My Pool Pump Runs On Low Speed But Not On High Speed

It’s really frustrating when you purchase an expensive item, install it, and it immediately malfunctions. For most pool owners, troubleshooting single-speed pumps can be tricky and annoying and time-consuming and… Well, you get the point. Now, imagine the frustrations you experience while troubleshooting your dual speed pump. Over the last few months, we’ve come across customers experiencing problems with their dual speed pump. The common complaint is, “My pump runs on low speed but not on high speed.”

As the heart of your pool system, it’s absolutely necessary to keep your pool pump operational. The purpose of this blog post is to help pool owners determine why their dual speed pump runs on low speed but not on high speed. 

Can I Run My Pump Only On Low Speed?

What happens when you purchase a new dual speed pump, install it, and it immediately gives you problems? Your pump operates smoothly on low speed but fails to function properly at high speed. What is the solution we hear from our customers the most?-  Run it on low speed forever and ever. If that works for you- great. Odds are, though, it won’t work for most pools. Serious question- why would you sacrifice a product you just spent hundreds of dollars on?-  You shouldn’t!

So, can you run your dual speed pump on low speed only? – Yes, but here’s why you probably shouldn’t.

If you cannot operate your pump at high speed, you may lose the ability to control your waterfalls, pop-up heads, spillovers, jets, and bubblers. Water features typically require more gallons per minute (GPM)  than what the low speed on pumps produce.

We also recommend checking the minimum GPMS your heater and salt chlorine generator require for operation. For most, the minimum is around 35 GPMS. If on the low speed your pool pump is pushing less than 35 GPMS, then you will lose functionality of your salt system and heater.

Lastly, depending on the size and shape of your pool, running your pump solely on low speed may not provide enough circulation. Or, it may provide just enough circulation if you’re running your pump all day.

Why Isn’t My Pump Running On High Speed?

Before we can get into why your dual speed pump isn’t working on high speed, we first need to determine when it stopped working altogether. Was your pump running on both low and high speeds initially? Or, did the problem arise immediately after installing your pump?

Recently Installed Pumps

If you just installed your dual speed pump and realized it isn’t working on high speed- don’t fret. There’s a possibility that you simply installed your pump incorrectly.

Below is a diagram of the correct and incorrect wiring of a DS pump.

In the example above, the motor will only run at low speed when switched to high speed. If the wire from the H position on the switch is connected to HIGH and the L is connected to COM, the motor will only run on low speed. In most cases, even when installed incorrectly, there shouldn’t be damage to your motor nor will it trip your breakers.

If you’re not familiar with wiring diagrams, it can seem like another language. We never recommend pool owners to complete tasks that they are uncomfortable performing.

Here are a few other helpful resources for wiring a dual-speed Pump:

How To Install a 2 Speed Motor and T106 Timer

How To Wire a PE154 Digital Timer to a 2 Speed 230v Motor

How To Wire the 1011431-001 Toggle Switch to a Century STS 2 Speed Motor

How to Wire the 18313301 Switch to 115 Flex-48 2 Speed Motor

How To Wire the 2512558-001 Toggle Switch to a Century 56Y 2 Speed Motor

Troubleshooting Two-speed Motors That Have Been Working

If your motor was running properly on both high and low speeds, but now it will only run at low speed, the issue is definitely related to the motor or control. On high speed, there is the main winding and a phase winding with a run capacitor. If any of these components aren’t functioning, the motor will not start. The first and easiest thing to check is the capacitor. If the capacitor checks okay, then the likely cause of the problem is a shorted phase winding.

Unfortunately, if the winding is bad, it cannot be replaced and you will need to replace your whole motor.

Windings and Two Speed Motors

Certain types of two-speed motors actually have two separate windings in one housing.  Most have a separate main and phase windings.  Still, a few two-speed designs only have a low-speed main winding.  This design always starts at high speed and switches to the low speed run winding within a couple of seconds.  This motor was a less expensive design since there was no low-speed start windings or a start capacitor.


Any of the troubleshooting guides that pertain to single speed motors can be applied to dual-speed motors. Remember, if the high-speed option isn’t working and you recently installed your pump, odds are you wired it up incorrectly. However, if the high speed stopped working after years of operation, check the capacitor and phase windings. It’s easier to replace a capacitor than a phase winding. Usually, pool owners purchase a new motor once the windings are bad. Lastly, if you’re having difficulties reading or understanding your wiring diagram, give us a call and speak to one of our technicians.

32 thoughts on “My Pool Pump Runs On Low Speed But Not On High Speed

  1. Could a bad relay in the control system of the pool cause the motor to only work in low speed? I don’t hear a “click” at the control box when I first attempt to start high speed… There is a click when the low speed starts.

  2. Your wiring diagram looks like it shows 230 volts to the pump on both the high and the low settings? Is that correct? What changes the pump speed?

  3. My Hayward VS900 pump when running at a high speed (2900 rpm) will cause my pool to lose water. When my filter cartridge (150 sq ft for a 23,000 gal pool) was dirty, the tank pressure built up and the circulation flow was reduced… water loss. When the new cartridge was put in and circulation flow increased I lost over an inch of water overnight. How can I fix this?

    1. If the filter was the main issue, you should see obvious signs of leaks on your equipment pad. The increased flow may have exacerbated an existing leak, it could be a crack in the skimmer, underground plumbing, or anywhere on the pressure of the pump. The pressure side is the plumbing and equipment after the pump.

      Have you checked that all drain or waste lines are closed? Was the pump running all night or was it off? This will help determine if the water leak is in the plumbing or the pool basin.

  4. I recently moved and setup a spa. The 2 speed pump starts in low, but when the pump goes into high speed, the breaker gets tripped. If I disconnect the pump from the control panel, the breaker doesn’t trip.
    I know the heating element is bad, but it’s currently disconnected, would blow the breaker as soon as power was turned on.

    Any advise would be helpful.

    1. Unfortunately, I don’t know the make and model of the spa or its wiring, so I can’t provide much guidance. It would be best if you had someone, either a pool/spa tech or an electrician, take a look at it in-person.

  5. I have a 2 speed motor 230v for a spa both relay work for low and high 120 on white black red all the time test all wires on motor 120v on all the can on top reads 250v on one side 78v on other side then switched to low 120v on both sides

  6. I have similar issue with my emerald spa. Has a waterway pump 3721621-1w5a.
    It starts and runs for a few seconds but then I get a load hum and the motor stops. I replaced the capacitor but it still acts the same. What is my next step? Replace motor? Since the hum makes me believe the controller is sending electricity to motor properly.
    Any ideas?

      1. Same problem and if I turn the shaft with a screwdriver the motor will start but on next cycle it will do it again. I ordered a capacitor but did not receive it yet.

  7. Mine is the opposite. I just installed a new Pentair 2-speed 1.5HP 230V motor for my filter pump. It works fine at high speed, but not low speed. Any suggestion how to fix it?

      1. I am having the same issue. Pump runs fine on high speed, hums loudly on low speed and kicks the thermal protection switch. 1.5 hp motor is pulling 24 amps (instead of 3.6) on low speed.

        1. I have the same issue on an older hot spring hot tub, jets work fine(heating doesn’t happen with jets on high pressure as it’s plug in) but won’t pump at all when the jets are off(when it should be acting as a circ pump to support the heating element) heating works, thermostats work, pressure switch works, so it seems like the pump has lost it’s ability to do a low pressure pump(or isn’t activating) it’s been a rabbit hole!

    1. I have had my pool for 5 years and it just recently stopped working. The pump will work on low but when you put it on high speed it shuts on and off every 20 mins or so. My pool guys says I need a new high low switch put it and the guy that I bought my pool from says I need a whole new pump. Please help I’m a single mom 😩

      1. As the article mentions, it is usually a wiring issue if it is a brand new motor and there are several troubleshooting guides linked in the bottom half of the article for older motors that have recently started to malfunction. Do any of the scenarios link in the article resemble your set up?

    2. Was working fine. Had a brown out thar lasted a minute after that no high speed. Motor and pump about 6 years old. What should I do?

  8. I know it’s an old thread, but FYI my 2 hp 2 speed started this yesterday, would start on low but not high speed. Could start on low then quickly switch to high and would run. Replaced the capacitor, and now works fine.

    1. Thanks for the post, I hope thats the case, my 2hp pump did the same, I noticed it was off and went to check it out and it wouldnt work on high, but it did on low. Just ordered a capacitor for it. Fingers crossed. $20 versus $350

    2. Well, you might have just answered my question. Have the same problem. I will try that! Thank you

    3. This sounds similar to my situation. My 2-speed Century pump has been working fine for 18 months, while on an automatic timer. Two days ago it was supposed to be running on high speed but it was not running at all. The motor felt very hot. I turned off the circuit and waited several hours to allow everything to cool. Now I get a short loud humming noise if I try to turn on high from scratch. Sometimes I make multiple attempts and receive loud sustained noise. The motor does not turn on. When the timer engages attempting to turn on high speed, I get the the loud quick humming noise.

      Finally I experimented with turning low speed on and off. If I wait too long after turning off the low speed, high speed will not engage. But if I turn off low speed and quickly switch to high speed, most of the time high speed will work. The first time high speed reappeared, the motor sounded awful, unusually loud. I switched it off. Now the high speed sounds fine and works fine…when I can get it to turn on in the first place.

      Does this sound like a capacitor? If so, can I do this myself? I have changed other capacitors many times, like on an HVAC, but I’ve never attempted it — or would know how to proceed — on a pool pump.

  9. AEP SWEPCO Louisiana has a $250 rebate for energy star variable speed pumps. The takes my Pure Line VS a done deal (and a steal!). =)

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