voltage drop

[slash]

So I'm trying to check my starter circuit because occasionally (on my 06 s2r1000 with 25K miles) the start pauses for a 1/4 sec when I'm trying to start it.  So I thought I'd do voltage drop test.

So when I measure + terminal battery to - terminal battery: 12.7 volts. 
+ terminal battery to ground on starter: 12.7 v

ignition switch on (low beam),+ terminal battery to - terminal battery:12.07
ignition switch on (low beam), + terminal battery to ground on starter:12.0 v

when I start up momentary drop to 11.0 v when I measure + terminal battery to - terminal battery then up to 14.5v.
when I startup momentary drop to 9.99 V when I measure + terminal battery to ground on starter.

And here's the part I don't get (no load, ignition off): +terminal battery to +terminal starter gives me 12.7 v....shouldn't it read 0 since it's hooked in parallel.

[Armor]

You're bypassing the solenoid and you're in series.  You are reading through the starter motor.  Try that with a wire and the starter will engage.

[slash]

Armour, thanks for explaining that.  If I want to test the voltage drop between the battery and starter what is the best (easiest) way to do it.  How do I hook the volt meter in parallel?

[suzyj]

Armour, thanks for explaining that.  If I want to test the voltage drop between the battery and starter what is the best (easiest) way to do it.  How do I hook the volt meter in parallel?

Voltmeters are always in parallel.  They measure the voltage across something.

To measure voltage drop, the best thing is to actually measure the voltage drop while under load, rather than measuring the voltage across the battery and the voltage across the starter, and trying to infer voltage drop from that.

The electrical circuit between the battery and the starter has a number of components, each of which can have relatively high resistance and cause a significant voltage drop.

On the positive side:

• A set of lug-bolt, lug, then lug-wire contacts on the battery positive terminal.
• Resistance of the battery positive to solenoid wire.
• Another set of wire-lug, lug, then lug-bolt contacts on the battery side of the solenoid.
• The solenoid itself.
• Yet another set of wire-lug, lug, then lug-bolt contacts on the starter side of the solenoid.
• The resistance of the cable between the solenoid and the starter.
• Yet another set of wire-lug, lug, then lug-bolt contacts on the starter positive terminal.

And completing the circuit back to the battery:

• Contact resistance between the starter and engine.
• Resistance of the actuall engine case.
• Yet another set of wire-lug, lug, then lug-bolt contacts on the engine case negative terminal.
• The resistance of the negative battery wire.
• And one last set of wire-lug, lug, then lug-bolt contacts on the battery negative terminal.

So when you ask "how do I measure voltage drop?" I first want to know what you're trying to achieve.  I assume you're trying to diagnose starting issues, so your plan of attack is to find which of these elements have the largest voltage drop across them, and then clean/retighten/replace the bits in question.

I'd start by pulling the leads off the plugs - having the bike start all the time is annoying.  Make sure your battery is well charged before you start.

Now put your multimeter on volts range, and put the positive lead on the battery + terminal (actually on the terminal, not the lug that contacts to it), and put the negative lead on the starter + terminal (actually on the bolt).  Crank briefly and write down the voltage.

Do the same for the negative side - positive lead on the case of the starter motor, negative lead on the negative terminal of the battery.  Crank briefly, write down the number.

Go through and repeat the tests across individual components.  You'll find that one connection or wire (or solenoid) has a much larger percentage of the drop than all the others - this is the one that wants your attention.

[ducpainter]

<snip>
I'd start by pulling the leads off the plugs - having the bike start all the time is annoying.  

<snip>

Some ecu's and coils don't like that scenario...