I have a 1996 CAT 320B that I don't use very often. It has about 4000 hours on it and sits a lot of the time. Lately, when I go to start the machine, sometimes it starts right up while other times it doesn't. The dashboard comes on and you can hotwire it by touching power to one of the solenoids, but I don't think the machine is really "on" because it won't operate. Also, intermittently, the swing seems to be locked. When you try to rotate the machine, you can hear the pump load but is will not swing. Then, if I put the safety lock down and back up and move forward and backward a few times the swing function comes back. Additionally, and also intermittently, but for longer periods of time, when you go to unlock the hydraulic safety lock, the machine won't operate. With this function, I've checked the microswitch, solenoid, and also the valve, and they all seem to be okay. All that being said, is it possible that the computer controller module needs checking or replacing?
It would help those people who can look up Cat parts/service information if you posted a Serial Number. Model Years mean nothing where Yellow Iron is concerned.
Sorry about that, the serial number for my machine is 3MR01001. Thanks
maybe should start with the intermittent starting problem - batts are good dash comes on you hear some clicking of some solenoids then turn the key to start and sometimes nothing - i have been playing around with the switch back of the right armrest up and down then play with the key and it starts or you can jump it on one of the solenoids is there a solenoid i am missing ?
When you turn the key to start and nothing happens, are there any red warning lights on the bottom of the display? If you cycle the key off and then try to start it 5 seconds later does it crank then?
there are 2 or 3 lights on at the bottom of the screen, but they have been on and off for years with no problem- cycle the key play with the switch on the back of the armrest and sometimes it starts sometimes it don't
Ok, my understanding of the start logic in the B series computer is that the computer does a self check of the critical warning light parameter (the red ones at the bottom of the screen) prior to allowing the machine to start. If one or more of these warnings are active, you have to cycle the key off then on again to acknowledge the warning, the machine will then start. On my B series an intermittent swing brake issue was a dirty ground (under the cab if I recall). I’m no electrical expert but many of your issues sound like they could be ground related.
@nesignal - If you want an ele3ctrical schematic appropriate to your machine you're welcome to one.
thank you Columbo going after some bad grounds is a good idea - even when i cycle the key does not seem to start - i was thinking there must be a solenoid i am missing to check ---hey Nige a schematic would be good - thank you
On the way. Check your messages.
there is a ground under the cab - took off and cleaned it up - wasnt bad looking but we will see what that does - also want to check all the grounding points
Hi Nige, I went to print the schematics you sent me and on the bottom right corner, it says this is for a 330BL, but the title page on the front of the document you sent me says it's for a 320B with the appropriate serial number. Just wondering why that would be. Maybe the wiring diagram is the same?
I bought a power probe 3 and now I'm a DC electrical genius. I found two things in the fuse box the engine governor and the hydraulic lock fuses have neither power or ground with the key on or off. Also, on the bottom of the ignition switch there are four poles: yellow, red, red and orange. With the key off there's power at both reds, yellow is a ground and orange has nothing. With the key on there's power at one red and the yellow, nothing at the other red and nothing at the orange. With the key to start position there's power at the yellow and one red and the orange and nothing at the other red. Just checking in to see if that's all normal.
I wondering if it isn't the main power relay (magnetic switch). Big red...battery 24v Big purple...switched 24v Little black...Ground Little yellow...24v from key switch When key is ON, the big purple is ON, controlled by little yellow. When that magnetic switch begins to fail (internally), you'll get those symptoms. Verify that the big purple has 24v everytime the key is on.
I didn't keep a copy of the message. If this is the title page it's the correct one.
Thanks Nige, I guess the 320 and the 330 wiring is the same.
Thanks, Heymccall. Checked on that relay yesterday and seems to be working fine. It has an audible click when you cycle the key, and the power seems to move through it as you described. There's got to be something else we are missing here. One clue that I think may be important is the hydraulic lock or park brake switch makes an audible click under your feet when the machine is working properly with just the key being in the on position (machine not running). Right now, with the "won't start scenario" and the key on, you don't hear that clicking under your feet like the park brake is getting no power. The strange thing is that the dashboard console lights up. Could it have something to do with the hydraulic lock circuit? I know that when it's engaged with the machine not running you can't start it until you lower the lever.
Most likely some draughtsman in the factory was using the 330 schematic as a starting point for the 320 one to avoid reinventing the wheel and forgot to edit the title box in the corner of the schematic. It happens.