mikeXJ1020

Preface: For some time this truck has had some electrical gremlins. In year 2009+ all would work fine but driving down a bumpy road I would get the ‘no bus’ error on gauge cluster and all gauges would die. If I smacked the dashboard the problem would go away for a while. No other electrical problems occurred around this time.

Since 2009 the truck has had the dreaded cowl water leak and I have yet to repair it. Instead I removed the carpet, herculined the floor and added drain plugs (hind sight I should have fixed this damn leak a while ago). Also since about 2012ish the roof is leaking at the windshield due to pinch well rotting. A little water leaks down the pillar onto the fuse panel (recently confirmed water leaking onto fuse panel).

Due to the water leak and musty smell I have the rear windows open a few inches on the truck all the time, sure a little rain gets in but it dries out and prevents a greenhouse in my truck.


Problems: The problem I have been fighting with since ~ 2013 is that when I turn the headlights on OR the interior dome lights -> the gauges die, rear wiper turns on, blinkers stop working, and the locks don’t work properly. If key is on, when the dome lights are turned on they don't light up, when key is off the dome lights are dim (clearly leg of power is being drawn from). A few months ago I found that when I pressed the master lock switch to ‘lock’ the truck the horn would go off OR if I pressed the master unlock switch repeatedly to ‘unlock’ the truck all of a sudden every electrical problem would disappear for a little while (a few minutes or sometimes until the next time I drove the truck). Also, sometimes if I hold the master lock switch to ‘lock’ the truck the center console lights and shifter lights will light up.

A few months ago on a wet rainy night, my horn turned on by itself and I had to disconnect the horn. So clearly we are talking a water issue. I know there are water leaks but where is the problem exactly?. Also, even when the truck is dry inside the problem described above will still happen (it happens pretty much always now).

What I’ve done/checked:
- Year ago I replaced Headlight Switch and Blinker Switch -> problem was not fixed
- All fuses on the Junction Block are good.
- There is a small amount of corrosion on the C3 connector (both the plug and JB but very little).
- I have removed the Junction Box from vehicle, peeled back the rear to check for corrosion (see pic). It looks fine even under the multiple layers of metal sheets

The truck does have old alarm system in it that does not work nor do I have remote for it. I have never tampered and never had an problem before.

My Jeep is very close to becoming a trail only rig due to this problem but with summer coming up I want it on the road. Every time I turn the headlights on the Check Engine light stays on for many miles. I can’t get it inspected and inspection + registration is up.

I uploaded a few videos of the problem
Jeep Cherokee Electrical Problem - guages die, blinkers die, rear wiper turns on - https://www.youtube.com/watch?v=7UpT...ature=youtu.be
Jeep Cherokee Electrical Problem - Interior light causes no bus - https://www.youtube.com/watch?v=pjg6...ature=youtu.be
Jeep Cherokee Inspecting Connectors at JB - https://www.youtube.com/watch?v=UCrR...ature=youtu.be

I thought the Junction Block might be badly corroded, only a little bit near the C3 connector area - here are some pics

BlueRidgeMark

Here's a temporary fix for the windshield leak: Aluminum foil tape, the kind used for air conditioning sheet metal. No, not the classic silver duct tape. Actual aluminum tape. Cover the place where the rubber meets the rooftop. It works.

Sounds like classic ground problems. Start there. Find them all, clean them all. Take them apart, make nice shiny metal, and keep it that way with dielectric grease.

Then stop the leaks, and fix any corrosion you find where water has been. That fuse box needs to be pulled out and inspected behind. It's probably not pretty back there. CRC Contact Cleaner is your friend.


Not a small task given how much water has been in there, and how long this has been going on, but it will probably clear it all up.


Sorry, no magic bullets. Just hard work cleaning things up.

97grand4.0

Well not too familiar with the 2009 but I am an electrician and mechanic. You should have bought an older jeep. ok. First off dont get into the mindset that it is necessarily a water problem, its just another problem. Is there a multifunction switch? How about a fuse or distribution box under the hood where the fusable link is? Doesn't look like one you have pictured is the blame. Sounds to me what you are looking for is some green funk somewhere and the associated open connection. Another thing that occurs is a wire harness all taped up, aluminum wires will vaporize when wet, I know thats kind of general. A fsm may shed some light too. This does not sound like a ground problem to me, but more like a distribution problem of the B+.

mikeXJ1020

Will do. I do know that the Ground Stap/Radio Noise strap from the firewall to headbolt is broken, I have a replacement going in. The truck is grounded at the battery to fender-well otherwise.... But doesn't this problem seem more like crossed wires? No ground = nothing would work. My case, power is being yanked from the dash guages and sent to the rear wiper. Bizarre


See pics from original post, I removed the junction box/fuse box (the fuse box by passenger kick well) and inspected behind…looks very clean except for a little corrosion on one of the rails but shouldn’t cause shorting out.

Quote:

Originally Posted by 97grand4.0

Well not too familiar with the 2009 but I am an electrician and mechanic. You should have bought an older jeep. ok. First off dont get into the mindset that it is necessarily a water problem, its just another problem. Is there a multifunction switch? How about a fuse or distribution box under the hood where the fusable link is? Doesn't look like one you have pictured is the blame. Sounds to me what you are looking for is some green funk somewhere and the associated open connection. Another thing that occurs is a wire harness all taped up, aluminum wires will vaporize when wet, I know thats kind of general. A fsm may shed some light too. This does not sound like a ground problem to me, but more like a distribution problem of the B+.

The Truck is a 1999 XJ - I bought the truck in 2008 and have been having problems since 2009+. The fuse box/junction box looks clean and all of the connectors. The fuse box under the hood has yet to be inspected. Also, no blown fuses anywhere.

97grand4.0

The Truck is a 1999 XJ - I bought the truck in 2008 and have been having problems since 2009+. The fuse box/junction box looks clean and all of the connectors. The fuse box under the hood has yet to be inspected. Also, no blown fuses anywhere.[/QUOTE]

Oh, ok. Pull the rear lights and find the harness connector. Look for green funk between the parking lights and the rear wiper wires.

BlueRidgeMark

That's not the problem. That one is just to suppress radio noise generated by the injectors firing.

Nope. Yes, you have a ground at the fender, but each circuit has its own ground to the body. If those get funky, the current will search for another way back to the battery, sometimes, via other things that are not otherwise related. Hilarity ensues.



Agreed.

Quote:

Originally Posted by mikeXJ1020

The fuse box under the hood has yet to be inspected.

I'd check on that, too.




Is not truck. Is SUV.



This is good advice!

mikeXJ1020

Apparently, there is a shared ground under the instrument panel (I have yet to inspect mine) for many circuits and in my case it includes some of the circuits that are going wacky on my truck. I would suspect all circuits to not work if this ground was bad. Perhaps there are other grounds to check. Reference http://www.jeepforum.com/forum/f11/e...l#post12609884

So I removed both rear tail lights, removed the plastic panel for rear hatch and plastic panels for rear fender wells and found no green corrosion on any of the connectors.

As for the main problem I have narrowed it down a bit. If the headlight switch pulled to enable DRL or DRL + Headlights the problem happens (gauges die, no blinkers, rear wiper on, CEL) BUT if i turn the headlight switch to dim the interior lights all the way until the lights are off -> (lights for gauges, center console switches, door swtiches, etc.) the problem disappears (although the airbag light stays on).
Looking at the Haynes manual a 15A or 20A fuse off the JB (Junction Box) feeds the headlight switch, then off of the dimmer circuit it feeds the 5A fuse at JB which feeds all the interior lights.
Farfetched idea: I suspect that perhaps the wiper circuit is enabled from the dimmer-switch 5A circuit but somehow the wiper yanks all the power from the gauges?

I will keep looking searching...

97grand4.0

My google search tells me it's the crank sensor or connections to the dash cluster
http://www.faqs.org/qa/qa-12673.html

try unplugging the crank sensor see what happens

BlueRidgeMark

Get over the idea that bad ground = nothing works. That's false. Grounds are not binary, ON or OFF. They can be partial, and things can get really weird then. There is no ground point that you can afford to ignore.

97grand4.0

This is complicated by the fact you could have two problems at the same time here. First you had the No Bus error when driving down a bumpy road that was fixed if you smack the dash. Apparently you never resolved that, and it seems it is a known problem with the connections behind the dash.

Secondly you have this mystery lighting problem. My advice on that one is to go back and pull the headlight switch again, this time check for voltage on the supply lines by nicking the wire insulation or backprobing. Go ahead and turn on the lights to make it act up and then check to see if any voltages are dropping off behind the switch at the connector. Also pay close attention to the spade connections at the connector to the switch; you need a strong flashlight and maybe a magnifying glass. Look particularly for a double wire connection that may be bad, or any sign of corrosion, any sign of burnt insulation approaching the connectors. If the voltage drops out with the park lights on, start working your way back to the fuse block (where you could end up anyway). I highly recommend a schematic from a factory service manual to aid that process.

I found_after exhaustive troubleshooting with a schematic from the fsm,_ that the +12 was dropping out between the fuse block and the switch, turned out the supply wire to the headlight switch itself was burnt through about 10" back up from the switch, for no apparent reason. Verified with the schematic that I was reading it right and just spliced in another piece of wire. Headlights came back on and my lights have never worked better since.

The troubleshooting is even more so important with the with the XJ headlight switch because from what I understand they do not use a relay for the headlights to reduce the current to the switch as opposed to the ZJ. And for that matter, even though you say you replaced the switch a year ago, if water is getting onto it that could surely wreck it or the harness connector behind it. If they are pricey pull one from the yard and swap it in. (at the risk of firing the parts cannon vs troubleshooting). Hope that helps.

nujeepguy

"If those get funky, the current will search for another way back to the battery, sometimes, via other things that are not otherwise related. Hilarity ensues."

"They can be partial, and things can get really weird then."

you are making stuff up. grounds are no mystery and they dont think. if open the device just doesnt work.
if they are loose they may act resistive reducing current in that circuit only. they dont look around for a place to make trouble. dont complicate stuff by making up stuff. this ground business is probably causing more confusion than help.
the ground side is just like the plus side. an open kills the circuit.keep it simple.

BlueRidgeMark

I am an electrical engineer with decades of experience and you, Art, are a self-mis-taught person of low intelligence who doesn't know enough to know what he doesn't know, and doesn't know when it's time to shut up and learn something form those who actually know what they are talking about.

That's why you are still parked on the railroad tracks.

mikeXJ1020

Update: So to rule out one questionable item. I got my hands on a clean Junction Box, installed it and the problem still happens. Closed.

As we know, before I can really troubleshoot the problem I need to fix the water leaks. I thought the main water issue was the "behind the dash - cowl air intake -common leak" but this actually doesn't bring in too much water into the truck. The real issue is the windshield. I pulled the headliner down a bit and on the passenger side, the upper part of the windshield sill is rotted about 16" across. I took the garden hose and sprayed the bad area and its bad - I have water dripping directly onto the floor boards along with dripping down the plastic trim and all over the JB and wiring harness. For the past year or so the Jeep has only been trailered to the woods, I didn't know the problem was so bad.

So, instead of buying a new Jeep just yet (i'm close) a true repair is going to require some fab work (have a shop remove the shield, cut, weld, etc.). What I am going to do is silicone the heck out of the top of the shield as a last ditch effort to stop the water from coming in (for now). Until that is repaired, I am basically chasing my tail with the electrical issue. I will report back what I find after I stop the water leak (if I stop it).

Thanks for everyone's help up to this point.

jordan96xj

Whenever I hear about a headlamp switch, no bus, and general electrical weirdness in the same sentence, I think about the following video:

Pine Hollow Auto Diagnostics (filmed at South Main Auto) : Jeep From Hell

Anyone who thinks that a single loose/bad ground connection can not cause all sorts of non-binary weirdness should watch this video. 2 very knowledgeable and experienced troubleshooters, using quality tools, and testing techniques spend hours chasing down some very strange weirdness that stems from the headlight switch, but is presenting symptoms on the comms bus voltages.

In the end, it turns out to be a single loose dash mounting bolt in the lower passenger side that acts as a large ground connection for the dash to the chassis. Due to it being left loose after a prior dashboard removal/reinstall it caused all sorts of weirdness in the electrical systems behind the dash. Basically, other circuits that would normally depend on that nice big low resistance ground, were finding other circuits in an attempt to ground. One of which was the comms bus lines, which was causing no-bus and check engine lights, and of course a variety of bus related weirdness in the gauges.

Anyone interested in automotive electrical, I encourage you to watch it from beginning to end. It is quite the process, and has a really nice conclusion, and the guys keep their sense of humor throughout. Its especially funny to listen to them talk about how much they should charge, because they ended up getting way deeper into it then they ever expected.

BlueRidgeMark

Don't waste your time with the silicone. Many of us here have been there, done that. Wasted time.

Get some aluminum foil tape, the kind that is used on ductwork. NOT THE STANDARD GRAY DUCT TAPE! (That's useless.)

Yes, it will look funky. Yes, it will seal it quite well. I have used it on two Cherokees.