Two post lift wont raise troubleshooting almost always starts the same way: a tech pulls a car onto the runways at 7:15 in the morning, hits the up button, and gets a motor that hums, groans, or does absolutely nothing while the carriages sit right where they were the night before. We get those calls from Ames, Des Moines, Cedar Rapids, and every small-town shop in between, and the good news is that most of the time the fix is cheap, fast, and something your own crew can handle before we ever load a service van. The bad news is that a few of the causes are the kind you do not want to guess at with a vehicle overhead. This walkthrough is the same order of operations we use in the field.
Power units, seal kits, check valves, contactors, cables, and cylinders for every major brand. Tell us your make, model, and serial number and we will match the exact part instead of shipping you a close-enough guess.
Start With Power, Not With the Pump
Nine out of ten times a lift refuses to move, the first thing a shop owner does is grab a jug of hydraulic fluid. Slow down. Before you touch the reservoir, find out whether the motor is actually getting the electricity it needs. Stand next to the power unit and press the up button. Silence means an electrical problem. A hum, a click, or a lazy growl means the motor is energized but cannot spin or cannot build pressure. Those two symptoms send you down completely different paths, and confusing them wastes an hour.
For a silent unit, check the breaker at the panel first, then the disconnect, then the contactor inside the power unit box. Single-phase 220V lifts pull hard on startup, and a tired breaker will trip or fail internally without looking any different. We have found more than one central Iowa shop running a lift on a shared circuit with a compressor, and every time the compressor kicked on, the lift browned out. Also check the up button itself. Those momentary switches take thousands of presses a year, and the contacts pit. Jumping the switch terminals for a half-second test tells you instantly whether the button is dead. If the motor runs on a jumper but not on the button, replace the switch and you are done. That is the cheapest possible outcome in two post lift wont raise troubleshooting, and it happens more often than people expect.
The Humming Motor: Low Voltage, Bad Capacitor, or Seized Pump
A motor that hums but will not turn is trying and failing. On single-phase units, the usual suspect is the start capacitor. It is a cylinder mounted on the side of the motor housing, and when it fails, the motor cannot get past its starting torque. Swollen tops, leaking goo, or a burnt smell are dead giveaways, but capacitors also fail invisibly. They are inexpensive, they are a common wear item, and every shop running a two post should keep a spare on the shelf.
The second cause is voltage drop. Long runs of undersized wire from the panel to the lift will let a motor start fine when the shop is quiet and hum when the welder, the heater, and the compressor are all pulling at once. We have re-pulled wire for shops that swore their power unit was defective, and the unit worked perfectly once it saw full voltage at the motor terminals. Measure under load, not at rest. The third cause is a mechanically seized pump or motor bearing, which usually announces itself with a burnt-electrical smell and heat you can feel through the housing. If the shaft will not rotate by hand with power off and locked out, the unit is done and it is time to talk about a replacement power unit rather than chasing parts.
Fluid Level, Fluid Type, and the Air You Cannot See
If the motor spins strong and the carriages still sit still, move to hydraulics. Pull the fill plug and look. Reservoirs on most two post lifts are small, and a slow leak at a hose fitting or the cylinder rod seal will drop the level below the pickup tube long before anybody notices a puddle. Fill only with the lift fully lowered, or you will overfill and blow fluid out the breather the next time it comes down.
Fluid type matters more than most shops think. AW-32 hydraulic oil is the standard in Iowa, though AW-46 works in warm shops. What does not work is transmission fluid, motor oil, or whatever was in the drum by the door. Wrong viscosity means the pump cavitates and the lift crawls or stalls. Air in the system produces the same symptom set: spongy movement, one column climbing faster than the other, and a lift that gets partway up and quits. Bleeding a two post is straightforward — run it to full height a few times, crack the bleeders at the cylinders, and top off. If the fluid looks milky, you have water contamination, usually from a shop that swings between humid summers and cold winters, and that fluid needs to come out completely. Our full two post lift hydraulic troubleshooting guide goes deeper on bleeding sequence and contamination.
Check Valves, Relief Valves, and Pressure That Goes Nowhere
Here is the scenario that stumps people. The motor runs beautifully. Fluid is full and clean. Nothing moves, or the lift rises two inches and settles right back down. That points at a valve. The check valve holds pressure in the cylinders; if a piece of debris props it open, every bit of fluid the pump moves flows straight back to the tank. Sometimes you can hear it — a distinct rushing sound at the power unit while the motor runs and nothing happens.
The lowering valve is the other half of this problem. It is a small solenoid or manual valve, and if it is stuck open, hung up on a bit of varnish, or has a broken return spring, the lift will never build pressure. On lifts with a lowering handle, check that the linkage is not binding against the cover. The relief valve is the third possibility. It is factory-set, and it should stay that way, but a relief valve that has drifted low or been cranked on by a previous owner will dump pressure before the lift can pick up a full-weight vehicle. The symptom is telling: the lift raises an empty rack fine but refuses a loaded pickup. That single clue separates a valve issue from a seal issue during two post lift wont raise troubleshooting, and it saves you from tearing into a cylinder that is perfectly healthy.
One Column Up, One Column Down
When only one side moves, the hydraulics are usually fine and the problem is mechanical. Most two post lifts equalize their carriages through cables running over sheaves at the top and bottom of each column. A stretched, frayed, or jumped cable lets one carriage climb while the other lags, and the lift’s own safety geometry will bind up and stop everything. Get under the covers and look at the sheaves. A cable that has jumped its groove and is riding on the sheave flange will chew itself apart in weeks.
Check the safety locks too. If one column’s lock pawl is dragging on the ladder — bent, gummed with grease and dirt, or with a broken release cable — that carriage physically cannot rise smoothly past each notch. In our experience, this is by far the most common reason a symmetric lift starts “walking” out of level. Lubricate the pawls, verify both release cables move freely and equally, and adjust cable tension so both carriages seat on the same lock at the same time. If a cable shows a single broken strand, replace both cables as a set. They wear together and they should be replaced together. Also see our notes on two post lift troubleshooting for lock and cable adjustment specifics by brand.
Cylinder Seals and the Slow Sink
A lift that raises but then drifts down over an hour, or one that will only reach half height with a heavy vehicle, is telling you the cylinder seals are passing fluid internally. This is the failure mode people misread most often. There is no external leak, no puddle on the floor, nothing visibly wrong — fluid is simply bypassing the piston inside the tube and going nowhere useful.
Confirming it is simple. Raise the lift empty and mark the carriage position. If it holds all day, the seals are probably fine and you are looking at a check valve. If it drifts with no load, or drifts noticeably faster with a vehicle on it, plan on a seal kit or a replacement cylinder. Chrome condition on the rod decides which. A rod that is pitted, scored, or rusted from sitting damp will destroy new seals in a matter of weeks, and at that point a new cylinder is the better spend. We stock seal kits and complete cylinders for Rotary, Challenger, BendPak, and most of the imported units that have come through Iowa shops over the last thirty years. This step in two post lift wont raise troubleshooting is also where we tell shops to stop and call a professional — pulling a cylinder means unloading the lift, supporting carriages properly, and relieving stored pressure safely.
Two Post Lift Wont Raise Troubleshooting: When to Stop and Call Us
There is a clear line between diagnosis and repair on lift equipment, and it is worth respecting. Checking power, fluid level, capacitors, buttons, and cable condition is normal shop maintenance. Adjusting relief valves, replacing cylinders, servicing safety locks with a vehicle in the air, or working around a lift that has already failed once under load is not. A two post carries several tons over a person’s head, and there is no acceptable margin for a guess.
Call us at 800-674-9302 and we will walk your tech through the sequence over the phone at no charge. Most of the time we get you running the same day with a part you already have or one we can ship overnight. When we do need to roll a truck, we cover Iowa and the surrounding states, and we bring power units, seal kits, cables, contactors, and lock hardware for every major brand with us. If the lift turns out to be beyond economical repair — and thirty-year-old units do reach that point — we will tell you straight instead of selling you a rebuild that costs more than a replacement. For related symptoms, our lift wont raise troubleshooting guide covers four-post and scissor units too. Good two post lift wont raise troubleshooting is mostly about checking things in the right order, and we are happy to be the second set of eyes.
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