1949 B turning on lights kills engine

   / 1949 B turning on lights kills engine #1  

w9trb

New member
Joined
Aug 27, 2014
Messages
7
Location
Tuscola, Illinois
Tractor
John Deere "B"
A fully restored B that we run in parades and an annual tractor drive. I was getting ready for a church hay-ride but when I switched on the lights the engine died. I have inspected as much of the wiring as I can see and none of the insulation is damaged. What can I check next?
 
   / 1949 B turning on lights kills engine #2  
Older thread.....might help

 
   / 1949 B turning on lights kills engine #3  
It sounds like a short to ground on the hot side of your headlight circuit. Your light switch may have failed internally or the wiring may be abraded or pinched at some point, possibly where it is routed through a hole or tight space. You may only have one wire from the light switch to the fixture itself. The other terminal on the bulb socket will be grounded. If the hot wire is grounded at any point it will kill the engine. You can troubleshoot visually for the obvious or with an ohmmeter or test light.
 
   / 1949 B turning on lights kills engine #4  
A fully restored B that we run in parades and an annual tractor drive. I was getting ready for a church hay-ride but when I switched on the lights the engine died. I have inspected as much of the wiring as I can see and none of the insulation is damaged. What can I check next?

the first thing I always check is the battery voltage. It takes very little power to run the engine, but a lot to run the lights. Did the starter crank normally when you started it?
Checking the battery voltage when it is running and then again after it has sat not running & with the lights on and off will tell you a lot about the whole system.
Use a digital multimeter. Check DC voltage across the battery. Copydown the numbers to two decimal places.
Compare to:
 
   / 1949 B turning on lights kills engine
  • Thread Starter
#5  
Update: I got new switches from Steiner and installed them this morning. Engine still dies when I attempt to turn on lights. With engine off battery voltage is 6.2, with engine running the voltage reading jumps around with readings from 4.6 to 6.4. Also, with engine off, the lights will not come on. The bulbs all have intact filaments and the wiring looks good. So, I am perplexed. Any ideas?
 
   / 1949 B turning on lights kills engine #6  
As you have realized,electrical problems on old machines that have undergone countless alterations over the years can be difficult to unravel. x that by 10 when you can't even see it,much less put a meter on it. That being the case,we need to know how well you understand readings from the multimeter. Do you fully understand "voltage drop" and instantly see it when it happen's during troubleshooting?
The fluxuating voltage while running shouldn't drop below 6v unless rpms are slow AND there's a heavy load on electric(ignition isn't a heavy load). Just a wag,but sound's like generator and/or regulator malfunction or more specificly lights and/or ignition connected to regulator circut instead of battery. This isn't very sintific but might lead us in right direction. Carfully disconnect generator wires,not alowing them to touch anything while off,note which go's to what post so they can be reconnected right. Will lights burn (they should). Will tractor start and run with wires off gen?(It should) Does engine still die when lights turned on? Is ignition origional points and coil type or has it been converted to something different (electronic,mag)? Is coil marked 6v or 12v ? What I'm thinking is that lights and/or ignition are tricking regulator and somehow disconnecting or going into series instead of paralell as they are supposed to be. That's enough until we get this behind us.
 
   / 1949 B turning on lights kills engine #7  
Update: I got new switches from Steiner and installed them this morning. Engine still dies when I attempt to turn on lights. With engine off battery voltage is 6.2, with engine running the voltage reading jumps around with readings from 4.6 to 6.4. Also, with engine off, the lights will not come on. The bulbs all have intact filaments and the wiring looks good. So, I am perplexed. Any ideas?

Ok. I wish I was there to help.

If the battery reads 6.2 volts was that right after charging? If so, we also need to check it after just letting it sit uncharged and unused a few days later to get a complete picture of the battery condition. I always hope it is just the battery because it is so easy to deal with. A few bucks and done.
BTW, which battery terminal is connected to the frame on your tractor? Plus or Minus?

If the tractor charging system was good, the generator should be putting out a constant 6.8 volts or more and not jumping around like that even if the battery is weak. That says there is definitely a problem with the generator or voltage regulator.

Jumping like that, the tractor isn't charging the battery, so my guess is that you have been putting the battery on a charger when you know you are going to be driving the tractor. That's why we are looking at the battery after it sits a few days.

Simple things first, so I'd check to see if the generator brushes are worn down. The generator has a wrap around cover on the back that you can take off to inspect the brushes. The carbon brushes are held in their brass brush holders and also pushed down against the commutator of the generator by a spring. When the brushes get worn down too far, the spring rests on the brush holder instead of on the carbon brush. That will make it irratic, and if it goes on too long the voltage jumping around will wear out the points in the Voltage Regulator. Brushes are easy to replace, but you might need to

Take a look at those brushes, measure the battery after sitting a few days off the charger, and also you might want to take a look at a couple of Threads in Yesterday'sTractors:

Good luck,
rScotty
 
   / 1949 B turning on lights kills engine
  • Thread Starter
#8  
Ok thanks for the replies. I will let it set for a few days and check battery again. It has been a month or two since I last put the trickle charger on. In fact it was just before we were going to do the Church hay-ride late October. I will investigate the generator brushes this weekend to see if that is the culprit.
 
 
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