Diagnostic 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.
Our diagnostic process
We arrive within a one-hour window, inspect the system end-to-end, read any active error codes, test temperatures and pressures, and identify the actual cause. You get a written quote before any repair work starts. The $129 diagnostic fee is applied to any repair you proceed with.
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 or raise repair cost. 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 require a diagnostic visit instead.
How much does diagnosis cost?
Our diagnostic visit is $129 flat, applied to any repair you proceed with. We will quote any repair before starting work.
Need a tech to take a look?
$129 flat diagnostic. Same-week scheduling across Vermont. Credited toward any repair.