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| Running a 1200 vacuum planter at higher vacuum speeds, you will typically see PFC system pressure of around 1900-1950 PSI. Depending on how large the planter is, the hitch pressure to raise might require only 1750 ballpark.
So yes: I have many times heard the vacuum fan RPM actually decrease when the planter is raised. If there are other hydraulic requirements on the tractor (spray rig, Rawson, etc.) I have seen vacuum fall off to the point that seed falls off the disk. Then you have to go through a priming procedure, or not plant seeds for the first 10 feet or so.
That doesn't happen if the #1 priority valve is running the vacuum fan. Yes, it can be an extreme PITA to adjust correctly, especially if your flow control cables or flow adjuster valve stems are sticking. Case-IH dropped the priority valve on the MX Magnums because operators were just having too much trouble with overheating, starved down-stream systems, etc caused by the #1 remote not being set correctly. | |
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Another Magnum question for Redwrench
