posted 05-01-2012 12:38 AM ET (US)

Low Profile Fuse

On the drive to work this morning I plugged my cellular telephone charging cord into the cigar lighter power socket on the dashboard of my car in order to charge the cell-fone. The charger LED did not illuminate, indicating there was no power from the cigar lighter socket.

A JCase fuse is a cartridge-style fuse in a recessed female terminal. The JCase Low Profile fuse has a lower profile and shorter male blade terminals but performs the same as a standard JCase. If you are thinking you have a blown fuse, this will help you find it in seconds. Remove each fuse 1 by 1 and immediatly replace it with same one if its good so you won't mix them all up. Keep going 1 by 1 and and put them each back untill you find the blown fuse. If you don't find any that are blown, then you have another problem. The fuse has a manufacturing defect. Is it a quality fuse or a cheap replacement? A blown fuse has been replaced incorrectly with a lower rated fuse. The device powered by the fuse is faulty, drawing a higher current. The fuse is OK, but something went wrong in the testing process. A car fuse wouldn't commonly fail because of. A blown JCASE ® fuse can be recognised from the top through the transparent housing B. Changing a fuse In some vehicles, a pair of plastic pliers for removing fuses is located on the inside of the cover of the fuse box in the engine compartment. The JCASE fuse is a rectangular shaped time delay, cartridge, fuse with a female terminal, design. The JCASE fuses are available in 32 and 58 volt DC versions. JCASE fuses are color coded for amperage rating identification. Littelfuse offers the JCASE fuse using the JCASE® brand name.

I thought about this for a moment, and realized what had gone wrong. Last week at work we were having a dispute about a particular DC-to-DC converter power supply, used for charging a laptop computer. It outputs 19-VDC and runs off the cigar lighter socket in a vehicle. The end-user said it did not work. The bench tech said it was fixed. I said, 'I'll try it in my car.' I did, and, no, it did not work. Now I realized that not only did the DC-to-DC converter not work, it probably had blown the fuse in my car's power outlet, too!

When I got to work, I checked the cigar lighter power outlet with a DMM. There was no voltage there, as I suspected. I opened the glove box and grabbed the owner's manual. Around page 246--it's a big owner's manual--I found the section on fuses. Even though my car is not particularly big or particularly fancy, it has two power distribution centers and enough capacity to have about 100 fuses. After carefully reading the list twice, I found what I thought should be the circuit for the cigar lighter socket, called 'Front Power Center' or something like that. The fuse was under the engine hood in the power center there.

Jcase Fuse Blown Fuse

When I opened the cover on the power center I was quite surprised. All the fuses were of a new type I had not seen before. The fuses were contained in rectangular cartridges, color coded for current rating. The cartridges have a clear cover and you can see into them to look at the actual fuse element. It was too dark in the garage to see if the particular fuse I thought was associated with the cigar-lighter was blown, so I pried it out of the fuse panel, using the test leads of the DMM. (No fuse puller accessory in the box under the hood.)

Once out of circuit, I checked the fuse with the DMM. Yup, it was open. OK, mystery solved. Now let's get a new fuse.

J Case Low Profile Fuses

Back at my desk, I GOOGLE'd for 'Ford cartridge fuse Fusion 2011' I got some results that were close, but not a perfect match for my fuse. From what I could tell, the fuse I had in my hand was a 'Jcase' fuse. Here the 'J' means Japan. This fuse style is apparently used on a lot of cars made in Japan. (My FORD was made in Mexico, by the way.) The Jcase fuses all looked too long for my fuse holder. Then I found a 'mini-Jcase' fuse. The size looked correct, but my fuse had some molded ridges along the sides that fit into guides on the fuse panel. These fuses did not.

I checked for vendors, but did not find much. Someone on Amazon was selling 'mini-Jcase' fuses for $9-each. Wow, that is an expensive fuse.

Finally, in desperation, I called the local FORD dealer and asked for the Parts counter. The parts counter guy looked up the FORD part and found he had them in-stock. 'It's a little blue rectangular cube,' he said, 'with '20' etched on the clear part.'

'That's the one I need,' I told him. (Now for the important part.) 'How much are they?'

Jcase Fuse Blown Plates

After a moment's pause, the parts guy said, 'Hey, not too bad, only $1.52.'

Jcase Fuse For Sale

'Set one aside for me,' I said, 'I will come over after lunch, about one o'clock.'

According to Littlefuse, the Jcase cartridge fuse has been around for a while. It is intended to supplant the MAXI-Fuse in automotive applications where a high current fuse with some time delay is needed. The Jcase cartridge also has an interesting design advantage over traditional fuses. The Jcase cartridge fuse carries the female contacts, and the Jcase fuse panel slots for the fuses have male contacts. This advantage is that every fuse brings with it a fresh female contact. In older designs where the fuse had male contacts, the socket on the fuse panel has a female contact. With every fuse insertion the female contact on the fuse panel is expanded slightly. The fuse panel contact had to be designed to withstand many insertions. With a Jcase cartridge fuse, the fuse carries with it a fresh set of contacts, and the Jcase fuse box or panel needs only the simple male contact portion.