Troubleshooting guide
Heat pump E5 / E6 / P5 error codes? Here is what is happening and what to do.
P5 (Mitsubishi) typically indicates a drain pump error or condensate overflow. E6 typically indicates a communication error between indoor and outdoor units. Both are common in Vermont, especially after winter when condensate lines can freeze. Both require a service visit, but neither is usually a major repair.
Likely causes, ranked by probability
- 1
P5: drain pump failure or condensate overflow
Mitsubishi drain pump or pan sensor issue. Common after winter freeze.
Likelihood 50%
- 2
E6: communication error
Cable, terminal, or board issue between indoor and outdoor units.
Likelihood 40%
- 3
Wiring corrosion at terminal block
Especially in outdoor installs.
Likelihood 10%
What you can try first
- · Power-cycle the unit at the breaker for 10 minutes
- · Verify the condensate drain line is not frozen or blocked
When to call us: Code returns after power cycle. Almost always requires a tech visit.
When a cleaning helps, and when to call a repair pro
A good portion of “something is off” symptoms (musty smell, weak airflow, water dripping from the indoor unit, surface mold) trace back to a dirty blower wheel, clogged drain, or biofilm on the coil. A full disassembly cleaning solves those. If we get on site and find an electrical or mechanical fault (a failing capacitor, a stuck reversing valve, refrigerant issues), we will tell you and recommend a heat pump repair contractor. We do not do repairs ourselves.
Frequently asked questions
Is heat pump e5 / e6 / p5 error codes dangerous?
Most causes of "heat pump e5 / e6 / p5 error codes" are not immediately dangerous, but ignoring them can damage the system over time. Code returns after power cycle. Almost always requires a tech visit.
Can a cleaning fix this?
Sometimes. Biofilm, dirty coils, and clogged drain lines often resolve after a deep clean. Mechanical or electrical issues need a heat pump repair contractor instead.
Do you do repairs?
No. We focus on cleaning and twice-yearly maintenance. If your system needs a part replaced or an electrical fix, we will tell you what we see and recommend a repair contractor.
Try a cleaning first.
If the symptom traces back to a dirty unit, we can fix it. If it does not, we will tell you and point you to a repair pro.