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Old 24-12-2014, 07:26   #1
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Charging Problem

The second alternator stopped working, so Tom installed a new one. It won't excite all the time. We've had the alternator bench tested, reattached the ground, replaced the relay and fuses, it's still not consistent. Any ideas?

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Old 24-12-2014, 07:43   #2
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Re: Charging Problem

What relay? And is there voltage present from the regulator to the alternator field connection?


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Old 24-12-2014, 07:50   #3
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Re: Charging Problem

So I'm guessing the alternator bench tested good. Do you have a volt/ohm meter?

I'm guessing your gauge is saying the voltage is low. You may have to take the load (s) off (disconnect the loads from) the alternator/batteries. Then crank it up and see if the voltage is good to the gauge. (or check it with a volt meter)

If it's good, then you can start to connect the loads back one device at a time to see which device/appliance is pulling down the power.

Something may be loading it down. There could be a partial short in one of the loads. Are any of the fuses blown that you replaced?

Or it could be the regulator if it's not part of the alternator.
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Old 24-12-2014, 11:31   #4
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Re: Charging Problem

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Originally Posted by Sailmonkey View Post
What relay? And is there voltage present from the regulator to the alternator field connection?


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Yes, it's an internal regulator.

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Old 24-12-2014, 11:34   #5
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Re: Charging Problem

You could also pull all the fuses to the loads and see if the voltage comes back up when you power up the alternator.

If it is, then you can replace one fuse at a time (turning the power off before hand) and that may tell you where the current draw is coming from if it is the load (s) that is the problem.
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Old 24-12-2014, 11:37   #6
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Re: Charging Problem

Quote:
Originally Posted by thomm225 View Post
So I'm guessing the alternator bench tested good. Do you have a volt/ohm meter?

I'm guessing your gauge is saying the voltage is low. You may have to take the load (s) off (disconnect the loads from) the alternator/batteries. Then crank it up and see if the voltage is good to the gauge. (or check it with a volt meter)

If it's good, then you can start to connect the loads back one device at a time to see which device/appliance is pulling down the power.

Something may be loading it down. There could be a partial short in one of the loads. Are any of the fuses blown that you replaced?

Or it could be the regulator if it's not part of the alternator.
Right now there is no load on it because the alternator is not charging. However, that is good advice for our energy problem.

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Old 24-12-2014, 11:39   #7
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Re: Charging Problem

I thought the alternator bench tested good?

Can you take the load of with a switch? You may not be seeing any "charging" because the alternator is being loaded down (unless you are able to remove the load with a switch or switches on you circuit breaker panel)
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Old 24-12-2014, 11:52   #8
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Re: Charging Problem

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Originally Posted by thomm225 View Post
You could also pull all the fuses to the loads and see if the voltage comes back up when you power up the alternator.

If it is, then you can replace one fuse at a time (turning the power off before hand) and that may tell you where the current draw is coming from if it is the load (s) that is the problem.
It's the alternator that is not working.

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Old 24-12-2014, 12:07   #9
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Re: Charging Problem

Ignition switch might be bad.
Thus, no alternator field current.
Are the gauges (temp, voltage) working?
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Old 24-12-2014, 12:10   #10
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Re: Charging Problem

Oh, sorry.

I thought when you said you had it bench tested, it tested good. So if it tested good, then did you hook it up wrong?

Drop or lose an insulator perhaps on one of the wires.
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Old 24-12-2014, 12:29   #11
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Re: Charging Problem

+1 on the ignition switch. The field (excitation) current passes through the ignition system somewhere, and a bad or sometimes bad connection can cause the symptoms you describe. Have a look at the engine manual to see if there is a wiring diagram.

A quick test, quite safe with an internally regulated alternator, is to build a little jumper to go from the B+ to the field terminal. Put a little toggle switch in the jumper. You should then be able to turn the alternator on and off at will. If that works then there's something wrong in the ignition switch/wiring to the alternator field.
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Old 24-12-2014, 12:45   #12
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Re: Charging Problem

Dsanduril is exactly right!

And, whatever you do, DO NOT switch the output wire from the alternator on and off as someone suggested above.......that's a sure way to blow the diodes. There should be no switch in that circuit anyway....only a big fuse at least 20-25% larger than the maximum alternator output.

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Old 24-12-2014, 12:45   #13
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Re: Charging Problem

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Originally Posted by thomm225 View Post
Oh, sorry.

I thought when you said you had it bench tested, it tested good. So if it tested good, then did you hook it up wrong?

Drop or lose an insulator perhaps on one of the wires.
We have a misunderstanding. The alternator tested good. It is correctly installed, it just won't always excite.

Maje
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Old 24-12-2014, 12:48   #14
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Re: Charging Problem

the exciter normally feeds thought the battery warning light bulb. if the bulb is dead the alt won't work (stupid but how many are done including cars).


I'm not sure why you have a relay on an internal reg alt.


I'm not sure why people are saying take loads off. alternators should be tested with lots of battery load. if batteries are full with no load then the alt doesn't need to do anything. if you put a 50a load on the batteries you should be getting 50+ amps out of the alt. measured with a clamp on ammeter. that is how you test an alt.


also lots of alts won't excite at idle. you need to rev up the engine.
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Old 24-12-2014, 12:50   #15
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Re: Charging Problem

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We have a misunderstanding. The alternator tested good. It is correctly installed, it just won't always excite.

Maje
Okay, thanks.

The guy above has a good idea with the jumper.

Or if you have a voltmeter, you can troubleshoot it with the wiring diagram seeing if there is voltage coming in and out of the ignition switch. If so, where is it stopping between the switch and the alternator.

If you don't have a meter and are really intent on kicking ass, you could probably use one of your gauges as the meter. (if you have a voltage gauge)
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