MF275 Not Charging

   / MF275 Not Charging #1  

Ron John

New member
Joined
Apr 4, 2013
Messages
13
Location
Victoria, BC
Tractor
Massey Ferguson 275
The alternator on my 275 stopped charging. I had it bench tested at a local repair shop and it was found to put out the spec voltage -14V. I put it back on the tractor - still not working (showed battery voltage (12 something) measured from the the + terminal on the alternator to the alternator case). I am thinking that it is something to do with a relays under the inst panel? Any thoughts? Thanks
 
   / MF275 Not Charging #2  
Check out the thread under the mf vintage section "73 MF135 perkins diesal" Alternator problems were gone over extensively in this thread and may give you some tips or answer your questions. Hope this helps.
 
   / MF275 Not Charging
  • Thread Starter
#3  
ok thanks will check it out
 
   / MF275 Not Charging #4  
There is a pressure switch behind the oil pressure gauge. That would be my guess to look first. If that relay stays open it's not going to charge without bypassing it which is how to verify it being bad. In other words. Once your oil pressure comes up it should be charging. -kid
 
   / MF275 Not Charging
  • Thread Starter
#5  
OK will bypass the pressure switch and see what happens. What in the heck is the logic of linking charging to oil pressure?
 
   / MF275 Not Charging #6  
OK will bypass the pressure switch and see what happens. What in the heck is the logic of linking charging to oil pressure?
Welcome to TBN.
Sorry for your trouble.
Maybe: no oil pressure, no charge so you don't try to start your engine when the sump is low?
 
   / MF275 Not Charging #7  
I believe the concept is this - the key switch does no more than engage the starter. It has no ignition or accessory positions. When the engine starts, oil pressure closes a switch and power is suppled to gauges, charging etc. On gas tractors a different switch is used and an ignition circuit is provided. This may seen odd to some, but Massey used for many years on a great many tractors.
 
   / MF275 Not Charging
  • Thread Starter
#8  
Thanks for all the replies which helped alot with working this out. I think that the deal is that the until the oil pressure goes up all the power goes to the starter, and also the alternator should be stopped from charging since under load it is harder to turn, and that bit of increase in resistance could make the difference in starting or not in some instances.

To get my alternator charging I disconnected the wire running to the pressure switch, started the engine and touched this wire to the positive terminal and bing! PROBLEM SOLVED 14V!. (or at least a pretty easy work around til I find the time to deal with the pressure switch).

Thanks again folks.
 
   / MF275 Not Charging #9  
This wire should be disconnected when the machine is not running,
or you take the chance of draining your battery.
Your alt has to be "energized" before you start your machine, for it to charge.
Hook this wire up to a toggle switch, one end on the battery and the other to your "wire.
Flip the switch ON, "before" starting your machine and it will charge.
When your done working and shut your machine down, flip this switch OFF.
You can also leave this wire attached to where it's suppose to go, "oil pressure",
and attach a wire to it leading to your switch.
 
   / MF275 Not Charging
  • Thread Starter
#10  
thanks for this. I like the idea of the toggle switch.
 
 
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