Tapio 400 harvester head

[grl]

Good Morning
I have a tapio 400 harvester head and it has suddenly decided not open its rear knives. my driver said it happened a couple of times before but now it is permanent. The hydraulics are fine as if i connect the wires for the front knives instead the rears work fine. They will also close with their own wiring so it seems that it is an electrical prob with the solenoid connection on the opening circuit. I have run the cable continuity tests and all seems well, the multimeter says that there is power to the solenoid connector when the open knives button is pushed but it just wont work. I have changed the solenoid connectors as well.  i am not any good with electrics, the solenoid connector shows it is getting about 11.3 volts could this be the prob? the front knives seem to open  with a similar voltage so i just dont know!  I will gladly pay someone to mend the machine as it is not cutting any wood!  any help will be very welcome.

thanks  Guy  (Kent England)

[snowstorm]

also check the button. those little switchs do wear out.  what voltage dose the computer require? a lot of them want 24 volts mine dose. the magnets for the valves can give trouble. check the voltage there. any fault codes on the computer?

[bushmechanic]

Hello Guy it seems to me you have covered all the bases in your trouble shooting.Did you change around your solenoids, you know swap them from the open circuit to the closed circuit? You changed the plug-in's so it can't be a connector. If the same voltage works on one function then it should work on another as you have deduced. There is one other problem that you may be overlooking, a hydraulic one. Sometimes when a seal fails on the piston in the cylinder what happens is the double acting cylinder will only work one way, this is called regeneration in the hydraulic world.The cylinder will usually close perfectly but won't open and when you try to open it it will close.Do you know if there is a pilot system on this head or is it direct acting of the valve? I have seen when cylinder kits fail the bits of rubber or plastic will lodge in the pilot spools and this stops the function in one direction.Hope this may be of some help to you. 

[barbender]

I have had several electrical problems with the forwarder I run, where there is 12 volt power to solenoids but there is a bad connection etc. therefore there's not enough amperage to make the solenoid work. Try running a jumper wire right from the battery to your solenoid, that way you can rule out electrical for sure. Then move on to bushmechanics post ;)

[thecfarm]

grl,welcome to the forum. What state are you cutting in? I know you are busy now,but when you have a minute check out this thread to see some logging equipment.

https://forestryforum.com/board/index.php/topic,13313.0.html

[Northern Timber Harvesting]

I had a similar problem with a logmax 7000 and it wound up being the spool. It had worn enough to where the solenoid did not have enough power to move it. I thought that i could have been a piece of o-ring or debris, took the spool apart cleaned it, didnt work, bought a new valve, worked good. be sure to eliminate any electrical problem first though, parts changing can be an expensive way to diagnose a problem.

[1270d]

I've had the piston  one right off of the rod.  It will open but not close.  No leaks.

[Ken]

We have had it happen twice to us in the last year and a half.  One time packing from a grab arm cylinder had gotten into the valve and another time rubber from the inside of a hose had gotten into a valve and caused the same sort of issue.  Good luck with your troubleshooting.

Cheers
Ken