12 volt gen.putting out 42.5volts ?
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Category: Allis Chalmers
Forum Name: Farm Equipment
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=130263
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Topic: 12 volt gen.putting out 42.5volts ?
Posted By: HudCo
Subject: 12 volt gen.putting out 42.5volts ?
Date Posted: 20 Oct 2016 at 9:44pm
| probley should have posted in differant part but heres the story, we had a 620 john deere in the shop today cleaned the comuntator and replaced the bearings in the gen also changed every thing to be neg ground fron pos ground ( voltage regulator was hooked back up in correctley when it got hooked back up when i put a test light on the bat terminal it seamed real bright so iput a meter on andit said 42v checked back at the battery and it said 12.40 checked with differant meter still said 42vdc WHAT HAPPENED ? ran it down to the the generater shop and it would motor but only make 13v do have another reg. on the way |
Replies:
Posted By: DrAllis
Date Posted: 20 Oct 2016 at 10:12pm
| 42 volts should have made your 12volt test light go off like a flash bulb on a camera, so I doubt that it's 42 volts. |
Posted By: steve(ill)
Date Posted: 20 Oct 2016 at 10:28pm
|
I have taken 12 volt generators , disconnected the lead to the battery and have them put out 36 volts........ the battery is a REGULATING BASE. This is why you can take a 6 volt generator and connect to a 6 volt battery or a 12 volt battery and have it work on either.. You need the BATTERY to act as the LOAD.... then the regulator does the fine tuning...... I would check your battery wire from the generator... might not be connected.... could be broke at the regulator or inside the reg. ------------- Like them all, but love the "B"s. |
Posted By: Gerald J.
Date Posted: 21 Oct 2016 at 8:27am
|
All it takes is turning the generator faster. The regulator takes care of controlling the voltage by controlling the field current. If its a 3 brush generator, as in many Allis, its not voltage regulated, just the third brush causes current limiting. Be sure to flash the generator before running the engine after changing the battery polarity, else the generator will build with the wrong polarity and fry the cutout contacts. Some regulators are polarity sensitive. Gerald J. |
Posted By: Tcmtech
Date Posted: 21 Oct 2016 at 9:07am
| If you had 42 volts at the BAT terminal on the regulator but 12.4 volts at the battery you have a broken connection somewhere between the two. |
Posted By: HudCo
Date Posted: 21 Oct 2016 at 9:19am
| i missed a word when i typed the original post, the reg was NOT hooked up correctly also the battery wire was hooked to light terminal on reg . the correct reg will be here today and hope we didnt ruin the gen yes 42 v couldnt belive that it didnt blow the test light even being rated for 24 |
Posted By: HudCo
Date Posted: 21 Oct 2016 at 9:25am
| there was also a broken at the ampmeter it had been (bat wire) it was hooked to ign. on the swicth thanks for the replies see new things every day helps keep a guy on his toes |
Posted By: Brian Jasper co. Ia
Date Posted: 21 Oct 2016 at 12:54pm
|
Look back a page or so where Tracy Martin was asking how to test his generator. I posted how to test a generator there. ------------- "Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford |
Posted By: HudCo
Date Posted: 22 Oct 2016 at 9:12am
| up date on the gen and reg . issue got a regulator dy the way delco # 1118792 from the john deere dealer, suprising the price was about the same as all the part stores, got stopped it at the generator shop we put it on and ran it on the machine and we would have to shut it of at 16v and would just sit and motor we could tap on the reg with a screw driver and make it stop. so it whent straight back to the the john deere store another one will be here agian on monday just as well stop at the generator shop with the next one also the johndeere part said made in india on it |
Posted By: Tcmtech
Date Posted: 22 Oct 2016 at 9:57am
Just for a heads up. I see two possibilities for what happened here. One. On the majority of those old mechanical regulators they need to be hooked up to a good battery before they will test and work properly. Especially for the ajti motoring disconnect function to work so they don't motor on. The reason being the relay inside the regulator for the disconnect between the ARM input and BAT output is set up with two windings that oppose each other's magnetic fields when the generator starts motoring. The main winding is the voltage sensing one that pulls the relay contacts together when the generators output voltage is high enough to start charging the battery. The other is a current sensing coil that works as the anti motoring cut out when the current flow starts going backwards from the battery back into the generator cancels out the voltage sensing coils magnetic field causing it to release the contacts. Without a solid circuit connection to a good properly charged battery and the generator physically connected to a sufficient mechanical load like a engine that disconnect relay can screw up and stay activated when it shouldn't be like if the battery is not taking a properly charge and the system voltage goes way high and the generator is being driven by an electric motor that has very little mechanical braking effect to make the generator draw a high current when it goes into motoring mode. Between the two conditions it's entirely possible to produce a situation where the voltage sensing coils magnetic field will be too strong for the weaker anti motoring coil to cancel out due to there being insufficient mechanical loading to drive the anti motoring coils counter magnetic field up to a point it can cancel out the voltage sensing coil field and release the contacts.  The other likely possibility is the regulator never got set up properly and its voltage regulation was never straight, running way too high, and the disconnect relay was set wrong as well hence needing the tap to get it to release. To me the need to tap it suggests that either of those may have been the situation. I've seen it enough times before to know what most often causes it. Either way a good competent service tech should have picked up on the likelihood of those possibilities right way and pulled the regulators cover off and tried adjusting things first before declaring it bad.
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HudCo wrote: