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Ford 3000 SOS wiring query


 
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mickotab
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PostPosted: Sat Jun 09, 2018 6:09 am    Post subject: Ford 3000 SOS wiring query Reply to specific post Reply with quote

Gday everyone,

I have a query for the experts amongst you all!

I have a '65 Ford 3000 Diesel with the SOS tranny. I'm in the process of doing some work on it and I'm replacing the wiring harness with an aftermarket harness.

My query is in relation to the 3 'electrical' wires that are coming out of the transmission cover. I know that 2 of them are for the safety switch and I have that covered, but the 3rd wire has me tricked. It is a smaller gauge wire and it was hooked up to a plain red wire on the original harness. I've looked at all the wiring diagrams in the service manual and there is no entry to what this wire is hooked up to. In the wiring table in the service manual it states that a plain red wire services the "Light switch the side and rear lamps".

Does anyone else have the same setup on their SOS or any ideas as to what it could be?

Thanks in advance

Mick
 
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pete black
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Location: alabama

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PostPosted: Sat Jun 09, 2018 6:17 am    Post subject: Re: Ford 3000 SOS wiring query Reply to specific post Reply with quote

Coming out the transmission it may be for the red warning light on the dash for "low pressure".
 
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TNford
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PostPosted: Sat Jun 09, 2018 7:46 am    Post subject: Re: Ford 3000 SOS wiring query Reply to specific post Reply with quote

There is an inset picture of the wiring diagram that shows the SOS part. It is the warning light above the shifter
 
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Bern
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PostPosted: Sat Jun 09, 2018 9:01 am    Post subject: Re: Ford 3000 SOS wiring query Reply to specific post Reply with quote

Low lube pressure warning light. If it were my machine, I'd have it hooked up and operational. It will warn you of hydraulic issues in your trans long before it becomes an expensive repair.
 
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Sean in PA
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PostPosted: Sat Jun 09, 2018 10:02 am    Post subject: Re: Ford 3000 SOS wiring query Reply to specific post Reply with quote

My '73 4000 S-O-S only has two wires coming out of the top of the trans. I am pretty sure that the 1965+ S-O-S transmissions did not have a low pressure warning light. There is nothing in the schematic in the service manual for one. The only "extra" wiring shown for rthe 1965+ S-O-S tractors vs. the manual tras modles is the illumination bulb for the gear selector so you could see the numbers for which gear it was in at night. A 1965 3000 is a fairly early one so they might have included the pressure warning light back then but I can't find it documented anywhere.

Easiest way to tell for sure is to measure the resistance of that wire to ground when the tractor is not running and again when it is running. f it is a pressure warning light wire then it should read infinite with the tractor not running and close to zero with it running, as the sender is just a switch for a warning light, not a variable sender like for a pressure gauge.
 
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Bern
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PostPosted: Sat Jun 09, 2018 1:31 pm    Post subject: Re: Ford 3000 SOS wiring query Reply to specific post Reply with quote

Lube light was discontinued in 1968 with the "new models" - image above is from the repair manual. And yes, the wiring diagram does show the
light in a separate box on the same page. If I owned an SOS, I would install one and make sure it works!

Testing of the circuit is backwards from what you describe. The light is designed to turn on with low pressure, therefore resistance should
be zero with the engine off, and vice versa. That said, the last SOS I worked on had a faulty switch, which I had to source aftermarket.

 
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mickotab
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PostPosted: Mon Jun 11, 2018 3:20 am    Post subject: Re: Ford 3000 SOS wiring query Reply to specific post Reply with quote

Excellent..... thanks very much Gents.

It all makes sense and it may me pay a bit more attention to the service manual which explains it all in black and white! Embarassed

Thanks again and I enjoying reading everyones problems and solutions.

Cheers
Mick
 
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