Locked out of hydrolics

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Billwoodm3

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Joined
Jun 21, 2016
Messages
11
I have a 2002 Bobcat 753G, and seem to be having a problem with the seat bar circuitry. The Bobcat will start up and run, but will not move. When I turn the ignition key to the RUN position, the seat bar light/LED on the BICS instrument panel (left side), starts flashing continuously in a series of three's. The instrument panel on the right side has four icons/lights that also come on at the same time, and stay on. They are: Engine Oil Pressure, Engine Coolant Temperature, Hydraulic Charge Pressure, and Hydraulic Oil Temperature. I replaced the seat bar sensor, and still have the same problem. I checked for service codes, and here are the seven service codes that were displayed: 11-06 – Seat bar sensor circuit shorted to ground. / 4-21 – Engine oil pressure out of range. / 5-21 – Hydraulic charge pressure out of range. / 7-21 – Hydraulic oil temperature out of range. / 8-21 – Engine coolant temperature out of range. / 12-21 – Front auxiliary PWM switch out of range. / 47-22 – 8 volt reference out of range. I checked, but could not find any loose or corroded ground connections. I also tested all of the fuses and relays with a multimeter, and they were all ok. Any help with this problem would be appreciated. Thanks, Bob
 

7LBSSMALLIE

Well-known member
Joined
Feb 2, 2012
Messages
1,290
the sensor circut. is an 8volt supply circut. the voltage is stepped down in controller( magic box that no one can explain. internal schematicts of nor give a represantation of how it works) anyway you one of two things goining on here. A controller let all the smoke leak out.( now a couple of factors here. controllers are prone to failure if 1. low batt voltage. 2. alt overcharge. 3 jump start. 4. improper welding on unit %. bad grounds. next step examine controller. what we are looking fo here is potted or non pot? non pot snap together lid. had a tendenacy to collect moisture etc and gro green crap on boards. potted . sealed molton plastic poured over board. evidance of failure is not vissually evident typically but not always you will see seraption of pot material from plastic case. #2 bad spot in harness shorted to ground. visually inspect prior to cutting tie straps. you want to fix it while its broke. or you may never find it just years of intermittent elect issues. start at bitter end of harness. ohm check probalby coolant temp. blue wire for coniounity to grd. if present leave meter in place and perform wiggle test to entire harness while watching meter. if that dont work disconnect sensors one at a time REASONING IS ONE BAD SENSOR WILL THROW ENTIRE 8 VOLT SUPPLY OFF. will not code for that specific sensor but mayhem it is. let us know what you found please . help the next dude. and if someonecould edit this. you are more than welcome. in fact please a lotta this could be tightened up. not my fortay.
 

mmsllc

Well-known member
Joined
Dec 29, 2015
Messages
715
the sensor circut. is an 8volt supply circut. the voltage is stepped down in controller( magic box that no one can explain. internal schematicts of nor give a represantation of how it works) anyway you one of two things goining on here. A controller let all the smoke leak out.( now a couple of factors here. controllers are prone to failure if 1. low batt voltage. 2. alt overcharge. 3 jump start. 4. improper welding on unit %. bad grounds. next step examine controller. what we are looking fo here is potted or non pot? non pot snap together lid. had a tendenacy to collect moisture etc and gro green crap on boards. potted . sealed molton plastic poured over board. evidance of failure is not vissually evident typically but not always you will see seraption of pot material from plastic case. #2 bad spot in harness shorted to ground. visually inspect prior to cutting tie straps. you want to fix it while its broke. or you may never find it just years of intermittent elect issues. start at bitter end of harness. ohm check probalby coolant temp. blue wire for coniounity to grd. if present leave meter in place and perform wiggle test to entire harness while watching meter. if that dont work disconnect sensors one at a time REASONING IS ONE BAD SENSOR WILL THROW ENTIRE 8 VOLT SUPPLY OFF. will not code for that specific sensor but mayhem it is. let us know what you found please . help the next dude. and if someonecould edit this. you are more than welcome. in fact please a lotta this could be tightened up. not my fortay.
On a lot of BOCAT skid steers, I have seen the wiring harness chaff severely on the sharp metal edge of the back of the cab. To check it out, just raise the cab & look for the wiring that connects the cab wiring to the main wiring harness. If it is chaffed, then whatever the wiring is conducting could be severed (AKA "broken" wire) or it could be shorted to the machine frame ground of the electrical system. Even if it is not chaffed or otherwise damaged, it is easily worth adding a rubber section of hose over that edge of the cab sheet metal. I am hoping that the damage is easily found there because it is SO easy to access & repair.
 

7LBSSMALLIE

Well-known member
Joined
Feb 2, 2012
Messages
1,290
On a lot of BOCAT skid steers, I have seen the wiring harness chaff severely on the sharp metal edge of the back of the cab. To check it out, just raise the cab & look for the wiring that connects the cab wiring to the main wiring harness. If it is chaffed, then whatever the wiring is conducting could be severed (AKA "broken" wire) or it could be shorted to the machine frame ground of the electrical system. Even if it is not chaffed or otherwise damaged, it is easily worth adding a rubber section of hose over that edge of the cab sheet metal. I am hoping that the damage is easily found there because it is SO easy to access & repair.
other rub spots are right there by saftey down valve.
 

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