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  #1  
Old October 30th, 2015, 11:08 AM
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Andy
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Electrical Short

Finally get the beast to pass MOT and on day 3 this happens...









I'm driving home last night and notice the lights flickering strangely. As I start to slow and as I depress the brakes the voltage meter starts to plummet towards 0. Eventually the lights go out and even stranger the temp gauge peaks. I pull off the motorway, pull over, the voltage meter goes back to the charge line, the headlights come back on, I check the temp with my IR gun, 180 degrees F, as I continue to drive home every time I hit the brakes the voltage drops significantly. Thoughts? Earth ground? Alternator? I just replaced the alternator last year. Other connections??
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  #2  
Old October 30th, 2015, 11:22 AM
javelinadave
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Andy,
If it happens only when you apply the brakes there has to be a short somewhere in the brake system wiring. I would look for a chaffing wire alone the frame or where it passes thru the body out to the fixture. At the very least pull out the fixtures away from the body and step on the brake pedal and see if that isolates it.
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  #3  
Old October 30th, 2015, 11:28 AM
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Robert Davis
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Check the brown wire circuits at the starter.
Sounds like when the brakes are applied it causes the connection to break... loose nut perhaps.

The brake light is green circuit fused, so a short there would just blow the fuse.
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  #4  
Old October 30th, 2015, 12:14 PM
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Ok,
So I just ditched work for the last 10 minutes and trouble shot again. The biggest drop seems to be when I apply more than one item combined with headlights on. With the headlights on only the gauge goes from the charge line to the 12 o clock position. Anything else combine with the headlights, especially the brakes takes below the 12 o clock position. On my next break I'm gonna check with the voltage meter and check the grounds.

------ Follow up post added October 30th, 2015 10:14 AM ------

Quote:
Originally Posted by rdavisinva View Post
Check the brown wire circuits at the starter.
Sounds like when the brakes are applied it causes the connection to break... loose nut perhaps.

The brake light is green circuit fused, so a short there would just blow the fuse.

and I'll check this as well...
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  #5  
Old October 30th, 2015, 12:48 PM
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Robert Davis
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Yes the brown circuit connects with the (+) battery cable at the starter.
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Uncle "Richard" Douglas has a Land Rover with big wheels that never gets stuck... until he breaks something so it won't go. Uncle Douglas always breaks something. - Anna Crowther at the Conclave 2012 (AKA Carburetor Neck)

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  #6  
Old October 30th, 2015, 01:08 PM
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I think I just found the problem



Seriously, this sounds like a grounding issue for sure. The voltage going to the ungrounded circuits tries to find a way back through other connections. Check all the grounds in your battery box, also check the rear lights are grounded and that the ground pigtails on the dash are all secure. There should also be at least on main grounding point behind the dash and inside the center dash fuse panel on the metal frame that holds the fuse blocks.

And, I hate to tell you this but the repair shown in the attached photo is a major fucking bodge, IDK if those are fuel lines or wiring or both but in no uncertain terms should they pass between two body panels like that. They should run along underneath the body and on top of the frame or on the indie of the frame. Whoever did the work apparently is either lazy as fuck or doesn't know landies. Assuming they left out a grounding cable or something in some other area of the vehicle.
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  #7  
Old October 30th, 2015, 01:08 PM
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Was there any chassis welding to get through the MOT? Did the harness get pulled out to do it?
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  #8  
Old October 30th, 2015, 01:35 PM
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I'm sure Ren is right.

I had a similar issue, depress brake pedal and engine would start to die.

I had a friend help and we found that my main wire harness going to the back of the vehicle, and more specifically the brake lights, lost the ground connection. As soon as we connected a ground test wire into the main harness ground circuit, everything worked fine.

He had to split the harness in a couple spots to test for the ground.

Good luck

Steve
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  #9  
Old October 30th, 2015, 02:32 PM
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Quote:
Originally Posted by Ren Ching View Post
I think I just found the problem



Seriously, this sounds like a grounding issue for sure. The voltage going to the ungrounded circuits tries to find a way back through other connections. Check all the grounds in your battery box, also check the rear lights are grounded and that the ground pigtails on the dash are all secure. There should also be at least on main grounding point behind the dash and inside the center dash fuse panel on the metal frame that holds the fuse blocks.

And, I hate to tell you this but the repair shown in the attached photo is a major fucking bodge, IDK if those are fuel lines or wiring or both but in no uncertain terms should they pass between two body panels like that. They should run along underneath the body and on top of the frame or on the indie of the frame. Whoever did the work apparently is either lazy as fuck or doesn't know landies. Assuming they left out a grounding cable or something in some other area of the vehicle.

Ok, copy all, will check all grounds tomorrow. As far as the botched job, I thought there was a specific cutout in the middle crossmember for these wires/fuel lines to pass through. It seems that way from the before and after pic. At any rate I will check this as well while I'm fumbling around in there.
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  #10  
Old October 30th, 2015, 02:33 PM
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Quote:
Originally Posted by broadstone View Post
Was there any chassis welding to get through the MOT? Did the harness get pulled out to do it?
Yes, he welded in a new middle and rear cross member. I am pretty sure that there is a harness in or near the rear cross member correct?
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  #11  
Old October 30th, 2015, 02:42 PM
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Quote:
Originally Posted by atpick View Post
Yes, he welded in a new middle and rear cross member. I am pretty sure that there is a harness in or near the rear cross member correct?
Yup, the brake light wiring goes along the frame to the left rear of the tub (at least it does on a 90) then across the rear crossmember to the right rear of the tub.
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  #12  
Old October 30th, 2015, 02:43 PM
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Quote:
Originally Posted by javelinadave View Post
Yup, the brake light wiring goes along the frame to the left rear of the tub (at least it does on a 90) then across the rear crossmember to the right rear of the tub.

Ok cool, as this is the only thing that has changed in the last year, I think I will start investigating here.
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  #13  
Old October 30th, 2015, 03:28 PM
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Quote:
Originally Posted by atpick View Post
Yes, he welded in a new middle and rear cross member. I am pretty sure that there is a harness in or near the rear cross member correct?
If the harness was not removed from the chassis (or at least pulled back 3-4 feet from the area welded) there is a chance wires were damaged inside the chassis when replacing the rear crossmember. Damage could be from heat, sparks, or the cutting to remove the existing crossmember, perhaps even a small fire if you have waxoyl inside the chassis.

If it is not obvious where the fault is in the exposed wiring such as brake lights then it might mean pulling the harness out to inspect it. It is not hard to do, I usually run 4 long lengths of mig wire together, taped together every 12 inches to use as a snake. I tie the wire to the harness with a bunch of clove hitches and tape it off nice and streamlined and pull it through along with the harness for easy retrieval.
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  #14  
Old November 2nd, 2015, 02:48 PM
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So I think I've narrowed it to the alternator. The wiring harness near the new crossmember checked out fine. All grounds seemed to be working properly. The only thing I could find was when a load was but on the battery with the alternate charging, the voltage across the battery was around 12.5. Drove down to the local shop today and left it there for the day and that was all he could find as well. Looks like a new alternator in my future.
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  #15  
Old November 2nd, 2015, 08:46 PM
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Some similarities to what I'm dealing with on my truck, just rewired the main ground and leads to the starter from my battery, rebuilt my alternator and am still getting a random issue where the truck stops charging. I wish I had something as consistent as your issue. I am chiming in to add that my fuel lines passed through that mid cross member that Ren Ching pointed out on my truck when I replaced mine. The notch there is for just that as far as I could tell, mine was like that from the factory. The harness is in the frame there...
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  #16  
Old November 3rd, 2015, 06:05 AM
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You may have a diode out on the alternator or you could still have a bad earth.
try a jump lead from the battery -ve to a clean point on the chassis then try to the engine.
have a good look at the earth straps from engine/gearbox to frame and the battery to frame connections.

Regards
Gren
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  #17  
Old November 3rd, 2015, 12:58 PM
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Ok, so the new alternator is in and now it reads 14+ amps after start. So the alternator is now charging the battery. However, when I apply a load (lights, heater, etc) the gauge still drops into the red. My mechanic informed me that the gauge is an amperage gauge vice a voltage gauge (most of you probably knew that but I didn't). Sooooo, perhaps the battery is shot or do you guys still think an earth problem. The voltage read 11.8 across the battery today which is a bit low.
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  #18  
Old November 10th, 2015, 03:05 PM
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Update. Ok, alternator has been changed and now the battery is being charged after the engine is started. The battery light now works as well as the wires that connect to the alternator were a bit of a mess. So two for 3. There still appears to be a grounding issue somewhere. When no load is applied, the gauge goes to the charge line. If I apply headlights, it will go to the middle line. Anything past that, wipers, blinkers, etc it will go below the middle line, but no longer in the red. Another interesting gremlin is that the temp gauge also increasing when the headlights are turned on....even if the engine is off. I tested the temp with my ir gun and its steady @ 180 F or less no matter what the temp gauge says in the truck. I attached pictures for reference.....these are before the new alternator was installed. The only difference from the pictures is that it will no longer go into the red when multiple loads are applied and it will go to the charge line when no loads are applied and the temp gauge decreases to almost normal. Guess I will go back to chasing grounds. I suspect something in the fuse box area as if I happen to bump it with my knee it can cause me to lose my gauges completely....bump it again and everything comes back.....electrical gremlins....
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  #19  
Old November 13th, 2015, 03:27 PM
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Man can't catch a break, anybody know what the strange light in the lower right hand corner means....it started coming on today as the voltage dropped.....couldn't get a picture in the truck so I grabbed a copy off the web....
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  #20  
Old November 13th, 2015, 03:29 PM
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Which one? There is no symbol in the lower right.
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