Dead "batt" circuit at the fuse block

For whatever reason the circuit that powers the 12v constant requirements at my 92's fuse block is dead from a bad connection somewhere. Every once in awhile my dome lights will work briefly and that's about it.

Rather than engaging on a never ending quest to find the faulty connection I wonder if it would cause any problems to run a new wire from the battery (fused) and repower this circuit by making a connection at the (BATT) terminal on the front of the fuse panel

any input or wiring diagrams would be appreciated

krochus said:

For whatever reason the circuit that powers the 12v constant requirements at my 92's fuse block is dead from a bad connection somewhere. Every once in awhile my dome lights will work briefly and that's about it.

Rather than engaging on a never ending quest to find the faulty connection I wonder if it would cause any problems to run a new wire from the battery (fused) and repower this circuit by making a connection at the (BATT) terminal on the front of the fuse panel

any input or wiring diagrams would be appreciated

Click to expand...

I think that because you are asking, you already know the answer: it can be done but it's an iffy idea. Technically it may work, but may create other problems now or down the road. The best way is to find and fix it properly.

Are you sure that the problem is between the battery and the fuse box? Is it just the dome light or are any other items affected. The dome light is not the only item on that circuit IIRC.

The cable from the battery and the fuse box is probably corroded inside, a common problem. Check it for continuity with a tester.

other items on this circuit are dead too including the memory for the radio.,

I figure a bad connection SOMEWHERE an It will test 12v on a meter but once a load is put on the circuit it ZERO's out

krochus said:

other items on this circuit are dead too including the memory for the radio.,

I figure a bad connection SOMEWHERE an It will test 12v on a meter but once a load is put on the circuit it ZERO's out

Click to expand...

Thats why you want to test with a test light. Voltage can still exist with a very bad connection and 1 small strand of wire, a test light will not get enough amps to light up under those condition.

Electrically there is no problem doing what you are proposing and I don't know why it should cause problems in the future.

I assume that you have checked with a meter to ascertain that you don't have current available at the hot side of the fuse and that you are going to pull the fuse and plug your new fused lead into the component side of the fuse contacts with a spade lug. Sounds good to me if you don't have time to troubleshoot right now.

I did something similar on that same circuit several weeks ago. I had the reverse problem where the interior lights stayed on intermittently. I got tired of not having the CD player with the 10amp fuse pulled so ran a separate lead to the radio memory and ran a fused lead from the fuse contacts to an under dash switch . I since found my original problem but now have the ability to turn the interior lights off when working on the xj with the doors open or whenever else it is convenient. A quick and easy way to gain this control.

You want to check for CONTINUITY (ohms of resistance) not voltage. A high resistance will mean the wire is bad. Test lights are not reliable, especially in instances like this.

robsjeepxj said:

You want to check for CONTINUITY (ohms of resistance) not voltage. A high resistance will mean the wire is bad.

Click to expand...

Ive not nothing at the fuse block. So what points would you test resistance between?

robsjeepxj said:

You want to check for CONTINUITY (ohms of resistance) not voltage. A high resistance will mean the wire is bad. Test lights are not reliable, especially in instances like this.

Click to expand...

Resistance is a crappy way of testing a bad cable connection. If a large cable has a good connection through 1 strand of wire, you can get full continuity. The best test for a bad connection is a voltage drop test, or a test from a test light. Why are you saying that a test light is unreliable?

http://www.engine-light-help.com/voltage-drop.html read this, maybe it can explain my reasoning a little better.

88 Wagonman said:

http://www.engine-light-help.com/voltage-drop.html read this, maybe it can explain my reasoning a little better.

Click to expand...

A good article. But it says to check VOLTAGE DROP, not RESISTANCE.

OK, hasta a large cable in good condition will have a very low resistance (OHMS), in comparison a large cable with every strand but 1 still making a connection or in this case intermittently making one will have a very high resistance, this will make troubleshooting very easy and definitive. Just simple electron theory.

winterbeater said:

A good article. But it says to check VOLTAGE DROP, not RESISTANCE.

Click to expand...

That was my point.

robsjeepxj said:

OK, hasta a large cable in good condition will have a very low resistance (OHMS), in comparison a large cable with every strand but 1 still making a connection or in this case intermittently making one will have a very high resistance, this will make troubleshooting very easy and definitive. Just simple electron theory.

Click to expand...

I disagree, maybe in the world of single strand wiring (before your edit you stated that you were an electrician) but not in stranded wiring. with single strand you either have a connection or you don't, it's not that way or stranded. For example, if you take a brand new wire the thickness of a hair fifty foot long ohm\continuity test it, it will show good. Take that same wire and hook it up to your headlight and see what happens, it will not light up, or it will be very dim. The same principle applies to corroded connections and worn out wiring.

That is a good article, however, as is stated, testing for voltage drop is most useful with high amperage circuits. If I understand correctly, all circuits associated with the fuse block are functioning correctly except for specific circuit in question (dome/memory). This suggests that adequate 12v current is getting to the panel but is not getting to the hot side of the 10amp fuse.

Probably not your problem but have to ask if you have a 5-speed and had clutch fluid dumped on the fuse panel at some point.

Aside from that, since you have an intermittent condition it can be difficult to spot the problem with normal diagnostics. I would run a wire directly from a 12v source under the hood and briefly plug it into the component side of the fuse in question just to verify that the dome lights are working correctly although you are already pretty sure they are. You could also probably get your 12v supply from one of the always hot contacts on the panel providing, of course, that those are working!

If the above describes your situation (that is that other circuits are working correctly), the problem lies within the panel. Whether you want to take that apart is up to you but I would use your original approach for the time being if you don't have time to mess with it now or don't have a warm place to work. It's always good to maintain OEM wiring but I will say again that there is no reason not to run a separate properly sized and fused wire to power your lights. Went there and did that for 20 some odd years with the crappy electricals on my '85.

Its pretty common to find corroded terminals in the bulkhead connector behind the fusebox on 84-96 models. Water or washer fluid get in there sometimes.

Running a seperate wire can be ok or bad depending on the failure. If it's just corroded open circuit it might be ok as long as your not backfeeding through other circuits. Bad could be if the wiring is open due to excessive current from a short.

And there is a difference between having voltage and current.

Voltage drop is a measure is what?..... hmmm resistance yeah that's it. So a test that measures voltage drop is a test of what?....hmmm oh yeah resistance sorry.:shhh:

robsjeepxj said:

Voltage drop is a measure is what?..... hmmm resistance yeah that's it. So a test that measures voltage drop is a test of what?....hmmm oh yeah resistance sorry.:shhh:

Click to expand...

It's a measure of resistance under a load, not the same thing.

Probably not your problem but have to ask if you have a 5-speed and had clutch fluid dumped on the fuse panel at some point.

Click to expand...

yes it is and judging by the paint in the area you're likely correct. I've just recently purchased this stripper model 4.0 4x2 5speed XJ and for the most part this is the only issue with the wiring or interior in general I've discovered.

I'll prolly just repower the circuit. I already have a fairly heavy gauge unused wire ran from the battery to the vicinity from a old alarm/ aftermarket power window install that just needs a fuse holder and a connector to serve.

I don't think it's a short as all the fuses are intact I just don't keep power. In a sense the dome light or radio acted like a voltage drop test for this.



I have an alternate power source I used for the radio I utilized. I may just power the dome lamp if I can find it's power source that way I can put a toggle inline and be able to switch the dome off when I want to leave the doors open for whatever reason

Wagonman is absolutely correct here.

Once again, I don't personally care now krochus handles this, but properly done (removing the fuse in the fuse panel as I stated above) there is no feedback. And krochus said that he was going to fuse the supply wire which will take care of any shorts. Actually, the best way to wire every circuit in the xj would be with a separate fused wire from a source near the battery but this is, of course, not practical.