720 PTO Switch/ Neutral Switch Starter Bypass

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   Hey Ya’ll

I’m new to the Allis Chalmers community and found this forum very helpful for troubleshooting some issues with my tractor. I recently purchased a 720 with a loader and everything was smooth sailing for a day. 
2nd day, I started having issues with getting the starter to engage. Ended up buying a new battery, and it was fixed. 

3rd day I noticed that my tractors forward and reverse need some fine tuning and it’s a little difficult to find neutral. In other words my tractor goes faster in reverse than it does going forwards. (Another issue i need to troubleshoot, assuming it’s tightening of a screw/spring.)

First issue is it won't start. All 3 days the starter sounded strong. I’ feel the issue is within the F/N/R switch, and I would like to bypass this somehow. I already tried the basic troubleshooting steps found in the forum with the PTO switches and such with no luck. I do hear the fuel pump clicking(assuming that’s the noise when the key is turned). is there a way for me to tie right into the starter and wire it up to a push button that bypasses all of the safety switches? Or a way to by pass the Gear selector switches? I been looking for a starter solenoid wiring diagram and can’t seem to find a color combination one.

Looks as if I have White (ground) Red and Yellow wires coming from the starter. I tried to add 12v to the red and yellow with no luck. I’m missing something. 

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Rcampbell Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 17 Aug 2024 Location: Colorado Points: 4	Post Options Post Reply Quote Rcampbell Report Post Thanks(0) Quote Reply Topic: 720 PTO Switch/ Neutral Switch Starter Bypass Posted: 17 Aug 2024 at 8:15pm
	Hey Ya’ll I’m new to the Allis Chalmers community and found this forum very helpful for troubleshooting some issues with my tractor. I recently purchased a 720 with a loader and everything was smooth sailing for a day. 2nd day, I started having issues with getting the starter to engage. Ended up buying a new battery, and it was fixed. 3rd day I noticed that my tractors forward and reverse need some fine tuning and it’s a little difficult to find neutral. In other words my tractor goes faster in reverse than it does going forwards. (Another issue i need to troubleshoot, assuming it’s tightening of a screw/spring.) First issue is it won't start. All 3 days the starter sounded strong. I’ feel the issue is within the F/N/R switch, and I would like to bypass this somehow. I already tried the basic troubleshooting steps found in the forum with the PTO switches and such with no luck. I do hear the fuel pump clicking(assuming that’s the noise when the key is turned). is there a way for me to tie right into the starter and wire it up to a push button that bypasses all of the safety switches? Or a way to by pass the Gear selector switches? I been looking for a starter solenoid wiring diagram and can’t seem to find a color combination one. Looks as if I have White (ground) Red and Yellow wires coming from the starter. I tried to add 12v to the red and yellow with no luck. I’m missing something.

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AcFordHawk Members Profile Send Private Message Find Members Posts Add to Buddy List Silver Level Joined: 12 Sep 2009 Location: Boone, IA Points: 226	Post Options Post Reply Quote AcFordHawk Report Post Thanks(0) Quote Reply Posted: 17 Aug 2024 at 9:15pm
	Bob, wiring diagram from a 620 but 720 should be similar. Something else to check on the F/R problem is the linkage off the hydrostat unit, the bushings can wear and cause sloppiness in the control. It is located under the transmission tunnel cover. Edited by AcFordHawk - 17 Aug 2024 at 9:21pm
	IB (restoring), MF GC1705, MF 2705E

steve(ill) Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 11 Sep 2009 Location: illinois Points: 81782	Post Options Post Reply Quote steve(ill) Report Post Thanks(0) Quote Reply Posted: 31 Aug 2024 at 9:50pm
	looks like the RED/ YELLOW wires are HOT ( 12v) all the time.... I wonder if the WHITE wire is not ground, but a 12v signal to energize the starter motor solenoid... Not 100% clear, but the white wire goes to the neutral and pto switches to make sure they are OFF when you try to start the motor.. have you tried grounding the white wire ? if that does not work, then i think it is a 12v signal to make the solenoid engage. Edited by steve(ill) - 31 Aug 2024 at 9:53pm
	Like them all, but love the "B"s.

Rcampbell Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 17 Aug 2024 Location: Colorado Points: 4	Post Options Post Reply Quote Rcampbell Report Post Thanks(0) Quote Reply Posted: 31 Aug 2024 at 10:17pm
	Thank you both for this information. I dove pretty deep into the schematics and took apart the dash. I ended up jumping the two white wires, 14awg and 16awg to run the starter and that worked. Later for a bypass, I took the two white wires under the dash at the ignition switch, then wired into a monetary start button. I’m trying to get in the habit of putting on the parking brake when I shut it off, and pushing in the clutch before starting since I bypassed the safety switches. I keep running into the issue where there isn’t enough voltage to run the starter, so I always have to jump the tractor with my jump pack. The battery is on its way out for sure but I will have 12.5v coming from the battery and 11.5v going to the starter. Heard there are some voltage boosters out there, does anyone have experience with those and have some recommendations? Another issue I just started having with my loader.. my bucket doesn’t stay up, it keeps wanting to “dump”. it started after picking up too much weight at too far of a reach repeatedly(added forks onto the bucket and moved some logs) Read on some other tractor forums that I may need to repack bearings and what not. I wonder if it could be an old hose issue? The hoses have seen better days.

steve(ill) Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 11 Sep 2009 Location: illinois Points: 81782	Post Options Post Reply Quote steve(ill) Report Post Thanks(0) Quote Reply Posted: 31 Aug 2024 at 10:47pm
	if you loosing 1 volt between the starter and the battery, then you CABLES are old and crappy. I would take them off and wire brush the flat terminals.. See if you see any gree crud growing up inside the crimp fittings... It may be time for some new cables.. Battery terminals can also get a BLACK OXIDE coating on them..They may look CLEAN, but have a dark film on them.. wire brush / sand paper the terminals and cable ends, and the GROUND cable.. If that does not help the voltage DROP to the starter, then you need a new cable.
	Like them all, but love the "B"s.

Steve in NJ Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 12 Sep 2009 Location: Andover, NJ Points: 11849	Post Options Post Reply Quote Steve in NJ Report Post Thanks(0) Quote Reply Posted: 02 Sep 2024 at 10:36am
	One of the many improvements I made from OEM on these model machines is the Battery cables. My cables are 4 gauge vs 8 gauge. Big improvement. Also, that Starter gets quite hot under that engine. Low voltage starts to take these Starters out. Eventually, they need a rebuild. I offer the rebuilding services as well for these Tractors. HTH Steve@B&B
	39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife

Rcampbell Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 17 Aug 2024 Location: Colorado Points: 4	Post Options Post Reply Quote Rcampbell Report Post Thanks(0) Quote Reply Posted: 02 Sep 2024 at 8:04pm
	My battery cables are 4 gauge already. I’m thinking about getting some new battery terminal connectors and running a 10/12 gauge wire to the starter. Not sure if that will help any but may be worth a shot with some extra wire I have lying around. I am going to buy another battery as well. Seen these are generally group 70 batteries but I know a 65 fits. Minimum ccas should be about 600?