Hi,i have a Universal Diesel in my boat have been going over the wireing and have found wire off back of alt.looking at the wireing diagram apears to go from switch to alt and is live when boat is running any ideas .could it be unhooked on purpose or vibrated off
alternator issues
- Thread starter David Cadwallader
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It may have been left off deliberately but if so
it should have been hooked up anyway or removed. If the alternator loses power when running it could affect (damage) the diodes. It may have originally been that source of power to the field and the PO or whoever, disconnected it in favor of a permanent hot lead to the alt. That would prevent accidentally turning it off from the cockpit, but no wire should have been left like that. It was a fire waiting to happen. If it's not connected, and your alternator is working correctly, it must be getting an input from somewhere. I would look again to see if it was something different, or watch and see if someone here has a better idea. Someone who is more familiar with your wiring arrangement. I'm just throwing out a possibility here, not a definite answer. Anybody else? Good luck Joe S
it should have been hooked up anyway or removed. If the alternator loses power when running it could affect (damage) the diodes. It may have originally been that source of power to the field and the PO or whoever, disconnected it in favor of a permanent hot lead to the alt. That would prevent accidentally turning it off from the cockpit, but no wire should have been left like that. It was a fire waiting to happen. If it's not connected, and your alternator is working correctly, it must be getting an input from somewhere. I would look again to see if it was something different, or watch and see if someone here has a better idea. Someone who is more familiar with your wiring arrangement. I'm just throwing out a possibility here, not a definite answer. Anybody else? Good luck Joe S
check for charging condition
Check to see if the alterator is charging. Put a voltmeter across the battery terminals, with battery selector in "both" position, and engine running. Charging voltage should be close to 14 volts. Sometimes the extra wires, not hooked up, can befor an accessory that is not installed on your boat, for example an ammeter gauge or voltage gauge.
Check to see if the alterator is charging. Put a voltmeter across the battery terminals, with battery selector in "both" position, and engine running. Charging voltage should be close to 14 volts. Sometimes the extra wires, not hooked up, can befor an accessory that is not installed on your boat, for example an ammeter gauge or voltage gauge.
If it's An Aftermarket....
...alternator, then the chances are good that there may be some extra hook-ups for i that have been left off, as mine has. So if you, now, keep a different spare, be sure that you keep the hookup instructions with it. Or in my case m the spare is the same as the aftermarket one. So I can use the existing one as a model if I after have to hook it up. The loose wire(s) should be taped off and out of the way.
...alternator, then the chances are good that there may be some extra hook-ups for i that have been left off, as mine has. So if you, now, keep a different spare, be sure that you keep the hookup instructions with it. Or in my case m the spare is the same as the aftermarket one. So I can use the existing one as a model if I after have to hook it up. The loose wire(s) should be taped off and out of the way.
Good thought, Mike...
...I never realized why there was extra wires because I don't have an amp guage, but I do have a voltage guage.
...I never realized why there was extra wires because I don't have an amp guage, but I do have a voltage guage.
one caution
Actually two cautions: 1. if the batteries are fully charged, most alts are field wired and sense a full charge resulting in cut-back such that you won't see a voltage rise. If you look at voltage under this condition as an indicator of mis-wiring, it may be misleading, and 2. there is no such thing as a generic wiring scheme for alternators. What alt do you have on this engine David?
Actually two cautions: 1. if the batteries are fully charged, most alts are field wired and sense a full charge resulting in cut-back such that you won't see a voltage rise. If you look at voltage under this condition as an indicator of mis-wiring, it may be misleading, and 2. there is no such thing as a generic wiring scheme for alternators. What alt do you have on this engine David?
Re: one caution
Voltage is voltage. The charging voltage should be within the range of 13.6 to 14.2volts. The field current will affect the number of amps being sent to the batteries. High ampere output indicates a low battery state of charge or heavy load on batteries.
Voltage is voltage. The charging voltage should be within the range of 13.6 to 14.2volts. The field current will affect the number of amps being sent to the batteries. High ampere output indicates a low battery state of charge or heavy load on batteries.
Good point Don.
" there is no such thing as a generic wiring scheme for alternators. What alt do you have on this engine " and which engine? There are 2 generic types of alternators that I am aware of. If you read in Nigel Caulder's "Boatowners Mechanical & Electrical Manual", the section on alternators describes the various types and gives generic wiring diagrams. You will also learn a lot. Do all of your gauges work properly? Tachometer, voltage etc. Are your batteries being charged (as per other posts)?
" there is no such thing as a generic wiring scheme for alternators. What alt do you have on this engine " and which engine? There are 2 generic types of alternators that I am aware of. If you read in Nigel Caulder's "Boatowners Mechanical & Electrical Manual", the section on alternators describes the various types and gives generic wiring diagrams. You will also learn a lot. Do all of your gauges work properly? Tachometer, voltage etc. Are your batteries being charged (as per other posts)?
Some things to check
Clearly it is for something. In addition to the + and - outputs there are the 2 field wires that control the output. That is all that is required to make an alternator work. Controling the field wires can be automatic (aka regulator) or manual (aka reostat). There is also the tach lead which has AC current taken from one of the stator (non-moving) coils prior to the diodes. A positive test (>5 volts) for AC means it is the tach wire. If you have an external regulator there should be a wire coming from it to the back of the alternator and another one on the same alternator plug that either goes to ground or back to the regulator. The + and - outputs are easy as they are much larger wires and bolt onto a terminal on the alternator back. You may or may not have a - output. If you only see a big red wire and no big black (or maybe yellow) one then you should find a ground wire on the motor somewhere that goes directly back to the batteries - terminals Since you say the diagram shows it going to a switch I suspect that it is the field ground and is used to "full field" the alternator to get max output. If you ground this (momentarily) while the engine is running and the output voltage goes to +16ish volts that is a sure sign it is a full fielding setup. How old is the boat? where does the other wire from the switch go?
Clearly it is for something. In addition to the + and - outputs there are the 2 field wires that control the output. That is all that is required to make an alternator work. Controling the field wires can be automatic (aka regulator) or manual (aka reostat). There is also the tach lead which has AC current taken from one of the stator (non-moving) coils prior to the diodes. A positive test (>5 volts) for AC means it is the tach wire. If you have an external regulator there should be a wire coming from it to the back of the alternator and another one on the same alternator plug that either goes to ground or back to the regulator. The + and - outputs are easy as they are much larger wires and bolt onto a terminal on the alternator back. You may or may not have a - output. If you only see a big red wire and no big black (or maybe yellow) one then you should find a ground wire on the motor somewhere that goes directly back to the batteries - terminals Since you say the diagram shows it going to a switch I suspect that it is the field ground and is used to "full field" the alternator to get max output. If you ground this (momentarily) while the engine is running and the output voltage goes to +16ish volts that is a sure sign it is a full fielding setup. How old is the boat? where does the other wire from the switch go?
alt issues
HI it the origanal that came on the engine .a 51 amp alt used on the 16 hp universal from 85
HI it the origanal that came on the engine .a 51 amp alt used on the 16 hp universal from 85
It's a conspiracy.
I've been rebuilding alternators since the '60's using nothing but an explanation/story in Hotrod magazine. But lordy, it gets harder with each new variation of these things. And the last one on my old truck was assembled from the outside. The stator had to be destroyed to take it apart. It could not be rebuilt. What's wrong with this picture?
I've been rebuilding alternators since the '60's using nothing but an explanation/story in Hotrod magazine. But lordy, it gets harder with each new variation of these things. And the last one on my old truck was assembled from the outside. The stator had to be destroyed to take it apart. It could not be rebuilt. What's wrong with this picture?
Quick Question...
...as related to me by a boat mechanic. Why do alternators on a boat go bad so quickly. Whereas on a car, they are almost never replaced, and often last the life of the car? This will support Fred's conspiracy theory.
...as related to me by a boat mechanic. Why do alternators on a boat go bad so quickly. Whereas on a car, they are almost never replaced, and often last the life of the car? This will support Fred's conspiracy theory.
I've had just the opposite experience
with alternators. One in our car went out after a few years. One in our boat lasted for 21 years. Of course, engine hours and car mileage are vastly different things. I would see no conspiracy theory at work here, some stuff lasts a long time and some doesn't. Do a hundred hours a year in a boat. At 55 mph, that's only 5,500 miles. Twenty times that is 110,000 miles in a car. Not too shabby.
with alternators. One in our car went out after a few years. One in our boat lasted for 21 years. Of course, engine hours and car mileage are vastly different things. I would see no conspiracy theory at work here, some stuff lasts a long time and some doesn't. Do a hundred hours a year in a boat. At 55 mph, that's only 5,500 miles. Twenty times that is 110,000 miles in a car. Not too shabby.
Fred, what's a house bank?
My admiral puts what little $$ we have in some vault in somebody's basement in an office building in Toldeo? Am I msissing something?
My admiral puts what little $$ we have in some vault in somebody's basement in an office building in Toldeo? Am I msissing something?
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