FD-75 drops too fast on new to me 750tt - The Combine Forum
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post #1 of 33 (permalink) Old 06-09-2019, 11:04 PM Thread Starter
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FD-75 drops too fast on new to me 750tt

Setting up a 40' Macdon FD-75 in cebis and calibrated endstops, other manufacturer flex head, etc. Header lower is faster than I would like, slams it down pretty good. Single detent position doesnt seem any slower than the second. Hitting the auto height float button drops it about the same rate also. Went into the CAC settings and ran the manual and automatic drop rates from -50% through +50% and saw no change. My dealer is long distance so its not worth a service call, but the tech mentioned either accumulators or the combine possibly being set for a lighter 35' head from a previous owner, but didnt get into specifics on what I can adjust. Anyone have any ideas?

'15 model machine.

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post #2 of 33 (permalink) Old 06-09-2019, 11:25 PM
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There is a weight setting in there too somewhere, that might make a difference.

Also someone posted a year or two ago detailed settings info or Youtube is always handy, especially if new to the machine.


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post #3 of 33 (permalink) Old 06-09-2019, 11:30 PM Thread Starter
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Ive been going through old threads and on page 2 of the Claas section Seedcleaner posted a really helpful link to simplifying Cebis that I plan to print out and keep in the machine. But I had not come across a header weight setting. Ill look again tomorrow.
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post #4 of 33 (permalink) Old 06-10-2019, 03:04 PM
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If you cannot change the manual drop rate with the setting in Cebis (Don't forget to "Enter" the new setting for it to take affect) then there is a problem with your combine. I agree that accumulator pressures and weight settings have some effect on HHC response; however,you should definitely see a change in drop rate when adjusting this setting.

There is a known software quirk that may affect the automatic lower rate, but that should not affect the manual lower rate.

Can you see a change in raise rate when changing the raise rate setting? If that one won't change either, you may have a controller problem.

If its just lower, I would suspect that you may have a collapsed spring or something in the Y087 lower valve, allowing it to go "wide open" when it should be only partly pulled open. This is the valve block under the feeder. But I'm not a hydraulics tech...talk to your dealer!

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post #5 of 33 (permalink) Old 06-10-2019, 11:37 PM
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Two things to keep in mind...

I like to calibrate the header with a block of wood under the feederhouse faceplate. When calibrating, you need the height sensor to fully compress, but no more than that. Movement between the header pins and the feederhouse is not good during calibration. The proper block of wood can really help make a good calibration.

Also, with a MacDon, or any other flex header, during calibration, you don't want the header to bounce up while it is "learning" This can easily happen if the large springs are set too tight on the MacDon. Calibrating with crop on the header and/or the reel fully extended can help prevent the header from drifting up while calibrating. I prefer to calibrate with the driveshaft unhooked. The two above procedures can really make for a good cal on our older 740.

Also, if you do a good calibration, and the combine tries to slam the header down when you want it to automatically lower, is the header drifting up while it is in the air? You don't want the header to drift up on its springs while automatically lowering. When it does, the combine thinks the header has made contact with the ground, even though it hasn't. Then when the header drops again from its springs, the combine tries to slam it down because it isn't sensing any ground. This can be fixed by reducing tension on the four large springs. I assume you are preparing for wheat, so you won't need much tension anyways.
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post #6 of 33 (permalink) Old 06-11-2019, 05:22 PM
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I discussed this with Jesse on the phone...the latest is his raise speed can't be changed either. He's going to talk to his dealer. My thought is if he can't change both the manual lower speed or the manual raise speed, something is not communicating between Cebis and the valve controller. I could be WAY off though.

Has anyone else ever experienced this symptom on a Lexion 700?? Any help is appreciated, as his dealer is like..6 hours away!

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post #7 of 33 (permalink) Old 06-11-2019, 10:00 PM Thread Starter
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Originally Posted by SWMan View Post
There is a weight setting in there too somewhere, that might make a difference.

Also someone posted a year or two ago detailed settings info or Youtube is always handy, especially if new to the machine.
Talked to my tech today and he also mentioned the weight setting, which I couldnt find, and he eventually said maybe only the c7x serial had that option. Mine is a c68
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post #8 of 33 (permalink) Old 06-11-2019, 10:11 PM Thread Starter
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Originally Posted by seedcleaner View Post

Also, if you do a good calibration, and the combine tries to slam the header down when you want it to automatically lower, is the header drifting up while it is in the air? You don't want the header to drift up on its springs while automatically lowering. When it does, the combine thinks the header has made contact with the ground, even though it hasn't. Then when the header drops again from its springs, the combine tries to slam it down because it isn't sensing any ground. This can be fixed by reducing tension on the four large springs. I assume you are preparing for wheat, so you won't need much tension anyways.
I dont think I have too much tension, but being that my header raises fast and i cant slow it down, it definitely bounces a bit at upper limit.

I talked with Jeff both yesterday and today and hes been incredibly helpful, but as he mentioned to me, I may have to fix the rate of drop/raise before I can even get the calibration and other settings right.

Im uploading a video now of how the header jumped and my header CAC sensitivities. After talking with my dealer tech, we adjusted my top line down to -35 and the bounce was eliminated. It really felt to me like the hydraulic flow was just much more than the machine expected while trying to find the perfect height...like as oversensitive autosteer or a rate controller that oscillates.

Main thing is that its picking now, or would be if not for unrelated issues, so i can get by for what little wheat i have.

Talked with my tech this afternoon about both directions being too fast and he still thinks its the accumulators. Tonight while looking up something else, I came across this in the service records. Im wondering if this previous valve leak could be the root cause.
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Last edited by HoRFarmsJesse; 06-11-2019 at 10:13 PM.
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post #9 of 33 (permalink) Old 06-11-2019, 10:21 PM Thread Starter
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post #10 of 33 (permalink) Old 06-12-2019, 01:01 AM
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Originally Posted by HoRFarmsJesse View Post
Talked to my tech today and he also mentioned the weight setting, which I couldnt find, and he eventually said maybe only the c7x serial had that option. Mine is a c68
Both my 780's have been C79 machines, so possible that wasn't on older units.


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