Bobcat 863 G Intermittent Seat Light and lockout

[Bobcat99]

Hello everyone,

I've been having a problem with my '99 863 G series Bobcat, where my seat bar light will not come on and shuts off intermittently while driving, causing a lockout of hydraulics and traction. I'll try to detail as best I can the scenario, and hopefully someone here will be able to point me in the right direction.

If I first go to start up the machine, I'll often get no seat bar light when the seat bar is put down. Then, after say 30 seconds or sometimes longer, it will come on, with the corresponding unlocking click of the solenoids for the hydraulic controls. Often it will stay on and operate fine for a while. Then it will flash on and off, locking me out while operating, but almost always flashing/switching and staying on, not flickering and staying off.

When the seat light is activated, the rest of the lights will light when the green operating button is pressed and all else works. I'm also able to override traction, when the seat bar light won't come on. (And I can override with the bar down, even though it's supposed to be up.)

I at first thought it might be the connector to the seat bar switch, as I noticed the protective mesh end was in the way slightly of the seat bar when it would be put down. I cut off the excess mesh to clear the bar and I closed the pin connectors a bit inside to make better contact (they seemed a bit spread from the seat bar rubbing the mesh). Anyway, that didn't change anything.

I cleaned and checked my battery negative, as that's caused me issues in the past, and I cleaned the main frame ground at the battery and checked for continuity to ground, and everything seemed fine.

Then, I opened the cab to inspect the wiring for chaffing, and to jiggle the wires a bit to see if I could stimulate the problem, but nothing proved consistent. I did find some chaffed wires, in particular a black ground after the cab harness connector to main harness down by the hydraulic reservoir. The wire was about 25% worn, but it did check out okay to the chassis for ground. I don't have a wiring diagram, but figuring I'd repair it anyway, I cut it to see if that would break the seat circuit, but it didn't, so not sure what it's for.

Anyway, I also removed the 7/16" or so retaining bolt on the seat switch itself and tried moving it about to see if maybe the magnet shifted, but that in combination with trying to move the seat bar up and down a bit did not make any difference with the seat bar light. I haven't actually removed the switch itself yet, but I'm not sure if anything could have shifted that much out of place on it or if being dusty perhaps would really affect it (and I did blow it out as best I could from the outside).

Now, seat bar switch itself aside for a moment, I pulled off the left hand control panel on the top left of the cab inside. I pulled off the connector and checked the ground there, and with key off I'm getting continuity to the frame fine. I'm also reading with the seat bar up 12.34 volts or so. But, when I put the seat bar down (and key on, not started), I'm getting fluctuating voltage, rapidly from 12.34-12.16 V then 12.2-12.09, etc. Now, I'm not sure if this is normal for the way the seat bar switch work, or if it's an indication of the problem. Maybe it's locking out when the voltage dips momentarily below the necessary voltage. That would seem to make sense

I'm able to check certain things with my multi-meter, but I'm not terribly good at diagnosing electrical issues. So, I'm not quite certain what to make of the voltage fluctuation. Is that normal? Or is that an indication of another bad ground elsewhere, which only becomes apparent when switch is on (seat bar down).

Also, on another possibly related note, I have a bit of leaking at my control valves, not much, but some. While I assume that could be messing with the solenoids, I don't think it would affect the lighting up of the seat bar circuit itself. Or am I wrong?

Anyway, I hope I've been clear in explaining my scenario. I'd appreciate any assistance you can offer.

Thank you very much.

Joe

 

[BC873G]

Are there any codes thrown when you do get locked out? That might help with the diagnosis and repair.

 

[Bobcat99]

Sorry, I forgot to mention the codes. When it first locked out, I believe it threw the traction lock code, 15-02 (or 03, I can't remember). Then afterward, when no seat light came on, it showed "NONE". Only one time in between, when I went to override the traction lock, did the traction light beep on me and show the traction lock code again.

But, other than that, with the no seat bar light coming on, it read "NONE".

Joe

 

[willie59]

You can't test the seat bar or seat sensor with a volt meter, those circuits are Hall Effect circuits, volt meters won't correctly read those circuits. I'm not familiar with the 863 G series, must be a very very early G series as Bobcat had pretty much done away with the seat switch by the time they started producing the G series. If it were me I'd get the kit from Bobcat to do away with that seat switch, it'll save ya a lot of grief down the road.

We need to know the codes you're getting, guessing at it doesn't help us or more importantly help you. If yours is typical of a G series machine, anytime a fault happens that the main controller monitors you'll hear three beeps from the alarm, this is an indication of active codes. Right then you need to push down and hold the headlight button, this will bring up the active codes in the hour meter display. Keep in mind, Bobcat machines don't "store" codes like automotive does, they only work with "active" (right now) codes, once you shut off the ignition it wipes clean on re-start, no codes.

 

[Bobcat99]

Hi Willie,

There's no seat sensor, just the seat bar switch, sorry if I was unclear.

As far as codes, I was getting "NONE" every time the seat bar light would not come on, which was intermittent. A few times, though, I would get the traction lock beeping and flashing light, and the code was 15-02.

I just spent some more time on the machine today, trying to see if I could test the wiring etc., and it's acting more consistently problematic. After turning the key on, I could not get the seat light to come on at all (and codes still show "none" at this point). I used the override to bring it outside to open the cab. Eventually, the seat light starting going on and off intermittently, but staying off a lot longer. Still showing no codes at this time.

A few observations. With the key on, I noticed a bit of a ticking noise coming from the left hand panel with the gauges, and the temperature and fuel level gauges seems to shake a bit. I don't know if that's normal, perhaps I hadn't noticed it before.

Also, as I mentioned above, there was a frayed ground wire on the main harness by the hydraulic reservoir. I have it temporarily spliced together with a small added piece of wire. If I test ground from that wire to any point on the chassis, it checks out fine when the seat bar is down and the light on. When the light flickers and goes off, though, I am showing some resistance.

Now, when I went to put the machine inside, I encountered a new scenario. I was getting both the intermittent seat bar light and now a flashing/beeping traction lock. I did not have them both go at the same time before tonight. And yes at this point, the 15-02 codes were flashing.

I shut it down, opened the cab up, and jiggled the wire harness going into the fuse panel, which also has a bit of chaffing where it goes over the left side foot pedal linkages. When I lifted the wire harness, I heard what seemed to be the clunk of the traction wedge dropping down. Perhaps the timing was coincidental, I don't know. I taped the chaffed area up roughly, and I was going to test the machine again, but I noticed a burning smell. I checked the traction lock solenoid, and it was burning hot (don't remember touching something that hot in a while...).

A year or so ago, I installed a new aftermarket traction lock solenoid. The relay at the time was okay, and so I did not change it. So I'm not sure if I have a separate issue of a stuck relay, or if the overheating is related to this whole seat bar situation. Tomorrow I will pull the fuse cover and see if the fuse actually burnt, but I can't imagine it wouldn't have.

Hopefully, some of this information will be useful in making sense of the problem, and again, I appreciate any assistance.

Thanks.

Joe

 

[willie59]

15-02, traction lock pull coil error on. Something is keeping the pull coil of the traction lock solenoid powered up when it's not supposed to be and the main controller is seeing this, and that's the reason it was hot to touch. The run down on brake solenoid operation. When you hit the push to operate button the main controller does two things related to that solenoid. It powers up the brake relay in the fuse box to power up the "pull" coil (white wire) of the solenoid which sends battery power directly to the pull coil. The pull coil is a high magnetic coil to pull the plunger of the solenoid, but it's also high amp draw. At the same time the main controller powers up the "hold" coil (red wire) of the solenoid. That power comes directly from the main controller. After only a few seconds of this operation the main controller takes away the signal to the pull coil relay, releases it. Meanwhile the hold coil circuit stays powered up and keeps the solenoid engaged to keep the brake released. The problem you're having is something is keeping the pull coil circuit powered up. The main controller has a wire coming from the brake relay that gives it reference of when that relay is sending output voltage to the pull coil circuit and when it's not. And that's what's happening with the 15-02 code, the main controller is seeing that relay is still engaged when it's not supposed to be.

What can cause this? Any number of things including a faulty main controller. But first, replace that relay. Could simply be a relay that has contacts sticking. But one thing is for sure, with a 15-02 code, it ain't your lap bar causing the problem.

 

[crewchief888]

I'd be willing to bet the keyed bushing in the seat bar is worn, causing your intermittent seat bar light.

 

[Bobcat99]

Thanks, Willie, for the detailed break down of how the traction solenoid works. I appreciate the information a lot. Aside from the main controller itself, could there be any related issue that would cause both the pull coil relay to keep getting signal when it shouldn't and also the controller not receive or send the signal from the seat bar switch?

Crewchief888, like you said, it may very well be the seat switch bushing is sloppy, and I have two unrelated issues at play at the same time. I just figured that if it were worn and out of position, then shifting the bar up and down and rotating the switch a bit in place would have picked up alignment at some point, which it doesn't seem to want to do. Could the magnet be weak or dirty enough not to close the switch? The intermittent action, when it's taking place, is often very quick; on, off, and right back on, split second flickering. Sometimes it goes back and forth like that for a while (half a dozen plus times maybe), and usually ending up staying on, if that indicates anything.

Joe

 

[Bobcat99]

An update on the machine.

Even though the traction lock solenoid got very very hot yesterday, hot enough to melt the plastic wire sleeve a bit, the fuse did not blow, which was surprising. I took the relay out and tested it, and it seemed to be open and okay, so maybe freed itself (or problem is elsewhere). But I put the new one in anyway.

I also pulled the seat switch out. The bushing key was not worn, though the round top of the bushing was grooved a little, where the steel of the seat bar arm rides. The magnet surface was somewhat dirty, but not too bad. I turned the key on and aligned the magnet by hand, and the seat bar light went on and the solenoid unlocked. I shifted the magnet around back and forth and it seemed to be working fine.

I put the switch back together, but then it wouldn't work. I took it apart again, and tried aligning the magnet by hand again with no luck. Only once when I bumped the magnet a little hard against the switch housing did it work, but even that stopped working. Now the intermittent behavior seems to have stopped, and I'm not getting anything out of the switch, even though it's taped together in alignment.

Then, I started the machine and overrode the traction, and I got a loud singular alarm beeping and oil light flashing above the ignition. The codes read 5-09, which I believe is hydrostatic pressure. I shut it down quickly. I checked my oil levels, just in case, but all were fine. I restarted it and got the same loud beep, and it threw the code 4-14, for engine oil pressure, and then it shut the engine down.

So, am I looking at a new controller?

Joe

 

[crewchief888]

those sensors, as well as the seat bar and RH aux PWM switch all run on the same 8v supply signal from the controller..

 

[heymccall]

I'm not familiar with the 863 G series, must be a very very early G series as Bobcat had pretty much done away with the seat switch by the time they started producing the G series. If it were me I'd get the kit from Bobcat to do away with that seat switch, it'll save ya a lot of grief down the road.

Every one of my 863G had a 3 wire seat switch. The moron squad here would get stuff jammed under the seat, causing issues. Only ever changed one, though.

 

[Bobcat99]

Crewchief, at this point, do you think there is anything left to check? I thought I remember reading someone said that one bad sensor can throw the others off, but not sure if that's the case here. If the magnet is working on the seat switch, and it's in alignment, that switch should be fine.

Is there a way to test the controller itself, or can only the dealer do that?

Heymccall, I'm pretty sure I don't have any additional seat switch on mine, as I only see wiring going to the seat lap bar itself.

Joe

 

[heymccall]

Mine had seat sensors, same as here

 

[crewchief888]

All those sensors run off the 8v power supply in the bobcat controller. Yeah it's true that 1 sensor an effect operation of any or all the other sensors.

If the 8v power from the controller is off by more than a 1/2 volt, things go haywire really quick

 

[Bobcat99]

HeyMccall, Thanks for the picture. No, my machine doesn't seem to have the seat switch. Maybe mine's a later model (1999, though), or perhaps original owner removed, I don't know. Either way, thanks for the picture to confirm.

Crewchief, regarding the sensors, is it possible I am missing anything in the seat sensor? In other words, I aligned the magnet by hand, which worked initially especially when I brought the magnet in direct contact with plastic housing of the switch (not spaced away), but then that stopped working. But could there be anything else wrong with the magnetic sensor in the switch itself? Is there an easy way to bench test the sensor?

Joe

 

[crewchief888]

i 'spose you could test it somehow, but i have no idea how

the switch is a hall effect type sensor, theres no way to bypass it, (ive seen many people try and fail) it could be a possibility that the magnet is weak or the sensor itself is bad.
as i mentioned it has an 8v input, as do the rest of the sensors. bobcat has a test box for the eng oil press & hyd charge press sensors. there is also a "test box" for the seat bar sensor, it "verifies" if the wiring to the sensor is good/bad or if the sensor itself is the problem.

my best guess with the age of the machine that the sensor is bad

 

[willie59]

i 'spose you could test it somehow, but i have no idea how

the switch is a hall effect type sensor, theres no way to bypass it, (ive seen many people try and fail) it could be a possibility that the magnet is weak or the sensor itself is bad.
as i mentioned it has an 8v input, as do the rest of the sensors. bobcat has a test box for the eng oil press & hyd charge press sensors. there is also a "test box" for the seat bar sensor, it "verifies" if the wiring to the sensor is good/bad or if the sensor itself is the problem.

my best guess with the age of the machine that the sensor is bad

What he said. And again, like I stated earlier, if you plan on keeping the machine for some years, even if it turns out the seat sensor isn't the problem this go round, I'd get the kit from Bobcat to toss that seat sensor, save yourself some grief on down the road 'cause it will eventually give you grief.

 

[Bobcat99]

Crewchief, I did a bit of reading on Hall effect sensors, and I determined that at the seatbar switch, the wires 3900, 3920, and 3910 represent the Input voltage, Output voltage Signal, and ground respectively.

I tested these wires at the seat switch connector to a chassis ground. Ground wire 3910 was fine, no resistance. The middle OUTPUT Signal wire 3920 read 5.0 ohms of resistance to ground. The Input (or Supply) wire 3900 showed 1.0 ohms to ground. I don't know if these wires should have shown complete resistance to ground, however.

As far as voltage, with the key on, the Input supply wire 3900 at the seat connector showed around 3.5 volts (initially 4 volts then dropped to around 3.5 v). The Output Signal showed basically the same voltage. My question is, should each of these wires (or at least the Input line) be showing a full 8 volts? Or is it somehow split between the input and output, hence the ~4 volt reading on each wire?

I'm not completely clear if this is how the switch works or if it's simply the problem, that I'm not reading a full 8 volts on the Input wire.

By the way, I also tested the wires from the seat switch connector to the corresponding main controller connector and the wires all showed continuity between the two points.

I'll probably wind up buying the switch to rule it out, but I'm curious to know if these readings point to anything, particularly the voltage readings.

Joe

 

[Bobcat99]

Willie, do you mean there's a bypass kit for the seat lap bar sensor, or do you mean for the sensor that goes underneath the seat? As far as I know, I only have the sensor for the seat bar.

Joe

 

[crewchief888]

if you are only seeing 4v input to the switch, i'd guess you found the problem.
just to be sure, check either the eng oil pressure or charge pressure sensors for 8v. you should see 8 v at both of them.
if you are only seeing 4v there i'd suspect the controller is the problem.
if you see 8v there i'd be looking for a broken/damaged wire somewhere between the controller and a seat bar sensor