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MS90U Control Pack X300739 - Bubbles Supply

MS90U Control Pack X300739

Part #: X300739

$684.68
In stock — ships today
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1-year warrantySame-day ship before 3pm CTPerfect Fit Guarantee30-day returns

About this control pack

The MS90U Control Pack X300739 is a genuine OEM heater control system designed for Master Spa hot tubs. This essential spa component manages your heater operation, ensuring consistent water temperature and resolving common issues like HH (high heat) and OH (overheat) error codes that can shut down your spa.

Built to Master Spa's exact specifications, this control pack delivers the precise fit and performance your spa needs. At Bubbles Supply, we guarantee an exact fit for your system and ship the same day to get you back to relaxing quickly. Every MS90U control pack comes with our comprehensive 1-year warranty for complete peace of mind. For proper operation, ensure this control pack matches your existing Master Spa model number and have a qualified technician handle installation to maintain safe electrical connections.

Exact part number

X300739

Save this for ordering or warranty claims

Also known as / Replaces

This part replaces or is interchangeable with:

  • Master Spa heater controller
  • MS90U control pack
  • X300739 heater control pack

Looking for an older part number? Check our supersession lookup tool

Common symptoms this part fixes

If your spa is showing any of these signs, this part is likely your fix:

  • HH (high heat) error code displayed on topside panel
  • OH (overheat) error code shutting down spa
  • Heater not activating or maintaining set temperature
  • Spa cycling on and off erratically due to control fault
  • Water temperature reading inaccurate or stuck
  • Heater lockout with no response from thermostat adjustments

Not sure if this is your problem? Try our diagnostic centre or .

Before you buy — quick checklist

  • Confirm your Master Spa model number matches known compatible units for X300739 before ordering
  • Verify the existing control pack part number printed on your current unit matches X300739
  • Check whether HH or OH codes are persisting after sensor reset — a failed control pack is one cause, but a faulty hi-limit sensor or temp sensor can trigger the same codes
  • Inspect wiring harness connectors on the existing pack for corrosion or burn marks before assuming the pack itself has failed
  • Have a licensed electrician or qualified spa technician handle installation — this component involves line-voltage wiring

Reading the checklist now prevents 90% of returns. Worth the 60 seconds.

Install difficulty: Hard — Technician recommendedTypically 60-90 minutes

Warranty

1 year manufacturer warranty against defects

Covers manufacturing defects. Does not cover improper installation, normal wear, or accidental damage.

Warranty claims: warranty@bubblessupply.com

Perfect Fit Guarantee

Ordered with our help and the part doesn't fit? Contact us before installation. We'll resolve it with an exchange, replacement recommendation, or return approval.

Learn about our Perfect Fit Guarantee →

Shipping

We ship across the US and Canada. US orders ship from our US warehouse to US customers; Canadian orders ship from our Canadian warehouse to Canadian customers — no cross-border shipping, no surprise duties. In-stock orders placed before 3pm CT ship same day. Standard shipping $9.95 flat rate. Free shipping on orders over $200. Express options available at checkout.

Returns

30-day hassle-free returns on unused parts in original packaging. Contact us before returning to receive your RMA number.

Frequently asked questions

Check the Compatibility section above to confirm fitment for your spa brand and model. If your model is not listed, use our fitment selector at /pages/find-my-part or ask our parts AI for a personalized recommendation.

In-stock orders placed before 3pm CT ship the same day. You will receive tracking information by email as soon as your order ships.

We accept returns within 30 days of delivery for unused items in original packaging. Email returns@bubblessupply.com with your order number to start a return. Installed electrical parts cannot be returned for safety reasons.

Yes, all new parts come with a 1-year warranty against manufacturing defects. Warranty does not cover damage from improper installation or normal wear and tear.

Customer reviews

AI Fitment Assistant

Tell us your spa model and we will confirm this part fits before you buy.

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