Starter Relay

Posted by john in la on November 15, 2004 at 05:40:52 from (66.157.27.124):

In Reply to: Ford Hundred Series 12V Conversion (very long) posted by john in la on November 15, 2004 at 05:32:11:

2) Starter Relay
Your 6v starter relay will work in the new 12v system; however any imperfections or worn spots will be multiplied by using 12v’s. If you need a new one get a 12v relay from Ford/New Holland. Just ask for the 4 post 12v relay that was used on the 801 diesel model. You can not use the 4 post relay from the car parts store. It is wired different and will not work with the grounding starter button on the transmission. If you are redoing a 600/800 with the 3 post relay you can get a new 4 post or use the old 6v 3 post.

Testing;
The 4 post relay used on the 601/801 works like this. The battery gets hooked to one of the large studs and the starter to the other. The small I terminal gets hooked to the terminal block so it has power only with the key on. The power goes through windings in the relay and out the small S terminal which gets hooked to the starter button on the transmission. You should have power at both small terminals and the starter button with the key on. When you push the start button it grounds this power causing the windings in the relay to magnetize and move a plunger that connects the two large terminals sending power to the starter.
The 3 post relay on the 600/800 works the same way except it does not have the small I terminal. It gets its power internally from the big battery terminal and not from the key. If you do not have power at the small terminal with the battery hooked up your relay is bad OR you have the battery hooked to the wrong big terminal.
The bad part about this relay is it has power to crank the motor all the time. All you need to do is push down on the starter button where as the 4 post relay can only crank with the key on. This is probably one of the main reasons Ford changed to the 4 post relay in the 601/801. They offered diesel motors and if it were to crank it could start as you do not need any power for a coil.

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