replacing solenoid on 12v 8n

Anonymous-0

Well-known Member
Apparently, my starter solenoid is bad; bought a new one, a similar four-post type but no orientation or idea how to wire to new one. Any ideas?
 
8Ns use a three post solenoid. small post is provided a ground by the saftey starter switch on top of trans. small terminal goes towards engine. 4 post , I have no clue how it was wired. You see all knids of set ups after 60 years.
 
Most 4 post types will not work on the N serie tractor with out doing away with the safety switch which is not a good idea. Take it back and get the correct 3 wire solenoid
 
unless your 4 post is a tractor type for an 01 series.. and a diesel at that.. being 12v.. it won;t work. IE... if it is a car solenoid.. it won;t work with the safety interlocked thumb switch.

if it is the tractor 4 post type. one small post to thumb button on trans top. one small post to key-on power. one large post to bat hot. one large post to starter..

so.. which ya got?
 
oe key switch is 2 terminal, on / off.. just controll signition.

oe solenoid was 3 terminal. safety interlocked thumb switch on the trans top grounds the 3rd terminal and actuates the solenoid..

i do not advise a key to start auto setup that bypasses the safety interlock start feature your tractor was made with.
 
I cant understand why a solenoid with an isolated coil cant be connected to the original transmission switch.We need someone who can do pictures to draw a diagram.Its hard to explain how to do it to someone who doesnt have a clue.
 
the 4 posts solenoids on the 01 series are isolated coil and work fine with the thumb tranny switches.

key on provides power to the coil, thumb button grounds it.
 
(quoted from post at 08:49:29 07/08/13) the 4 posts solenoids on the 01 series are isolated coil and work fine with the thumb tranny switches.

key on provides power to the coil, thumb button grounds it.
n response to 36coupe, it is as sounDguy says........but the problem arises when the 4 post unit is NOT an isolated coil type solenoid AND this happes more often than not, because so many cars/trucks used a non-isolated coil unit with the 4th post being utilized to power the ignition coil during start-up. So this latter unit, being so very common, is what the counter jockey hands you at the auto parts house when you ask for a 4 terminal solenoid. Look same, marked same "S" &"I", but not right for a 'starter safety' interlocked tractor.
 
This is a good system because it keeps kids from playing with the starter button.My f150 has a diode across the coil to keep voltage spikes out of the computer.
 
i used to get intot he habit of putting diode protection across all the lil relays and such that i had on vehicles back when ECU electronics were a lil less robust.
 
Okay, now bought a 3-post solenoid; connected the 'BAT' terminal directly to the battery cable and to one side of the key-switch; small terminal to the other side of the switch; third terminal to starter positive terminal. Still, no go. Have bench-tested starter: it spins and retracts the "Bendix" apparatus. Odd thing is, it has started and ran(for no apparent reason) twice in the last week.
 

Take a wire and hook it to the small terminal. While sitting in seat with it out of gear, touch the other end to a good ground. The starter should turn over.
 
incorrect wireing!


the small 3rd terminal on an oem 8n solenoid goes to the GROUNDING SWITCH on the top of the tranny.
 

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