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Hi there. I have an older 1680 that has the stack valve up by the cab. The pump tests fine and the primary prv tests fine. The problem happened sitting in the barn. I ran it about 3 months ago and all was good. Let it sit and now no hydraulics. Propulsion works fine. No steering, no header raise, no reel raise, and no auger swing. I have flow to the stack and all plugs and spools have been pulled and cleaned. All electronics are proper according to my service manual. All the solenoids activate and have proper voltage. I shimed the secondary prv, no change.

I'm running out of options here. I isolated the steering from the stack and still no change, so I know the steering is'nt it.

One other thing is I pressure washed the stack valve when I last moved it. Is there another safety relay or something somewhere close to the stack that I cant see from the top cover removed? What else have i over looked?

Thanks for any help.
 

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Re: 1680 hydraulic control valve issues. Need help

Maxie, to test the pump I unhooked the mainline to the stack and capped it, installed a guage just before the cap. This machine has the primary relief mounted to the pump mounting plate. So the cap was installed after the relief. I had the engine cranked with the starter and instantly got over 2,000lbs pressure.

Next I rehooked the mainline and went to the stack valve. It has the secondary (priority) relief at the header valve. I unhooked the steering supply line and plugged the supply line, and installed a guage with a cap. At this guage I got 500lbs at 1500 rpm.

I then built a guage loop and went back to the pump mainline and installed that guage loop to leave there perminently. Now I have 2 guages to watch for differences. As it should work, once the pumps mainline was reattached, and the secondary relief is either not functioning or spmething, the whole systems returns to the 500lbs reading. I removed the secondary relief again and put some shimms under the spring thinking it would show at least a few pounds difference, it did not. I took out evey plug that was take outable by tools, and inspected and cleaned all orfices and spools. Everything looked fine. Thing is, it haas to be something either safety switch oriented or something silted or dirty to quit while sitting after working just fine.

I then got out the electrical part of the service manual and went through all the electrical testing of the solenoids. To do this I had to jumper across the engine oil pressure switch. All electrical test showed proper according to the book. I could even hear the solenoids clicking open.

Any ideas you have, I'd apreciate.
 

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Good day
I am also having similar problems with my combine. I see you had these problems 5 years ago, but I am curious as to how you fixed yours?
 

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There is a pressure switch on the engine that can cause no hydraulics. I assume you checked this. You can bypass the switch by taking two of the three wires and splicing them together. I do not remember the colors but search here or on agtalk for one of my posts on 1680 where I stated how to bypass it.
 
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