Low Voltage Warning

[chpthril]

Just a thought. Are you absolutely sure that all your ground connections are correct (including the battery ground to the engine block)? While not related, I ran into a situation last year with a septic pump. When we check the voltage coming from the power pole it metered out at the correct voltage, however whenever the float switch activated the pump, voltage would drop significantly (i.e., dropped under significant amperage load). Could that be what's happening here? It could even be a bad ground issue somewhere completely different in your wiring harness. You may want to just check all the connections to make sure there's not a marginal ground connection in there somewhere.

I had a question on the isolator for some of the other guys. Should the starting battery be on a separate ground to the engine block or should it really be grounded on the same ground loop as the deep cycle? chpthril, anyone?

On 12v systems, ALL the grounds must come together, either through the chassis on a car, or to the engine block on a boat (as they have no chassis) Reason being is that the ground completes the loop. In theory, current flows ground to positive. You can hook a lead off the alternator to a battery, without a ground, that battery will never receive the charge from the alt, even though you can measure 13.5V's on that wire if you placed the meter lead on the engine ground. As soon as that missing ground it hooked up, the circuit is complete and the battery will begin receiving that 13.5v. It was there all the time, but with out a ground, the battery could not be charged. Ask DomZ06, he discovered this 1st hand on his batteries.

I may have read more into your question then what was needed, but at the end of the day, it doesnt really matter where the grounds are connected i.e. block or other battery, but they all need to be connected in order to complete the loop.

[MRMoffat1]

On 12v systems, ALL the grounds must come together, either through the chassis on a car, or to the engine block on a boat (as they have no chassis) Reason being is that the ground completes the loop. In theory, current flows ground to positive. You can hook a lead off the alternator to a battery, without a ground, that battery will never receive the charge from the alt, even though you can measure 13.5V's on that wire if you placed the meter lead on the engine ground. As soon as that missing ground it hooked up, the circuit is complete and the battery will begin receiving that 13.5v. It was there all the time, but with out a ground, the battery could not be charged. Ask DomZ06, he discovered this 1st hand on his batteries.

I may have read more into your question then what was needed, but at the end of the day, it doesnt really matter where the grounds are connected i.e. block or other battery, but they all need to be connected in order to complete the loop.

So the alternator is connected to Gnd via Engine, correct? So I need to ensure the engine block is grounded properly (assuming via the large ground wire from the starting battery - I did not trace that one down - will do tonite. That said - I believe all ground wires are connected in some manner at the starting and deep cycle batteries - but still need a ground path to alternator.

[chpthril]

So the alternator is connected to Gnd via Engine, correct? So I need to ensure the engine block is grounded properly (assuming via the large ground wire from the starting battery - I did not trace that one down - will do tonite. That said - I believe all ground wires are connected in some manner at the starting and deep cycle batteries - but still need a ground path to alternator.

Correct, the internal circuitry of the alt is grounded to the alternator case, which in turn is bolted to the engine.

[MRMoffat1]

Sure enough - the starter batter ground cable is firmly connected to the bolt by the starter. It's getting frustrating. Went over the whole boat looking for wiring that seemed out of place. Only one - see photo of engine comparment below. Grasping for anything at this point.

[MRMoffat1]

... and here is a shot of the positive cable to the starter.

[MRMoffat1]

Also, after putting it all back together, I put the autobildge pump wire on the positive post of the deep cycle battery - I think that is where it belongs but forgot to mark it. It's the one with the 3A in line fuse. If anyone can confirm, appreciate.

[Timmy!]

I think those wires that aren't connected are used for test equipment, every Marine Power engine I have seen has those like that.

[MRMoffat1]

I think those wires that aren't connected are used for test equipment, every Marine Power engine I have seen has those like that.

Yeah - I think I already new the answer!! Thanks. Looks like the boat is headed for the shop.....

[MRMoffat1]

... so I am reading the engine manual tonight. Purple wire from alternator? Purple wire to Volt Meter and Ignition switch? Grasping

[MRMoffat1]

Boat is going in next week. Service Tech is up to speed, needs to read fault codes for additional info. Suggested re-looking/retest with:
1. Take Deep cycle out of the circuit
2. Take Isoloation out of the circuit

Now could be a number of possible items - possible short somewhere, etc, etc.

Discussed impellar, ignitition circuit, throttle circuit, temp/oil sensor, amps, .........

[chpthril]

Measurements today (reference to Engine Mount Gnd):

Engine Off:
A/B = 0V
C/D = 12.72 V
E/F = 12.82 V
G = 0V

Engine Idle:
A/B = 14.7/14.66 V decay slowly to 13.8 over maybe 10-15 min
C/D = 13.84/13.83 V decay to 13.1
E/F = 13.87/13.87 V decay to 13.2
G = 12.8 V decay to 12.1 (visual only)

Bumping the RPMs in neutral to >1000RPM, the Alt bumped up from 13.8 to 14.5V and all points rose in voltage an equal amount

The Isolator followed the Alt Voltage at about a .8 V drop. The voltmeter seemed to be about 1V below the isolator voltage at all times (Voltmeter never got above 13V which seems strange since I know the voltmeter has been above 13-13.5 V normally). [Side note: If anyone owned a 1999 2100V, you know you had to "pulse" the RPMs a little after starting the engine to get the Alternator to "stick" above 13V, but not on these 22Ves.]

At about time=10 to 15 min into idle, when Voltmeter had decayed to around 12.1V and respectively Alternator to 13.8V, the constant "beep" went off continually. The engine kept idle this time.

Turned off, turned engine back on, and idled fine, beep stopped, volt meter 12.8 to 13V.

Idled out past the dock and did not get too far and the beep went off as the voltage dropped again. Cycled thru the turn engine on/off to get back to dock and go home. Beeped again as I pulled up to dock.

Ideas? Alternator?

When you performed these checks, where did you have the ground lead for the meter clipped? Probably doesnt matter alot because you are reading Alt output at both batteries tells us that both battery banks are connected.

"G" is the B+ on the back of the gauge, correct? Did you check it with key on to see how is compared to the static charge of the batteries? Sound like it may be a bad ignition switch. Do you know how to do a voltage drop test? Do one on the switch, might be losing a volt or 2 across it.

[MRMoffat1]

When you performed these checks, where did you have the ground lead for the meter clipped? Probably doesnt matter alot because you are reading Alt output at both batteries tells us that both battery banks are connected.

"G" is the B+ on the back of the gauge, correct? Did you check it with key on to see how is compared to the static charge of the batteries? Sound like it may be a bad ignition switch. Do you know how to do a voltage drop test? Do one on the switch, might be losing a volt or 2 across it.

Ground lead at the engine mount right below the alternator.

G in theory B+ on back of gauge, in practice was my eyeball looking at the needle.

Did you check it with key on to see how is compared to the static charge of the batteries? (No)

Do you know how to do a voltage drop test? (No)

[chpthril]

Do you know how to do a voltage drop test? (No)

Voltage is nothing more then a difference in potential from the + to the -. That's why we measure 12V (actually more, but lets keep it simple) when we measure across a battery's pos and neg posts. Well, a voltage drop test measure the difference in voltage from the beginning of a circuit to the end of a circuit. If the circuit is good, you will have near 0v drop. As resistance goes up, there is a difference, in voltage, that will be measured, this is the voltage drop, in other words, the difference in potential. Remember back in the day when cars had only an ID-10-T light for the alt? When the alt started to go, the light would glow very dim. This was due to a voltage drop. One side of the light was on battery, the other side was fed by the alt, but was grounded when engine was off - this was why the light was bright when engine was off. When the engine started and the alt began to charge, the bulb received voltage on both sides and went out. With a bad alt, the bulb had 12v on one side and less on the other, so it started to glow dim.

So, for you, measure from the B+ on the back of the switch across to the terminal that is hot with key on. Cant remember what its labeled. Any more then .5 a volt would be suspect.

[MRMoffat1]

Voltage is nothing more then a difference in potential from the + to the -. That's why we measure 12V (actually more, but lets keep it simple) when we measure across a battery's pos and neg posts. Well, a voltage drop test measure the difference in voltage from the beginning of a circuit to the end of a circuit. If the circuit is good, you will have near 0v drop. As resistance goes up, there is a difference, in voltage, that will be measured, this is the voltage drop, in other words, the difference in potential. Remember back in the day when cars had only an ID-10-T light for the alt? When the alt started to go, the light would glow very dim. This was due to a voltage drop. One side of the light was on battery, the other side was fed by the alt, but was grounded when engine was off - this was why the light was bright when engine was off. When the engine started and the alt began to charge, the bulb received voltage on both sides and went out. With a bad alt, the bulb had 12v on one side and less on the other, so it started to glow dim.

So, for you, measure from the B+ on the back of the switch across to the terminal that is hot with key on. Cant remember what its labeled. Any more then .5 a volt would be suspect.

Appreciate Chpthril - Thanks. Sorry for the quick post yessterday - was in a hurry. I've been in and out of tigeowners.com quite a bit looking for anything. Will pull boat out and measure today.

This piece of info could be completely off on a tangent, and a secondary problem: two items with the ignition switch that weekend, first, the whole switch came loose and almost fell out of the dash, and, second, the key needs to be manually clicked back one notch to left after starting the boat. When turning the key full right to start boat, didn't it use to "spring" back one notch automatically?

[MRMoffat1]

Static measurements referenced to ground (engine not running):

Starting Battery: 12.6
Deep Cycle: 12.7

Ignition Switch (B/A/I/S):
Off: B (12.65), A (0), I (0), S (0)
On: B (12.4), A (12.4), I (12.36), S (0)
Acc: B (12.65), A (12.6), I (0), S (0)

Voltmeter [Volts](Purple/Black)
Off: Purple (0), Black (0)
On: Purple (12.26), Black (0)
Acc: Purple (0), Black (0)

Voltmeter (Needle Visual)
Off: (0)
On: (approx 11.75)
Acc: (0)

Voltage Drop tests accross Ignition Switch:

B-I
Off: (12.68)
On: (.02)
Acc: (12.68)

B-A
Off: (11.83)
On: (0)
Acc: (0)

B-S
Off: (12.6)
On: (12.26)
Acc: (12.6)

Looks like all checks out to me. Now that I am under the dash, continuing inspection.....