I was helping a guy try to diagnose a battery drain on his Cat 242B skid steer last night. It just started doing this since on some of the colder days we've been having. I've isolated the problem to the hydraulic interlock system, but I can't determine if the behavior is normal. Was curious if anyone else was familiar with this, or has this machine or a similar Cat skid loader that would be able to check functionality.
What I found was that the door microswitch was a little bit sticky, and I suspect it was not releasing when the door was opened after the machine was shut down. I cleaned the lubed the switch, and he is now aware of what causes the drain, and I will replace the microswitch if it continues to be an issue.
My question is whether the observed behavior is normal. It goes like this:
1. Enter machine, lower safety bar and start engine. Hydraulic interlock light is lit.
2. Close cab door. Hydraulic interlock light goes out.
3. Operate machine.
4. Turn off machine. Alternator/Battery light flickers dimly.
5. Open cab door, door switch opens and the alternator/battery light goes out. Zero amp draw.
If you reverse the last two steps and open the cab door first, and then turn off the machine, the light goes out as well. So basically as long as the switch works, he shouldn't have an issue. I'm having trouble understanding what the connection is between the two. I can't think of a reason to keep the interlock circuit powered once the machine is shut down.
Here is a schematic of the interlock circuit and the flickering light.
Attached Thumbnails
Caterpillar CAT 242B Hydraulic Interlock and Battery Drain
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