Rinnai Tankless Water Heater Code 13 — Combustion Fan Fix

What Does This Error Mean?

Code 13 is a combustion fan fault — the fan that pushes exhaust through the vent isn't running, isn't running at the right speed, or the controller can't read its feedback.
Listen at the unit when you turn on hot water — do you hear the fan spin up?
If silent, the fan motor or its driver has failed.
This is an internal repair — call a licensed installer.

Affected Models

Rinnai RU series
Rinnai V series
Rinnai R75LSi
Rinnai RU199iN
Rinnai RUR series

Common Causes

Combustion fan motor seized or failed
Fan speed sensor failed
Wiring loose between fan and control board
Excessive lint or debris jamming the fan blade
Control board fan driver section damaged

How to Fix It

Power-cycle the unit.

Press on/off.
Wait 30 seconds.
Press again.
Run hot water briefly.
Listen at the unit — is there a fan sound, or silence?
This single observation tells you 80% of what the technician needs to know.
Listen carefully when calling for hot water.

Within 2 seconds of calling for hot water, you should hear a soft fan whirr from the heater.
That's the combustion fan starting before ignition.
If you hear nothing, the fan is dead.
If you hear it labor, grind, or run intermittently, the bearings are gone.
Check for nearby lint sources.

If the heater is in a laundry area near a dryer, lint accumulating on the fan blade is a known cause.
The fan blade unbalances and slowly degrades the bearings.
You can't clean this from outside the casing — the technician will when they replace the fan.
Don't open the unit yourself.

The combustion fan lives inside the sealed combustion chamber.
Working in there means handling components in the gas-side of the unit.
This is licensed-installer-only territory.
Don't try to access it through the vent or by removing covers.
Schedule service.

Provide the model number and Code 13 history when calling.
Most installers carry replacement combustion fans for popular Rinnai models.
Fan replacement is 150–300 USD parts plus an hour of labor.
Total bill typically 300–450 USD.

Frequently Asked Questions

Can dust cause Code 13?

Yes — dust accumulating on the fan blade adds weight unevenly, vibration increases, and over months the bearings wear out.
Heaters in dusty mechanical rooms or near lint sources fail combustion fans first.
Annual service includes a fan inspection that catches this early.

How long should the combustion fan last?

8–12 years of typical residential use.
Heaters used heavily (large families, all-day demand) wear them faster.
If your heater is past 10 years and Code 13 has appeared, replacement is normal end-of-life maintenance, not a defect.