Radio Wiring - Problem With The "keyed On" Wire

[Comanche County]

Gents,

 

My radio is cutting out, I'm having a problem with the "switched on" 12V wire going to the radio.

 

Sometimes it gets ~12V while the key is on or in the acc position, but now its only getting ~2v and the radio is not turning on.

 

My gut is telling me the problem is related to my melted and contorted fuse block. When I bought the MJ long ago it had a leaky Clutch master and the fuse block felt the pain.

 

My question is, where does the Switched On radio wire draw power from? I could hot wire the radio but I want the radio to turn off with the key. The fuse block has plenty of constant 12V terminals but I want it to work correctly with the key.

 

My main fear is there is some sort of electrical issue that could burn down the truck. So at the very least, now I'm in the market for a fuse block in good condition. The second priority is tracking down that darn wire and figuring out why its not getting power when it should so I can listen to some tunes.

 

Any ideas?

 

Thanks,

Jay

[mvusse]

I would not worry about the radio until you get the fuse block replaced. Then if it still doesn't work reliably start tracking it down.

[87MJTIM]

I would not worry about the radio until you get the fuse block replaced. Then if it still doesn't work reliably start tracking it down.

 

Are fuse blocks compatable across years? Mine is an '87. Will later years be the same?

[mvusse]

Up through 90 should be the same. Newer than that might be (look the same to me) but don't know for sure.

[HOrnbrod]

Are fuse blocks compatable across years? Mine is an '87. Will later years be the same?

86-90 XJ/MJ fuse blocks are interchangable. Get one preferrably from a donor w. the auto tranny for obvious reasons. The only difference is if it's from an XJ that has the rear hatch wiper, but it still can be used as a replacement.

[Comanche County]

I got it figured out all is well now.

[johnj92131]

I got it figured out all is well now.

 

That is great! But tell us what you found and how you solved it, so the next Guy who uses the search function will know how to solve the problem!

[Comanche County]

When I wiggled the RR Wipe fuse it caused the radio to go on and off. Once I discovered that I used a multi-meter to check all the fuses and found that the radio fuse had no power going through it. The RR Wipe fuse opening is not used in the MJ and only has one female clip, a fuse was in it anyway, but that clip also shares power with the radio fuse. If you look at the back of the fuse block, you'll see that several of the fuses share power from the same strip. Hard to explain without a good pic, but look at your fuse block and you'll see that they are in line with each other. Turns out the female ends of the radio fuse were a little loose and it wasn't making good contact with the radio fuse so when I wiggled the RR wipe fuse it was pushing the radio fuse to contact. I clean up the fuse block and used a small screw driver to bend all the female contacts in the fuse block so that the fuses were nice and snug.

 

Simple really. I was just scratching my head because I knew I had a good radio fuse. Another clue was that the cigarette lighter also draws power through the radio fuse and it wasn't working either. Now the radio works and I can charge my iphone.

[HOrnbrod]

The RR Wipe fuse opening is not used in the MJ and only has one female clip, a fuse was in it anyway, but that clip also shares power with the radio fuse.

 

In a pinch you can use a male spade connector shoved into one of the unused fuse block female clips for a 12V connection. It makes for a pretty solid connection.

 

[Comanche County]

Good idea!