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Simple Generator Test

Your old Chris-Craft electrical system can be a challenge. If it runs on "juice" pose your questions and offer your advice here.

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mwhetzler
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Simple Generator Test

Post by mwhetzler » Tue Aug 05, 2014 9:03 pm

We have a '47 Chris Craft Special with an ACE engine. Our battery goes dead after a short while. We had the battery tested, and the results showed that the battery was good. We did a quick review of the wire connections and wiring condition and all looked good. We are wondering if it is the generator (or something else). Any suggestions? Is there a simple way to test the generator without having to uninstall it (it looks like the carburetor would have to be removed to provide sufficient clearance to remove the generator). Any suggestions would be appreciated. Thanks

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mfine
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Re: Simple Generator Test

Post by mfine » Wed Aug 06, 2014 5:49 am

1) have you tried disconnecting tv battery between uses to make sure it is not being drained by a leakage or unexpected load?

2) what gauges do you have? Amp meter or voltage? What do they show?

Rather than pulling the generator, I would start by measuring voltage at the battery before starting, then after starting with the engine running about 1000-1200 rpm. You should see a voltage rise as the generator starts recharging the battery.

mwhetzler
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Re: Simple Generator Test

Post by mwhetzler » Wed Aug 06, 2014 7:23 am

1) We charged the battery on Sunday, hooked it up and have not used it yet. We will back at the boat on Thursday night. So, we can test the battery then to see if there is drain.

2) We have an amperes guage on the dash. I have not looked closely at it, but I do not recall it working.

I will check the battery with the engine off and then running with a volt meter. My understanding is in the off state the meter should read 12v and with it running it should be between 13.8 and 14.4 volts. I know that it is a 12v system. Is this correct?

We have only had the boat for three weeks and have been taking very slow cruises in it. Could a contributor to our situation be that we have not been giving the generator enough rpms and so it has not been charging (I would assume the regulator should at least prevent the generator from running as a motor, thereby draining the battery)?

Thanks for your help.

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drrot
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Re: Simple Generator Test

Post by drrot » Wed Aug 06, 2014 8:56 am

Take your boat out and run it at 2000RPM. Have someone disconnect the battery cable. If it dies it is not charging.
Jim Staib
www.finewoodboats.com


1947 Penn Yan 12' Cartopper WXH474611
1950 Chris-Craft 22' Sportsman U-22-1532
1957 Chris-Craft 26' Sea Skiff SK-26-515
1968 Century 17' Resorter FG-68-174

mwhetzler
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Re: Simple Generator Test

Post by mwhetzler » Wed Aug 06, 2014 9:46 am

Jim,

This is a good suggestion. We did this with it idling, and the engine turned off. We certainly did not have it at 2000 rpms; it was probably only at 500 rmps.

Thanks,

Mark

jfrprops
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Re: Simple Generator Test

Post by jfrprops » Wed Aug 06, 2014 10:31 am

idle speed not enough, clearly.

Jim Staib: does that pull the cable at 2K rpm work for an alternator as well? guess so?

John in Va.
1980 Fairchild Scout 30
19?? custom Argentine Runabout 16'
1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)

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mfine
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Re: Simple Generator Test

Post by mfine » Wed Aug 06, 2014 11:01 am

mwhetzler wrote:My understanding is in the off state the meter should read 12v and with it running it should be between 13.8 and 14.4 volts. I know that it is a 12v system. Is this correct?
That is what I would expect to see on a 12v system, give or take half a volt or so. You are probably going to have to get the RPM's up a bit before you see the voltage rise, 500 rpm at idle isn't going to be enough.

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drrot
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Re: Simple Generator Test

Post by drrot » Wed Aug 06, 2014 7:35 pm

jfrprops wrote:idle speed not enough, clearly.

Jim Staib: does that pull the cable at 2K rpm work for an alternator as well? guess so?

John in Va.
Alternators charge at idle. Generators do not. You could pull the cable of an alternator at idle.
Jim Staib
www.finewoodboats.com


1947 Penn Yan 12' Cartopper WXH474611
1950 Chris-Craft 22' Sportsman U-22-1532
1957 Chris-Craft 26' Sea Skiff SK-26-515
1968 Century 17' Resorter FG-68-174

jfrprops
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Re: Simple Generator Test

Post by jfrprops » Wed Aug 06, 2014 8:33 pm

yes, thought so, thanks,

John in Va.
1980 Fairchild Scout 30
19?? custom Argentine Runabout 16'
1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)

mwhetzler
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Re: Simple Generator Test

Post by mwhetzler » Thu Aug 07, 2014 7:00 am

Thanks for all of the good suggestions. We will let you know what we find out this weekend.

Mark

mwhetzler
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Re: Simple Generator Test

Post by mwhetzler » Sat Aug 09, 2014 7:47 am

We did two tests yesterday:

1. We checked the battery without the boat running. It was 12.4v. We then checked it running in neutral at 2200 rpms. It still was 12.4v.

2. Also, while running at 2200 rmps, we pulled the ground off the battery, and the engine shut down.

Is there any suggestions as to what is next?

Thanks much,

Mark

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mfine
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Re: Simple Generator Test

Post by mfine » Sat Aug 09, 2014 8:46 am

Pull the generator for test and repair, or upgrade to an alternator?

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evansjw44
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Re: Simple Generator Test

Post by evansjw44 » Sat Aug 09, 2014 9:08 am

Time to check the wiring between the generator and the regulator. Also check the wiring from the regulatorto the the ammeter. You might measure the voltage at the "Batt" terminal of the regulator with the engine at idle and at about 1500 RPM. Its possible the generator field needs to be "flashed". The field must have some residual magnetism in order for the generator to develope voltage to pick up the regulator cut-out. Measure the voltage at the generator "Arm" (armature) terminal with the engine running at idle and increase the revs to 1500 RPM. At idle I'd expect 8 - 10 volts. As the revs increase the voltage should increase up to 12.8 at which time the regulator cut-out relay should pick-up and connect the generator armature to the battery and the generator supply power. If the voltage increases above 14 volts check the voltage at the "Batt" terminal of the regulator. If its 12.4 the the cut-out relay is not picking up and you have a defective regulator. If the voltage at the "Batt" terminal on the regulator goes up with the generator armature voltage, the cut-out has picked up and there is a wiring open circuit between the regulator and the ammeter. In this test you should also measure the voltage on the "field" terminal of the generator and regulator. The regulator gets current from the generator armature and routes it to the field. If the field doesn't get power from the armature the armature voltage will lay flat. There's more test you can do by yourself with a multi-meter if you're so inclined.

Hope this is helpful to you.
Jim Evans

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