I've been working on an issue with a 2001 Fabtek 153 with a 240 head. In the first few minutes of running the machine when you go to lower the main boom it will slam down a couple feet and then the main boom function will stop working for a couple seconds. When you go to the IQAN screen and look at the voltage output that it's supposed to be sending to the coil it reads fine 990-1100 mA. However when you measure the current and voltage at the coil while the boom has stopped functioning you get absolutely nothing. After the couple seconds of it not getting any current at the coil, everything goes back to normal and it works fine for the rest of the day! I've tested through the harness from the IQAN to the valve bank and everything checks out, coils are fine, joystick are smooth so all I'm left with is the IQAN MG module itself! I talked with Wayne Ocker, knowledgeable CAT guy from WI and he seems to thing the same that it's an issue with the IQAN he told me that CAT offers an update kit to replace the obsolete IQAN MG system for $15k, obviously that is something I'd like to avoid so I'm looking to you guys for any advice!
Can the hydraulic system itself be ruled out of the problem? How many hours are on this machine?
Maybe a bad valve that is sticking until warm & freed up?
I wanted to rule out electrical before I moved to hydraulic, as far as i can see the problem is definitely electrical, I can't catch the exact moment it screws up, but when I go to move the boom after it drops jarringly, I get no voltage or current at the coil in either direction. Then I move the joystick up and down for a couple cycles, maybe 30 seconds or so, and voltage returns to the coil and the boom operates smoothly. All the while the IQAN is saying that it's outputting the correct current to the coil. The machine has 14,000 hours on it.
Plenty of hours! In my experience computer systems are pretty good at telling you when an electrical of electronic component is bad although in 2001 the systems were pretty crude in many ways. Have you checked the coil with an ohm meter? Are you saying that when nothing is moving and you show no volts or current going to the boom control coil that the computer is showing the system as normal? Are you also saying that this only happens when the fluid temperatures are cool or cold and that when warmed up everything works normal?
I was hoping to see the IQAN MG system throw an error code but it doesn't seem to be very good at self diagnosing this issue, resistance on both coils is even and good with the other ones, around 6 ohms each. When the function first acts up the boom slams down quickly almost like a current spike, after it slams down quickly it doesn't respond, you move the joystick and even though the computer says it's outputting current, nothing shows up at the coil. This seems to only happen once per start up, even if the machine is hot, if you shut it down for a couple of minutes and start it back up the issue will probably show up again.