Goodman Furnace 9H Error Code: High Pressure Switch Open

Quick Answer

Goodman 9H indicates the high pressure switch opened - either not closing during startup or opening unexpectedly during a heat cycle. On two-stage condensing furnaces (GMVC96), this often points to a restriction in the secondary heat exchanger caused by condensate backing up. A blocked condensate drain is the most common root cause and the first thing to rule out.

9H usually shows up during the first real cold snap of the year. If you've got a high efficiency Goodman, this code often means the furnace is literally choking on its own water. When that condensate can't drain away, it pools in the secondary heat exchanger and blocks the airflow the pressure switch is trying to measure. It's a safety lockout designed to prevent incomplete combustion or exhaust leaks into your home, and you shouldn't just reset it and walk away.

GoodmanFurnaceSeverity: highDifficulty: intermediate74% DIY Success

Time to Fix

30–90 min

Difficulty

intermediate

Parts Cost

$20 – $45

Tools Needed

Phillips #2 screwdriver, Flat-head screwdriver

What Does the 9H Code Mean?

Think of this as a breathing problem for your furnace. While the board blames the high stage pressure switch, the switch is usually just doing its job correctly. I always start by looking for sloshing sounds in the inducer housing or water backed up in the clear plastic tubing. It's rarely a bad part and almost always a plumbing issue, which is actually good news because drain lines are way cheaper to fix than pressure switches or heat exchangers.

Most Likely Causes

Based on aggregated repair data, here is the probability breakdown for this error code:

Clogged secondary heat exchanger from condensate backup40%

Condensate drain line blocked or frozen24%

Pressure switch failed or out of calibration22%

Vent pipe restriction or bird/debris blockage14%

Symptoms You May Notice

Furnace fires up, inducer gets loud, then shuts off after about 2-3 minutes every single time without heating the house.
Control board flashing 9 times, pause, then 1 more flash in a repeating pattern you can actually count.
You can hear water sloshing or gurgling inside the furnace cabinet when the inducer spins up, that's condensate sitting where it absolutely shouldn't be.
Puddle of water forming around the base of the furnace, or the condensate overflow float switch keeps tripping and killing power.
House won't get above 60 degrees even though the thermostat is cranked and the furnace keeps cycling on, trying, and failing.

Can you reset a Goodman furnace to clear the 9H code?

Flip the service switch or breaker off for 30 seconds, then back on. The 9H code clears automatically when power cycles. But here's the deal: if you haven't fixed the actual drain or vent problem, it'll trip again within a few minutes once the furnace ramps up to high stage. Only reset after you've cleared the root cause, otherwise you're just wasting time and stressing the inducer motor.

Tools Required for Diagnosis

Phillips #2 screwdriverFlat-head screwdriverWet/dry vacuumMultimeter with continuity settingFlashlight or headlampManometer or inclined U-tube gaugeFlexible bottle brushBucket and old towels

Diagnostic Checklist

Follow these steps in order. We start with the easiest external fixes before opening up the machine.

Replacement Parts

If your diagnostic testing proves the component has failed, you will need a replacement. We recommend OEM parts over aftermarket for water-handling components.

Part Name	OEM Number	Estimated Price
High-Stage Pressure SwitchB1370732 · $20–$45	B1370732	$20 – $45

Frequently Asked Questions

What is the secondary heat exchanger on a Goodman 96% furnace?

Think of the secondary heat exchanger as a radiator that catches leftover heat from the exhaust. Because a 96% efficient furnace extracts so much heat, it actually condenses that exhaust gas into liquid water, which is why these are called condensing furnaces. In Goodman units, if that water can't escape through the drain, it fills the bottom of the heat exchanger. It's basically a straw in a glass of water effect where the inducer motor can't pull enough air through, and the 9H pressure switch trips to protect the system from running in a dangerous condition.

How is 9H different from F02?

F02 is usually a problem before the furnace even gets going, like the pressure switch is stuck open before the inducer motor builds any vacuum at all. 9H means the furnace actually got started, ran at high stage, but couldn't maintain the pressure it needed. 9H is way more common in dead winter when drains freeze or when the furnace has been running hard for hours and producing a ton of condensate it can't clear fast enough. If you're seeing F02, check your switch wiring and inducer motor first. If you're seeing 9H, go straight to the condensate drain.

Can I clean the secondary heat exchanger myself?

You can definitely handle the external stuff yourself, clearing the drain lines, flushing the condensate trap, vacuuming out the vent pipes. That covers probably 80% of 9H calls. But if the blockage is deep inside the collector box or the secondary heat exchanger fins are caked with mineral deposits, you're looking at a pretty serious teardown that most homeowners shouldn't attempt without experience. If you've cleared all the lines and 9H keeps happening only at high stage, call a tech with a manometer who can actually measure the pressure drop and tell you exactly what's restricted.

How much does it cost to fix a Goodman 9H code?

Depends entirely on the root cause. Clogged drain trap you clear yourself? Free. A new pressure switch is about $25-45 for the part, plus maybe an hour of labor if you call someone, so figure $150-250 installed. Frozen drain line with heat tape installed typically runs $100-200. If the secondary heat exchanger or collector box is cracked, you're looking at $400-800 in parts and labor. And honestly, on a furnace that's 15 or more years old at that price point, get a quote on a full replacement before spending that kind of money on a repair.

Will ignoring the 9H code damage my furnace?

Yeah, it can. The obvious risk is carbon monoxide if there's actually a vent restriction and you keep bypassing the safety. But even if you're just dealing with a frozen drain, repeatedly cycling the furnace against restricted airflow stresses the inducer motor hard. Those motors run $200-400 to replace. What usually happens is people reset the code 10 or 12 times over a weekend, the inducer finally gives up, and now they've turned a $30 drain line problem into a $300 motor replacement. Fix the root cause the first time and you'll save yourself a much bigger headache.

Related Goodman Furnace Error Codes

Code: HUBGoodman Furnace Error Codes: LED Flash Code Guide for GMVC and GMSS Series Code: F02Goodman Furnace F02 Error Code: Pressure Switch Stuck Closed Code: E5Goodman Furnace E5 Error Code: Pressure Switch Error Code: RESETHow to Reset a Goodman Furnace and Clear Error Codes

Models Known to Experience 9H Errors

This repair applies to most Goodman furnaces with this error code. Common model numbers include:

GMVC96 0403BN, GMVC96 0603BN, GMVC96 0804CN, GMSS92 0453AN, GCVC96 0603BN, AMVC96 0804CN, ASST96 0603BN, GMEC96 0402ADAA

Written by

Raj Patel

HVAC & Water Systems Specialist · 15 years experience

Last verified for technical accuracy on March 14, 2026