I need some help from someone familiar with Bobcat excavators. I've been working on a Bobcat 335G ser. no. A16U11454 w approx. 4000 hrs. with the deluxe monitor panel, that has had a starter issue. Customer called and said the starter had quit working, they picked up and installed a new starter from a local electrical company, 40 hours later they called again and said it wouldn't start and had a strong burnt electrical smell. I went out, pulled the starter and it was obvious that it had stayed engaged until it came apart. They then ordered another new starter from Bobcat which I installed. While checking out the system the starter would occasionally continue running, even after pulling the starter relay. It would not do it every time, maybe once every 20-30 or more times starting. If I disconnected the battery, it would stop running and be OK again for 20-30 starts. At the same time, it would occasionally just click and not turn over or turn over very hard, like a low battery. When clicking I was only getting 5 volts to the starter excite terminal, when the starter continued to run, I found I was getting a continuous 2 volts to the excite terminal. There are 2 red wires going to the excite terminal, 1 runs directly to the starter relay and 1 goes to the monitor, plug J4 pin D. My downloaded schematic is bad enough that I cannot read wire numbers nor what that wire does. It looks like it's labeled starter status on the monitor? When I cut the monitor wire at the starter excite terminal everything works fine, I no longer have any problem with the low battery symptoms nor with the starter continuing to run. It appears there is a problem with the monitor, the customer is fine with leaving the wire cut since the monitor is just short of $2000.00. I'm just curious what the monitor wire does and if anyone has had this problem before. Thanks for reading my long-winded question.
Hello E, I am not familiar with your machine at all. But Have some questions which might help. You have so many symptoms and each one is not normally found all together like this. The fact you saw 5V at the start terminal makes me wonder if what you are calling starter relay is not the safety interlock relay for the starter which can cause that.? The fact you saw 2V makes me wonder weather the back EMF diode is leaking and they are sometimes at the relay, or fuse box with the safety interlock diodes or in the monitor.? When you say it some times does not turn over hard that is low battery voltage and nothing to do with starter or relay. Another symptom you are describing is the clicking. Now that can be two things. One is low battery voltage. The other is low voltage being applied to what you are calling the excite terminal. The way it works normally is the plunger in the starter solenoid gets draw in pulling the Bendix into the ring gear, and at the end of the stroke the contacts will close powering the starter. But occasionally the pinion will not go into the ring gear and in that situation the excite terminal has to be provided with more than normal current. As the plunger is draw in it has to compress a heavy spring behind the Bendix which is not normally compressed. When it gets to the end of its stroke power is applied to the motor and as it begins to turn the compressed spring behind the Bendix slams the pinion into mess of the ring gear. So low voltage at that terminal which you have measured would severely limit the pulling power of the plunger and they just click like you have described. The plunger does not get to the end of the solenoid to engage the motor. Regards