it and wire into the compressor. I suspect it will go a bit quicker attached directly to the battery, too.


Found these at Lowes - Should work for what I need http://www.lowes.com/ProductDisplay?productId=4582295 Rated for 30 amp.
 
The center terminal usually doesn't have much contact area and it promotes overheating. 12v receptacles were originally designed for intermittent cigarette lighter use. They really need to be redesigned for modern devices with constant current draw.
 
Originally Posted By: pcoxe
The center terminal usually doesn't have much contact area and it promotes overheating. 12v receptacles were originally designed for intermittent cigarette lighter use. They really need to be redesigned for modern devices with constant current draw.
+1 Some jacks have a "fusable link" inside as well as the fuse, and replacement links are available.
DC motors tend to draw MORE current when the voltage drops, and as others have said, the center contact on the lighter jack is not very big and is not a "zero ohm" connection. One approach is to run high current devices such as air pumps and car vacs with the engine on to reduce current draw. There are also "heavy duty" lighter plugs available which may show lower resistance all around.
 
That is A LOT OF CURRENT to be pulling through any lighter socket. Especially with that type of connector & especially connected to a DC motor, which is an inductive load.

For a one-time or two-time emergency use, OK but definitely not designed for repeated & regular use. No wonder they both burned up.

I highly suggest powering that type of load, used regularly & repeatedly, straight from the battery.
 
Sounds like you are expecting too much from a 12v outlet. We are constantly replacing fuses for them due to people trying to overuse them. Had to explain to a customer with a 92 Taurus that his vehicle came out before everyone had cell phone chargers and his was literally only intended for turning on a cigarette lighter.
 
Also the center connector on the male plug is spring loaded and not springing with too much force. If it scraped sideways it would self-clean. Get in there with a pencil eraser once in a while...
 
Avoid ciggy plug/12v receptacles whenever possible on anything drawing more than 6 to 7 amps.

They are horrid horrid electrical connectors that waste power heating up spring steel.

They might be ubiquitous, but they are an insult to anything drawing more than ~60watts.

While your compressor might draw only 12 amps at 12.8v, So much voltage drop is occurring over the too thin wiring and poor connectors, less than 10 volts might be getting to the motor, which means the amp draw will raise significantly, causing more voltage drop, on and on until the socket or plug burns out.

Cut off the Ciggy plug, add alligator clamps or utilize a better connector like Anderson powerpoles in the 30 or 45 amp flavor.

Your compressor will run significantly faster the more voltage you can get to the motor, over proper wiring through as few connections as possible. Exactly opposite of using a Ciggy plug/12v power port though stock vehicle wiring.

This ubiquitous 12v connector needs to be phased out entirely. It is truly junk, with NO redeeming qualities whatsoever.
 
Originally Posted By: Miller88
I can't seem to set of leads that will clip on to a battery that are rated for 15A.


Just get the cheapest set of jumper cables you can find.
 
Originally Posted By: eljefino
Originally Posted By: Miller88

I can't seem to set of leads that will clip on to a battery that are rated for 15A.


HF has a 28 pack of alligator clips; the big ones should do fine.

They are cheezy in construction (goes without saying), but electrically okay.

http://www.harborfreight.com/28-piece-electrical-clip-set-67589.html


Looks like the two sets of big ones are rated for the size of the compressor. It's fitting, since this is a harbor freight compressor. I have two of them and I think I will be doing this with both of them, actually.
 
I bet it will run a lot better connected to the battery and heat up a bit. With the vehicle running, it only had (before they burnt out) 12V to the power outlets.

The alternator and battery run at 13.5 - 14 or so ...

Old wiring.
 
Those little 12v compressors suck. I bought one of these about 10 years ago, it's perfect for topping off tires and can run on 12v if need be.

51CCP2KHWAL.jpg
 
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