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TheMiddleMan 11-19-2011 10:15 PM

Electrical ground points
 
Hey all,

I have been trying to fix a lighting problem with no luck for a while now. While I have been working on this a question popped into my head that I thought I'd throw out there...

How many ground points are there within a Cherokee's electrical system (Chassis and otherwise)?

Haynes is great for base knowledge, but not always great at problem solving. It's like they expect me to do the work :)

Anyway, I thought this might be a way to get to know the system better and possibly help solve my lighting issue at the same time.

:cheers2:

Reptile 11-19-2011 11:39 PM

There is a ton. The main ones are the two ground points from the engine, and the negative of the battery. For the rest, every single light can possibly have individuals or combined ground points. As long as they're connected to the frame, there is your ground. If you need one, you can drill your own with a self tapping screw, as long as you don't damage anything hidding where you drill. What's the problem you're trying to resolve?

TheMiddleMan 11-20-2011 12:12 AM

Quote:

Originally Posted by Reptile (Post 12535045)
There is a ton. The main ones are the two ground points from the engine, and the negative of the battery. For the rest, every single light can possibly have individuals or combined ground points. As long as they're connected to the frame, there is your ground. If you need one, you can drill your own with a self tapping screw, as long as you don't damage anything hidding where you drill. What's the problem you're trying to resolve?

Thanks for the reply Reptile;

I'm trying to get a grasp on the grounds ahead of time.I know something will go wrong and I want to be ready. I appreciate the help.

My right side dash indicator is stuck on when I turn my lights on (headlights and running lights). When I put on my right blinker, go out and check it, it is very very dim. But there is minimal power getting to it. Basically it looks like I'm making a left turn all the time because of my dead right side. Changed bulbs, checked fuse, housing is all good and socket wiring seems to be in tact. I'm lost on this one.

Thanks!

Reptile 11-20-2011 12:48 AM

Quote:

Originally Posted by TheMiddleMan (Post 12535114)
Thanks for the reply Reptile;

I'm trying to get a grasp on the grounds ahead of time.I know something will go wrong and I want to be ready. I appreciate the help.

My right side dash indicator is stuck on when I turn my lights on (headlights and running lights). When I put on my right blinker, go out and check it, it is very very dim. But there is minimal power getting to it. Basically it looks like I'm making a left turn all the time because of my dead right side. Changed bulbs, checked fuse, housing is all good and socket wiring seems to be in tact. I'm lost on this one.

Thanks!

No problem. You're going to need a voltmeter (preferrably a digital one). Remove the bulb. Find out what voltage you're getting at the bulb when you turn on the blinker (from the hot prong).

Now, the way you go about this is plugging the negative terminal of the voltmeter on a KNOWN ground. Because you don't know for sure the ground prong of the bulb is good, you need to find a ground that you know works (such as screws anchored in the frame, etc). A known ground is a point of contact with the frame where you get a steady 12V reading between the positive of the battery (or any hot connector) and that point of contact.

You should get the full 12V or so at the bulb (on and off since it's blinking). If you don't, you have a problem on the hot side. You're gonna need to work your way through the circuit (wire, switch, fuse box, etc) and find out where it is compromised.

cruiser54 11-20-2011 05:49 AM

I've got the factory wiring manual with a Ground Distribution page in it.

There are 2 points on the left inner fender.

There is the engine dipstick tube stud. SUPER IMPORTANT!!

There is the ground to the lower diagonal dash brace to the left of the steering column.

There is one in behind the trim panel where the spare tire mounts.

The one on the instrument panel brace grounds a ton of things. Probably too many things as a matter of fact, given it's poor mounting point on the brace with a self tapping screw. I remove the screw that it's held on with, extend the wire, using the same gauge or bigger, and terminate it to the stud near the fusebox.

There are also grounds from the engine to chassis, notably the poor one from the back of the head to the firewall but that wouldn't affect your dash lights. Not that the engine to chassis grounding shouldn't be addressed. I'm working on a write-up for that in the near future.

Reptile 11-20-2011 11:57 AM

Quote:

Originally Posted by cruiser54 (Post 12535370)
I've got the factory wiring manual with a Ground Distribution page in it.

There are 2 points on the left inner fender.

There is the engine dipstick tube stud. SUPER IMPORTANT!!

There is the ground to the lower dash brace to the left of the steering column.

There is one in behind the trim panel where the spare tire mounts.

The one on the instrument panel brace grounds a ton of things. Probably too many things as a matter of fact, given it's poor moounting point on the brace with a self tapping screw. I remove the screw that it's held on with, extend the wire and terminate it to the stud near the fusebox.

There are also grounds from the engine to chassis, notably the poor one from the back of the head to the firewall but that wouldn't affect your dash lights. Not that the engine to chassis grounding shouldn't be addressed. I'm working on a write-up for that in the near future.

Wow. What a gold mine of info. Thanks Cruiser.

cruiser54 11-20-2011 12:31 PM

Just improve the ground wire for the instrument panel like I described above and see if your voltmeter reads higher :).

TheMiddleMan 11-20-2011 02:50 PM

Very cool, thanks Cruiser.

Thanks to the both of you. Works out well because I get Voltmeter's at cost through my work, so I think I know what my Monday purchase is going to be.

Great list too Cruiser, will be a big help down the road I'm sure.

Here goes nothing!

cruiser54 11-21-2011 05:54 PM

I added some things to my original post. The ground wire for the instrument panel is located on a DIAGONAL brace under the driver's side dash.

Always use the same gauge wire or a size larger when extending the ground to reach the stud in the kick panel near the fusebox.

TheMiddleMan 11-21-2011 09:08 PM

Thanks guys, I definitely got the expertise I needed.

This is a bit of an ironic question seeing that I work in an electrical wholesaler, but when replacing the block-firewall ground strip, would you know what guage wire I can replace it with? Right now it is the stock braided wire and is starting to show its age, I have heard you can go with a #2 or #4 wire as a replacement. I know going bigger is ok, but obviously I don't want to risk going smaller.

Thanks for the help guys, many a headache saved :thumbsup:

Reptile 11-21-2011 09:34 PM

Quote:

Originally Posted by TheMiddleMan (Post 12545794)
Thanks guys, I definitely got the expertise I needed.

This is a bit of an ironic question seeing that I work in an electrical wholesaler, but when replacing the block-firewall ground strip, would you know what guage wire I can replace it with? Right now it is the stock braided wire and is starting to show its age, I have heard you can go with a #2 or #4 wire as a replacement. I know going bigger is ok, but obviously I don't want to risk going smaller.

Thanks for the help guys, many a headache saved :thumbsup:

There is a part for that, altough 4 AWG wire should work fine, just make sure the insulation doesn't touch the engine...

O'Reilly part #CA756

TheMiddleMan 11-21-2011 10:19 PM

Quote:

Originally Posted by Reptile (Post 12545980)
There is a part for that, altough 4 AWG wire should work fine, just make sure the insulation doesn't touch the engine...

O'Reilly part #CA756



Thank you!

Reptile 11-21-2011 11:23 PM

No problem.

cruiser54 11-22-2011 05:35 AM

#4 will be fine and don't bother putting it back to the head bolt/stud. Just run it to the intake manifold to a heat shield bolt. Be absolutely sure to scrape the paint off the firewall at the mounting point.

Carl48 11-22-2011 05:03 PM

Not sure about the 88, but the early 90s XJ have a black rectangular front lighting harness connector behind the left headlamp under the airbox that is prone to corrosion...check it out. Also, make sure all the front and side lamp sockets are absolutely clean and dry. Make sure the replacement lamps you installed are the EXACT replacements as specified in the owners manual. Trouble in any of these areas can cause the symptoms you describe. Note: this is not to say that you don't have a ground problem...check them out also as you have been advised. Good luck with your troubleshooting. :)


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