742 - warning light on RH side ??????

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M700man

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Alright, time for a dumb question. Does the red warning light, on the right hand side, indicate a restriction in the hydro circuit or extremely high hydro oil temperature????? Or, something else entirely ? Further, if this is the case, is it tied into a shutdown system which would stop the machine from running ? Any help greatly appreciated. Thanks guys, John
 

Tazza

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Not dumb at all.
It could be one of 3 things, over temperature, low charge pressure or engine oil pressure is low.
I'm not too sure what light is connected to what but that gives you a starting point. Disconnect each sender one at a time and you can work out what it is.
They are not connected to a shutdown system. I want to install one that will but that will come in time. Thats basically the BOSS system that newer machines have. The problem is one bad sender and you simply can't run the machine.
 

M700man

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Not dumb at all.
It could be one of 3 things, over temperature, low charge pressure or engine oil pressure is low.
I'm not too sure what light is connected to what but that gives you a starting point. Disconnect each sender one at a time and you can work out what it is.
They are not connected to a shutdown system. I want to install one that will but that will come in time. Thats basically the BOSS system that newer machines have. The problem is one bad sender and you simply can't run the machine.
Thanks for the reply, Tazza. I talked with a Bobcat service tech today, and he seemed to think that it indicated the charge pressure, and further, that it also controlled the hour meter. Incidentally, the hour meter quit working about the same time the light problem showed up, but I attributed this to the two connectors which are right below the seat on the left hand side. The drive system and lift seem to work with ample power, although I have not put a pressure gauge on it, as he suggested. For some reason, he said to put the test gauge into the female coupler on the remote outlet. Frankly, I would think that it would make no difference, as both sides should have pressure. This would of course show the vane pump pressure value which controls the lift cylinders/bucket cylinders as well as charges the hydrostatic pumps. Additionally, he mentioned that it could be simply a faulty sensor. I don't want to ruin the machine but I am really at a loss here at the moment, mainly due to lack of concrete technical info. I had just changed the hydro filter yesterday and the light came on almost immediately. It did go out momentarily, from time to time but not more than for a few seconds. Today, I cranked it back it up and the light came back on after about 10 minutes of operation. Any more ideas ? Thanks, John
 

Tazza

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Thanks for the reply, Tazza. I talked with a Bobcat service tech today, and he seemed to think that it indicated the charge pressure, and further, that it also controlled the hour meter. Incidentally, the hour meter quit working about the same time the light problem showed up, but I attributed this to the two connectors which are right below the seat on the left hand side. The drive system and lift seem to work with ample power, although I have not put a pressure gauge on it, as he suggested. For some reason, he said to put the test gauge into the female coupler on the remote outlet. Frankly, I would think that it would make no difference, as both sides should have pressure. This would of course show the vane pump pressure value which controls the lift cylinders/bucket cylinders as well as charges the hydrostatic pumps. Additionally, he mentioned that it could be simply a faulty sensor. I don't want to ruin the machine but I am really at a loss here at the moment, mainly due to lack of concrete technical info. I had just changed the hydro filter yesterday and the light came on almost immediately. It did go out momentarily, from time to time but not more than for a few seconds. Today, I cranked it back it up and the light came back on after about 10 minutes of operation. Any more ideas ? Thanks, John
It does sound like charge a pressure warning light.
As for the hour meter, i wired mine into the volt meter, when ever the ignition is on the meter will click over.
It could indeed be the sender, the only way to be sure is to attach a pressure gauge. What you were refering to earlier about the pressure of the quick couplers just indicates if you have a problem with your relief valve pressure setting.
Does the machine squeel? or does it have heaps of driving power? Hydraulics are totally seperate in this situation, we only need to know about drive.
I doubt it is air in the system, as it seems to purge pretty fast after a filter change.
 

M700man

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It does sound like charge a pressure warning light.
As for the hour meter, i wired mine into the volt meter, when ever the ignition is on the meter will click over.
It could indeed be the sender, the only way to be sure is to attach a pressure gauge. What you were refering to earlier about the pressure of the quick couplers just indicates if you have a problem with your relief valve pressure setting.
Does the machine squeel? or does it have heaps of driving power? Hydraulics are totally seperate in this situation, we only need to know about drive.
I doubt it is air in the system, as it seems to purge pretty fast after a filter change.
Drive power seems to be unaffected, as it will spin the wheels if it can't move what's in front of it. Lift arms/tilt seem to have sufficient power as well. Several months ago, just motoring around the shop, the light came on a few times, briefly and then went back off. After starting this cleanup job, the light would come on for a few seconds, occasionally, but after changing the hydro filter(which I filled with oil) prior to installation, it came on and stayed on for about 15 minutes, although I saw no changes in performance. Yesterday late, I cranked it back up and run it for a few minutes and the light came back on. It would seem that it probably run just long enough to heat up the oil and thin it, which of course would drop the pressure. Incidentally, I had taken it back to the shop, and while I was doing repairs, I washed the radiator/oil cooler out thoroughly, just to be sure. So, obviously it was not a case of a restricted air flow to the oil cooler, which I first suspected. I normally use Baldwin filters, but got this last one from NAPA. It appeared to be the same, but now I am beginning to wonder if it may not be to fine of a screen to let sufficient oil flow through. But if that was the case, then it seems that it would lose drive power, etc.
 

Tazza

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Drive power seems to be unaffected, as it will spin the wheels if it can't move what's in front of it. Lift arms/tilt seem to have sufficient power as well. Several months ago, just motoring around the shop, the light came on a few times, briefly and then went back off. After starting this cleanup job, the light would come on for a few seconds, occasionally, but after changing the hydro filter(which I filled with oil) prior to installation, it came on and stayed on for about 15 minutes, although I saw no changes in performance. Yesterday late, I cranked it back up and run it for a few minutes and the light came back on. It would seem that it probably run just long enough to heat up the oil and thin it, which of course would drop the pressure. Incidentally, I had taken it back to the shop, and while I was doing repairs, I washed the radiator/oil cooler out thoroughly, just to be sure. So, obviously it was not a case of a restricted air flow to the oil cooler, which I first suspected. I normally use Baldwin filters, but got this last one from NAPA. It appeared to be the same, but now I am beginning to wonder if it may not be to fine of a screen to let sufficient oil flow through. But if that was the case, then it seems that it would lose drive power, etc.
If your hydraulics work well i doubt its the main filter as the oil for the hydrostatica don't get filtered constantly. Its pretty well a closed loop that gets replenished by the charge pressure.
I'd check the pressure or throw another sender at it.
 

M700man

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If your hydraulics work well i doubt its the main filter as the oil for the hydrostatica don't get filtered constantly. Its pretty well a closed loop that gets replenished by the charge pressure.
I'd check the pressure or throw another sender at it.
Tazza, I ordered a manual on this machine (more about that, later) and it shows, if I'm reading the schematics correctly, that the wires from the temp sending unit and the charge pressure unit are tied together, going to the light. The light is described as a "Transmission" light. Seems somewhat useless as you have to test each function. It takes awhile for me to absorb written info, unlike some years ago! Anyhow, I must get to the bottom of this and determine whether it's a false alarm or the real thing. Thanks for your input. Will report my findings. Thanks, John
 

Tazza

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Tazza, I ordered a manual on this machine (more about that, later) and it shows, if I'm reading the schematics correctly, that the wires from the temp sending unit and the charge pressure unit are tied together, going to the light. The light is described as a "Transmission" light. Seems somewhat useless as you have to test each function. It takes awhile for me to absorb written info, unlike some years ago! Anyhow, I must get to the bottom of this and determine whether it's a false alarm or the real thing. Thanks for your input. Will report my findings. Thanks, John
Yeah, they generally do tie those 2 systems together. They just have the engine separate as its a little more venerable.
Good luck with finding the issue.
 

M700man

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Yeah, they generally do tie those 2 systems together. They just have the engine separate as its a little more venerable.
Good luck with finding the issue.
For those interested, I hopefully have got the bottom of the problem - just not sure how I got there! I removed the charge pressure switch and put a run tee in, screwed the switch back in and reconnected the wires. I then had a 4' hyd. hose made up which would route up through where the wiring harnesses come through the bottom of the cab. Then installed a hyd. pressure gauge. Took the temp sending unit wire off, substituted another wire, took a second wire and tied it to the temp wire. Stripped these two wires back and routed them through also. Plan was, when the light came on, to first disconnect these two wires which would take the temp sending unit out of the circuit. Obviously, if the light didn't go out, and the gauge showed proper charge pressure, then the charge pressure switch would be the problem. BUT, the light never came back on. I had taken the charge pressure sending unit out to be sure I got the correct fittings, and when I came back, a considerable amount of oil had drained out of the port on top of the center plate. 3 1/2 gals, to be exact. Charge pressure was constant at 100#'s, with the service manual calling for 85#'s. So, I don't know if one of the sending units wires were loose, or, if the fresh oil boosted the pressure. I ran the machine hard for about 45 minutes, the light never came on and it worked like a mule. Relieved of course, that the charge pressure was more than sufficient, but I always like to find the "smoking gun". Any thoughts, anyone? Thanks, John
 

Tazza

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For those interested, I hopefully have got the bottom of the problem - just not sure how I got there! I removed the charge pressure switch and put a run tee in, screwed the switch back in and reconnected the wires. I then had a 4' hyd. hose made up which would route up through where the wiring harnesses come through the bottom of the cab. Then installed a hyd. pressure gauge. Took the temp sending unit wire off, substituted another wire, took a second wire and tied it to the temp wire. Stripped these two wires back and routed them through also. Plan was, when the light came on, to first disconnect these two wires which would take the temp sending unit out of the circuit. Obviously, if the light didn't go out, and the gauge showed proper charge pressure, then the charge pressure switch would be the problem. BUT, the light never came back on. I had taken the charge pressure sending unit out to be sure I got the correct fittings, and when I came back, a considerable amount of oil had drained out of the port on top of the center plate. 3 1/2 gals, to be exact. Charge pressure was constant at 100#'s, with the service manual calling for 85#'s. So, I don't know if one of the sending units wires were loose, or, if the fresh oil boosted the pressure. I ran the machine hard for about 45 minutes, the light never came on and it worked like a mule. Relieved of course, that the charge pressure was more than sufficient, but I always like to find the "smoking gun". Any thoughts, anyone? Thanks, John
I'd blame the sender, you may have had a bad connection. 100 psi is good, it will lower under load but either way its exactly where it should be.
 

skidsteer.ca

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I'd blame the sender, you may have had a bad connection. 100 psi is good, it will lower under load but either way its exactly where it should be.
Perhaps a small piece of dirt, or tefelon tape etcv was floating in front of the sender and intermittantly blocking the orifice into the sender causing faulty readings. loosing the oil flushed it out. who knows
I did have a engine that had eradic oil pressure reading and the guage I had installed was block with t tape, One start it was fine , the next no oil pressure. of course we though the worst initially, its important not to skip past the little things.
Ken
 

M700man

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Perhaps a small piece of dirt, or tefelon tape etcv was floating in front of the sender and intermittantly blocking the orifice into the sender causing faulty readings. loosing the oil flushed it out. who knows
I did have a engine that had eradic oil pressure reading and the guage I had installed was block with t tape, One start it was fine , the next no oil pressure. of course we though the worst initially, its important not to skip past the little things.
Ken
Actually, guys, I mistakenly quoted the service manual as showing a charge pressure of 85#'s, when, after rereading it this am, I find that for this particular machine, it should be 95 - 115#'s. I do recall that it maintained this 100#'s plus during hard operation yesterday, so at least that is something I don't have to worry about. I will post again if problem resurfaces. John
 

bfingar

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Actually, guys, I mistakenly quoted the service manual as showing a charge pressure of 85#'s, when, after rereading it this am, I find that for this particular machine, it should be 95 - 115#'s. I do recall that it maintained this 100#'s plus during hard operation yesterday, so at least that is something I don't have to worry about. I will post again if problem resurfaces. John
John

I have a 642 which says that the charge pressure should be around 100psi. The charge pressure will drop on mine occasionally when lifting heavy loads after the machine is hot and been run hard for some time, this in turn will illuminate the “Transmission” warning light. I also installed a gauge to display the charge pressure and also an engine oil pressure gauge. On older machines, it is a necessity to have proper information. If your indicator light come on and stays on all the time, you must stop doing what you are doing and figureout if the issue is real or just a bad sending unit. I did have my sending unit fail.
 
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