Hello all, My skiploader 210LE SN 882983 started having intermittent problems a few months back. The unit has a column mounted shifter. The transmission would go abruptly in Neutral. I would need to shift speed or sometimes had to apply the parking brake and release it to re-engage the transmission. This behavior also has been described in this forum on a 310SG which shares the same system. This behavior clearly implies that the K10 timer relay is malfunctioning. This relay disengages the clutch packs for 1 second when the user is going from F to R or R to F. My unit had already been modified to use the AT464505 timer relay. This is an "upgrade" from the original and now obsolete AT180485. This was a Mopar 2030005D timer used in 2000s vintage dodge stratus convertibles and some other applications. The socket for that timer relay is difficult to find and had been previously removed from my machine. The AT464505 is made by Artisan Controls and is PN EPC-14037. It is hard wired in the harness. I actually connectorized the new one with a 4 pin weatherpak connector set. The new K10 ($400!) did not solve the problem. After a lot of experimenting, I figured out that the return to dig circuit was involved in the problem. The transmission would only disengage when the bucket was curled around the switch point. Normal travel without bucket operation would never induce the problem. If the Y9 solenoid located under the hydraulic valve block is disconnected at its terminal, the problem also stops. Looking in the diagrams found in TM1691, it turns out that both circuits are totally independent and mostly in different harnesses. It turns out that the return to dig solenoid has no anti parallel diode across it. This is terrible and will stress the switch and the solenoid as well as generate a large spike in the harness when the switch turns off. I therefore put a diode across Y9. The problem does not seem to be present anymore. I also added anti parallel diodes on the Forward and Reverse solenoids Y11 and Y12. This can be done by replacing V11 and V12 with a diode bridge and connecting the negative terminal of the bridge to ground, the positive going towards K10. Part of the difficulty in figuring this out was that the SE9 schematic page is wrong : V11 and V12 are in the opposite direction from the one drawn in the schematic. They actually both go towards K10. The internals of K10 show a diode going in followed by a resistive divider 2.4k/2K to ground to drop the input signal to about 5V from 12V. So this would never work as drawn as all the diodes would block each other. The problem seems cured or at least greatly improved as of today. The future will tell... One issue is that I don't really know why this problem appeared after 20 years of service. P.S> the AT464505 is polyurethane potted and the PCB is conformally coated. The simple logic is done by an 8-pin 12F508 microcontroller. It uses an IR3313 solid state switch to activate its output.
Welcome to HEF! Wow, that's a lot to digest. First off, congratulations on discovered the root cause of the problem. You then analyzed the circuit and discovered that "return to dig was involved". Isn't that crazy. Last, but not least, you came up with some upgrades to the circuit. Touche! Thanks for sharing.
Welcome wildcattle. Excellent analysis and yes the back EMF [ElectroMotive Force] from a solenoid is akin to step up transformer sending a reverse polarity spike into the circuitry which as you indicate can be smoothed by a diode. Components don't like heat and a board of discrete parts can sometimes physically show a stress area where there is discolouration from those that have over heated, typically resistors / solenoids and if mounted near capacitors, both could be faulted. If there is electric [off / on] pulse stress and heat as well, solder will break down and form a dry joint, sometimes these are visible and oddly enough tend to emerge at 'change of season' either hot to cold and vice versa where moisture condenses in the fragmenting solder and oxidises the connection with resistance. Weak points can take many years to emerge and as technology has shifted the old style [discrete components] has merged into modular which tend to be boxed and throw away to diagnose and solve. Similar brand and incident in this thread: HeavyEquipmentForums
A follow up to this: The problem definitely disappeared! I also changed the return to dig switch AT184726 ($180). I think it may have been chattering and making things worse. It turns out that I am pretty sure it is a CPI E1117 limit switch, which is a bit cheaper. You'll just have to add the weatherpak connector. All the best, WC- P.S> CPI also seems to make the diff lock switch which also costs an arm and a leg (could be PN J4001 to be verified)