Isolating parasitic draw
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Location: South Central, PA Near the MD Border
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My CAN bus bike has 3 fuses, the main fuse, 40A, A 10Amp fuse for most of the components and the last one 15Amp for the tender charging lead. So in reality my bike only has one fuse. Everything else on the bike is reliant on the BCM to control current flow and protect itself from over current situations which is powered direct after the 40Amp main fuse.
Wiring diagram here:- 94000402pdf_en_us - 2017 Wiring Diagrams | Harley-Davidson SIP - select Sportster. The first sheet is the battery supply.
First you need an Ammeter that you connect in circuit to see current draw then using the wiring diagram you can pull the connectors to disconnect each component in turn.
When the bike is switched off each one ought to be drawing around 1mA.
Wiring diagram here:- 94000402pdf_en_us - 2017 Wiring Diagrams | Harley-Davidson SIP - select Sportster. The first sheet is the battery supply.
First you need an Ammeter that you connect in circuit to see current draw then using the wiring diagram you can pull the connectors to disconnect each component in turn.
When the bike is switched off each one ought to be drawing around 1mA.
Last edited by Andy from Sandy; 07-22-2024 at 05:58 AM.
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WP50 (07-22-2024)
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My CAN bus bike has 3 fuses, the main fuse, 40A, A 10Amp fuse for most of the components and the last one 15Amp for the tender charging lead. So in reality my bike only has one fuse. Everything else on the bike is reliant on the BCM to control current flow and protect itself from over current situations which is powered direct after the 40Amp main fuse.
Wiring diagram here:- 94000402pdf_en_us - 2017 Wiring Diagrams | Harley-Davidson SIP - select Sportster. The first sheet is the battery supply.
First you need an Ammeter that you connect in circuit to see current draw then using the wiring diagram you can pull the connectors to disconnect each component in turn.
When the bike is switched off each one ought to be drawing around 1mA.
Wiring diagram here:- 94000402pdf_en_us - 2017 Wiring Diagrams | Harley-Davidson SIP - select Sportster. The first sheet is the battery supply.
First you need an Ammeter that you connect in circuit to see current draw then using the wiring diagram you can pull the connectors to disconnect each component in turn.
When the bike is switched off each one ought to be drawing around 1mA.
That's what I was afraid of. With fuses, it's simple to isolate each section in turn. With can bus, it's all connected up in one big system.
By pulling connectors, I guess you mean each individual wire - a real headache.
I did do a draw test, but I'm not sure I did it exactly right. But....using a meter, and checking daily, I lose about 0.04V per day, which seems excessive to me.
If I let the bike sit for a month, it would lose 1.2V and probably not start. That's why I started another thread about installing a battery shutoff switch.
Still thinking things over. I like my current Sportster, but things were a lot simpler with my last one - a 1997.
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First...
Tell us what the issue is so we know what to troubleshoot.
What makes you think there is a parasitic draw?
It is not a common issue.
Before you start disconnecting stuff, first determine if you actually have a parasitic draw.
Forget about voltage, parasitic draw is measured in milliamps.
Disconnect the negative battery cable.
Set the meter to milliamps.
Touch one probe to the negative battery post, touch the other probe to the disconnected negative battery cable terminal.
Measure the milliamps, what does it read?
Tell us what the issue is so we know what to troubleshoot.
What makes you think there is a parasitic draw?
It is not a common issue.
Before you start disconnecting stuff, first determine if you actually have a parasitic draw.
Forget about voltage, parasitic draw is measured in milliamps.
Disconnect the negative battery cable.
Set the meter to milliamps.
Touch one probe to the negative battery post, touch the other probe to the disconnected negative battery cable terminal.
Measure the milliamps, what does it read?
Last edited by Dan89FLSTC; 07-27-2024 at 10:36 AM.
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