Shocker i know, and i also know this has been beat to death, but im stumped, and no amount of googling or service manual studying is getting me anywhere. Sn 147-65221 Machine has a NOS oem external harness i scored off ebay. Pressure, angle, pump solenoids, speed, dp sensors are all new from china. Pvc is also new from china Ec is original So it started with jittery controls, something in the high speed solenoid circuit. I did a bunch of tests. Swapped sensors, etc. Finally the pump went full swash. Tested everything again, installed chinese pvc. Fire machine up, same thing, full swash after a few minutes. Found a bad alternator, Voltage climbed to 33 before i shut it down. So i disconnected the alternator...and boom machine was functioning fantastic, i ran it for hours like this with no issues whatsoever. I replaced the alternator with one from db electrical, and its charging at 28.5v, however with the new alternator installed im back to square one! Pump goes full swash after a few movements. Doesnt seem to matter if its tracking, digging, turning, etc. When the pump goes full swash, i did notice the voltage drops from 28.5 to 27 ish...which seems like a clue, but i have no idea whats pulling it down. Sos any help is greatly appreciated. Im lost and way too invested in this machine to give up Thanks
Welcome to HEF dc93 . When the pump is stuck at full swash confirm that there is a constant 24-28 volts at the 2 pump solenoids. The pump control relay (at key on,relay is closed by the PVC) has been known to drop out for no rhyme or reason. As a test, ground terminal 2 of the pump control relay and see if that resolves the issue.
Thanks dave! Yes i have 28 ish at both solenoids when the machine goes full swash. I unplugged the small 2 wire connector at the alternator, leaving the main power and ground connected, and the machine seems to operate flawlessly. With it connected it goes full swash within 2 or 3 movements (doesnt seem to care what movements i make). Disconnected i dug dirt for 10 minutes this morning no problems. Edit: just realized this isnt a chevy alternator, and needs those two wires to charge. The wiring diagram i have shows those two wires going to the starter solenoid and the monitor controller. this is where im lost. I believe something is causing the computer to ground out one of the high speed solenoid(s) on the pump, but what the charging circuit has to do with that i dont understand. Edit: one final test i did was to manually excite the alternator with a fused jumper wire, which confirmed this is 100% voltage related. The machine operates perfectly at under 25v, but with the alternator excited at 28v it goes full swash almost immediately.
“ but what the charging circuit has to do with that I dont understand “ That is the million dollar question. Regarding the 2 terminals (L and R) at the alternator connector, the schematic shows the “L“ terminal going to the starter relay and the monitor controller. The schematic shows at the “R“ terminal only a jumper wire to the alternator “B“ battery post. With the connector plugged in remove the jumper to the B post and see if that resolves the issue.
Same deal, if i remove the larger wire that goes to b+ machine operates normally. Additionally if i jump power directly to the field coil so the machine charges with the l+r disconnected it goes full swash. It seems directly related to voltage...25v and under it operates as it should. 27-28 and it goes full swash
Where are you measuring the charging voltage, at the alternator or across the battery's? 33V is ironically around the maximum voltage a lot of sensors can tolerate so you might have strained one. This sounds like a classic bad earth situation or battery isolator or wiring problem. If every thing and i mean every thing does not have the same ground potential you have currents flowing in the wrong direction every where. Maybe not the voltage causing the issue so much as the alternator when it excites becomes a new source of energy for the system and is trying to find a good Positive and Negative path to the battery's. And it will flow down sensors or any item conducting and disrupt every thing.
Voltage was measured at the fuse panel, with the multimeter grounded to the cab. Understood. I hadnt really thought about a ground issues. Ill verify everything is well grounded. Thanks
I have seen a temperature sensor cable turned into a ground cable because the ground cables from chassis and frame were no good. Even seen a tachometer cable turned into ground and junked. Check those things over carefully. If you stab Dead Center of Battery negative ( That being the Battery with a Ground cable going to frame) with one test lead and Use the other Test lead to stab clean steel on the frame, cab, engine block, Alternator housing and inside the cab on clean steel somewhere while running some lights and heater fan to flow some current you should not see more than 0.5 volts on your meter in DC volts or you have excess resistance. Try these tests to rule out a bad ground connection or failed ground strap or rusted bolt in housing. Simon C
So im at the machine playing with my multimeter - grounds appear to be okay, checked and cleaned everything up. I decided to check my angle sensor again, since dave mentioned sensors not liking the higher voltage. Sure enough it was reading 4.7 volts instead of 4.4, so i adjusted it and ran it for 5 minutes until it went full swash again....shut it off, fired it back up and ive been digging for half an hour now no issues.... Guessing maybe my angle sensor got partially cooked from the overvoltage condition?
At least this way you rule out simple but often overlooked stuff like ground connections. Hope it gets resolved. Simon C
Hey dc93, when I read your first post i realize I'm doing the same thing as you have, harness from China, different sensors, PVC etc. I havent looked at my alternator yet, but first on my list this morning. I also bout a Dr.EX from China and ran a comparison reading pump swash angle and the pump swash angle control signal. The pump swash angle is at 239 degrees and the pump swash angle control signal is at 50 degrees. I have a 1991 120-2. Do you know if I have to drain my hydraulic tank to pull the angle sensor off the pump? Good luck to you.
Hey sorry for the late reply. Ive been busy with work. The angle sensor comes off without any oil loss - or it should. Where did you order your dr ex? Did you get the palm pilot version?
I got it off Amazon. Since then I have communicated with the seller on wechat and bugth several parts, solenoids, etc. I got it with a tablet already installed and ready to go. Thanks for the tip on the A sensor. I assume the speed sensor would be similar.
No, speed sensor is a direct hole into the pump. I taped an old shop vac to my hydraulic tank and let it run while swapping speed and pressure sensors and it worked well.
Good tip. I will try that. Thanks