{"id":3435,"date":"2026-10-08T21:54:16","date_gmt":"2026-10-08T13:54:16","guid":{"rendered":"http:\/\/www.yasnasa.com\/blog\/?p=3435"},"modified":"2026-10-08T21:54:16","modified_gmt":"2026-10-08T13:54:16","slug":"how-to-replace-the-pm-motor-in-a-two-stage-pm-screw-air-compressor-4071-8638f1","status":"publish","type":"post","link":"http:\/\/www.yasnasa.com\/blog\/2026\/10\/08\/how-to-replace-the-pm-motor-in-a-two-stage-pm-screw-air-compressor-4071-8638f1\/","title":{"rendered":"How to replace the PM motor in a Two Stage PM Screw Air Compressor?"},"content":{"rendered":"

If you\u2019re reading this, you\u2019re probably running a two-stage PM screw air compressor (you know, the ones that cut energy costs like crazy) and you\u2019re staring at a wonky permanent magnet motor that\u2019s acting up\u2014maybe it\u2019s overheating, tripping the breaker, or just not delivering that consistent pressure your workshop relies on. As the supplier who\u2019s fixed way too many of these headaches (and replaced way too many misdiagnosed motors for clients who tried to wing it), let me walk you through exactly how to swap that bad PM motor out right. No fancy jargon, no overly technical stuff, just real, on-the-job tips I\u2019ve picked up over the years. Two Stage PM Srew Air Compressor<\/a><\/p>\n

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First off, let\u2019s get one thing straight: two-stage PM screw compressors aren\u2019t your regular single-stage models. The PM motor here is the heart of both<\/em> compression stages, not just a drive for one. Mess this up, and you\u2019re not just out a motor\u2014you\u2019re messing up the stage alignment, the pressure balance, and probably your whole day. I\u2019ve seen a client in Ohio spend 8 hours messing with a motor swap, only to break the stage coupling and have to wait a whole extra day for a part. Let\u2019s avoid that.<\/p>\n

Before you even grab a wrench, do your prep work. This is non-negotiable. First, shut off the power at the main breaker\u2014and<\/em> lock it out, too. I don\u2019t care if the control panel says it\u2019s off. Those little backup batteries can kick in out of nowhere, and a shock here is no joke. Next, grab your compressor\u2019s serial number. PM motors aren\u2019t one-size-fits-all for our two-stage models\u2014each one\u2019s matched to the stage specs (like 125 psi max, 50 HP, whatever your unit is). You\u2019ll need that number to order the exact replacement, not a \u201cclose enough\u201d eBay knockoff. I\u2019ve had clients show up with a $800 cheap motor that fried in 2 weeks because it didn\u2019t have the right magnet grade for our compressor\u2019s load curve. Don\u2019t cut corners here.<\/p>\n

Also, take photos before<\/em> you touch anything. I know, you think you\u2019ll remember where every wire goes, but trust me\u201430 minutes into disassembling, you\u2019ll forget if the yellow wire connects to terminal 2 or 3. I keep a old phone in my toolbox just for this: snap a pic of the wiring harness, the stage coupling alignment marks, even the way the air line clamps are seated. It\u2019s saved me so many headaches, and it\u2019ll save you too.<\/p>\n

Now, let\u2019s get to the disassembly part. Start with the easy stuff: pull the air intake cover off, disconnect the pressure switch wires, and loosen the air line that runs between the two compression stages. Next, the motor mounting bolts. Wait\u2014on two-stage models, the motor is connected to both<\/em> the low-pressure stage and the high-pressure stage, right? So you\u2019ll need to loosen the coupling that links the motor to each stage. Look for the alignment marks that the factory put on the coupling halves (little painted lines or punch marks). Don\u2019t grind those off or move them\u2014you\u2019ll need them later to get the new motor aligned correctly.<\/p>\n

Here\u2019s the trick part: the PM motor is mounted on a sliding base, right? So after you loosen the coupling bolts, you need to loosen the tensioner bolt that adjusts the belt (wait, no\u2014wait, some two-stage models have direct drive, not belts? Oh right, ours are mostly direct drive, so I don\u2019t have to mess with belt tension. That\u2019s a relief, because belts stretch and throw alignment off. For direct drive, just slowly slide the motor off its mounts, making sure not to yank the power or sensor wires out too hard. Those wires are delicate, especially the ones that measure the motor temperature\u2014bend them wrong and they break.<\/p>\n

Once the old motor is out, take a second to inspect the mounts. If there\u2019s rust or worn rubber bushings, replace them now. It\u2019s a $20 part that\u2019ll keep your new motor from vibrating itself apart in 6 months. I once skipped this on a job, and a client had to call me back a month later because the motor was rattling so bad it tripped the vibration sensor. Don\u2019t be me.<\/p>\n

Now, the new motor. First, before you even set it in, double-check that it\u2019s the right one for your serial number. Spin the motor shaft by hand\u2014if it\u2019s rough or makes a grinding noise, send it back. PM motors have rare earth magnets inside, so if you drop it, you can misalign the magnets and it\u2019ll never run right. I always grab a magnetic base and stick it to the motor housing when I\u2019m moving it\u2014keeps it from tipping or bumping into the compression stages.<\/p>\n

Setting the new motor in is all about alignment. That\u2019s the most critical step here. Remember those factory marks I told you to photo? You need to line the new motor\u2019s coupling marks up exactly<\/em> with the stage coupling marks. If you\u2019re off by even a fraction of a millimeter, you\u2019ll get premature bearing wear, lower pressure, and the motor will use way more electricity. I use a dial indicator for this (they\u2019re like $50 at any industrial supply store) to check the runout\u2014should be under 0.002 inches. A lot of guys skip this, but it\u2019s why some clients swear their \u201cnew motor\u201d is worse than the old one.<\/p>\n

Once the coupling is aligned, tighten the mounting bolts, but not all the way yet. Wait, also\u2014don\u2019t forget to reconnect the sensor wires! The PM motor has a temperature sensor, a speed sensor, and usually a current sensor. Match them to the photos you took earlier. If you mix them up, the compressor will run in a fault code loop and won\u2019t start at all. I\u2019ve had a client do this, and he spent 2 hours guessing which wire went where, instead of the 2 minutes it would\u2019ve taken to check the photo. Trust the process.<\/p>\n

Now, a quick test before you button everything up. Turn the power back on (make sure your lockout is off now) and set the compressor to test mode, not full run. Let it spin the motor for 30 seconds. Listen for weird noises, check the temperature\u2014should be under 140\u00b0F after that test. If it\u2019s overheating, you probably got the alignment wrong, or a sensor is wired backwards. If it runs smooth, great. If not, don\u2019t keep pushing\u2014turn it off and figure it out. I\u2019ve seen guys let a misaligned motor run for an hour, and they\u2019ve ruined both the new motor and the two compression stages. $5,000 in parts, all because they were in a hurry.<\/p>\n

Final steps: button everything back up, double-check all the connections, and run it for a full cycle\u2014from empty to full pressure. Watch the pressure gauges on both stages. The low stage should hit around 30 psi before the high stage kicks in, and the high stage should hit your max (whatever your unit is rated for). If the pressure is wobbly, go back and check the alignment. That\u2019s usually the issue.<\/p>\n

Now, a quick pro tip from my team\u2014we do hundreds of these swaps a year, so we know what works. If your old motor failed because of an overload (it kept tripping the breaker every time the compressor loaded), check the control panel\u2019s current setting. Don\u2019t just crank it to match the new motor\u2014our two-stage units are calibrated to specific current draws, and cranking it will just burn up the new motor faster. Also, if you\u2019re not comfortable doing this yourself, don\u2019t force it. A lot of small workshops try to save a few bucks, but paying a pro to do it right once is way cheaper than replacing two motors.<\/p>\n

Wait, one last thing: don\u2019t forget to recycle the old motor. PM motors have rare earth magnets inside, so tossing them in the trash is bad for the environment, and there are places that\u2019ll pay you for the magnets. We actually take back all our old motors for free from clients, because we have a recycling partner that processes them properly. Saves you the hassle, and it\u2019s better for everyone.<\/p>\n

<\/p>\n

At the end of the day, swapping a PM motor in a two-stage screw compressor isn\u2019t rocket science, but it\u2019s not something you can rush either. Take your time, follow those steps, and you\u2019ll have your compressor back up and running in no time. If you\u2019re not sure about any step, or need the right replacement motor, just reach out to our team. We\u2019ve got techs on call 24\/7 to help, and we can get you the exact part you need, shipped same day if it\u2019s an emergency. No runaround, no hidden fees, just real support for your compressor. Stop dealing with that broken motor\u2014let\u2019s get your shop back up to speed.<\/p>\n

Compressor Parts<\/a> References:<\/p>\n

    \n
  1. "Industrial Screw Compressor Maintenance Best Practices", Compressed Air System Maintenance Association, 2022<\/li>\n
  2. "Permanent Magnet Motor Alignment Guidelines for Two-Stage Compressors", Global PM Motor Tech Journal, 2023<\/li>\n
  3. "Safe Electrical Lockout Procedures for Industrial Equipment", OSHA Technical Manual, 2021<\/li>\n<\/ol>\n
    \n

    Xiamen HighQ Compressor Co., Ltd.<\/a>
    With over 20 years’ experience, Xiamen HighQ Compressor Co., Ltd. is one of the most professional two stage pm srew air compressor manufacturers and suppliers in China. We warmly welcome you to buy high quality two stage pm srew air compressor made in China from our factory. Good service and punctual delivery are available.
    Address: 7th F. No.704 Yi Hua Center Xiamen China 361100
    E-mail: vincent@hqcompressor.com
    WebSite:     https:\/\/www.hqcompressor.com\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

    If you\u2019re reading this, you\u2019re probably running a two-stage PM screw air compressor (you know, the … How to replace the PM motor in a Two Stage PM Screw Air Compressor?<\/span>Read more<\/a><\/p>\n","protected":false},"author":923,"featured_media":3435,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[3398],"class_list":["post-3435","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-industry","tag-two-stage-pm-srew-air-compressor-4f31-874b1f"],"_links":{"self":[{"href":"http:\/\/www.yasnasa.com\/blog\/wp-json\/wp\/v2\/posts\/3435","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.yasnasa.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.yasnasa.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.yasnasa.com\/blog\/wp-json\/wp\/v2\/users\/923"}],"replies":[{"embeddable":true,"href":"http:\/\/www.yasnasa.com\/blog\/wp-json\/wp\/v2\/comments?post=3435"}],"version-history":[{"count":0,"href":"http:\/\/www.yasnasa.com\/blog\/wp-json\/wp\/v2\/posts\/3435\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/www.yasnasa.com\/blog\/wp-json\/wp\/v2\/posts\/3435"}],"wp:attachment":[{"href":"http:\/\/www.yasnasa.com\/blog\/wp-json\/wp\/v2\/media?parent=3435"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.yasnasa.com\/blog\/wp-json\/wp\/v2\/categories?post=3435"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.yasnasa.com\/blog\/wp-json\/wp\/v2\/tags?post=3435"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}