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Common Issues & Fixes: What to Do If Your GE Wall Unit Isn’t Heating or Cooling Properly (Mike’s Troubleshooting Guide)

You woke up sweating… or freezing… or listening to your GE wall AC make a noise that sounds like a squirrel tap-dancing. And now you’re wondering:

“Is my GE AJEQ12DWJ broken, or is there something simple I can fix?”

Good news:
Most problems with through-the-wall AC units—especially the GE 12,000 BTU model with electric heat—are easy to diagnose and often easy to fix without calling a pro.

In today’s guide, I’ll walk you through every common issue I’ve seen over 20+ years in HVAC fieldwork, explain WHY it happens, and give you simple troubleshooting steps that actually solve the problem—not the vague “just reset the unit” advice you see online.

1. First Things First: The GE AJEQ12DWJ Is a Solid Unit—But Not Problem-Free

Before we dive into the fixes, understand this:

95% of issues homeowners experience with this GE model come from:

airflow blockage
dirty filters
dirty coils
electrical supply issues
incorrect mode settings
wall sleeve or drainage problems
thermostat misreads

Only about 5% come from actual component failures.

That’s good news, because it means most fixes are simple.

Reference: Room AC Troubleshooting and Diagnostics Guide

2. Issue #1: The Unit Isn’t Cooling (Most Common Problem)

This is the #1 call I get—especially during the first hot week of the year. Let’s break down the causes.

Cause A: Dirty Filter

This is the classic “my AC isn’t cooling” culprit.

Symptoms:

weak airflow
warm air blowing
visible dust on filter

Fix:

Remove front panel
Wash filter in warm soapy water
Dry it completely
Reinstall

I recommend washing the filter every 30 days.

Cause B: Blocked Air Intake or Outlet

If furniture is in front of the unit, air can’t circulate.

Fix:

Keep 3–4 feet of clearance in front
Don’t block the side vents

Cause C: Dirty Evaporator Coil

This one sneaks up on people.

Symptoms:

unit runs constantly
little cold air
coil looks like dusty felt

Fix:

Remove front panel
Spray coil with coil cleaner
Let foam break down
Rinse lightly (avoid electronics)

Cause D: Wrong Mode or Wrong Fan Speed

Make sure you are in Cool Mode, not “Fan” or “Energy Saver.”

Fix:

Set mode to Cool
Set fan to Auto or Low for strongest cooling

Cause E: Refrigerant Leak (rare but possible)

If you hear hissing or see oil stains, call a pro.

This GE model is sealed—you cannot recharge it at home.

Cause F: Hot Air Leaking Around the Sleeve

This is extremely common.

If your sleeve isn’t sealed, the unit is fighting the outdoors.

Fix:

Apply foam insulation around sleeve
Seal interior gaps with caulk
Seal exterior gaps with flashing

3. Issue #2: The Unit Isn’t Heating

This GE model uses electric resistance heat, so when heat fails, it’s usually related to electrical supply or airflow.

Cause A: Wrong Mode

Make sure you’re in Heat Mode, not “Fan” or “Cool.”

Cause B: Tripped Breaker

Heating element draws a lot of power.

Fix:

Reset breaker
If breaker trips again → electrician time

Cause C: Airflow Blocked by Dust

Heater overheats and shuts down for safety.

Fix:

Wash the filter
Vacuum the intake grill
Clean the heater coil

Cause D: Incorrect Voltage Supply

This unit requires 208/230V, not 115V.

Symptoms:

heating barely works
low airflow
unit cycles on/off strangely

Reference: Residential HVAC Electrical Performance Guidelines

Fix:

Confirm outlet voltage with tester
If wrong → electrician required

Cause E: Heating Element Failure

Rare, but happens with age.

Symptoms:

fan blows, but air stays cold
no odor of warm air
heat stops suddenly

Fix:

Call a pro; part replacement needed

4. Issue #3: Unit Blows Cold Air in Heat Mode

Happens more than you think.

Cause A: Fan Speed Too High

High fan = cooler discharge air.

Fix:

Set fan to Low

Cause B: Room Too Cold

Electric heat struggles to recover if room drops below 50°F.

Fix:

Preheat room with supplemental heater
Then use GE unit to maintain warmth

Cause C: Air Bypass Through Sleeve

Cold air leaks around the sleeve, mixes with warm output.

Fix:

Insulate sleeve gaps properly
Seal around trim kit

5. Issue #4: The Unit Makes Loud Noise or Vibrates

Noise issues are 80% installation, not the AC.

Cause A: Sleeve Not Level

If sleeve leans sideways, unit vibrates heavily.

Fix:

Check level
Shim sleeve

Cause B: Sleeve Not Secured

Metal-on-metal rattling is common in older sleeves.

Fix:

Tighten mounting screws
Add foam insulation where sleeve meets wall

Cause C: Debris in Fan

You’d be amazed at the things I’ve found:

pine needles
insects
kids’ toys
insulation chunks

Fix:

Remove front panel
Inspect blower wheel

Reference: Noise and Vibration Control Recommendations

Cause D: Loose Rear Grille

A rattling grille is loud enough to drive anyone crazy.

Fix:

Tighten screws
Replace rusty or loose grilles

6. Issue #5: Water Leaking Inside the House

This one scares homeowners—and rightfully so. It’s nearly always a sleeve or drainage issue.

Cause A: Sleeve Pitch Is Wrong

This is the #1 cause.

The sleeve must slope ¼ inch downward outside.

Fix:

Shim back edge
Re-seal sleeve

Cause B: Blocked Drain Holes

Check the back of the sleeve.

Fix:

Clean drain channels using a brush

Cause C: Ice Melt on Evaporator Coil

Dirty coil → freezing → melting → leaking.

Fix:

Clean coils
Check filter

Cause D: Excessive Humidity

Basements especially.

Fix:

Run unit on “Dry Mode”
Add dehumidifier

Reference: Wall Sleeve Installation and Drainage Specifications

7. Issue #6: The Unit Turns On and Off Constantly (Short Cycling)

Short cycling kills compressors.

Cause A: Oversized Unit for the Room

Common with 12k BTUs installed in 200 sq. ft. rooms.

Fix:

Use Low fan
Use thermostat offset
Improve airflow

Cause B: Thermostat Sensor Misplacement

Sensors can shift or bend.

Fix:

Make sure sensor is near coil but not touching metal

Cause C: Dirty Filter or Coils

Causes compressor overheating.

Fix:

Clean filter
Clean coils

Cause D: Electrical Supply Issues

Weak voltage = unstable operation.

Fix:

Test outlet
Call electrician if voltage fluctuates

8. Issue #7: Unit Won’t Turn On At All

Let’s diagnose like a pro.

Step 1: Check Breaker

This unit draws serious power when heating.

Step 2: Check Outlet Voltage

Needs 208/230V.

Step 3: Check GFI or AFCI

Some rooms use GFI circuits.

Step 4: Check the Front Control Panel

Sometimes buttons wear out.

Step 5: Check for Burnt Smell

If yes → unplug & call a pro.

9. Issue #8: Thermostat Not Responding or Wrong Temperature Reading

Very common.

Cause A: Sunlight or Lamps Near Unit

Heat source confuses sensor.

Fix:

Move lamps
Use curtains

Cause B: Blocked Return Air

Furniture blocking intake.

Fix:

Move furniture

Cause C: Dirty Sensor

Dust acts like insulation.

Fix:

Wipe sensor gently with dry cloth

10. Issue #9: Unit Smells Bad

Odors come from two places:

dust
mold

Cause A: Dust on Heat Coil

You’ll smell “burning dust” the first time heat runs each season.

Fix:

Let heater run 10–15 minutes

Cause B: Mold on Evaporator Coil

Warm, dark, wet places = mold paradise.

Fix:

Clean coil
Use coil cleaner with antimicrobial solution

Cause C: Water Stagnation in Sleeve

Sleeve isn’t draining.

Fix:

Clean drain holes
Re-pitch sleeve

Reference: Wall Sleeve Installation and Drainage Specifications

11. Issue #10: Weak Airflow

If airflow is weak, the unit can’t heat or cool effectively.

Cause A: Filter Dirty

Clean it.

Cause B: Coil Dirty

Clean it.

Cause C: Fan Wheel Dirty

Remove debris.

Cause D: Return Air Blocked

Clear furniture.

Cause E: Ductless Adapter Installed Incorrectly

Some people try to use duct adapters—not recommended.

12. Preventing Future Problems (Mike’s Maintenance Rules)

If you want your GE unit to last 10–15 years, follow this schedule:

Monthly

Wash filter
Inspect airflow

Every 6 Months

Clean evaporator coil
Clean heater coil
Clean blower wheel

Annually

Inspect sleeve pitch
Reseal any gaps
Clean drain channels
Check rear grille screws

Every 2–3 Years

Recheck electrical outlet
Check foam and insulation
Tighten sleeve fasteners

13. When to Repair vs. When to Replace

Repair it if:

Unit is under 8 years old
Issue is airflow or electrical
Heating element still works
Compressor runs normally

Replace it if:

Cooling coil leaks refrigerant
Compressor fails
Electrical board fried
Sleeve heavily rusted
Efficiency has declined severely

Repairs can cost $200–$500.
New unit costs ~$700–$900.
Do the math.

14. Final Verdict: Most Problems Are Easy Fixes

Here’s Mike’s no-BS conclusion:

✔ Cooling issues?

99% caused by airflow problems.

✔ Heating issues?

Usually electrical or coil related.

✔ Water leaks?

Sleeve pitch or clogged drains.

✔ Noise problems?

Almost always installation-related.

✔ Unit won’t turn on?

Voltage or breaker.

✔ Bad thermostat readings?

Sensor placement or airflow.

✔ Smells?

Dust or mold—easy to clean.

The GE AJEQ12DWJ is a tough, dependable unit.
Take care of it, and it’ll take care of you for years.

In the next blog, Mike will help us with the maintenance guide.

Tags: Cooling it with mike

WRITTEN BY

Mike Sanders

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