490E PVC Finally Fixed

[Knivens894]

I purchased a used 490 E about 6 years ago cheap. The engine ran well, everything functioned, but it was easy to stall in operation. I had the JD dealer do a service call for the stalling problem. He reported someone had installed a 5 amp fuse in the fuse block for the computer. The angle sensor was bad and the computer had been smoked. Those were replaced, it functioned better, but was easy to run hot hydraulically, so much so, that it could only run for two hours or so before it had to be shut down to prevent over heating damage. I went through every system, looking for the source of the heat, but did not find any. The machine failed sensors regularly, multiple angle sensors, DP sensors and pressure sensors. In the process, I learned the manual's specifications for sensors is totally outdated and do not apply even to JD supplied sensors.

I received advice from a number of people to sell the machine and get another one, "because this was a first generation computerized machine and I may never find the problem", but I am stubborn and refuse to let a piece of equipment beat me. The machine would also take out the computer fuse (1 A) from time to time. After going through everything, and I do mean everything, I considered rewiring the machine, but harnesses for the machine are not currently available. I used an ohm meter to check every wire, they all had continuity.

Drawing on a previous experience with defective wiring, I then used a meg ohm meter. The "megger" applies a high voltage (500-1000V) (using 2 "C" cell batteries) to the wire to test the insulation on the wires. CAUTION HERE: REMOVE ALL COMPUTERS BECAUSE IT CAN DAMAGE THEM. I tested all sensor leads to and from the computer with the megger and found no faults in any of them. When I tested the power into the computer from the fuse block, it was bad. It had a direct path to ground. I opened the harness and visually nothing appeared wrong with the wire. The wire was replaced. After removal, the old wire felt "crunchy" inside.

Long story short, the 3 feet of 18 Ga wire had been overheated by the idiot that installed the 5 A fuse where the one amp had been specified before I got the machine. The new wire to the computer increased the output from the computer to the sensors. They had to be readjusted. The low voltage to the computer had been causing the sensor failures and out of "normal" range indications to the computer caused the overload of the hydraulic system resulting in the machine overheating. It took me several years and more money to find this problem than I like to think about, but perhaps someone else can benefit from my learning curve.

 

[TVA]

It’s supposed to be a habit of a good technician to check all ECU powers and grounds UNDER LOAD ( load pro , Power Probe IV or higher, or just a 55 amp head light is your friend!) before doing other tests!!!

Be careful with Megger!!! It puts out 1000 volts, although next to no amps but if you touch one hand to one lead and another to another lead and this voltage will go across your heart - might have some issues!!!

 

[mg2361]

Good Job Knivens!! 490E's were plagued with wiring issues and yes, many people out there would replace the 1 A fuse with something higher insuring a fried PVC.

 

[Knivens894]

TVA: Please tell me EXACTLY how you would have found this problem. Continuity was there, 24 V was there. How would you have found the break down in the insulation of the wire?

Also you said, "Be careful with Megger!!! It puts out 1000 volts, although next to no amps but if you touch one hand to one lead and another to another lead and this voltage will go across your heart - might have some issues!!!"

The megger tests the insulation of the wire to ground. Touching the probes just causes a fault to show on the meter. How else would you find a fault in the wire insulation? If the megger was a danger to health, do you think the company would still be in business? I had a technician with 37 years experience tell me he had never heard of a megger, but now that he knows they exist, he wished that he had one years ago. They test insulation of wires for paths to ground. It is much cheaper than completely rewiring an entire machine.

 

[excavator]

It’s supposed to be a habit of a good technician to check all ECU powers and grounds UNDER LOAD ( load pro , Power Probe IV or higher, or just a 55 amp head light is your friend!) before doing other tests!!!

Be careful with Megger!!! It puts out 1000 volts, although next to no amps but if you touch one hand to one lead and another to another lead and this voltage will go across your heart - might have some issues!!!

GM electronic ignition is 60,000 volts with very little amps and I've been bit many times. Years ago I spent some time on the local police dept. and that was about the time that stun guns came out. About the same volts & amps and we tried them out a time or two also, makes you jump and twitch a bit.

 

[Knivens894]

We once charged the capacitors out of coil distributors with points and laid them around the shop to see who would get hit too. That is a totally different animal. The Supco M-500 & M-1000 Megohmmeter is purpose made to test the effectiveness of wire insulation and will not hurt the user. They have been making them for decades. It is a different kind of ohm meter. It is the only way I know to find wire insulation defects to ground. Both ends of the wire must be disconnected to do the test. It tests the insulation for more than 1000 megohms of resistance to ground. It finds insulation failures not apparent in visual inspection. The nature of insulation failure in low voltage wire systems is erratic behavior of that system, particularly in a vibrating machine.

 

[TVA]

I got hit with 120/230 volts with more then 100 amps and still typing here!
The big difference is where the current enters and where it leaves!
If it’s only enters your body but has no exit - you only twitch and jerk!
If it will find the exit and goes through the most of your body, especially heart and brain - most likely the pine box will be your new home!
If it’s a high current then you will be crispy, smelly and smocky before they put you in to your new home!

 

[excavator]

Never say never but 1000 volts and virtually no amps is not a problem. Amps, not volts is what kills you.

 

[Knivens894]

TVA: Years ago I worked at the Navy Yard in Charleston, SC, in electronics when it was active. Sometimes we worked around thousands of volts and around capacitors which would kill anyone getting across terminals. I have seen 500A fuses blow like dynamite and send people out on stretchers. Have you EVER been hurt by a multimeter? The SUPCO megger meters, either at 500V or 1,000V will not hurt the user. Both are powered by two "C" cell batteries. They are sold on E-bay and Amazon, and have been around for decades. They test the insulation of wires for a fault to ground. Put your fingers across the probes, press the button, and all you will get is a defective insulation indication. They can hurt sensitive electronics only because they cause the connected conductor to seek a path to ground. Most computers work in low voltages, so the stress caused by the testing (if they are connected) at higher voltage can internally damage sensitive electronic components.

Excavator is completely correct in his comment above. As but one example, a Vandergraf generator can produce voltages upwards of 140,000 V. It will arc to your body if it is 2 feet away, make you hair stand on end, but has no health side effect. Amperage is your enemy, voltage is not. Voltage arcing through faults in wire insulation is measured by the meter. It provides a convenient and economical method of isolating defective wiring insulation.

 

[CatKC]

Never say never but 1000 volts and virtually no amps is not a problem. Amps, not volts is what kills you.

Correct. . .volts is the power but amps does the work. Not even -one amp- but 65 mA (65 thousandths of an amp) will kill someone if applied near the heart.

If you feel lucky and are so inclined, use the back of your hand/fingers to test a wire. Should you be dumb enough to do so, touching it with your fingers can cause a muscular spasm and make you 'grip' the wire and you won't be able to turn loose.

 

[excavator]

My father was a plumbing/electrical contractor so growing up I spent summers working with him and my brothers. My oldest brother was always my "boss" as older brothers can be and he had a bad habit of telling me the breaker was off when in fact it wasn't. So needless to say I've been bit many times, seemed like usually while standing on top of a 10 foot step ladder. There was another elect. contractor in town who would check to see if breakers were working by touching both sides with his fingers, both 110 & 220. It never got him but I always figured they made meters for that so why take a chance? The only time I've heard of not being able to "turn loose" was when it was damp or they were standing in water.

 

[delectric123]

It’s supposed to be a habit of a good technician to check all ECU powers and grounds UNDER LOAD ( load pro , Power Probe IV or higher, or just a 55 amp head light is your friend!) before doing other tests!!!

That looks like a great diagnostic method that might have helped me find some headache problems in the past.

Be careful with Megger!!! It puts out 1000 volts, although next to no amps but if you touch one hand to one lead and another to another lead and this voltage will go across your heart - might have some issues!!!

I actually did just that in ignorance once, with voltage set to 1000V. It just gives an unpleasant tingle.

 

[Buendia98]

I have a 96 490e i bought it 4 months ago... my problem is that every time i move any hydraulic function my engine want to die my pvc wasnt working i replaced it. Now im going to replace the angle sensor. My question is, what does the angle sensor do and how does it function any help TIA.

 

[mg2361]

what does the angle sensor do

The short version is the angle sensor provides feedback to the PVC on pump swash plate position to help determine pump flow.

Make sure the F7 fuse is a 1 amp fuse and that it is good. Also check F4 fuse (1 A), F8 and F9 fuses (5 A each). If your machine is still stalling when moving a function try swapping the solenoid assemblies on top of your pump first to see if the problem reverses (does not come into stroke).

 

[Buendia98]

Fuses are good i swapped the solenoids on the top and its really really slow but it won't stall the engine.

 

[mg2361]

Then one of the solenoids needs to be replaced.