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Where does the black ammeter wire connect to?

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Old 02-12-2018, 05:28 PM   #1
GKO777
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Default Where does the black ammeter wire connect to?

Hi,

I replaced my ammeter with a working unit (tested with a 9v battery), but it's not working because I get 12V at the B/W wire, but nothing at the black wire.

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I think the B/W wire connects to the horn relay through the orange fusible link, but I'm not sure where the black wire connects to?

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Any thoughts where I should start looking?

Thanks!
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Old 02-12-2018, 05:30 PM   #2
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Ah yes, it's a 1972 no AC car...
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Old 02-12-2018, 06:17 PM   #3
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Default horn relay

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Originally Posted by GKO777 View Post
Hi,

I replaced my ammeter with a working unit (tested with a 9v battery), but it's not working because I get 12V at the B/W wire, but nothing at the black wire.

Attachment 48254241

I think the B/W wire connects to the horn relay through the orange fusible link, but I'm not sure where the black wire connects to?

Attachment 48254242

Any thoughts where I should start looking?

y
Thanks!
They both go to the horn relay. The black wire changes to red and goes to horn relay and the bl/wh changes to white and thru fusible link. They are both on 12+ at horn rela
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Old 02-12-2018, 07:39 PM   #4
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This may help...
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Old 02-12-2018, 08:53 PM   #5
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Looks like the BLACK goes to the starter and the B/W goes to the Horn relay.

https://docs.google.com/viewer?a=v&p...GE5N2EzZGI2Mjc
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Old 02-12-2018, 11:13 PM   #6
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a wiring diagram for your car is one of the most valuable tools to have.... you will use use it again, and again, and again.....
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Old 02-13-2018, 07:56 AM   #7
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Quote:
Originally Posted by joewill View Post
a wiring diagram for your car is one of the most valuable tools to have.... you will use use it again, and again, and again.....
You are right, and I do have them, but I'm sometimes lost at the electrical bulkhead connector at the firewall. In the schematics they don't always match 'the other side'. Don't understand, but that's just me probably...

Having a picture (like how the black wire for the ammeter is connected to the red wire going to the starter) helps a lot, it's not always clear how that's done by looking at schematics...
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Old 02-13-2018, 10:09 AM   #8
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Old 02-13-2018, 04:12 PM   #9
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Default found it!

Today I opened up the wiring harness and first found the black wire, with a blue female connector attached. Opened the harness some more and found the red wire going to the starter that clearly was fused together with the yellow connector you see.

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Thanks for all your help so far!

Now I would ideally find a pigtail that is cut from an original harness, with the 2 red wires, the black wire and the fusible link in between. That would be the easiest to install, given the difference in wire sizes... If anyone has this and wants to sell, I'm interested!

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Old 02-13-2018, 05:36 PM   #10
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Check on the forum under parts. Should be lots around. I bough one off a member. You can make you own as well. A fusible link has the wire 4 wire sizes smaller so if the red is a #10 then you put in a #14 wire. Too much current will burn the smaller wire quicker than larger.
Looks way better with a original though. If you find one use heat shrink and solder the wires together to repair to eliminate voltage drops as it is your ammeter circuit. Congrats on finding your problem
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Old 02-13-2018, 11:17 PM   #11
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Default Does this help?

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Originally Posted by GKO777 View Post
I'm sometimes lost at the electrical bulkhead connector at the firewall. In the schematics they don't always match 'the other side'.
Put both your hands in front of you with the palms up.
Your thumbs now face away from each other.
Now bring your hands together as if to pray.
Now all the fingers match.

The bulkhead connectors show left and right if you bring them together they match.

Let's say you follow a wire to the LEFT top dot, the wire exits the other half at the top RIGHT.
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Old 02-14-2018, 08:11 AM   #12
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Quote:
Originally Posted by Peterbuilt View Post
Put both your hands in front of you with the palms up.
Your thumbs now face away from each other.
Now bring your hands together as if to pray.
Now all the fingers match.

The bulkhead connectors show left and right if you bring them together they match.

Let's say you follow a wire to the LEFT top dot, the wire exits the other half at the top RIGHT.
That helps a lot, thanks! I always placed them on top of each other and couldn't figure it out. Basuc stuff like that is never explained in a manual, so thanks for explaining it to me!
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Old 02-14-2018, 08:23 AM   #13
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The ammeter leads are both connected to the same power wire in the harness. But, they are connected at a fixed distance apart (around 12" or so). That length of wire between them acts as a 'current shunt' and produces a voltage drop which is proportional to the current flowing in that wire. The small voltage drop on that length of wire is sent to the ammeter which is scaled to read "AMPS".

Although that sounds complicated, the wiring is very simple: two ammeter leads run to one [main] power wire and attached at a fixed distance apart.

You cannot run those ammeter leads to ANY location on that wire or at a terminal connector and get the ammeter to read correctly. They must tie into that power lead at specific locations for the ammeter to be calibrated properly.

Last edited by 7T1vette; 02-14-2018 at 08:23 AM.
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Old 02-14-2018, 08:33 AM   #14
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maybe a new wiring harness is needed, to eliminate your problems??
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Old 02-14-2018, 08:44 AM   #15
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Quote:
Originally Posted by 7T1vette View Post
The ammeter leads are both connected to the same power wire in the harness. But, they are connected at a fixed distance apart (around 12" or so). That length of wire between them acts as a 'current shunt' and produces a voltage drop which is proportional to the current flowing in that wire. The small voltage drop on that length of wire is sent to the ammeter which is scaled to read "AMPS".

Although that sounds complicated, the wiring is very simple: two ammeter leads run to one [main] power wire and attached at a fixed distance apart.

You cannot run those ammeter leads to ANY location on that wire or at a terminal connector and get the ammeter to read correctly. They must tie into that power lead at specific locations for the ammeter to be calibrated properly.
Ok thanks for that. I suppose the yellow connector was placed instead of the original connection with the fusible link to the ammeter wire, so if I reinstall the fusible link in that location the ammeter will be calibrated properly...
Now just see if I can buy the original pigtail from someone with the fusible link still in place...
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Old 02-14-2018, 10:36 AM   #16
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You are right that is the correct location for the fusible link just to the passenger side of the wiper motor in harness
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Old 02-15-2018, 02:25 PM   #17
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One last question: the brown connector seems to fit both ways on the ammeter. In the first picture you can see how it is connected now (B/W wire to the bottom of the cluster, Black to the top), but I saw another picture on this forum where the the connector seemed fitted the other way around.
I have to close the dash up again before I can test (I don't have the fusible link yet), so I want to have it connected the right way...
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Old 02-15-2018, 02:37 PM   #18
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Originally Posted by GKO777 View Post
One last question: the brown connector seems to fit both ways on the ammeter. In the first picture you can see how it is connected now (B/W wire to the bottom of the cluster, Black to the top), but I saw another picture on this forum where the the connector seemed fitted the other way around.
I have to close the dash up again before I can test (I don't have the fusible link yet), so I want to have it connected the right way...

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Old 02-15-2018, 03:09 PM   #19
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Ok, very clear, thanks!
So I had the connector connected the wrong way around. Just switched it...
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Old 02-15-2018, 06:17 PM   #20
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there should be a couple of dimples on the spade terminals, these go on the open side of the plastic connector, to fit on easily, that is why they make it that way.
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