980h boom lowering

[rmllarue91]

Jms670 hey hef. I got another fix this problem that don't act up when your around. Boom won't go down. Intermittently...... Some times 6 hours sometimes 1 some times shutting it off helps sometimes. Sometimes it comes back on it's own. Rain does not effect. Doesn't seem to be bouncing or vibration related. No codes. current to both up and down solenoids is identical. I don't know if its electrical pilot or main control. Any ideas? Was over charging just replaced alternator fixing over charge. It hit 35 volts 3 times according to diagnostic. Codes no events.

 

[Mark250]

Hi, if you have access to ET you could set up the data log recorder to monitor the electrical side of things. IE lever position, current to solenoids etc.
or you could tap into the boom lower wiring at the control valve and run a temporary lead connected to your digital meter and get the operator to keep an eye on what happens when the fault occurs
also I think on the control valve spool end caps there is provision to fit a test port /you could run a temporary gauge in the cab and monitor also
Mark

 

[rmllarue91]

Thanks mark it was the boom lowering spool/solenoid vavle coil was good the spool was sticking. Pain in the behind to diagnose. It acted up once for 5 mins I was able to verify current to coils on et. Had gauges hooked to main spool on pilot side and got lucky and it acted up verifying lack of pilot pressure swamped pilot valve to bucket and it switched. It's always and adventure.

 

[kshansen]

It's always and adventure.

I was following this one as where I retired from we had three 980G Cats. Always hated those intermittent problems that always seem to show up when you are in town chasing parts for some other machine! Forget how many months it took me to find a problem with a false "Plugged Oil Filter" indicator on a 988H, that one turned out to be a failing temperature sender!

Always nice when you can swap parts and have the problem follow the part!

 

[komatsukid]

Here are a few ideas;
1 replace pilot control solenoid. Takes about 15 min. Even with system voltage at the coils the spool still might not be shifting.
2 check for oil contamination.
3 recalibrate the ecm and potentiometers.