Bobcat 753, problem with sensors when electrifying the machine

[electrified 753 Bobcat]

Good evening! Thanks for letting me enter this forum! I'm currently electrifying my 753 Bobcat with BOSS. The machine is electrified with a 3-phase electric motor powered by a cable that is automatically un rolled an rolled up by a spring drum. Now I'm having trouble while "tricking" some sensors that are not used anymore, for example the sensor for engine oil pressure. I tricked it with a resistor giving a resistance to the computer that "makes the BOSS terminal" happy. But still the display shows "EP3" which means "engine oil pressure sensor, wiring not connected". Does anybody know how the system "checks" if wiring is connected or not? Or does anyone have an idea of how to resolve my problem...? Thank you so much in advance for your highly appreciated help!

 

[reaperman]

Sounds like a interesting project, keep us posted. Sorry I cant help with the sensors.

 

[Acj2001]

Sounds like a interesting project, keep us posted. Sorry I cant help with the sensors.

I too am not overly family with these units, but maybe I can speculate a little from a logic standpoint. You are feeding the machine with a constant value or input. Maybe the logic programming in the controller is smart enough to know that this value should never remain fixed. IE maybe it is smart enough to know when the key is on with zero rpm's the value should be different than when it is operating at 2000 rpm. Some programs and computer logic build in features such as this to know when a sensor fails. Side note upload a video of this thing working. The idea of it scares it me. I would be afraid it is a 480V 3 phase electric chair. Reminds of a bumper car. Check out my channel Flat Thunder Channel

 

[electrified 753 Bobcat]

I too am not overly family with these units, but maybe I can speculate a little from a logic standpoint. You are feeding the machine with a constant value or input. Maybe the logic programming in the controller is smart enough to know that this value should never remain fixed. IE maybe it is smart enough to know when the key is on with zero rpm's the value should be different than when it is operating at 2000 rpm. Some programs and computer logic build in features such as this to know when a sensor fails. Side note upload a video of this thing working. The idea of it scares it me. I would be afraid it is a 480V 3 phase electric chair. Reminds of a bumper car. Check out my channel Flat Thunder Channel

Thanks for the replys! Does anyone knwo a bit more about how the "BOSS" works or for example how the "BOSS" recognizes a Sensor that is not connected...? Thanks a lot!

 

[Hotrod1830]

Thanks for the replys! Does anyone knwo a bit more about how the "BOSS" works or for example how the "BOSS" recognizes a Sensor that is not connected...? Thanks a lot!

I have never worked on a Boss system. But have 25 years of automotive experience. Beyond just a ohm reading on the circuit, like Acj2001 stated, it may be a plausibility logic. If it doesnt see an RPM signal, but see's oil pressure the Boss module calls bullshit and assumes the sensor is faulty. Just an idea.
More than likely your going to have to simulate ALL the sensors related to a engine running condition. Are you providing an RPM signal?

 

[electrified 753 Bobcat]

I have never worked on a Boss system. But have 25 years of automotive experience. Beyond just a ohm reading on the circuit, like Acj2001 stated, it may be a plausibility logic. If it doesnt see an RPM signal, but see's oil pressure the Boss module calls bullshit and assumes the sensor is faulty. Just an idea.
More than likely your going to have to simulate ALL the sensors related to a engine running condition. Are you providing an RPM signal?

Hi hotrod, Thank you for sharing your knowledge! The "old" RPM sensor is still connected, but it does not send any signal. I have not tried yet to provide an artificial RPM signal. -----------------------When i switch on ignition to start the BOSS system, the following error codes appear: ---------------------------------"Engine Coolant level; Shutdown (ECl-1)" This sensor I took away and just put a brigde over the two cables, this did not make the error disappear, but even though the error code is displayed, the BOSS does not "auto-shutdown" when the sensor cables are brigded. -------------------------------"battery, voltage low (b-2.2)" The computer power supply that I use to power all the 12V applications on the Bobcat seems to be a bit to low in voltage for the BOSS system... ----------------------------"Hydrostatic Fluid Pressure, Wiring not connected (HP-3)" "Hydrostatic Fluid Temperature, Wiring not connected (HC-3)" This ist quite strange, because the original sensors are in place and connected...??? ----------------------------"Engine Oil Pressure, Wiring not connected (EP-3)" This is also quite strange, because this sensor I replaced with a 100Ohms resistor which seems to work, the BOSS display shows 8 bars for engine oil pressure... -----------------------------"Engine Coolant Temperature, Wiring not connected (EC-3)" This sensor is similar to "Engine Oil Pressure", I replaced the sensor with a 1kOhms resistor which is displayed as a pretty cold engine by the BOSS display, it shows 1 bar for Engine Coolant temp -------------------------"Engine speed, no signal (ES-6)" As I sad the sensor is connected, but not in place. -------------------------------"Air filter, no signal (AF-6)" sensor is disconnected. ------------------------------------"Hydraulic charge filter condition, no signal (HF1-6)" The sensor is connected as "usual"...? ------------------------------------Thank you so much for any more help or ideas about how the BOSS system works, and how I could "trick it"... Or would I rather take it out....? -------------------sorry, HTML enabling in forum settings did not work, that is, I could enable it, but then I couldn't enter text anymore...

 

[flyerdan]

Hi hotrod, Thank you for sharing your knowledge! The "old" RPM sensor is still connected, but it does not send any signal. I have not tried yet to provide an artificial RPM signal. -----------------------When i switch on ignition to start the BOSS system, the following error codes appear: ---------------------------------"Engine Coolant level; Shutdown (ECl-1)" This sensor I took away and just put a brigde over the two cables, this did not make the error disappear, but even though the error code is displayed, the BOSS does not "auto-shutdown" when the sensor cables are brigded. -------------------------------"battery, voltage low (b-2.2)" The computer power supply that I use to power all the 12V applications on the Bobcat seems to be a bit to low in voltage for the BOSS system... ----------------------------"Hydrostatic Fluid Pressure, Wiring not connected (HP-3)" "Hydrostatic Fluid Temperature, Wiring not connected (HC-3)" This ist quite strange, because the original sensors are in place and connected...??? ----------------------------"Engine Oil Pressure, Wiring not connected (EP-3)" This is also quite strange, because this sensor I replaced with a 100Ohms resistor which seems to work, the BOSS display shows 8 bars for engine oil pressure... -----------------------------"Engine Coolant Temperature, Wiring not connected (EC-3)" This sensor is similar to "Engine Oil Pressure", I replaced the sensor with a 1kOhms resistor which is displayed as a pretty cold engine by the BOSS display, it shows 1 bar for Engine Coolant temp -------------------------"Engine speed, no signal (ES-6)" As I sad the sensor is connected, but not in place. -------------------------------"Air filter, no signal (AF-6)" sensor is disconnected. ------------------------------------"Hydraulic charge filter condition, no signal (HF1-6)" The sensor is connected as "usual"...? ------------------------------------Thank you so much for any more help or ideas about how the BOSS system works, and how I could "trick it"... Or would I rather take it out....? -------------------sorry, HTML enabling in forum settings did not work, that is, I could enable it, but then I couldn't enter text anymore...

One thing I can think of is that the senders may require the body to be grounded in order to function properly. An old oil pressure switch would just complete the ground circuit to the idiot light; maybe the newer style has a similar requirement, especially if they have three wires.
If you don't already have it, there is a 753 book in the manual thread that might help. Also, the 500 came in a factory version with a three phase electric option like what you're attempting, you might grab that book as well for some insight. Of course that was several decades before all the whiz-bang electro-BOSS systems, they didn't need that for unloading coal ships. I'd be inclined to remove all the bells and whistles and take out the pedal lockouts so it worked and call it good.
If you're having trouble with the text box and formatting, try hitting preview and then back to edit mode. I have to do this on every reply and do all html coding by hand. The forum is buggier than an Air Tractor leading edge, but we make do.

 

[Hotrod1830]

One thing I can think of is that the senders may require the body to be grounded in order to function properly. An old oil pressure switch would just complete the ground circuit to the idiot light; maybe the newer style has a similar requirement, especially if they have three wires.
If you don't already have it, there is a 753 book in the manual thread that might help. Also, the 500 came in a factory version with a three phase electric option like what you're attempting, you might grab that book as well for some insight. Of course that was several decades before all the whiz-bang electro-BOSS systems, they didn't need that for unloading coal ships. I'd be inclined to remove all the bells and whistles and take out the pedal lockouts so it worked and call it good.
If you're having trouble with the text box and formatting, try hitting preview and then back to edit mode. I have to do this on every reply and do all html coding by hand. The forum is buggier than an Air Tractor leading edge, but we make do.

Having all of those codes with all the sensors connected is interesting. Have you tried unplugging the sensors and shorting the connector( 2 wires together) to see if the code changes?(if there is such a code?) that would tell you the wiring is good and the ECM recognizes the signal)
You can unplug the sensors and measure voltage at the sensor supply circuit. I am guessing it will be 5 volts. One wire will be supply, the other will be signal return to ecm. one wire should have voltage, the other wire nothing.
A wiring diagram would help if the supply voltage is not present. Usually with a supply voltage problem, multiple sensors will be effected because they are all fed by the same circuit.
You mentioned you are supplying a artificial 12 volt source. How many volts is it? A fully charged lead acid battery is 12.6 volts. Must be above that to charge. Usually around 13.5 volts minimum. Also, since you are using a artificial source, make sure there is no AC induced voltage. Think of it as a alternator with a failed rectifier diode. 12 volt DC systems with a computer control do not tolerate AC voltage spikes well, and can wreak havoc on ECM's. Easy way to check is hook your DVM up to a 12 volt power source on the machine with the meter set to AC volts and measure. Should be a millivolt reading of 500mv or less(.5v on the meter.)
Dont forget grounds. Measure from the ECM ground wire(s) to the power source ground in series(voltage drop) Should be 50mv or less(.050v on the meter)

 

[Hotrod1830]

Having all of those codes with all the sensors connected is interesting. Have you tried unplugging the sensors and shorting the connector( 2 wires together) to see if the code changes?(if there is such a code?) that would tell you the wiring is good and the ECM recognizes the signal)
You can unplug the sensors and measure voltage at the sensor supply circuit. I am guessing it will be 5 volts. One wire will be supply, the other will be signal return to ecm. one wire should have voltage, the other wire nothing.
A wiring diagram would help if the supply voltage is not present. Usually with a supply voltage problem, multiple sensors will be effected because they are all fed by the same circuit.
You mentioned you are supplying a artificial 12 volt source. How many volts is it? A fully charged lead acid battery is 12.6 volts. Must be above that to charge. Usually around 13.5 volts minimum. Also, since you are using a artificial source, make sure there is no AC induced voltage. Think of it as a alternator with a failed rectifier diode. 12 volt DC systems with a computer control do not tolerate AC voltage spikes well, and can wreak havoc on ECM's. Easy way to check is hook your DVM up to a 12 volt power source on the machine with the meter set to AC volts and measure. Should be a millivolt reading of 500mv or less(.5v on the meter.)
Dont forget grounds. Measure from the ECM ground wire(s) to the power source ground in series(voltage drop) Should be 50mv or less(.050v on the meter)

btw, if your actual voltage reading is close but above/below what I stated, dont sweat it. It will either be close or waaaay off.

 

[Hotrod1830]

btw, if your actual voltage reading is close but above/below what I stated, dont sweat it. It will either be close or waaaay off.

As for sensor simulation, you need to simulate the sensors in the middle of the range. ECM's are only programmed to self test sensor reading that are out of range or implausible. You cant use the cluster display to set up your resistors. It may show OK on the display reading, but actually reading low/high/cold/hot by the ECM. Remember, all the ecm see's is voltage, and if the voltage is outside what is programmed as a limit it sets a code.
the Rpm sensor will be tricky. I was thinking a gear driven speed sensor out of an automotive application powered by a small 12v motor when system in "running". if your electric motor is running at all times, you may find a way to run it off that. seeing as how you have gotten this far, you can probably figure out a way to simulate it as well.

 

[Bswwood]

As for sensor simulation, you need to simulate the sensors in the middle of the range. ECM's are only programmed to self test sensor reading that are out of range or implausible. You cant use the cluster display to set up your resistors. It may show OK on the display reading, but actually reading low/high/cold/hot by the ECM. Remember, all the ecm see's is voltage, and if the voltage is outside what is programmed as a limit it sets a code.
the Rpm sensor will be tricky. I was thinking a gear driven speed sensor out of an automotive application powered by a small 12v motor when system in "running". if your electric motor is running at all times, you may find a way to run it off that. seeing as how you have gotten this far, you can probably figure out a way to simulate it as well.

Why not completely remove the BOSS and just power the brake and BICS coils as needed?

 

[Tazza]

Why not completely remove the BOSS and just power the brake and BICS coils as needed?

I like the idea of this thread, i think we need pictures. Sounds quite interesting.
I too think it's not a bad idea to just pull the BOSS system out, you don't need temperature or fuel levels, the only thing it will control is the aux hydraulics, but you can do that with relays, as i don't believe this model had proportional controls for the aux hydraulics.

 

[electrified 753 Bobcat]

Why not completely remove the BOSS and just power the brake and BICS coils as needed?

Thanks for your reply Bswwood; I am not against removing BOSS but I want to keep it as simple as possible and until I tried "faking" the sensor signals, I thought it would be easy to trick the ECM... As far as I know the errors that are displayed at the moment are just "cosmetic" problems, because the ECM doesn't block hydraulics and even if it forced a shutdown it wouldn't have any effect, as the shutdown relay is not used in my (planned) setup.

 

[electrified 753 Bobcat]

Thanks for your reply Bswwood; I am not against removing BOSS but I want to keep it as simple as possible and until I tried "faking" the sensor signals, I thought it would be easy to trick the ECM... As far as I know the errors that are displayed at the moment are just "cosmetic" problems, because the ECM doesn't block hydraulics and even if it forced a shutdown it wouldn't have any effect, as the shutdown relay is not used in my (planned) setup.

@Tazza; I agree, no proportional control of aux hydraulics, the "fork" opens with a loud "bang"... = ) see also my response to Bswwood... what parts would you like to have pictures of, and where should I upload them? thank you for your interest and time!

 

[electrified 753 Bobcat]

As for sensor simulation, you need to simulate the sensors in the middle of the range. ECM's are only programmed to self test sensor reading that are out of range or implausible. You cant use the cluster display to set up your resistors. It may show OK on the display reading, but actually reading low/high/cold/hot by the ECM. Remember, all the ecm see's is voltage, and if the voltage is outside what is programmed as a limit it sets a code.
the Rpm sensor will be tricky. I was thinking a gear driven speed sensor out of an automotive application powered by a small 12v motor when system in "running". if your electric motor is running at all times, you may find a way to run it off that. seeing as how you have gotten this far, you can probably figure out a way to simulate it as well.

@ hotrod; thank you for all your ideas! unfortunately I did not have time yet to try it all out... as soon as I go any further I will keep you informed.

 

[electrified 753 Bobcat]

One thing I can think of is that the senders may require the body to be grounded in order to function properly. An old oil pressure switch would just complete the ground circuit to the idiot light; maybe the newer style has a similar requirement, especially if they have three wires.
If you don't already have it, there is a 753 book in the manual thread that might help. Also, the 500 came in a factory version with a three phase electric option like what you're attempting, you might grab that book as well for some insight. Of course that was several decades before all the whiz-bang electro-BOSS systems, they didn't need that for unloading coal ships. I'd be inclined to remove all the bells and whistles and take out the pedal lockouts so it worked and call it good.
If you're having trouble with the text box and formatting, try hitting preview and then back to edit mode. I have to do this on every reply and do all html coding by hand. The forum is buggier than an Air Tractor leading edge, but we make do.

@ flyerdan; thank you for your help with my bobcat and with the forum... what is strange about the sensors, and the displayed errors, is that before I started the conversion to the electric motor, I had no error at all, an now even the sensors that are concerning the hydraulic oil, that are still in place and connected, are seen by the ECM as "wiring not connected"... the sensors all have only 2 wires. though I guess that there should not be an issue with grounding...? thanks for the information about the 500 electric version, it was fun reading about it on the internet. thanks for the information about the manual, I already have the service manual.

 

[gyzmo]

@ flyerdan; thank you for your help with my bobcat and with the forum... what is strange about the sensors, and the displayed errors, is that before I started the conversion to the electric motor, I had no error at all, an now even the sensors that are concerning the hydraulic oil, that are still in place and connected, are seen by the ECM as "wiring not connected"... the sensors all have only 2 wires. though I guess that there should not be an issue with grounding...? thanks for the information about the 500 electric version, it was fun reading about it on the internet. thanks for the information about the manual, I already have the service manual.

not sure if you solved this issue? I have had this a couple of times on my 753, I think it is the connector on the oil pressure sensor next to the hydraulic oil filter up in the top right hand side of the engine bay. possibly the connector its self. I am going to swap the connector and see if it fixes it. good luck, would love to see pics of your electric beast.