Hobart AM-15 Wash Arm Bearing Replacement Intervals — High-Volume Kitchens
Hobart AM-15 wash arm bearings are the wear part nobody schedules until the chamber stops spraying mid-service. A field tech's interval map for hotel banquet kitchens, banquet halls, and 800-cover-a-night restaurants.
A Brickell hotel banquet kitchen ran a Hobart AM-15 door-type dishwasher through 612 racks on a Saturday wedding push. By 11 PM the lower wash arm was scraping the rack rail and the chamber sounded like a coffee grinder. The bearings were gone. Wash arm bearings on an AM-15 are a wear part — they don't fail, they grind themselves into noise and then into chamber damage. The interval depends on rack count, water hardness, and whether the prior tech replaced the upper and lower bearings as a matched set or one at a time. This is what a working warewashing tech tells the F&B director when the question is when to schedule the next replacement.
1. What the AM-15 wash arm bearing actually is
The Hobart AM-15 (and the AM-15T tall version) uses an upper and lower stainless wash arm, each rotating on a nylon bushing that rides on a hub welded to the chamber wall. The official Hobart part is the wash arm bushing kit 00-873952. Two bushings per arm, four total per machine. The kit lists at $48 to $62 depending on supply chain, plus an hour of labor for the full swap on a typical AM-15.
The bushing is nylon, not a ball bearing. Hobart spec'd nylon because the chamber sees 180°F sanitizing rinse plus alkaline detergent at every cycle. A steel ball bearing would corrode in months. Nylon wears slow but predictable. The wear shows as widening clearance between bushing and hub, the arm wobbles, and the wobble pulls the arm into the rack rail or the upper spray pipe.
2. Interval by rack count — the real number
Hobart's service literature suggests inspection every 6 months. That number is for low-volume operators. A high-volume kitchen running 400+ racks a day burns through bushings in 8 to 14 months. We've pulled measurably-worn bushings off AM-15 units in Miami Beach hotels at 13 months and 18,200 cycles. The same model in a small bistro doing 80 racks a day will go 3+ years between bushing replacements.
Rule of thumb: count racks per day, divide by 50, that's your inspection-month interval. A 600-rack-day operator inspects bushings every 12 months and replaces at 18. An 80-rack-day operator inspects at 36 months. The cost of running past the interval is not just the bushing — it's the wash arm itself ($340 to $420 OEM), the spray pipe, and occasionally the chamber wall where the arm scrapes a groove.
3. The water hardness multiplier
Miami municipal water runs 200 to 280 ppm total dissolved solids depending on the system. That hardness deposits as scale on the wash arm hub and the bushing inner diameter. Scaled bushings wear the same nominal hours but at higher friction, which heats the nylon, accelerates wear, and shortens life by 25 to 40 percent versus a softened-water installation.
If your AM-15 is on raw municipal water without a softener, your bushing interval is 60 percent of the nameplate schedule. If it's on a softener with sub-50-ppm output, your interval is 110 percent. A wash arm hub coated in scale also wears asymmetrically — one side of the bushing wears faster than the other, the arm runs eccentric, and the symptoms (vibration, rack contact, uneven spray pattern) show up before the bushing is fully gone.
4. The diagnostic — by hand, before pulling parts
Power off, lock and tag the AM-15 at the disconnect. Open the chamber door. Grab the lower wash arm at one end and lift. New bushings give you 1/16-inch vertical play, no more. 1/8-inch play is the threshold for replacement. 1/4-inch play and the arm is dragging on rack rails during the cycle.
Spin the arm by hand. Smooth, quiet rotation with even resistance is healthy. Grinding, catching, or a click-click-click as the arm passes over the hub is worn nylon. Pull the arm — it lifts off the hub with one hand on the AM-15, no tools — and inspect the bushing bore. A round bore is healthy. An oval bore is the failure mode. Hobart sells the bushings, the spray jets, and the hub wear cap together as a kit because they all wear together.
5. Replacement procedure — full set, not partial
Replace upper and lower bushings as a set, even if only one is visibly worn. The arms are at different temperatures during the cycle (lower sees the wash tank, upper sees the rinse), and asymmetric replacement creates an asymmetric wear pattern that shortens the next interval by 40 percent. The 30-minute extra labor cost on the second set is dwarfed by the next service call.
Pull each arm, clean the hub with a non-chloride descaler — Hobart Stera-Sheen is the spec'd chemical, $42 a gallon — and let it sit for 20 minutes before scrubbing. Install new bushings by pressing in by hand. No grease, no oil — the rinse water lubricates the nylon in operation. Re-seat the arm and rotation-check by hand before re-energizing.
6. What it costs to skip the interval
A worn bushing that takes out the wash arm costs $340 to $420 for the OEM arm, an hour of additional labor, and one shift of downtime if the parts aren't on the truck. A bushing that takes out the chamber wall — yes, this happens — is a $2,200 to $3,800 chamber rebuild and 2 to 4 days of downtime depending on parts availability. The bushing kit itself is $48 to $62 plus an hour of labor.
For a hotel doing 600 racks a day, one day of warewashing downtime is roughly $1,400 in temp-rental dish service plus the F&B impact of plated service slowdowns. The math on the interval is straightforward. Replace bushings on the schedule, not on the symptom.
7. Why the AM-15 specifically — versus AM-12 and AM-16
Hobart's AM-15 is the most-installed door-type machine in Miami-Dade hotels and country clubs. The AM-12 predecessor and the AM-16 successor share the same bushing geometry, so the interval math is transferable. The AM-15T (tall door for sheet pans) sees the same bushing wear plus added stress on the upper arm from sheet pans clearing the upper spray.
If your machine is an AM-14 or older, the bushing kit is different (Hobart 00-846473) and the chamber geometry is tighter — wear shows up faster. If your machine is the newer AM Select line, the bushing system is similar but accessed differently. We'll bring the right kit for whatever's installed.
8. NSF, FDA Food Code, and the service log
NSF/ANSI 3 governs commercial warewashing. The wash arm condition feeds into spray pattern, which feeds into sanitization effectiveness. A health inspector seeing a wobbling wash arm or a chamber wall scrape mark will document it on the inspection report. A documented preventive replacement schedule with logged dates is the answer to that finding.
Berne Commercial issues a service log for each AM-15 visit including the bushing wear measurement, the rack count since the last inspection, and the next-due interval. The form goes to the kitchen manager and a copy stays in our dispatch system for the next visit. That's what compliance audits look for.
Same-day Hobart warewashing service
Berne Commercial Repair runs same-day dispatch for Hobart AM-15, AM-15T, AM Select, CL series, and FT series warewashing equipment across Miami-Dade, Broward, and Palm Beach. $89 commercial service call, free if you go ahead with the repair. COI on file for hotel and corporate clients. Call (754) 345-4515 or book a tech through our commercial dishwasher repair page.
For premium residential dishwashers running comparable wash-arm geometries (Miele G7000, Bosch Benchmark), Berne's premium residential team handles that platform.
$89 commercial service call, free with the approved repair. Same-day dispatch across South Florida.
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