John Deere B Amp Gauge shows no charge

pmarkel

Member
I have a 1948 John Deere B that starts and runs real nice and has done so for about one year on a new battery (replaced Aug 14'). However, the amp gauge shows no indication of charging taking place. I changed the gauge thinking it might be defective but the new one shows the same. When the lights are turned on, the gauge does show power being drawn from the battery. Might this be a problem with the voltage regulator? And if so, what is the process for installing and polarizing a new 12 volt voltage regulator? Thank you for your time.

Sincerely,

Peter Markel
 
Ground the F terminal on the generator. It should charge full charge. If it doesn't the gen. is bad. If it does, trouble with reg. Make sure the reg. is properly grounded. Reg. doesn't get polarized, gen does by putting battery power to A terminal. Polarize before starting.
 
If it's still starting and running fine after a year, then it's very likely that the charging system is working fine and just not showing battery charging current due to the way the amp gauge has been rewired in the years since it was new. This can be determined to be so by tracking down the wiring at the amp gauge itself.

If you have two wires at the gauge connected to the gauge post that is connected to the copper starter bolt, then the 'other' gauge wire on that same gauge post there is from the voltage regulator that charges the system and that charging current is bypassing the amp gauge, in effect being connected directly to the battery. Move only it to the other post of the amp gauge and now you will see charging current on the gauge. The 'battery' post on the amp gauge should only have one wire on it going to the battery via the main connection at the copper starter bolt where the large battery cable is connected.
 
You don"t mention the battery going dead. If it does not go dead (and after a year I"d surely think that likely) I"d be real suspicious of things just not being wired correctly at either the regulator or at the ammeter. They"re likely close but just not quite right.

The late B"s used a 4 post regulator and there really should be only two wires on the ammeter. The one from the battery (via the starter post) on one post and the white wire from the regulator on the other. The light switch"s battery feed should be from the black wire connected to the regulator post marked an "L" for load or lights. If the tractor is properly wired removing the L wire at the regulator should make the lights NOT work!

Some wonder why but the deal is, if the lights are not fed by the L terminal of the regulator or if it has only a 3 post regulator with both the white and black connected to the B post of the regulator, the engine (with the stock generator) will need to be run near wide open to keep from discharging the battery! On a 4 post regulator with the lights fed by the black wire on the L post at the regulator, they need only to be slightly off dead idle to feed the lights and NOT discharge the battery. Using the L terminal to feed the lights really helps the charging system!

Since your ammeter shows a discharge when the lights are on, the ammeter is likely not the problem. It sounds like you need to check the wire connections because.... if the battery isn"t going dead on you, the charging system is working but the tractor is just not correctly wired to allow ammeter to show it! I"d almost bet the white wire from the ammeter to the battery and the white wire from the generator to the ammeter are both on the same post of the ammeter and some other wire feeds the lights from the OTHER post of the ammeter to the light switch.

Hope that helps.
 

I could be wrong, but I think the regulator on my B only has 3 terminals. It was converted to 12 volt, but long before my purchasing the tractor. Needless to say, nothing is marked or color coded anymore. As is, there are two wires from the generator to two terminals on the regulator and one wire from the regulator to the ammeter. As is, I believe there are three wires connected to the ammeter: one wire from the voltage regulator, one wire to the light switch and one from the battery. I dont know of a 4th terminal on the regulator', but I will check tomorrow in the daylight (no lights in the shed yet). Do some regulators only have 3 posts? And if this is the case, do I have any option but replacing the regulator with a 4 post?
 
Yes 3 post regulators will work. They just work a bit different than the 4 posters.

Which wire is where on the ammeter makes all the difference in the world! If one post of teh ammeter has both the wire from the battery and the wire from the regulator on it and the lights are fed by the other post, the ammeter will read EXACTLY as you say in your message!

Before doing anything else... do your lights make the ammeter show a discharge when they are on and the engine is not running? If yes, the battery feed wire and the light's feed wires are on the right ammeter posts.

The wire between the regulator and the ammeter should be on the same post as the lights feed wire and I almost bet it's right now on the post with the batery feed wire. Switching the regulator wire to the same ammeter post as the feed wire to the lights will likely fix your problem.

This way the current going to the lights will come from the generator when it running as long as the engine is running fast enough to keep up. If it is not running fast enough to keep up with the demand of the lights, the ammeter should show a discharge but not as big a discharge as it shows when the engine is not running. That discharge should go away when you turn off the lights.

Sounds to me like the wires are all there & working but just not on the right posts of the ammeter!

Hope that helps.
 
(quoted from post at 15:20:12 09/30/15) Yes 3 post regulators will work. They just work a bit different than the 4 posters.

Which wire is where on the ammeter makes all the difference in the world! If one post of teh ammeter has both the wire from the battery and the wire from the regulator on it and the lights are fed by the other post, the ammeter will read EXACTLY as you say in your message!

Before doing anything else... do your lights make the ammeter show a discharge when they are on and the engine is not running? If yes, the battery feed wire and the light's feed wires are on the right ammeter posts.

The wire between the regulator and the ammeter should be on the same post as the lights feed wire and I almost bet it's right now on the post with the batery feed wire. Switching the regulator wire to the same ammeter post as the feed wire to the lights will likely fix your problem.

This way the current going to the lights will come from the generator when it running as long as the engine is running fast enough to keep up. If it is not running fast enough to keep up with the demand of the lights, the ammeter should show a discharge but not as big a discharge as it shows when the engine is not running. That discharge should go away when you turn off the lights.

Sounds to me like the wires are all there & working but just not on the right posts of the ammeter!

Hope that helps.

Having spoken too soon before, the tractor failed to start yesterday for the first time in a year. As currently wired, the wire from the regulator is connected to the right post of the ammeter. On that same right post, a wire connects the ammeter to the light switch. On the left post of the ammeter, a wire connects the ammeter to the starter. When the light switch is pulled to activate lights, the amp meter shows a draw whether running or not. This seems to be the correct way as you described above?

However, my concern would then ,lie with the regulator wiring to the generator. A wire currently connects the terminal on the generator marked "F" to the regulator terminal commonly marked F, though no mark is present on any of the regulator terminals. The armature ground on the generator has a wire running to the middle terminal on the regulator which is commonly marked as "Bat". The wire from the regulator to the ammeter is run off of the third terminal of the generator which I believe is commonly designated "L". There is no terminal on the bottom part of the regulator where I believe the armature wire is supposed to be?
Does this seem problematic to you? Is it possible that the generator has been polarized incorrectly due to previous attempts at wiring the tractor?
 

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