Parasite draw?

[67stang]

So I have been going through my mustang and obviously have found some previous mistake and issues. So my next question is Parasite draw. I have point .10 amp of parasite draw. Seems high as i should have nothing on at all on this 1967 mustang. Is this normal?

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[msell66]

Regular bug spray should get rid of the parasites.

 

[Horseplay]

I suggest checking circuit by circuit to find the draw. As you say there is nothing in a stock set-up that would account for it so finding the culprit should not be that difficult

 

[Midlife]

Yup, too high. Should be 30 milliamps or less. Here's the way I provide all my customers to check for shorts (same as parasitic losses)

When ready to check out the harness, close all doors, turn off all lights, ignition key in the OFF position, accessories off, etc. Make sure both battery connectors are disconnected. Connect the positive battery cable to the starter solenoid. Leave the negative terminal disconnected from the battery. Then use a digital volt meter to measure the current draw across the battery. Place one probe of the DVM on the negative battery cable terminal, and the other probe on the negative battery post. Be sure that the DVM is set to amps, DC. If there are no shorts in the wiring connections, the reading should be on the order of 30 milliamps or less. Anything above 1 amp indicates some accessory is on; readings above 10 amps (may blow the fuse on the DVM) indicates a dead short.

If you have a short, disconnect all other wiring from the starter solenoid post where the battery connects and re-measure the current. If current drops, the source is the underdash wiring harness or the harness from the starter solenoid to the firewall. Reconnect the wiring to the starter post and then disconnect the underhood harness from the firewall and test again to isolate the source of the short.

If the short is not in the underhood or underdash harness, the problem lies in the alternator or voltage regulator. Disconnect each of these in turn to isolate the source.

If the short or high current comes from the underdash region, keep the battery negative side disconnected and remove one fuse at a time. Measure the current as above. If you now see low current, there is either a short or an item on that particular fuse circuit is on. Turn off that item and continue checking.

Eventually, you’ll have low current readings with all fuses installed and all wiring connected. This series of tests checks all of the battery directly powered systems. To check the Accessory systems, now repeat all of the tests above with the ignition key in the ACC position. The current with the key in the ACC position may be up to 1 amp or so. When all of the tests are done and no anomalous current is noted, at that time, and only at that time, is it safe to connect the negative battery cable to the battery.

 

[67stang]

Yup, too high. Should be 30 milliamps or less. Here's the way I provide all my customers to check for shorts (same as parasitic losses)

When ready to check out the harness, close all doors, turn off all lights, ignition key in the OFF position, accessories off, etc. Make sure both battery connectors are disconnected. Connect the positive battery cable to the starter solenoid. Leave the negative terminal disconnected from the battery. Then use a digital volt meter to measure the current draw across the battery. Place one probe of the DVM on the negative battery cable terminal, and the other probe on the negative battery post. Be sure that the DVM is set to amps, DC. If there are no shorts in the wiring connections, the reading should be on the order of 30 milliamps or less. Anything above 1 amp indicates some accessory is on; readings above 10 amps (may blow the fuse on the DVM) indicates a dead short.

If you have a short, disconnect all other wiring from the starter solenoid post where the battery connects and re-measure the current. If current drops, the source is the underdash wiring harness or the harness from the starter solenoid to the firewall. Reconnect the wiring to the starter post and then disconnect the underhood harness from the firewall and test again to isolate the source of the short.

If the short is not in the underhood or underdash harness, the problem lies in the alternator or voltage regulator. Disconnect each of these in turn to isolate the source.

If the short or high current comes from the underdash region, keep the battery negative side disconnected and remove one fuse at a time. Measure the current as above. If you now see low current, there is either a short or an item on that particular fuse circuit is on. Turn off that item and continue checking.

Eventually, you’ll have low current readings with all fuses installed and all wiring connected. This series of tests checks all of the battery directly powered systems. To check the Accessory systems, now repeat all of the tests above with the ignition key in the ACC position. The current with the key in the ACC position may be up to 1 amp or so. When all of the tests are done and no anomalous current is noted, at that time, and only at that time, is it safe to connect the negative battery cable to the battery.

Holy smokes I found the wire!! But I don't know where it goes. Lol. I think it goes through the driverside firewall near the brake booster. Any ideas or should I disconnect the wire and turn on the car and see what doesn't work?

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[Midlife]

I believe that is one of the ammeter lines, and does belong there. However, are you tapping into any of the ammeter lines along the way? What does your ammeter read when everything is off and compared to when the line is removed from the starter solenoid?

 

[67stang]

I believe that is one of the ammeter lines, and does belong there. However, are you tapping into any of the ammeter lines along the way? What does your ammeter read when everything is off and compared to when the line is removed from the starter solenoid?

Omg. My am meter has never worked!! This is probably why. Dang you guys are pretty damn smart. So it should be okay to try and start and drive the car with it disconnected right?




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[Midlife]

Please protect that ring connector from touching any grounds; it may be hot (unfused) working through the ammeter itself.

And as far as me being "pretty damn smart", you need to get a 1000 second opinions from the wifey; she'll set you straight.

 

[67stang]

Please protect that ring connector from touching any grounds; it may be hot (unfused) working through the ammeter itself.

And as far as me being "pretty damn smart", you need to get a 1000 second opinions from the wifey; she'll set you straight.

Okay I will run disconnect the probable ammeter wire at the solenoid and protect it. The I will start my car and I'm pretty confident it will run just fine without it.

Going forward I was thinking instead of spending countless hours searching for the short. I would just just the wire disconnect wire at the ammeter gauge. Then run a new wire. I assume the wire goes straight from the started solenoid to the ammeter? No fuses or fuse boxes?




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[Midlife]

Correct. There are two plugs in-between: headlight to underdash, underdash to dash cluster.

 

[67stang]

Correct. There are two plugs in-between: headlight to underdash, underdash to dash cluster.

I ran the car for a few minutes having the subject pink cable disconnected from the solenoid but the tach turned off. Hmm any ideas were I should look?


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[Midlife]

Oh...let's see now. If you have a factory tach, then you don't have an ammeter. If you have an ammeter, you said you did, then you have an aftermarket tach. An aftermarket tach needs power, signal, and ground. What do you think about that line being tach power? If it is, it shouldn't be connected to battery power (that's your parasitic drain), but to a RUN-only line. Looking very closely at your picture, there are still 3 lines attached to the battery solenoid: battery, what looks to be a red wire with a blue crimp-on connector (most interior), and what I believe is the alternator line.

If the wire you removed is truly an ammeter line, it should read 12V if your ammeter still works. Can you follow the line that you removed to see where in the harness it goes? Does it go to the headlight harness that goes under the passenger headlight and radiator? Is it part of the factory wrapped harness, or outside?

Dammit, man, you're not telling us everything about your car.

 

[67stang]

Oh...let's see now. If you have a factory tach, then you don't have an ammeter. If you have an ammeter, you said you did, then you have an aftermarket tach. An aftermarket tach needs power, signal, and ground. What do you think about that line being tach power? If it is, it shouldn't be connected to battery power (that's your parasitic drain), but to a RUN-only line. Looking very closely at your picture, there are still 3 lines attached to the battery solenoid: battery, what looks to be a red wire with a blue crimp-on connector (most interior), and what I believe is the alternator line.

If the wire you removed is truly an ammeter line, it should read 12V if your ammeter still works. Can you follow the line that you removed to see where in the harness it goes? Does it go to the headlight harness that goes under the passenger headlight and radiator? Is it part of the factory wrapped harness, or outside?

Dammit, man, you're not telling us everything about your car.

Lol. Sorry man. Aftermarket tach and a alternates gauge which never worked (I don't know why).


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[67stang]

Lol. Sorry man. Aftermarket tach and a alternates gauge which never worked (I don't know why).


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So it has to be related to a power source to the tach and alternates guage. Because when I unplug it. I have almost no parasite draw. And when I run the car now the tach does not work.


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[67stang]

So it has to be related to a power source to the tach and alternates guage. Because when I unplug it. I have almost no parasite draw. And when I run the car now the tach does not work.


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I'm obviously no nothing about electrical but the tach is connected to the alternator/oil pressure guage??


Not sure what to do now. Even though I have narrowed it down to that pink wire I still stumped. Disconnecting the wire everything will run just perfect except the aftermarket tach and the the alternator gauge, funny the oil pressure gauge still works.


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[67stang]

I'm obviously no nothing about electrical but the tach is connected to the alternator/oil pressure guage??


Not sure what to do now. Even though I have narrowed it down to that pink wire I still stumped. Disconnecting the wire everything will run just perfect except the aftermarket tach and the the alternator gauge, funny the oil pressure gauge still works.


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Why is that white wire connected from the alternator gauge to the tach?


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[Midlife]

What I see is that the white wire taps into the dash lamp. I see another tap at the far right, but can't make out what's connected to it. If it is the solid red wire that goes to the ammeter, then that's your problem. You need to tap into the red/yellow wire that goes to the brake light, as the red/yellow wire is RUN-only.

 

[67stang]

What I see is that the white wire taps into the dash lamp. I see another tap at the far right, but can't make out what's connected to it. If it is the solid red wire that goes to the ammeter, then that's your problem. You need to tap into the red/yellow wire that goes to the brake light, as the red/yellow wire is RUN-only.

Sorry I'm a little confused. Is the subject problem wire that I circled in red. Should I disconnect that? Then use that red and yellow strip wire with a purple arrow pointed to it?








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[Horseplay]

I don't know that years cluster well so hard to make everything out but would bet anything the white wire is simply power for gauge lights being jumped to the tach. Turn the headlights on and I bet the tach lights up (as will all the gauges) even with that red wire disconnected.

I think Mid has your real issue narrowed down and solved. Connect the red tach wire to a keyed source and you're good to go.

 

[Midlife]

Disconnect your dash cluster and find out what the red wire from the tach is tapped into. If it is the red wire from the dash cluster, remove it from that and tap into the red/yellow wire you have the arrow pointing to. Then leave the dash cluster red wire attached and re-attach the red wire with the ring connector to the starter solenoid. Check your current draw (parasitic). You should be good to go.