Rinnai HE Series How To Use Manual page 175

1. Check thermistor wiring harness for loose, broken or damaged connections from thermistor
back to PC board.
2. Remove thermistor from fan motor housing and check resistance readings of this component
using a volt/ohm meter capable of reading 20K ohms. Set meter to proper setting for checking
20K ohms and insert meter leads into each end of the thermistor plug. Then apply heat to the
thermistor bulb. You will notice the thermistor resistance reading start to drop when heat is
applied. A simple way to apply heat is to place the thermistor bulb between your thumb and
another finger and apply pressure. The heat from your body will cause the resistance reading to
decrease. If the thermistor reading starts to decrease with heat applied normally that indicates
the component is functioning properly. The resistance reading will increase if ice is placed
against the bulb. Typical resistance values are 11.4 – 14K ohms at 59 degrees ⁰F, 6.4 – 7.7K ohms
at 86 ⁰F, 3.6 – 4.5K ohms at 113⁰F, 2.2 – 2.7K at 140 ⁰F or 0.6 – 0.8K at 221 ⁰F.
If thermistor readings are correct re‐install this component into the thermistor well. Next re‐fire
the unit to see if you still get a code 34. If so, proceed to item #3 below.
3. Verify the unit is connected to the proper gas type; see rating plate for gas type of unit.
4. Check to ensure this unit has ever been converted from one gas type to another? If it was
converted verify conversion was performed per manufacturer's specifications. See conversion
procedure for the model number unit at your location.
5. Verify proper clearances were maintained around unit and vent terminals.
6. Verify all dip switches are set per manufacturer' recommendations, contact Rinnai for details on
proper settings if you need assistance.
7. Verify force low and high fire manifold gas pressures, check using a manometer. Procedure for
checking these pressures can be found on the back side of the front cover. If you need
assistance contact Rinnai technical services 24/7 for details on now to check these pressures.
You must have a manometer to check operating gas pressures.
8. Inspect burner manifold, burner assembly and heat exchanger copper fins for debris build‐up or
blockage.
9. Verify venting is within vent clearance specifications and lengths per manufactures'
recommendation.
10. If code 34 still appears after performing the above inspections, replace thermistor.
Code 34 Troubleshooting Procedure
Combustion air temperature thermistor (Internal units ONLY)
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