Installed New Wiring Harness-Need Help
Race Director
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From: Dayton, Ohio
JMO
Racer
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From: Mesa az
That #12 RED feeds the car, and starter switch, during starting. It then passes current back to the battery for charging when the engine starts. The current in this wire is "measured" by the ammeter, and depending on which direction it's going, to or from the battery, the meter indicates direction and value.
The ammeter circuit may have been damaged if it was still connected without the #12 in place. It is tied in parallel with the #12 wire.
The ammeter circuit may have been damaged if it was still connected without the #12 in place. It is tied in parallel with the #12 wire.
Race Director
Joined: May 2006
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From: Dayton, Ohio
That #12 RED feeds the car, and starter switch, during starting. It then passes current back to the battery for charging when the engine starts. The current in this wire is "measured" by the ammeter, and depending on which direction it's going, to or from the battery, the meter indicates direction and value.
The ammeter circuit may have been damaged if it was still connected without the #12 in place. It is tied in parallel with the #12 wire.
The ammeter circuit may have been damaged if it was still connected without the #12 in place. It is tied in parallel with the #12 wire.
Race Director
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From: Dayton, Ohio
EDIt-the question is will the starter engage with the #12 at the relay disconnected-I think the best way is to just disconnect it and try it.Just for Fun !!! I'll report back.
Last edited by ...Roger...; Jul 7, 2008 at 04:55 PM.
Thread Starter
Instructor
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From: Midlothian Ill.
there is power to the relay from the #12 red wire, disconnected it and still nothing. put meter at purple from coil and got power when key is turned on but nothing happins (bad coil) i dont no
Race Director
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From: Dayton, Ohio
Coil? meaning solenoid on starter?Look at the pic jim2527 posted and look at the 12 purple on the small S term on solenoid --that is where you need 12 volts when the key is in the START position
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Thread Starter
Instructor
Joined: May 2008
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From: Midlothian Ill.
what next (new solenoid) ?
Race Director
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From: Dayton, Ohio
It is possible to read 12 volts and not have enough amperage to kick the solenoid-is your battery up?
edit -gotta run to the store if you dont get it and someone else doesnt chime in I'l help you a litle later
Last edited by ...Roger...; Jul 7, 2008 at 08:21 PM.
Thread Starter
Instructor
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From: Midlothian Ill.
Yes it sounds that way unless your starter is not grounded.If you want recheck putting your black lead from your meter on the starter case and your red lead on the purple and see if you still get 12 volts.If you do I would say the solenoid is bad.
It is possible to read 12 volts and not have enough amperage to kick the solenoid-is your battery up?
It is possible to read 12 volts and not have enough amperage to kick the solenoid-is your battery up?
Casey
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OK Update ----Went out and on a 69 disconnected the 12 red at the horn relay.Then took a test light and checked and everthing in the car still has power including the alternator.Turned the ignition key to start and the solenoid engages.Mystery solved.The horn relay is being fed through the ammeter and the interior is fed the normal way through the horn relay.
Racer
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From: Mesa az
I just have to ask. Did you disconnect the #12 red coming from the starter or the #12 red going to the fan motor? They're tied to the same terminal.
Unless someone has added a wire, there is only one #2 black wire coming from the battery + to the starter. There is only one wire, the #12 RED leaving that post. The other end of that RED wire is connected at the horn relay. If either end of the RED wire is disconnected there cannot be any connection to the battery (unless some has added another wire.) As I mentioned earlier, the ammeter circuit will connect the starter to the horn relay if the RED wire is removed from the horn relay, but do NOT try to start the car, there's a very good chance you'll burnup the ammeter. It is not designed to handle any of the loads or the car.
And as one post indicated, measuring 12 volts at a terminal does not mean there is enough capacity there to handle any kind of load.
Unless someone has added a wire, there is only one #2 black wire coming from the battery + to the starter. There is only one wire, the #12 RED leaving that post. The other end of that RED wire is connected at the horn relay. If either end of the RED wire is disconnected there cannot be any connection to the battery (unless some has added another wire.) As I mentioned earlier, the ammeter circuit will connect the starter to the horn relay if the RED wire is removed from the horn relay, but do NOT try to start the car, there's a very good chance you'll burnup the ammeter. It is not designed to handle any of the loads or the car.
And as one post indicated, measuring 12 volts at a terminal does not mean there is enough capacity there to handle any kind of load.
Thread Starter
Instructor
Joined: May 2008
Posts: 206
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From: Midlothian Ill.
I just have to ask. Did you disconnect the #12 red coming from the starter or the #12 red going to the fan motor? They're tied to the same terminal.
Unless someone has added a wire, there is only one #2 black wire coming from the battery + to the starter. There is only one wire, the #12 RED leaving that post. The other end of that RED wire is connected at the horn relay. If either end of the RED wire is disconnected there cannot be any connection to the battery (unless some has added another wire.) As I mentioned earlier, the ammeter circuit will connect the starter to the horn relay if the RED wire is removed from the horn relay, but do NOT try to start the car, there's a very good chance you'll burnup the ammeter. It is not designed to handle any of the loads or the car.
And as one post indicated, measuring 12 volts at a terminal does not mean there is enough capacity there to handle any kind of load.
Unless someone has added a wire, there is only one #2 black wire coming from the battery + to the starter. There is only one wire, the #12 RED leaving that post. The other end of that RED wire is connected at the horn relay. If either end of the RED wire is disconnected there cannot be any connection to the battery (unless some has added another wire.) As I mentioned earlier, the ammeter circuit will connect the starter to the horn relay if the RED wire is removed from the horn relay, but do NOT try to start the car, there's a very good chance you'll burnup the ammeter. It is not designed to handle any of the loads or the car.
And as one post indicated, measuring 12 volts at a terminal does not mean there is enough capacity there to handle any kind of load.
Last edited by Casey Griffin; Jul 8, 2008 at 02:33 PM.
Race Director
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From: Dayton, Ohio
Race Director
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From: Dayton, Ohio
Team Owner
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From: Crossville TN
The ammeter circuit DOES NOT have any real power/current running through it. This is a gross misunderstanding of how the circuit works. The ammeter circuit measures the millivolts that are generated across a shunt resistance (specified length of power feed wire in the engine bay harness). That length of 'shunt' wire does have the vehicle's current running through it. You can have the ammeter connected and still not have any power coming to the interior.
Racer
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From: Mesa az
In engineering terms: The ammeter and the short portion of #12 wire are two circuits in parallel. Both have current, both have voltage, both have power. The distribution of that current is dependent on the relative resistance in either circuit, with the #12 having the smallest resistance and thus the larger share of the current. The current in the ammeter is not measuring "voltage", it's responding to its share of the current. The current in the #12 is generally +-0 to 40 amps. If the design/wires/meter are correct the current in the ammeter will probably be in the 0 to 10 or 20 milliamps (I've never measured the ammeter itself, but would initially assume this range, though it might be in the few 100 milliamps.) It is not a "voltmeter", it is a millamp meter. Its needle motion is determined by the current going thru it. The voltage across the two circuits is the same, so the power is, Power = Volts * Current. Since they both have the same Voltage, the #12 has the much larger power, the meter circuit the smaller.
