JLG 800AJ - Service Manual

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Questions and Answers

jonesjamesAug 6, 2025

Why is my JLG 800AJ Boom Lifts system operating hot?

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Lisa MyersAug 6, 2025
Your JLG Boom Lifts system might be running hot due to several reasons. It could be due to an insufficient amount of hydraulic fluid, which fails to meet the system's cooling demands. In this case, fill the reservoir to the proper level. Another cause might be a failing or obstructed heat exchanger, which also prevents adequate cooling. Make sure the heat exchanger is receiving enough air flow and is in good condition; repair or replace it if needed. Finally, a system relief valve that's unseated for too long or malfunctioning could cause overheating. Repair or replace any faulty relief valves and check that the machine's loads aren't too high.

Shawn GomezAug 21, 2025

How to fix excessive noise and vibration in JLG 800AJ?

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Dennis CopelandAug 21, 2025
Excessive noise and vibration in your JLG Boom Lifts can stem from several issues. Insufficient hydraulic fluid can cause cavitation, leading to system noise; ensure the reservoir is filled to the correct level and that oil supply to the motor is adequate and unobstructed. Trapped air in system lines or the motor can also cause cavitation; make sure all system lines and components are purged of air. A loose or incorrect shaft coupling can produce vibrations; verify the correct coupling is used and fits properly. Misaligned shafts create frictional vibration; ensure shafts are properly aligned. Finally, hydraulic oil viscosity above acceptable limits can cause cavitation; replace the hydraulic oil with the appropriate fluid for your operating conditions.

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