1951 WD 9.1 VOLTS
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=194151
Printed Date: 19 Jul 2025 at 8:48am
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Topic: 1951 WD 9.1 VOLTS
Posted By: 1951WDNWWI
Subject: 1951 WD 9.1 VOLTS
Date Posted: 19 Mar 2023 at 7:23pm
| My WD had both head lights all of a sudden get bright and a couple minutes later both burned out. It is a 6 volt Autolite GGR 4801 generator. These were used on the WDs thru 1951. I measured the voltage at the battery and the output of the generator at 9.1 volts and with the switch pulled out to the second and third stops it measures 8.76 volts. I checked the wiring and it is not shorted to ground and the 3.0 ohm resistor measures 3.5 ohms. Where do you look on the Autolites for voltage adjustment? Or maybe a wire inside the generator is shorted? |
Replies:
Posted By: Gary
Date Posted: 19 Mar 2023 at 7:30pm
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What size is your battery? You didn't by mistake install an 8 Volt Battery? G |
Posted By: 1951WDNWWI
Date Posted: 19 Mar 2023 at 7:39pm
| 6 volt battery. With tractor off and battery disconnected it reads 6.3 volts. I have owned this tractor for 24 years. I use this for plowing snow and I was about an hour and a half into pushing snow when the lights all of a sudden got real bright and a couple minutes later burned out. The rear work light is a different size bulb and it just got brighter. |
Posted By: steve(ill)
Date Posted: 19 Mar 2023 at 8:24pm
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I dont know if there is a way to "adjust" the generator.. What i do know is that a 6 volt generator will put out 12 volts or so if NOT CONNECTED to the battery.. The battery is a "voltage sink" and keeps the charge down to 6.5 -7 volts ......... is it possible you have a bad connection on the battery terminals or ground strap ? Hard to beleive it would crank if bad connections......... but the generator will put out excessive voltage if not connected to the battery.. ------------- Like them all, but love the "B"s. |
Posted By: 1951WDNWWI
Date Posted: 19 Mar 2023 at 8:28pm
| That is the mystery. It cranks and starts great. |
Posted By: steve(ill)
Date Posted: 19 Mar 2023 at 8:33pm
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i dont know your wire diagram, but is it possible that the battery cable is connected good to the starter, but the GENERATOR wire is not connected to the battery, but IS connected to the lights ?? ------------- Like them all, but love the "B"s. |
Posted By: 1951WDNWWI
Date Posted: 19 Mar 2023 at 8:35pm
| Measuring across the battery terminals 9.1 vdc when running and 6.3 vdc when tractor is off. |
Posted By: steve(ill)
Date Posted: 19 Mar 2023 at 8:39pm
|
if your ammeter failed, or you broke wire #5 from amp to starter... that might cause this problem....... you probably have a PUSH BUTTON starter switch ? also, do you have a CUTOUT on the generator ( or a real VOLTAGE REGULATOR ?) ...I asume a cutout, since you talked about the light switch and resistor... might put a JUMPER wire from the "G or "A"" terminal of generator to the battery NEG terminal ( 6 volt positive ground ?? ) ... and then measure the battery voltage when running.. That wire will bypass the cutout, ammeter and misc wires.
 ------------- Like them all, but love the "B"s. |
Posted By: Les Kerf
Date Posted: 19 Mar 2023 at 10:43pm
|
I typed out the relevant passage from my Model B-C service manual which has a similar third-brush type generator with the cutout relay and light switch regulation. "The light switch must be replaced if found defective due to poor contact points. The resistance unit provides the means of reducing the charging rate of the generator by limiting the amount of electricity allowed to flow through the field coils of the generator. If the generator is in good condition and the high charge rate cannot be obtained, it indicates the resistance unit contact points do not open. If the low rate cannot be obtained it indicates the resistance unit points fail to close, are dirty, or the winding burnt out or broken”. I would be taking a close look at the light switch, also the condition of the third brush. |
Posted By: DaveKamp
Date Posted: 19 Mar 2023 at 11:18pm
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Generator going to an uncontrolled (high) voltage means the generator's field is not being limited, it's going to full flow... and once it does that, the system voltage rises... ...which flows more current through the generator field, so it builds a bigger field, which pushes output voltage up... .... which flows more current through the generator field... See what's happening there? it compounds to self-destruction... check the wiring and the dash switch, as well as the contacts in the cutout (that little box on the side of the gen) ------------- Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest. |
Posted By: Les Kerf
Date Posted: 20 Mar 2023 at 1:32pm
This is, of course, correct. I am wondering if this particular situation is actually going "full field". My late Father-in-law ran an 8 Volt battery in his WD for many years, which required the stock generator to be bumped up to something above 9 Volts in order to charge the battery; this was accomplished by adjusting the third brush in the generator. I suspect the OP still has at least some resistance in the Field return circuit which is limiting it to the 9.1 Volts. It certainly needs to be addressed or damage is sure to happen. |
DaveKamp wrote:Posted By: Steve in NJ
Date Posted: 20 Mar 2023 at 7:26pm
|
I'm coming in on this kinda late, but it sounds to me like the Battery Pos. ground cable lost it's ground either at the terminal or where its grounded. Clean all your Battery cable connections on both ends. Snow gets things wet, (especially grounds) and you can lose a ground at the Battery. Battery lost the ground, 8-9 volts went to the lights....Poof! Also, could be a broken or worn brush or brush holder and grounded on the case inside. Do the easy stuff first. Clean the Battery terminals on both ends..... Steve@B&B ------------- 39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife |
Posted By: 1951WDNWWI
Date Posted: 21 Mar 2023 at 6:05pm
| Cleaned grounds and terminals on generator and battery and ran for 10 minutes. Starts out at 7.3 volts and climbs to 9.1 volts 15 amps. Took cover off generator and bare wires with shreds of insulation hanging off them. Pressing on the brush I could reach would drop the voltage to 8.5 volts. Looks like rebuild or change out time to 12 volts. |
Posted By: Ted in NE-OH
Date Posted: 07 Apr 2023 at 5:10pm
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There is a screw on the back of the generator that when loosened allows the third brush to be moved to increase or decrease the charging rate. You will need to take off the sheet metal band and use your finger to move the brush. Do this without the tractor running. ------------- CA, WD, C, 3 Bs, 2 Gs, WC, I-400, 914 |
Posted By: Newwood
Date Posted: 08 Apr 2023 at 2:05pm
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1951: so just as a followup-- did you solve the problem or are you doing rebuild or going the alt route? I've posted with a similar high voltage high amp problem on my '49 WD and inquiring minds want to know where you're headed! jack
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Posted By: 1951WDNWWI
Date Posted: 08 Apr 2023 at 8:51pm
| I am going the 12 volt route. Caution if you do it. The present generator top bracket 'may' fit but after so many years the bolt holding it and the water pump was worn about a third of the way through. I worked it back and forth but the bolt snapped off. I have been treating the broken off bolt with PB Blaster as well as the other two bolts that hold the water pump on. I bought the alternator bracket and replacement lightbulbs from DJs tractors and the 63 amp single wire alternator and pulley came from a local shop. The original radiator had enough leaks that I will be replacing it also. Also. The transmission leaks enough from worn seals that I plan on having that repaired later. Don't know if I will tackle that or take it to a shop that is familiar with the WD Allis. This is a working tractor. |
Posted By: 1951WDNWWI
Date Posted: 18 May 2023 at 9:51pm
| New one wire Delco alternator, brackets,temperature gauge, northern radiator and hoses. Used an on/on dpdt switch for the magneto switch so the voltmeter (replaced ammeter) gets voltage and light when switch is on. Just need to fix or have fixed the transmission seals that are leaking. Starts and runs great. Plowed and disk garden the other night and pulled some down branches from our winter storms to the brush pile. |