So I have a 1995 or 96 bobcat 753 # 512723302 that I bought for next to nothing with some problems. I got it running with a new ignition switch and it runs fine but the error code hp-3 flashes? Also for some reason the only way to get the bucket to raise or tilt back is to have your thumb holding the auxiliary switch to the left, you also have to hold the switch when moving forward or backwards or it moves real slow. When you relese your thumb the engine bogs down slightly as if it is under more load. Any advice would be great. Also when you lift the cockpit up there is about 7 weather proof wire connectors throughout the harness that are just hanging around not connected to anything. Are they for models with other options? I have searched around but there is nothing that I can see that they go to. Once again ANY help would be very appreciated. Thanks.
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SkidRoe
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Sounds like you are having to hold the switch to prevent the aux. hydraulic valve from engaging, but I think that may be only part of the problem. Does the harness show signs of being tampered with? It is not unusual to have some unconnected connectors under the seat, depending on what options your machine does or doesn't have.
SkidRoe
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The HP3 code your are getting is for a hydraulic pressure switch/sensor (hp) that has an open circuit (3). Some place to start , I guess.
The harness appears to be not tampered with however, behind the plastic panel that houses the ignition switch there nare wires cut, non-factory wire butt connectors, and what appear to be factory connectors again not hooked to anything. There was no key when I bought it so I ordered some bobcat keys but they were very different, so I put a universal automotive ignition switch on it. Everything seems to work; gauges, lights, etc.
I would start buy unplugging the coils for the aux on the control vavle one at a time. I'm think one coil is picking up volatge to shift the aux vavle and by pressing the the thumbe switch, you are powering the other and it is neutralling out. I'm betting if you unplug both, it should be runable for the time being. As for the hp3 code, the sensor just up and die.
Yup, that did the trick bobcatdan. The universal ignition switch is a 2 position and I must have put the aux. release that would normally be on by turning the key all the way left on a constant hot terminal. I wasn't aware of that feature at the time I installed the switch. Thanks for your help! As for the hp-3 error code I think I will start at the replenishing valve, any suggestions?
7LBSSMALLIE
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stop. the hp3 as BCD said.is probally sensor there are three sensors located on hyd filter head, 1 ,hyd temp 2 pressure differantial (indicates a plugged filter, 3 charge press sensor. (this is boss i assume led rh panel), be sure to tell parts dude this:: the one to far right is the one youre looking at, the new one will look differant and will require new jumper harness. (probally) you are going to have an extra butt connector ther if you hook this up you just smoked new sender. if new sender does not clear code , you will need to verify actual charge press.. if charge is actually low this will need addressed pronto. catastrhopic failure soon to follow. if not (charge press good) is a whole nother ball game but one step at a time, so in closing .. get new charge sender and jumper if needed. if that does not correct , put a manual guage in same hole sender came out of.
o.k. I will order the sensor. It appears to have been changed out at some point in its life because there was electrical tape a few inches from the connector and butt connectors where someone had retrofitted a updated pigtail on it. I have however been using the machine and all seems fine, it does "whine" a little under load. Is this common? I am almost finished with my project which requires hauling 3/4in drain rock from my drive way to the side yard. should I stop using the machine? I run it from a maximum of 15 minutes at a time. Thank you guys for all of you help and advice, Its a neat thing you do!
7LBSSMALLIE
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if you do have actuall low charge press yea its too lat e damage done remove boot and extract bullet, if it just indicated and not actuall youre ok. but it sounds like my buddys wife check eng light came on for low oil . drve to wallmart for oil, ( got halfway there eng locked up)
SkidRoe
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I agree, better get the charge pressure thing checked out before going too much further. Better safe than sorry.
i have a bobcat 753 that has had the pump rebuilt from bobcat was working fine then fuel line rotted off in tank had to drag the machine on a trailer with bucket down seems like the pedals are stuck in float blade mode or isnt getting hydraulics to work pedals barely move with no hydraulic activity can some one give some ideas please thanks
The problem is simple: You can't use a universal ignition switch. It makes the aux hydro activated, the same as when you turn the key all the way to the left to release the hydros. put in a regular bobcat switch and your problem is solved. Don't ask how I figured it out.....
I have a similar thing going on with my old 753( not BOSS). I don't know of anything that preempted it, but the machine started having almost no response with bucket or lift arms, and was running very slow. It sounded like it was fighting itself to do anything. I cleaned out the hydraulic block and didn't find anything at all, but i finally happened to disconnect one of the aux solenoids and then the machine worked fine, same speed and full bucket movement. But now i want to use my grapple and when i hooked it up, the jaws would open normally with the thumb switch but i couldn't close them.. I hooked the solenoid back up and the jaws closed like a trap and now the machine is acting slow again and the thumb control doesn't do anything. That rear solenoid has 12 volt power to it full time and is seems to jam up everything else. I even disconnected the leads coming out of the right joystick and it still has power to the solenoid. tonight i am going to switch the wires to the front solenoid and see what that does. Anybody have any idea what to look for?
SkidRoe
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Definitely sounds like a short some where. The slowness is caused from the solenoid being activated full time. Once you grapple cylinders stroke, there is no where for the oil to go other than over the relief valve, hence that is the only flow you are getting, and at system pressure to boot.
To help with the trouble shooting, you can check the solenoid with a screw driver blade as you disconnect/reconnect things. the solenoid will be magnetic while it is powered.
Like one of the last posts said, check the ignition switch too. Turning the key all the way to the left fires the Aux solenoids, relieving the pressure so that the QD's can be disconnected.
Let us know how you make out.
Cheers - SR
Bingo. I must have a aftermarket switch on mine also. The wire to the solenoids was connected to the ignition so it had power whenever it was turned on. after disconnecting it i have full use of bucket and grapple. It made sense, because i couldn't get it to release pressure in the aux lines. I think i will just add a toggle switch to that line so i can give it power to bleed the pressure, rather than getting a bobcat switch and doing the "key to the left" routiine. I'll just hit the toggle for a few seconds and that should do it.
SkidRoe
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