When a two post lift power unit quits working, most Iowa shops assume the worst — a dead pump or a burned-out motor — and start pricing a whole new unit before checking anything else. In our experience running service calls across the state, two post lift power unit troubleshooting almost always starts with something simpler: a tripped breaker, low fluid, a stuck valve, or a loose wire nobody noticed. We’ve torn into hundreds of these units, and we’d rather walk you through the same checklist our techs use than have you replace a perfectly good pump because of a bad relay.
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Start With Power, Not Hydraulics
Before you open the reservoir or touch a single hose fitting, confirm the unit is actually getting power. A shocking number of the service calls we run for two post lift power unit troubleshooting end with us flipping a tripped breaker or resetting a GFCI outlet that the shop swore was fine. Check the breaker panel first, then check the disconnect box near the lift itself if your installation has one. Iowa garages that share circuits with welders, compressors, or space heaters are especially prone to nuisance trips during cold months when everything runs at once.
If the breaker holds and the motor still won’t hum, grab a multimeter and check voltage at the motor terminals. No voltage there but voltage at the panel usually points to a bad contactor, a failed relay, or a chewed-up wire somewhere in between — mice love hiding in power unit housings over an Iowa winter. If you hear a hum but the motor doesn’t turn, that’s often a seized motor bearing or a capacitor going bad, not the pump itself. Sorting out power delivery first saves you from tearing apart hydraulics that were never the problem to begin with.
Listen to the Motor Before You Touch Anything Else
The sound your power unit makes tells you almost as much as a diagnostic tool would. A motor that hums loudly but won’t spin usually means the start capacitor has failed or the motor shaft is seized from age or rust. A motor that runs fine but sounds like it’s straining under load, with the lift barely creeping up, points toward a worn pump or a relief valve set too low. Total silence with no hum at all almost always traces back to the electrical side we just covered, not the motor itself.
We also pay attention to how long the motor runs before cutting out. If it kicks on, runs for a few seconds, then trips a thermal overload repeatedly, the motor is likely drawing too much current because the pump is struggling against something downstream — a stuck check valve, contaminated fluid, or a lift arm binding mechanically. Don’t just keep resetting the overload and running it again; that’s how you cook a motor that was otherwise fine. If your two post lift power unit troubleshooting gets to this point, it’s worth shutting the unit down and moving to the hydraulic side before you burn out a good motor chasing a valve problem.
Check Fluid Level and Condition
Low or contaminated hydraulic fluid causes more problems than shop owners expect, and it’s the fastest thing to rule out. Pull the reservoir cap and look at both the level and the color. Fluid that’s milky or foamy usually means water has gotten into the system, which is common in unheated Iowa bays where condensation builds up over humid summers and cold winters. Fluid that’s dark brown or smells burnt has likely overheated from a struggling motor or a pump working overtime against a restriction.
Low fluid alone can cause a pump to cavitate, which sounds like grinding or whining and can quickly damage the pump if it runs that way for long. Always check fluid level with the lift fully lowered, since the reading changes based on ram position. If the fluid looks fine and the level is correct but the lift still won’t rise, move on to the valve body next — clean fluid at the right level rules out one of the most common causes we see in the field and narrows the search considerably.
Inspect the Valve Body and Solenoid
The valve body is where a lot of two post lift power unit troubleshooting calls actually end up, especially on units that have sat unused for a season. Down valves and solenoids can stick from varnish buildup when fluid sits stagnant, which is common on lifts that only run occasionally in seasonal shops. A stuck-closed down valve will let the lift raise fine but never lower, while a stuck-open valve can cause the lift to drift down on its own even when the motor’s off.
Tap the solenoid gently while someone operates the switch — sometimes a stuck plunger will free up with a light knock, though that’s a temporary fix, not a real one. If the solenoid coil has failed electrically, you’ll usually get no click at all when the switch is engaged. We generally recommend replacing the whole cartridge valve rather than trying to clean varnish out of it, since a valve that’s gummed up once tends to gum up again within a season or two.
Rule Out Pump Wear
Pumps wear gradually, so the symptoms creep up rather than appearing all at once. A worn gear pump will still push fluid but with less pressure, meaning the lift rises slowly or struggles under a heavier vehicle even though it worked fine on lighter cars last month. If you’ve already confirmed good power, good fluid, and a functioning valve body, and the lift still lifts weak, the pump itself is the most likely remaining culprit.
One trick we use in the field is listening for a whining pitch that changes with load — that’s usually internal pump wear rather than an electrical or valve issue. Pumps on units running 10 years or more in daily-use commercial shops are due for a look regardless of symptoms, since internal wear happens whether or not it’s showing obvious signs yet. Replacing a pump on a unit with a solid motor and housing is usually more cost-effective than replacing the whole power unit assembly.
Check for Mechanical Binding, Not Just Hydraulics
Sometimes the power unit is fine and the real problem is mechanical — a bent equalizer cable, a dry-rotted slide block, or debris jammed in the column that’s making the whole system work harder than it should. If your motor strains and trips overloads only on one side of the lift, or one arm rises faster than the other, that’s a mechanical symptom being misread as a power unit problem. We’ve seen shops replace a perfectly good pump when the actual fix was greasing the columns and adjusting the cables.
Before assuming the power unit needs full replacement, cycle the lift empty and watch both columns closely for uneven movement. If one side clearly labors while the other moves freely, focus there instead of the hydraulics. For a deeper walkthrough of column-specific symptoms, our guide on two post lift won’t lift troubleshooting covers mechanical causes in more detail, and our broader two post lift troubleshooting resource walks through the full system end to end.
Know When to Call for Help
Most two post lift power unit troubleshooting can be handled by a reasonably handy shop owner with a multimeter and some patience, but there are times it makes sense to call in a technician instead of guessing further. If you’ve checked power, fluid, valves, and the pump and the lift still won’t behave consistently, there may be an intermittent electrical fault or a control board issue that’s harder to isolate without experience. Safety also matters here — a lift that drifts, drops unexpectedly, or lifts unevenly shouldn’t stay in service while you troubleshoot on your own schedule.
We handle service calls across Iowa for exactly these situations, and we also stock power unit parts for the major brands we install so you’re not stuck waiting weeks on a special order. For a closer look at the hydraulic side specifically, our hydraulic power unit troubleshooting guide digs deeper into pump and valve diagnostics. Whether you need a part shipped or a tech on-site, getting the diagnosis right the first time saves you money and keeps your bay running.
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