Electrical question

[Nick duBois]

Hi,

For the last few weeks I have noticed that the rate of charge indicated on my ammeter has been less than normal. I replaced the alternator belt today. What a riot that was, I had to take off the pulley as the belt would not fit between the block and the pulley. The onboard battery charger was on overnight so the battery voltage on a voltage meter was 12.52volts. When I start the engine the ammeter does move over to the right a bit and if I take the positive battery cable off the engine it does continue to run. I measure the voltage at the battery with the engine running and it is about 12.8 volts. I measure the voltage at the alternator output post and it's 13.8 volts. Shouldn't I get that 13.8 into the battery? Last season the ammeter needle swung over to the right to at least 15 amps and now it just moves over a bit. Am I loosing that voltage somewhere?

[BunnyPlanet169]

Nick -

From your description I'd look at loose connections first. You're correct that with the alternator running, the voltage should be pretty much the same along the circuit, and if you lose much more than 0.1V one end to the other there's definitely something to fix.

From the alternator output -> fuse? -> ammeter (usually an internal shunt resistor on smaller meters) -> battery post on starter -> and the big cable back the start battery is the usual circuit.

Don't disconnect the alternator output circuit while it's running. Probably won't fry a new regulator, but it's possible. Shut down, fix a crimp, and fire it up again.

How old is the wiring? Wiggle every crimped connection to check for higher resistance intermittent stuff. Cracks in the insulation? Near anything wet?

Sometimes when I start my engine, I have to rev it once to get the alternator field excited. Then both full voltage (14.2 ish) and current show. Pre-rev: 12.5 and nothing. ???

When you're not losing voltage, then put a load on the DC system (turn on all your lights) and check the ammeter. No indication - then I'd replace the meter. I did that three years ago myself, when the needle indicated a wiggle, but no real charge.

[Nick duBois]

Jeff,

I have to rev my engine up as well before I see a charge. The boat is a 1980 Catalina 27 the wiring must be original as far as I know. I cleaned the ground now I will Check the wiring as you mentioned. God knows how many ghosts I may stir up there.

Thanks

Nick

[ndutton]

Look for, hopefully find and remove the dreaded trailer plug in the engine harness, a Catalina specialty. There may be two: one at the engine and the other at the instrument panel.

[BunnyPlanet169]

Yikes

Neil's picture would definitely fall into the category "something to fix"

The alternator circuit is usually a pretty simple one. It's also (usually, should be anyway) one of the bigger wires in any harness. Take your time, and move deliberately. You'll find it.

[Nick duBois]

I know where these plugs are. the bigger wire from the alternator goes into one just above the engine and then that same wire goes through the second plug before it goes into the left hand side of the ammeter. So if I cut the wire then ran a 10 gauge wire from the alternator to the ammeter that should do the trick right?

[ndutton]

I know where these plugs are. the bigger wire from the alternator goes into one just above the engine and then that same wire goes through the second plug before it goes into the left hand side of the ammeter. So if I cut the wire then ran a 10 gauge wire from the alternator to the ammeter that should do the trick right?

Not quite. True, the orange wire goes from the alternator to the ammeter but then there's the big red wire that feeds the power back to the battery. The best thing is to get rid of the plug(s) in its (their) entirety. That's eight wires worth. If the plug(s) are present the harness is likely original and in my opinion overdue for replacement anyway.

Consider doing away with the ammeter and replacing it with a voltmeter. There are plenty of threads in the forum archive discussing it and drawings are available in the Drawings category.

[ndutton]

Neil's picture would definitely fall into the category "something to fix"

And my engine ran fine with that monstrosity. I was on borrowed time to say the least.

[BunnyPlanet169]

Careful....

Don't start by snipping!

I'd measure voltage drops first and find your fault.

Can you remove the wire (lug, ring, faston, spade) from the back of the ammeter? Mine are something like 6-32 or 8-32 nuts on posts.... Tape it back so it doesn't short out on something.

Make sure you have the correct leg on the ammeter.... there should be two fatter wires in that bundle. One to the ammeter, one away. But I don't know Catalinas the way others do, or what's done up on the panel.

Then you could try a jumper of #10 or #8 from the now empty terminal to the alternator output.

When you rebuild/rewire, best practice and the Moyer schematic shows this I think, is also a fuse at the start motor return side... This one circuit has full battery potential at all times, and you don't want a #10 wire shorting.

[BunnyPlanet169]

crossed replies

Do what Neil said!

[ndutton]

Here's the rub:
If you decide to replace the entire harness AND dump the ammeter for a voltmeter AND have electronic ignition, be advised you will have significantly improved voltage everywhere which can affect the ignition system balance of coil voltage, resistance and current. Read up carefully on how to properly set up an EI system so you avoid trouble before it rears its ugly head.

Kelly's 'coil input' thread covers it as well as several others.

[Dave Neptune]

Nick, I just did mine in a 1970 Ericson. I did a complete rewire of the engine to panel and it was really no big deal. It did a lot for the charging circuit as the path in mine was over 15 feet from the alt to the analog amp meter, and then back to the battery switch. It is now a 3 foot run and I still use an ammeter however I went with one of the new VDO full sweep shunt type units.

It made a big difference in how the charging system works, a lot more of the "power" is getting to the batteries. I also redid my battery wiring to and that eliminated 45 feet of #4 and turned it into a total of 6 feet and that includes the battery to switch to engine. That is what did make the biggest improvement.

My harness between the plugs was 25 feet long and had two coils of it "stapled" to a bulkhead. It only needed to be around 8~9 feet, that too means better readings and power to the engine too.

I did mount a volt meter where the ammeter was in the control panel and have the VDO below on a separate engine panel I have at the nav station.

It was a bit of work and the downside was my wife couldn't "see" any improvement for the work and time I put in. Oh well I did.

Dave Neptune

[sastanley]

Here's the rub:
If you decide to replace the entire harness AND dump the ammeter for a voltmeter AND have electronic ignition, be advised you will have significantly improved voltage everywhere which can affect the ignition system balance of coil voltage, resistance and current. Read up carefully on how to properly set up an EI system so you avoid trouble before it rears its ugly head.

Kelly's 'coil input' thread covers it as well as several others.

I am the poster child for this problem , as it is exactly what I did over a couple years' time.

After a couple Ω's worth of resistor in front of the coil, I think I am good to go now.

It was a bit of work and the downside was my wife couldn't "see" any improvement for the work and time I put in. Oh well I did.

Dave Neptune

Isn't it funny how every time the Admiral comes down to the boat, it always looks the same with the cushions and everything in place?? "So, what is all this work you were doing honey?"..

[BunnyPlanet169]

Metering

The rev for alternator excitement is not unusual, I believe. My engine now starts easily at idle with the choke on. As a result, the alternator starts softly and under load, and the field never gets up to power. A quick goose of the throttle 'fixes' that. If I forget my throttle is up a bit and over-rev at start, there's no problem.

I really like both Volts and Amps to go with my Oil Pressure, RPM, and H2O Temp on the outside. They're not super accurate, but they don't have to be - they're really useful indicators while you're out in the cockpit, and shouldn't have a negative effect if wired carefully.

Gotta admit: I like how they look too...

For my boat's alternator (the 55A Moyer), carefully wired means a #8AWG wire from the alternator to the ammeter and back. My voltage drop along that run is basically just the resistive meter shunt (and probably near my DVM resolution), even though it's about 15 feet total wire length.

More careful and precise monitoring could be very useful below, if you need that information. I'll be installing good volt meters on both of my batteries for monitoring, and they're going to be installed as close to the batteries as possible and still be useful. I don't have multi-step charging, charge monitoring, etc. for my (currently simple) needs - the voltmeters will be enough.

[hanleyclifford]

Hi,

For the last few weeks I have noticed that the rate of charge indicated on my ammeter has been less than normal. I replaced the alternator belt today. What a riot that was, I had to take off the pulley as the belt would not fit between the block and the pulley. The onboard battery charger was on overnight so the battery voltage on a voltage meter was 12.52volts. When I start the engine the ammeter does move over to the right a bit and if I take the positive battery cable off the engine it does continue to run. I measure the voltage at the battery with the engine running and it is about 12.8 volts. I measure the voltage at the alternator output post and it's 13.8 volts. Shouldn't I get that 13.8 into the battery? Last season the ammeter needle swung over to the right to at least 15 amps and now it just moves over a bit. Am I loosing that voltage somewhere?

Not sure how you got that 12.52 volt reading, charger on or off; either way an on board charger should deliver more than that. Are we sure the battery is still good, capable of accepting a charge? BTW, not good to disconnect battery with engine running.