Voltage Regulator internals

First I would like to thank all the help I have received on this forum. I had to replace a head gasket and in the process I discovered a bent exhaust valve. I replaced the valve, guide, spring, and keepers. I also replaced the original tappet with an adjustable tappet. I had to make a tappet holding tool so I could adjust it. I had a cracked distributor cap so I went ahead and replaced the points, rotor, cap, and plug wires. I also cleaned the carburetor. After all that it cranked and ran better than it has in years! I could not have done this without postings and searches of the forums.

Now I want to understand how the internals of the voltage regulator works. I have a 49 front mount 6v system with the 8n100000B generator (non adjustable). It is wired correctly (I ohmed this out with wires disconnected - also made sure no shorts within the harness by ohming between the wires). With the VR cover off, I observed the 2 relays. What is the function of each and when is each on supposed to activate? I also noticed there is a 20 ohm resistor (approx.) on the underside of the regulator. What is it for? I have a new battery and it reads 6.3 volts when not running. I don't think it is charging because when running I have 6.4 volts at the battery. The generator "motors" with the belt removed and hooked up to act as a motor so I think it works. Since I don't understand how the VR works, it limits my troubleshooting. any help would be appreciated. Thanks.
 
I can't argue w/ the explanation in the link FLAcharlie posted.

The flow chart will help you diagnose the problem.
RevisedFlowChart.jpg

75 Tips
 
Thanks. I read that twice. I will have to read it several more times to fully digest it (wife says I'm slow on the uptake sometimes). The VR does more than I thought.
 
(quoted from post at 19:18:05 08/08/14)

Now I want to understand how the internals of the voltage regulator works. I have a 49 front mount 6v system with the 8n100000B generator (non adjustable). It is wired correctly (I ohmed this out with wires disconnected - also made sure no shorts within the harness by ohming between the wires). With the VR cover off, I observed the 2 relays. What is the function of each and when is each on supposed to activate? [b:22e632c00e]The 'relay' with its contacts normally open at rest is the cut out function. It should close as generator output increases to a preset voltage and functions to connect the battery to the gen armature. Additionally to disconnect arm from battery when gen slows such that its output is too low to charge the battery & would if not disconnected, drain the battery.[/b:22e632c00e] [b:22e632c00e]The other 'relay' is to control the field current in the generator. It is normally at rest closed & is supplying a ground to the field coils, which are receiving voltage from the ARM within the gen. It will stay closed for maximum charge and will begin to vibrate/cycle at various rates for intermediate charge rates as battery reaches full voltage & will open to cut field current & thus gen output to a minimum at full batt charge, so as not to overcharge the battery. If the field contacts do not close good, as if corrosion on them, then you won't have much of a measurable gen output. Short field to ground to check for this condition & output should jump up.[/b:22e632c00e] I also noticed there is a 20 ohm resistor (approx.) on the underside of the regulator. What is it for? [b:22e632c00e] That is an arc suppression resistor whose purpose is to quench the arc created by opening an inductive load (the fields) & thus give the contacts a longer life. It is connected directly across those field contacts.[/b:22e632c00e] I have a new battery and it reads 6.3 volts when not running. I don't think it is charging because when running I have 6.4 volts at the battery. The generator "motors" with the belt removed and hooked up to act as a motor so I think it works. Since I don't understand how the VR works, it limits my troubleshooting. any help would be appreciated. Thanks.
 
google "how does a voltage regulator work on a tractor" Get the PDF "Instructions for Testing and Installing a Voltage Regulator fo.....", that looks like it might be helpful.
 
Thanks. Its raining tonight and I will be visiting family in Atlanta until middle of next week, but I'll check VR operation later and post back. This is a big help.
 
You may think how a VR functions is a MYSTERY... It is an even BIGGER mystery how an exhaust valve would get bent on a Ford "flatty"!
 
(quoted from post at 05:17:59 08/09/14) You may think how a VR functions is a MYSTERY... It is an even BIGGER mystery how an exhaust valve would get bent on a Ford "flatty"!
I don't know either, but I poured gas on top of all valves to make sure they were sealing and this one wasn't. I took it out (these are probably originals since they had the old "FoMoC" logo on top of each valve). So I removed it (very difficult) and thought it looked slightly bent so I chucked it up in a drill and it wobbled. Bought new valve, lapped it and it sealed against the seat. Maybe it fatigued over time, maybe it got stuck once in the guide, maybe, maybe,maybe..... I have no explanation, but it just wouldn't seal. These are older valves that you had to grind to get the correct clearance but I replaced it with non-rotating type valve and adjustable tappet. Good point but I have no clue as to why it was bent.
 
(quoted from post at 08:48:22 08/09/14)
(quoted from post at 05:17:59 08/09/14) You may think how a VR functions is a MYSTERY... It is an even BIGGER mystery how an exhaust valve would get bent on a Ford "flatty"!
I don't know either, but I poured gas on top of all valves to make sure they were sealing and this one wasn't. I took it out (these are probably originals since they had the old "FoMoC" logo on top of each valve). So I removed it (very difficult) and thought it looked slightly bent so I chucked it up in a drill and it wobbled. Bought new valve, lapped it and it sealed against the seat. Maybe it fatigued over time, maybe it got stuck once in the guide, maybe, maybe,maybe..... I have no explanation, but it just wouldn't seal. These are older valves that you had to grind to get the correct clearance but I replaced it with non-rotating type valve and adjustable tappet. Good point but I have no clue as to why it was bent.

I would imagine a foreign object that gets trapped between head and seat can bend it.

TOH
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top