Voltage Drop

[raven1978]

OK electrical guru's...heres the deal.
My problem is that after unwrapping the boat and installing fully charged batteries, I turn the key on and voltmeter reads 9V. Hmm ok check the wires on the back of the gauge to verify gauge isnt faulty. 9V on the wires. Started looking for voltage drops, cleaning all connections as i go. Unplug Main engine harness, BINGO 12v on the gauge. Tore every wire off the engine, Alternator, starter etc. no go, still 9V. Take leads of ignition coil, BINGO, 12V, but the coil is very hot. Not so hot that it would burn your hand, but still damn hot. My questions are should this coil be that hot and isnt a 3V voltage drop excessive ? it is a points system and currently points are closed. Batteries are brand new last year, not being drawn down. Only thing reading 9v is the dash gauges...batteries are at 12.6

BTW all gauges had 9v to them, take iggy coil out and all have 12v now. Iggy coil is a NAPA coil and has part# 903 on it.

Should i just replace this thing and be done with it, cuz i dont think that is normal. Didnt really notice what it read last year KOEO but KOER the voltmeter read 12V.

Ideas ???

 

[UncleWillie]

Re: Voltage Drop

My first guess is that you just installed a Fully Charged, but Very Dead Battery.

Measure the voltage with the Ignition On at the Battery Terminal Posts, NOT the Battery Clamps, The Battery Posts!
If the Voltage At The Battery Posts is 9 volts, then the Battery is in bad shape.
If the Voltage is 12 volts on the Battery , but 9 volts elsewhere, come back and we'll talk you through it.

The ignition coil will get HOT if the ignition is ON and the Points happened to be closed when the motor stopped.
The coil was not designed to be powerd up for a long time without the points operating.
Not Good , but not destructive.

If the battery was Good, and the Coil was so bad that it could pull a fully charged Battery down to 9 volts,
Something would be in Flames in short order!

EDIT:
Will the Engine crank?
Just hit it for 1/4 Second!
Don't let it start, Don't worry about water.
Pull the coil wire off.
We just want to see if the battery and wiring has the guts to make the motor make 1/2 a revolution. No More!

 

[raven1978]

Re: Voltage Drop

as i stated in my post the batteries are at 12.6 volts...the only thing reading 9v are the gauges. checked batteries before installing into the boat and afterwards when i discovered the 3v drop. batteries read 12.6 at the posts and the ONLY things 9v are the gauges. Batteries DO NOT draw down, there is no drain on the batteries.

 

[pyrotek]

Re: Voltage Drop

This doesn't make any sense to me. Can you confirm the ignition coil is getting power from the battery in the back of the boat? The battery switch is also right next to the battery in the back of the boat?

Without understanding it, I would suspect grounds or connections to the gauge. A bad connection will create a higher resistance and make the voltage drop go up (proportionally with current draw). Can you get a DVM on the gauge to verify the voltage reading? If the DVM is saying 9V, then its some wiring connection issue between the gauge and the battery which is reading 12.6 volts.

 

[Silvertip]

Re: Voltage Drop

You were asked to check the voltage at the battery posts with the ignition ON -- not after the key was turned off again. A discharged battery will recover somewhat after being discharged for a period of time. So check the voltage at the battery posts, then turn the ignition on and watch the voltmeter (the one on the batery). If this is a points style ignition system there is typically a ballast resistor or a piece of resistance wire in the feed to the coil. This drops the voltage to avoid overheating the coil. When starting the engine that resistor is bypassed by the "R" terminal on the starter solenoid to provide a full `12 volts to the coil for starting. If the gauges all have 9 volts on the "I" terminal then check at the "I" terminal on the ignition switch. If you see 9 volts there, check at the "B" terminal on the switch. If you see 9 volts there continue to work back toward the battery. But -- the key to all of this is again at the battery. If it shows 9 volts with the key on then the battery is headed for battery heaven. Charge it and then have it load tested at any auto store.

 

[UncleWillie]

Re: Voltage Drop

OK, Battery Reads 12.6 at Battery with Ignition ON.
The Panel Gauge reads 9 volts, and we have no reason to suspect otherwise.

You did not mention if it will crank! Very important point!
I know a lot of this seems redundant, but we are trying to troubleshoot from the West End of Lake Erie.
Humor us, Please!

Assuming the feed for the house wiring is sourced at the starter solenoid...
With Ignition ON and Panel Meter reading 9 volts, measure these...

Neg Meter Lead on Engine Block;
Pos Meter lead on Ignition/Spark Coil;
EDIT: Or Ballast resistor if you have one ... If NOT 9 Volts, Your Panel meter is lying to you.

Neg Meter Lead on Engine Block;
Pos Meter Lead on Starter/Solenoid. ... If 9 Volts, Do the next Two Test.

Neg Meter Lead on Engine Block;
Pos Meter lead on Pos Battery Post? ... If 9 Volts, Bad Neg. Battery Wiring to Engine Block!

Neg Meter Lead on Neg Batt Post;
Pos Meter Lead on Starter/Solenoid? .... If 9 Volts, Bad Pos. Battery Wiring to Starter/Solenoid.

If all that passes, try ...

Neg Meter Lead on Engine Block;
Pos Meter lead on Ignition switch Term "B" and "I" ... If 9 Volts, Bad connection in Wiring Harness!

Waiting for results.

 

[raven1978]

Re: Voltage Drop

Thanx willie yes it will crank over, battery is 12.6 KOEO. I will check this all tonite after work and post back. I appreciate the help here.

 

[UncleWillie]

Re: Voltage Drop

Thanx willie yes it will crank over, battery is 12.6 KOEO. I will check this all tonite after work and post back. I appreciate the help here.

Thanks, Good news!

This confirms that the battery is definitly NOT at 9 Volts under a minor load.
And that the major battery leads are good.

Your problem is in the Low current wiring.
Start at the Ignition switch at the helm and work toward the battery if it is bad there.

----------

Again...With Ignition ON and Panel Meter reading 9 volts, measure these...

Neg Meter Lead on Engine Block;
Pos Meter Lead on Ignition switch Term "B" and "I" ... If 9 Volts, Bad connection in Wiring Harness!

Neg Meter Lead on Engine Block;
Pos Meter Lead on Ignition/Spark Coil (or the Ballast Resistor, if you have one) ...
. . . . . . . . . . . . . . . . . . . . . . If NOT 9 Volts, Your Panel meter is lying to you. (Not Likely)

 

[raven1978]

Re: Voltage Drop

Neg Meter Lead on Engine Block;
Pos Meter Lead on Ignition switch Term "B"

= 12.6

and "I" ...

= 10.5

Neg Meter Lead on Engine Block;
Pos Meter Lead on Ignition/Spark Coil (or the Ballast Resistor, if you have one)

= 9v

Bad ignition switch? How much voltage should drop @ "I" ?

Am I being to anal about this, i mean everything works, i have B+ at the dash with the engine running and i dont need KOEO for my accessories (ie stereo, it's on its own circuit). Boat is 28 yrs old, cleaned main harness connector and all connections etc.

 

[UncleWillie]

Re: Voltage Drop

Bad ignition switch? How much voltage should drop @ "I" ?
... Boat is 28 yrs old, cleaned main harness connector and all connections etc.

I think you just called it!

It is supposed to be a switch. ON or OFF, no inbetween!
There should be NO Voltage drop!

B is the Direct Feed FROM the Battery.
I is the Switched Feed TO the Ignition. (And everything else.)

Try turning the Switch On and OFF a dozen times quickly.
That may clean up the contacts temporarily.

A 2 volt drop should be making something warm in the switch or "I" connector!

 

[UncleWillie]

Re: Voltage Drop

Am I being too anal about this?

Not at All.
The Devil is in the details.
You just dodged a bullet buy paying attention to what the gauge was telling you. (Good Job!)

It will NOT fix itself! It is only going to get worse.
Better to find it now, than a mile out to sea.

 

[raven1978]

Re: Voltage Drop

Thank gawd...this is gunna be a cheap and easy fix. This would make sense cuz if there is 10.5 at the "I" and factor in how many connections there are from there at the helm with a 0.2v drop per connection, this would explain it.

Thank you UncleWillie

If you're floating by Kingston someday i'll buy you a beer or 3 lol

 

[UncleWillie]

Re: Voltage Drop

...This would make sense cuz if there is 10.5 at the "I" and factor in how many connections there are from there at the helm with a 0.2v drop per connection, this would explain it.
....

Your Welcome, but that still raises the question of how the 10.5 becomes 9.0 ???

A 0.2v drop per connection is NOT to be expected and is NOT acceptable!

Did you measure on the Ballast Resistor or a coil lead.
If you measured after the Resistor, that would explain the drop.

We want to see 10.5 (12.6) back on the engine also! At least within 0.2v !!!
9.0 is very suspicious, there may be another problem. Anal is Good!

 

[raven1978]

Re: Voltage Drop

I measured on the coil feed (+) & Cannot locate said resistor but the coil itself says use with external resistor, so im guessing there is a resistor somewhere (altho i cannot see it)

 

[Don S]

Re: Voltage Drop

Might help if everyone knew what you are working on. What engine and drive, and year. Boat make means nothing.

 

[raven1978]

Re: Voltage Drop

1985 VP AQ125A w/270 O/D should have posted this earlier...my bad

 

[UncleWillie]

Re: Voltage Drop

Very well, For the moment we will assume the switch is the only problem, and there is a resistor in there somewhere.
If the coil has two wires, one goes to the Starter, and the other will go to the resistor.
If there is only one wire, it goes to the resistor.
The resistor may not look like what you would expect, and is likely bigger than you think.
But let's get the switch working first.

%%%%%%%%%%%%%%%%%%%%%%%%

And now for something completely different! (This is definitly NOT directed at you Raven!)

I see that a lot of people have been watching this thread.
I hope many have learned that even though the a boats electricals are not overly complicated, attention to detail is required.
Boats, and cars use low voltage systems with relatively high current circuits.
These require big wires, good connections, and very low resistances to work.
High currents and low resistances are difficult to measure.
Often indirect means will be needed to accomplish the task.
The Devil IS in the details!
When you have the need to ask advice of the many fine people on this forum, be prepared to swallow a little pride and follow the advice to the letter. Get Anal!
You may not Understand why someone is asking you to do something that does not make much sense, but keep in mind that you are asking for assistance BECAUSE you do not Understand.

If you just go with the flow, hopefully the light come on in the end and it will all make sense!

This is the part where I get Off the Soapbox!

 

[raven1978]

Re: Voltage Drop

There are 2 wires on the coil + & - . So question...if i measure voltage at the coil, neg on the block & pos on the + at the coil with the key on, what should my voltage be? 12.6v or 9v ? Electrical is NOT my strong point but am trying to learn.

 

[bruceb58]

Re: Voltage Drop

Voltage at the coil should be approx 9V with points closed or battery voltage with points open.

 

[jhebert]

Re: Voltage Drop

OK electrical guru's...heres the deal.
My problem is that after unwrapping the boat and installing fully charged batteries, I turn the key on and voltmeter reads 9V. Hmm ok check the wires on the back of the gauge to verify gauge isnt faulty. 9V on the wires. Started looking for voltage drops, cleaning all connections as i go. Unplug Main engine harness, BINGO 12v on the gauge. Tore every wire off the engine, Alternator, starter etc. no go, still 9V. Take leads of ignition coil, BINGO, 12V, but the coil is very hot. Not so hot that it would burn your hand, but still damn hot. My questions are should this coil be that hot and isnt a 3V voltage drop excessive ? it is a points system and currently points are closed. Batteries are brand new last year, not being drawn down. Only thing reading 9v is the dash gauges...batteries are at 12.6

BTW all gauges had 9v to them, take iggy coil out and all have 12v now. Iggy coil is a NAPA coil and has part# 903 on it.

Should i just replace this thing and be done with it, cuz i dont think that is normal. Didnt really notice what it read last year KOEO but KOER the voltmeter read 12V.

Ideas ???

What do "KOER" and "KOEO" mean"