need help with alternator

[compedgemarine]

hopefully someone can help me with this on my '81 Eagle. I replaced all the wiring to the alternator and the regulator and to the regulator relay as it was cobled up and not charging properly. with it running I get 0 volts at the relay post on the alt. and the relay is inop and it is not charging. if I unhook the relay wire I get 12 volts at the post but no charge. if I power the relay to close the coil and feed power to to regulator it charges 13.5 at idle and 14.5 on high idle. why do I lose voltage at the relay post if it is hooked to the relay? also if I feed power to the relay with the relay post wire hooked up it sparks pretty good. is there a problem in the alt. with wherever it gets the 12 volts from for the relay post? the alt. works if you power the relay so hopefully there is an easy fix.
any ideas?
thanks
steve

[Dreamscape]

Hi Steve,

I will fire mine up tomorrow and check what readings I get. When I was having problems I found that I needed to adjust the voltage regualtor to a higher reading. Don't know how much differant yours is than mine. I have a 68 Eagle 01, 8v71. What engine and alternator do you have? Is everything grounded properly? Do you have a manual? My manual describes in great detail what to do and how to troubleshoot.
I'm sure others will have more ideas.

Happy Trails,

Paul

Dreamscape

[compedgemarine]

engine is a 6v92. all the grounds are good and I have the manual and made sure that I hooked it up the way it showed and it matched the way it was hooked up. my understanding of the manual is that as soon as the alt. starts charging the relay wire should have 12 volts and trigger the relay sending 12 volts to the regulator. as it is the only way to get the 12 volts to the regulator is to trigger the relay with 12 volts from a source not related to the alt. at which time it kicks in and starts putting out 14 + volts. also I show about 2 volts less on the gauge at the dash than at the alt. it is not the gauge as it matches my voltmeter. not sure why I lose 2 volts from rear to front.
thanks
steve

[Jerry Liebler]

Steve,
     You replaced the relay that's hooked to the 'r' terminal.  Could you have replaced it with the wrong relay.  The relay that is hooked to the 'r' terminal must be rated at 1/2 the voltage of the system so if your bus is a 12 volt bus you need a 6 volt relay coil connected to the 'r'  terminal.   Also the resistance of the coil of the relay on the 'r' terminal must be high enough that the alternator can 'pull it in' with no field current, just residual magnetisation.    If you have used the correct relay then you may have an internal short inside the alternator's stator or an open diode in the alternator.  If it's a 50DN you can open a cover over the diodes, disconnect them and test them and check for stator shorts.
Regards
Jerry 4107 1120

[compedgemarine]

well I didnt know that it needed to be a 6v relay so maybe that is part of the problem. does the manual state that it is 6v and I just missed that or is it just little known fact? also are there any other relays that are 6v? what is the relay over a couple that says motor? I cant seem to find it in the book. thanks for the ideas and I will swap out the relay for a 6v tomorrow and see what happens.
thanks
steve

[Jerry Liebler]

Steve,
    It's in the manuals for my GM.  The voltage at the 'r' terminal is like the positive half of a sine wave with a peak positive voltage of 0.7v more positive than the alternator's output, so it's only on about 1/2 the time, the other 1/2 the time it's actually 0.7v negative.
Regards
Jerry 4107 1120 

[Jerry Liebler]

Steve,
    If it turns out to be an open diode or shorted stator these can be replaced without removing the alternator from the engine.  You should be able to get the parts through a local alternator re builder.
I had a shorted stator in mine and got a replacement and the 'o' rings from a shop in Portland Or.
Regards
Jerry 4107 1120

[Jerry Liebler]

Steve,
     You have a second problem with the voltage drop from rear to front.  There may be some drop but it should be less than 0.1 volts.  You'll need to look over all the 'connection' points, one or more are loose and or corroded.  Cleaning and tightening should fix it or you may have a wire into a terminal that's no longer properly crimped or is corroded badly. 
Regards
Jerry 4107 1120

[buswarrior]

and the corrosion may be inside the cable, look carefully up the inside of the crimps and the shrink covering, bend it around a little, getting dust out/seeing some green is not good.

Factory battery cables corroded right through under the heat shrink in three years on several new Prevost at one of my places of employment, so it'll happen to us easy too!!!

happy coaching!
buswarrior

[pvcces]

Jerry, the generator does not use residual magnetism to start it, as far as I know. In the 4106, there is a resistor that is powered up when the master switch is turned on that provides a tickle current to the field. While that current is not high enough to get it to start the generator while the engine is idling, it will start the generator if the engine is revved up beyond the high idle RPM.

That's why we always have to goose the old Detroit to get the generator started.

After the generator starts charging, the tickle current from the resistor is cut off, and the regulator has full control over the output.

For those of you that don't already know it; the generator is really an alternator; I used the term generator the way that the service manual uses it; the DN50 is an alternator and uses alternator type charging circuits.

For what it's worth.

Tom Caffrey

[Jerry Liebler]

Tom,
     You are correct about how GM did things.  I once again looked at my manual and it appears that the relay connected to the 'r terminal is only used to allow the HVAC blowers to turn on, it is not in any way involved in the operation of the regulator or alternator control.  When the 'engine run' switch is turned on the regulator is connected to the 'generator'.  The regulator then immediately starts supplying battery power to the field and is in full control of the 'generator's' output.  Steve's Eagle must be different from the 'symptoms' he described.
You must have either a low battery or a 'sick' regulator if you have to 'rev' the engine to get the 'generator' started, I sure don't have to rev mine, it starts charging immediately after starting, at low idle.
Regards
Jerry 4107 1120

[compedgemarine]

OK, I tried the 6v relay and same problem. I have 5.5 volts or so at the relay post but if hooked to the relay to actiavate it the voltage goes to 0. if I trip the relay and send the voltage to the regulator the alt.
comes alive and charges at 14.5 volts(regulator may be set high). as I understand the wiring diagram the relay post is just turning on the regulator when the engine is running so that it is not powered when the key is off. being a diesel it is just replacing the ignition wire on a gas engine that would normally power the regulator? could I cheat and use a keyed wire off the front switch to activate the relay? I am doing a lot of rewiring anyway so a dedicated wire to the rear to power keyed items is not a big deal.
any thoughts?
thanks
steve
1981 Eagle 10 #20241

[compedgemarine]

P.S. the alternator is an air cooled 50DN

[DrivingMissLazy]

On my 80 Eagle with 8V92, I wired a relay to energize and apply power to the regulator when the run switch was turned on. Depending on the charge status of your battery, 14.5 volts sounds about right.
Richard

[Jerry Liebler]

Steve,
     I don't think your suggested fix is cheating at all because as I said in a previous post that's what GM did.  On the GM buses a relay connects the regulator input to the alternator output, and thereby the battery, when the engine run switch is on.
Regards
Jerry 4107 1120