520-HC 9 pin

[cafoose 3,777]

Does anyone know or any diagram available that shows the 9 pin on the 520 where each pin goes on the engine side? Looking for an actual picture of the pin showing the numbers so I can see which pin corresponds to which number on the actual connector. I have the demystification guide and wiring diagrams but they show the 9 pin in a straight line. @lynnmor @cleat @gwest_ca

Edited Wednesday at 06:02 PM by cafoose

[cafoose 3,777]

This correct?

 

9    6    3

8    5    2

7    4    1

[peter lena 9,944]

@cafoose  just curious , ever think about  changing that  hot wire  routing issue ?  favoring hot engine discharge  zone ?  drive belt  guard , venting , its always there , pete

[cafoose 3,777]

18 minutes ago, peter lena said:

@cafoose  just curious , ever think about  changing that  hot wire  routing issue ?  favoring hot engine discharge  zone ?  drive belt  guard , venting , its always there , pete

  Yes that's on the list just trying to determine where the wires go for my Vanguard swap.

 

 

 

[squonk 47,410]

I chopped that 9 pin right out of there. Used 2 4 flat trailer plug kits with long pigtails. Marked them "A" and "B" changed 1 wire at a time and documented what circuit when onto what pin in what connector. Move the whole thing to the other side of the tractor away from the heat. 

[sqrlgtr 3,271]

demystify.pdf there is a good diagram in here somewhere toward bottom of pdf... i cant get link to work maybe someone else can get for ya.. Its in the manuals section on here

Edited Wednesday at 08:07 PM by sqrlgtr

[sqrlgtr 3,271]

try this one

[cafoose 3,777]

6 hours ago, sqrlgtr said:

demystify.pdf there is a good diagram in here somewhere toward bottom of pdf... i cant get link to work maybe someone else can get for ya.. Its in the manuals section on here

Got it already 

[gwest_ca-(File Mod) 12,361]

I do not know if they are the same but in the first model year 1988 the engine to tractor connector is numbered. Click on the fuzzy picture to see it.

 

[953 nut 67,440]

On 7/22/2026 at 4:02 PM, cafoose said:

just trying to determine where the wires go for my Vanguard swap.

The 9 pin was an Onan  thing. It offers no advantages unless you plan on doing frequent engine swaps. I would suggest you are much better off wireing the engine connections from scratch. The Onan is a battery ignition engine and the Vanguard is a magneto ignition so you will probably want to insert a "KILL RELAY" in the rewire.

 

[cafoose 3,777]

1 hour ago, 953 nut said:

you will probably want to insert a "KILL RELAY" in the rewire.

Thanks Richard I already consulted Grok AI and have a relay ordered coming here Tuesday 

Many cheap relays have inconsistent wire colors, so testing the pinouts yourself is the smart way.
How to identify the terminals once you have the relay
Standard 5-pin Bosch-style pin numbers (look on the bottom of the relay itself):
85 and 86 = Coil (the two that make it click)

30 = Common
87a = Normally Closed (this is the one we need for the kill)
87 = Normally Open (we leave this unused)
Simple testing method (with a multimeter or just a 12 V battery)
Find the coil (85 & 86)
Put 12 V across any two of the small wires/pins.
When you hear a solid click, those two are 85 and 86.
It doesn’t matter which is

which for our purpose.
Find 30, 87a, and 87
With the relay not powered (no click):
Continuity between 30 and 87a → that is the Normally Closed pair.
Power the coil (make it click):
Continuity switches to 30 and 87.
Mark the wires
Once you know:
The wire that is always connected to 30 when the relay is off = 87a (Normally Closed)
The common wire = 30
Final connections for your kill circuit
Vanguard black kill wire → Relay terminal/wire 30
Relay 87a → Chassis ground
One coil terminal (85 or 86) → “I” (Ignition) terminal on the 520 switch
Other coil terminal → Chassis ground

That’s it. Test by turning the key — engine should run in RUN and die in OFF.
When the relay arrives, do the click-and-continuity test above and you’ll know exactly which wires to use, regardless of the colors. Let me know the results if you want a double-check.

Edited Friday at 01:51 PM by cafoose

[953 nut 67,440]

9 hours ago, cafoose said:

How to identify the terminals once you have the relay

You will probably be best off buying a five pin relay socket from any good auto parts store. The relay will have the numbers cast into the base.

 

[lynnmor 8,912]

Perhaps this might help.

Be aware that colors aren't consistent over the years. 

[lynnmor 8,912]

On 7/24/2026 at 8:44 AM, 953 nut said:

The 9 pin was an Onan  thing. It offers no advantages unless you plan on doing frequent engine swaps. I would suggest you are much better off wireing the engine connections from scratch. The Onan is a battery ignition engine and the Vanguard is a magneto ignition so you will probably want to insert a "KILL RELAY" in the rewire.

 

 

The 9 pin is a Wheel Horse thing, they wanted a plug and play wiring system so they came up with the 9 pin nonsense to allow attaching the headlights and tach along with engine needs.