willie59
Administrator
Electrical problems can be one of the most tedious things to repair on nearly everything. I decided to post this, not to offer specific info, but to show an example of some of the methods one must employ to troubleshoot electrical failures. Just some of the crap mechanics have to go through blindly, feeling your way as you go. Bah ha haha 
Saturday, yep, at work. Boss stopped in, told him (jokingly) "One of these days...I'm gonna hang you and that rental sales guy from the shop overhead crane! You guys are driving me crazy!" Three times in the last two weeks, we've had a crawler dumper that boss had purchased come in and I find out we were waiting on it to be delivered to a rental job. What? A used machine you purchased, no nothing about, and got a rental job waiting on it! :Banghead
Well this is the latest one. Komatsu CD110R-1. Unloaded off truck late on Friday, rental customer is coming to get it on Monday morning. I give the machine a quick check, seems to be a sound machine. No leaks, runs and operates good. Engine oil is clean, antifreeze good. Has a few minor things to do, nothing that would hinder rental. But one problem, cab heater not working. I told boss, air conditioning is more about operator comfort. But heat, involves operator comfort, but it's been below freezing here the last few nights, winter is coming, you can't defrost the ice/frost from the windows without heat, kinda necessary, and for certain something a rental customer will complain about.
So, it's Saturday, and I'm in here trying to figure this thing out. Well, rip the cab apart, pull the seat, and tear into the heater box.
Yep, this is my tight working space for the day. Dang, my knees sure feel it.
Checked the harness connector where wiring goes into heater box, had power and ground. Pulled the control panel, no power on any of the switches. So, tear into the heater box. Seems pretty simple in there, nothing electronic, mostly old school controls. Problem is, no wiring schematic, have no idea which wire goes where. And Komatsu color coding of wires is no help. Red wire with black dots, yeah, right, seems like there's red wires with black dots going everywhere. LoL. Only one thing I can do, rip the heater/AC control harness out of it and do surgery, slice it open, so I can tell how power supply is working.
Even then, it's a time consuming process, and things are still not all that obvious. But tracing down power supply paths, it appeared that power supply first went to the fan speed resistor panel. Typical speed resistor panel, one low resistance wire coil for mid fan speed, and one high resistance wire coil for low fan speed. But the power input to heater box went to a ceramic resistor in between the two speed coils. Hmm, haven't seen that before. Don't really know why they are using the resistor, but it had power coming in on one side, but nothing coming out the other side. Well, it's worth a shot, put a jumper lead across the posts.
Saturday, yep, at work. Boss stopped in, told him (jokingly) "One of these days...I'm gonna hang you and that rental sales guy from the shop overhead crane! You guys are driving me crazy!" Three times in the last two weeks, we've had a crawler dumper that boss had purchased come in and I find out we were waiting on it to be delivered to a rental job. What? A used machine you purchased, no nothing about, and got a rental job waiting on it! :Banghead
Well this is the latest one. Komatsu CD110R-1. Unloaded off truck late on Friday, rental customer is coming to get it on Monday morning. I give the machine a quick check, seems to be a sound machine. No leaks, runs and operates good. Engine oil is clean, antifreeze good. Has a few minor things to do, nothing that would hinder rental. But one problem, cab heater not working. I told boss, air conditioning is more about operator comfort. But heat, involves operator comfort, but it's been below freezing here the last few nights, winter is coming, you can't defrost the ice/frost from the windows without heat, kinda necessary, and for certain something a rental customer will complain about.
So, it's Saturday, and I'm in here trying to figure this thing out. Well, rip the cab apart, pull the seat, and tear into the heater box.
Yep, this is my tight working space for the day. Dang, my knees sure feel it.
Checked the harness connector where wiring goes into heater box, had power and ground. Pulled the control panel, no power on any of the switches. So, tear into the heater box. Seems pretty simple in there, nothing electronic, mostly old school controls. Problem is, no wiring schematic, have no idea which wire goes where. And Komatsu color coding of wires is no help. Red wire with black dots, yeah, right, seems like there's red wires with black dots going everywhere. LoL. Only one thing I can do, rip the heater/AC control harness out of it and do surgery, slice it open, so I can tell how power supply is working.
Even then, it's a time consuming process, and things are still not all that obvious. But tracing down power supply paths, it appeared that power supply first went to the fan speed resistor panel. Typical speed resistor panel, one low resistance wire coil for mid fan speed, and one high resistance wire coil for low fan speed. But the power input to heater box went to a ceramic resistor in between the two speed coils. Hmm, haven't seen that before. Don't really know why they are using the resistor, but it had power coming in on one side, but nothing coming out the other side. Well, it's worth a shot, put a jumper lead across the posts.
