490E Blowing pump control module

[Knivens894]

I have a 490E which started stalling under load. I had the dealer make a service call. He found the pump control module had failed. Purchased another module, installed it, and the machine worked fine for about 8 hours, then went back into the stall mode. Inspection of the control module shows it failed in the identical area as the first, burning up the 4 watt 10 ohm resistor and melting the diode next to it.

Has anyone seen this problem before? Any suggestions for finding the cause of these failures would be appreciated.

 

[rgl726]

yes. you have an angle sensor thermal problem.

replace your angle sensor first. you can replace the resistor in the PVC.

 

[Ronsii]

Also check the wiring harness from the angle sensor to the control module and make sure there are no rub throughs or shorts.

 

[Knivens894]

Thank you RGL726! Sounds like you have experienced it before.

I have ordered a new angle sensor. The existing sensor checked cold at 842 ohms which is within spec of 810 Ohm plus or minus 240. I rang out the wiring, finding no faults, but will further carefully inspect wiring for damage.

On the replacement resistor for the control module, the closest I could find in stock was 10 watts and 10 ohms, 2.5 times the wattage rating of the original. Any comments upon my intentions to use the 10 watt resistor? On the diode which the resistor melted, the numbers are T5Z 27 3E. I have looked all over for a replacement diode, but find no source. Anybody have any idea as to a source for replacement diodes? I plan upon attempting to fix the best looking board by scavaging a diode from the older board. I could fix both boards if a replacement diode can be found.

Will advise of the end results on this issue. Thanks!!

 

[lantraxco]

As long as the resistance value is correct, using a higher wattage resistor should never be a problem. Only issue would be that if whatever caused the orginal to burn up is not corrected your 10 watt resistor may not burn up but something else surely will.

Diodes are typically very generic, unless it's a zener for voltage regulation. Ohm out the unburnt one, if it's near infinite ohms in one direction and less than a hundred in the other you can probably use a 1N4001 or similar. YMMV.

 

[Knivens894]

I would much rather have a fuse to blow rather than replace a resistor and diode. I don't understand why they did not put one or more fuses on this board. Is this a multi layered board? Today I remove the resistor to clean the board and found a soldered in copper layer under the resistor. The resistor got so hot that it melted the solder from two of the under lying holes. I will fill them back in, clean the copper and reseal them before installing the new components. I have not been able to find a schematic for the board. If I had the operating voltage of the resistor, I would install my own fuse to prevent further problems.

 

[lantraxco]

Same reason they don't put a five cent diode in the power supply circuit for radios and such, if you reverse the polarity the manufacturer would much rather you smoke the unit and buy another than protect it.

 

[Knivens894]

I am pleased to report that replacement of the resistor in the pump control module worked! The unit is now operational again. Thanks to RGL726, who saved me an $800 used (or after market) module or a $3,500 JD module. The machine will not be run until the new sensor is received in two days. Once that is installed we will determine the durability of the fix.

 

[spitzair]

You'll want to make sure that the fuse that runs the computer is a 1 amp fuse. They're not as easy to find but anything bigger will cause problems for the computer. There could be any number of issues that cause the computer to fry in addition to the angle sensor, faulty wiring harness being a likely culprit. The wiring harness in my EX200-2 was what was causing my computer to let it's smoke out... Rewired it and it's been perfect ever since!

 

[Knivens894]

Was the wiring defect found through visual inspection, or was it hidden internally, or did you just replace the whole harness due to the recurrng problem? Did the defect in wiring show up on ring out to ground? Because the second PVC operated for 8 hours before failing the module, I tend to believe it is a heat related problem and thermal breakdown of the angle sensor makes sense, but I would be interested in learning more about your experiences in how you found the wiring problem.

 

[spitzair]

On my machine, it was a combination of all the things you mentioned... Some spots had "repairs" done where somebody twisted wires together and wrapped them in electrical tape, which came off over time allowing the ends to touch each other and/or ground causing shorts and other problems. Then there were also brittle and broken sections of insulation all over the place so when water got in there somewhere it would short stuff out. And then there were also open circuits where the wire had broken where you couldn't see it... Drove me nuts! I finally tore the entire harness out and put a new one in... The whole job took 2 days, and it was well worth it. I spent probably a week trying to fix all the problems I found and it still didn't help... I wrote all about it here: https://www.heavyequipmentforums.co...-Hitachi-EX200-2-computer-question&highlight=

 

[Knivens894]

Thank you for your informative reply. My machine is all original wiring wise. The outer plastic shielding sheath of the harness is crumbling, so I will replace it today. The internal wires of the harness all appear good. I have visually inspected it and check each wire with an ohm meter. I find no faults or shorts. Hopefully the sensor is the problem. I will update with my findings.

 

[Deeretracks]

I usually start back by the pump. Since the muffler is right above it there is a ton of heat build up in that compartment that is hell on the harness. Also seen many times where sticks have come up through the bottom panel and damaged the harness.

 

[Ronsii]

It is best to visually inspect every inch of the harness as shorts may not show up except under heat and other use conditions of use, I have seen wiring that looks new in one place and just a few inches down the line the wires crumbling apart from years of heat and oil contamination... like deeretracks says make sure to check around the hotter areas.

 

[Knivens894]

We have now inspected every inch of the harness and found nothing wrong with the harness. The brittle outer sheath has been replaced with new. Today, after Spitzair gave me a clue, I did learn there IS a pump control module fuse in the main fuse box which is supposed to be 1 amp. Someone "brillent", before my ownership of the machine, changed it out to a 5 amp fuse. That explains how toast can be made out of a pump control module repeatedly. The 1 amp fuses are available through NAPA, and mine has now been changed out. Hopefully no more toasted PVC modules.

Also, when I bought this machine, the muffler was shot on the bottom side and exhaust gases had melted the engine control cable. I replaced the muffler and the engine control cable with new when I got it. This may explain the cause of the thermal break down of the angle sensor. The new sensor is here. I have requested an experienced service tech to install and adjust it. The failure of the PVC also caused the pump to run hot (185 degrees F) (which could have also been a source of the thermal breakdown) so I changed out all the filters, cleaned out the hydraulic tank and installed new JD fluid. I plan to get the whole hydraulic system tested because I have a lot of work to do with the machine and these break downs are hurting my performance.

 

[Knivens894]

The new angle sensor is installed and the machine is running fine. Upon removal, the old angle sensor had an internal melt down as evidenced by the black melted plastic oozing from around the shaft. Turning the old sensor shaft by hand was difficult and nothing like the new sensor which turns freely. The lessons learned are: (1) when the muffler develops a leak, replace it, the damages done by letting it go will later cost you dearly; (2) check all your fuses for the proper amperage and instruct all operators to ONLY use the fuse size specified for the slot; (3) this site is terrific in solving problems not before seen. RGL726 hit it spot on with his first comment and others lead me to fixing the PVC and finding the fuse problem to avoid the problem in the future! Many thanks to all!!!