Hi, I am new to the forum and tried doing a search for a similar Thumb issue on a 307D but no luck. I am helping friend with his 307D Excavator he believes it is a 2008 the Product Identification Number is CAT0307DEDSG00184 I am relatively new with working on Cat equipment but have a wide range of experience with hydraulics on other equipment. Here is the story, the machine runs fine but he wanted to add a hyd. thumb to it so he put the thumb off his Bob cat excavator on it but had to make few modifications to do so. It is all plumbed up but does not work. He had a Cat mechanic come over in a service truck and spent 4 hours with it and said that the electronics are fine but he did not have his test guage kit to go any further and requested that the machine be brought into the shop. I looked at it briefly and it does idle up when he hits the button on the RH joy stick but not function what so ever. I disconnected one of the plugs to the solenoid that controls is and with a cheap volt meter i had 2 volts constantly and about 24v to the one solenoid I disconnected when he functioned it (the meter was set to 20V so I didn't get a accurate reading). My thoughts are I really need a ORFC hydraulic test kit so I verify that the solenoid operated control valve has pilot pressure and then check for pressure at the main control valve. The only issue is that the hyd test kit is over 300 bucks but it would be helpful. Any insight, schematics and help on this issue is really appreciated .
Still looking for help. I checked the 2 solenoids that operate the thumb Cat part# 111-9916. I ohmed one of coils out and it had 11.4 ohms I tested for power with one coil unplugged and it has 28v when activated but with it plugged in only 8v. So I think it doesn't have enough voltage to stroke solenoid valves. I think I found the power is coming from the ECM behind the cab.
The S/N checks out. Built December 16th 2008. I've sent you the electrical schematic. Check your PMs.
After do a little testing I found that the aux solenoids were stuck. I pulled them out, cleaned them up and function tested them to verify movement. Installed them and now the thumb is functional again. Thanks again for the help on this site.