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  #11  
Old 04-16-2021, 03:44 PM
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ExtraKatana ExtraKatana is offline
 
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Default

Thanks Mike. That would be the input for terminal 3 on this regulator.

Since the problem manifests while the engine is running, should this test be done with engine running? Master on? .
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Last edited by ExtraKatana : 04-16-2021 at 03:48 PM.
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  #12  
Old 04-16-2021, 07:14 PM
PilotjohnS PilotjohnS is offline
 
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Location: Southwest
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Default Ohm check

Quote:
Originally Posted by ExtraKatana View Post
Thanks Mike. That would be the input for terminal 3 on this regulator.

Since the problem manifests while the engine is running, should this test be done with engine running? Master on? .
The first test is to make sure the bus sense on the regulator is hooked up to something. Then ohm it out and make sure it senses bus voltage (very low resistance to battery or main bus)
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  #13  
Old 04-16-2021, 07:49 PM
N49ex N49ex is offline
 
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Default Bus Voltage HIGH

The job of the voltage regulator is to shove current into the field of an amount needed to make the regulation voltage (at terminal 3) come up to the set point. Presumably, the regulation voltage is very close to if not pretty much the bus voltage. (it should be provided that way,for example with a separate or low load breaker)

So, the first thing is to verify what in fact is showing up at terminal 3. You will need to either bring that out with a wire, or be able to access it with a reliable meter right at the terminal, with the engine running. The most likely situation will be that the regulation voltage at terminal three is not the bus/battery voltage. So if it is low or not connected at all, the regulator will interpret that as a command to jack up the field current and thus the bus/battery voltage, until an over voltage trip occurs. If it turns out that the regulation voltage is the same as the bus voltage, and tracks up with the bus voltage, then likely the regulator is defective. (like for example a broken circuit board trace from terminal 3...)
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  #14  
Old 04-17-2021, 04:38 AM
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ExtraKatana ExtraKatana is offline
 
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The voltage at terminal 3 is almost the same as the Bus voltage. It's terminal 6 that is going up outta sight and popping the CB on the panel. Resting voltage on terminal 6 is very close(.2 volt lower) to bus voltage also. When i start the engine it's another story however.
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  #15  
Old 04-17-2021, 06:56 AM
lr172 lr172 is offline
 
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I chased a problem like this for a while. Turned out the screw holding the ring terminal on the back of the field breaker had become loose and was adding resistance to the sense circuit, thus driving up the regulated output voltage. I have a std ford style regulator, which takes the sense voltage from it's primary input, unlike the B&C. The screws has lock washers, but obviously not strong enough.

Best to confirm good continuity on the full sense input wiring.

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Last edited by lr172 : 04-17-2021 at 07:01 AM.
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  #16  
Old 04-17-2021, 12:50 PM
Avanza Avanza is offline
 
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Default ALT PROBLEM

If the Field wire at the back of the L40 alternator is bad, the F-current
will be chopped (on/off/on/off) when engine is running due to vibration.
The voltage from the alternator will then be lower than required.
Bus and sense wire voltage will be lower than the regulator set point.
The regulator will try to increase voltage fed through the Field wire to the alternator. When the field wire at the back of the alternator makes contact,
the voltage at the bus will be so high that the regulator trips the circuit breaker.
Just a thought.
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  #17  
Old 04-17-2021, 02:41 PM
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ExtraKatana ExtraKatana is offline
 
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Iíve done all the voltage and Ohms tests. Terminal 3 is hooked to its own fuse on a fuse block. Not jumpered. Will look closely this evening for loose connections.
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  #18  
Old 04-17-2021, 03:50 PM
rapid_ascent rapid_ascent is offline
 
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Tim,

Where are you taking your voltage measurements? You want to see what the voltage regulator is seeing. So you should use the ground on the regulator when you measure the sense voltage on the regulator. When you run the engine if the voltage goes up to the 16V then the regulator isnít regulating correctly. If that voltage is low for some reason then the regulator will try to push the voltage up.
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  #19  
Old 04-17-2021, 04:01 PM
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ExtraKatana ExtraKatana is offline
 
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I didnít check voltages to ground in that manner but I will this evening. The ground wire showed continuity to the terminal and was .1 ohms
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  #20  
Old 04-17-2021, 04:58 PM
N49ex N49ex is offline
 
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Default Bus Voltage HIGH

Quote:
Originally Posted by ExtraKatana View Post
The voltage at terminal 3 is almost the same as the Bus voltage. It's terminal 6 that is going up outta sight and popping the CB on the panel. Resting voltage on terminal 6 is very close(.2 volt lower) to bus voltage also. When i start the engine it's another story however.
This doesn't make sense. Terminal 3, as the regulation input, should be the same as the bus voltage, which you say apparently it is. But terminal 6, as the bus field supply input, should also be solidly at bus voltage, being separated from the bus only by a field breaker, and perhaps a master switch contact. So, if you say it is going up, it shouldn't, can't if wired/measured right. So, time to verify all wiring, grounding, and measurement technique to get past what doesn't make sense.

Again, if the bus is in fact for sure going up, then the sense input should follow, so if it isn't, then there is a sensing continuity issue.
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