Ammeter grounded out.

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C

Chopper 7

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I'm hooking my electrical up after it being apart for years. Checking out some stuff to ground before I put the battery in the system and Ive made it as far from the positive battery lead to the ammeter. The downstream side of the ammeter is a good size black wire that appears to go a lot of places. Should it have continuity to ground? Thanks for any help.
 
Ok the very first thing we need to know is "what year make and model" are you working on, because I doubt it's a hemi powered Farmall

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Then if you don't have one, download a service manual

some here

http://www.forabodiesonly.com/mopar/showthread.php?p=1970088617

and some more here

http://www.mymopar.com/index.php?pid=31

Also at the above MyMopar site are non-factory but somewhat simplified diagrams. These are not always exact, but are sometimes easier to follow

Then go read the MAD electrical article:

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

especially because that article has a simplified basic diagram of the main power

Look at the MAD diagram (from the article):

amp-ga18.jpg


In the above diagram, follow along. The black wire from the ammeter has a FACTORY WELDED splice a few inches from the ammeter. This splits off and feeds "some stuff" depending on the year. Feeds the fuse box "how" buss, the headlights, and the input to the ignition switch at the very least.

Then it goes back out through the bulkhead connector to the ALTERNATOR

This is the very first thing I'd try----disconnect the alternator output wire (big black) and see if the short goes away

To troubleshoot this, disconnect the battery ground cable, and hook a test lamp from the battery NEG post to ground. When it stops lighting up, you have fixed the short. Don't forget to turn everything off, including the dome and other lights
 
tedsweet said:
that wire is the main power feed not a ground
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X2, the power goes through the amp gauge and on to power all the cabin devices.
Nothing along the path of the big black wire is a ground. (all positives)
 
If you are simply removing the black wire and testing it there you will have continuity to ground because you are reading the ground through the parking, dash, dome, etc. light filaments.
 
Shorthorse said:
If you are simply removing the black wire and testing it there you will have continuity to ground because you are reading the ground through the parking, dash, dome, etc. light filaments.
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Should not be if they are all shut off.
 
Snake said:
Can someone tell me why that black is + 1 would think it should be RED what gives.
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I would guess red for one side of the ammeter and black for the other as an assembly aid to get the ammeter connected in the right direction.
 
just a word of advice to Chopper7 : follow 67Dart273's instructions, step by step, and you'll solve your issues. The man is an asset to this board with all of his knowledge.

Believe me, I've been through electrical issues. LMAO!
 
Black wire was cheaper, they needed 2 colors so the assembly guy knew which side they went on, they wanted the red to connect to the battery so customers didn't get confused...JK ....Those are just answers I imagined when I asked myself why they did it.
 
Well remember that only in (parts of) the industry is black ever ground. In building AC circuits, black is NEVER "ground"
 
nm9stheham said:
If the OP has the car's door open, it'll read the low resistance of the dome light to ground. That one ALWAYS gets me.... LOL
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Yup. I always have to "step back" and look around and think, "Ok what did I forget?" These modern rigs with junk like automatic modules to control everything must be a nightmare to find
 
Snake said:
Can someone tell me why that black is + 1 would think it should be RED what gives.
Click to expand...
So the ammeter will function correctly?? If the leads are switched around, the gauge will read discharge when the battery is actually being charged.
 
67Dart273 said:
Yup. I always have to "step back" and look around and think, "Ok what did I forget?" These modern rigs with junk like automatic modules to control everything must be a nightmare to find
Click to expand...
Most don't even try to find, they just start replacing parts!
 
2 Darts said:
So the ammeter will function correctly?? If the leads are switched around, the gauge will read discharge when the battery is actually being charged.
Click to expand...

Yup. Could'a been any two colors, passion pink and chartreuse, LOL
 
If you don't have any lamps on (dome light, ...), you should measure very high resistance to gnd from either ammeter wire, if the battery is out. I would guess >10 Kohm. That would be the normal leakage thru the alternator's diodes. What are you measuring?
 
Great response from everyone I took 67Darts advice with the tester light put the ammeter wires together and started unplugging everything. When I unplugged a front parking light my tester turned off. I put everything back together and turned on the headlights for the first time in 8 years. A small but needed victory. Some good info on the MAD site about bypassing the ammeter and some other electrical upgrades. I was also thinking of adding a grounding pigtail to the instrument cluster when it goes back in I suppose could hook it up anywhere on the back of the cluster.
 
Yes, grounding the cluster is a good idea. Also, are you aware of repairs on the cluster connector? The pins have a habit of getting loose, and you must re-solder them. Mine was in such bad shape, I just soldered pigtails to the copper traces and ran them off to a pair of "Molex" style connectors

On some years, you must be careful repairing the connector, as it can short against the casting behind it. Check over your gauge mounting nuts (tight) replace the instrument voltage regulator if there's any question as to it's age, and make sure the IVR connections "work." I had to solder jumpers across on mine.

This is the IVR socket on mine. The spring contacts were not actually making contact with the traces.

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