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NAA Starter Relays Sticks Closed

Brian I recently converted my NAA to a 12 volt system. I am now having trouble with the starter relay occassionally sticking in the closed position. I have tried four different relays, replaced the starter switch and ensured that there is not a stray ground connection causing the relay to close. The problem can occur when staring the tractor with the tranny mounted switch or the button on the bottom of the relay. The relay sometimes sticks closed when I have removed the starter button connection and started the tractor with the button on the relay. Everything points to a sticky relay, but can I really have gotten four bad relays? Is there a better quality relay out there? I did a lot of research before I did the 12 volt conversion and I believe that the wiring is correct. Everything else works greaat. Any input would really be appreciated. Thanks. Brian
Bob G Don't believe I have ever seen a starter solenoid with a button on it. Not saying there ain't tho.It sounds to me like you have the wrong style of solenoid. I would install a 6 volt oem soleniod. It will work fine with 12 volts.
Jim Loveridge You have tried four different relays and get the same results? I would get a Ford type of relay for a 12 volt. If I remember right Ford vehicles switched over to 12 volt around 1954 or '55. But still used the remote type of starter relay.
mark sr My 53 NAA has the solenoid with the button on the bottom and it works fine. The NAA and my 51 F1 use a lot of the same igntion parts including the same solenoid. The same solenoid works with either 6 volt or 12 volt. I suspect the problem is with the wiring. Did this issue not appear until you switched to 12 volt?
Brian The problem began after changing over to the 12 volt system. I compared multiple wiring diagrams before starting the project to ensure that it was done correctly. Everything else seems to work perfectly, except for the occasional glitch with the relay.
Jim Loveridge Brian, I re-read your post and I take back what I said about getting a 12 volt relay. I can visualize what's happening, but I don't know why others haven't had the same problem. The 6 volt starter is now drawing twice the current across the contacts in the relay and that's causing them to arc and actualy weld together temporarily. Go to this web site and contact this guy and see what he says. Then let us know please.
Jim Loveridge Just thought of this. Maybe your starter motor has some shorted field windings or armature and that's why others haven't had this problem. Is slow cranking why you converted to 12 volt?
Brian Jim,
That is a very useful website. I will contact him today. The timing of your post was very interesting. Last night I took one of the solenoids apart for an inside look and found signs of arcing in the contact points. I think we are onto something here. Brian

Bob G this sounds like it it entirely possible. the lower the resistance in the starter the more current flow there will be.
Brian I got a very nice reply from Kevin at My Ford Tractors. He agreed that it could be problems with the starter causing an excessive current draw through the solenoid that is creating arcing/sticking between the contact points. He suggested that I try a higher quality, 12 volt solenoid. He also mentioned that with the higher voltage (12 V) a lot more heat is created in the starter, particularly if cranked more than a few seconds. Fortunately my NAA starts easily. I spoke with the local starter shop and he suggested I checked the voltage at the starter for a voltage drop during cranking. Lower voltage would create a higher current draw. Also, I will pull the starter and have it tested. Sooner or later, we'll figure this one out. Thanks to all for your input. Brian
Brian OK. Here is what I've learned so far. A man at the local starter shop contends that the solenoid must be replaced when completing a 6 to 12 volt conversion to prevent arcing inside the solenoid. He also suggeted that I check the voltage at the starter during cranking. If the voltage drops below 10 volts, the current draw will possibly be excessive and will cause problems in the solenoid. Causes of an excessive voltage drop could be bad connesctions, a bad battery or a problem with the starter. I purchased a quality, American made solenoid (Cole-Hersee for $24). I removed the starter and had it bench tested. It surged to about 125 amps and quickly dropped to a steady 75 amp draw. Next I tested the voltage at the starter while cranking. It measured about 10 volts. No stick occurred in the solenoid so far. With a good starter and clean connections, the next step is to check the battery to ensure that it is fully charged and no bad cells.
Bob G I have never seen any instructions to change the solenoid to a 12 volt one when doing a 12 volt conversion.
If you have a voltage drop, you will get a decrease in current flow, not an increase. Do a google search for ohms law and check out one of the caclators you will find.
I equals current
V equals volts
R equals resistance

ohms law is I=V/R do the math.

Bad connections will cause a voltage drop during cranking.

check out this site for ohms law

I agree that excessive current flow could cause the contacts to arc and burn., but i think it would be because of low resistance allowing the high current flow.
look what happens when you short out one battery post to the other. Direct short, no resistance, lots of arcing from real high curren flow.

maybe you have fixed your problem this will mean little.
Good luck

Jim Loveridge Is that 125 amp surge normal when you had the stater bench tested? I don't know, just asking.
Brian Jim,
From what I've read that's pretty normal.

dan hill Any one who has worked on 12v systems knows that the arc potential is much stronger in 12v systems.Those who say the 6 volt starter can take the extra voltage without problems are wrong.The speed is increased when the voltage is increased.If you could see the contacts when they close you would see a large arc.DC is hard on switches because of arcing.
dan hill Ford cars and trucks switched to 12v in 1956.I was working in a Ford garage that year.Chevy cars made the switch in 1955.
Brad Cardwell I am having the same issue. I just switched over to 12V and I replaced the old solenoid with one from tractor supply made for "6V or 12V". It also had a button, my old one did not.
I think I am going follow Brian and grab the heavier duty one from Cole Hersee.

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