Mid & High-Efficiency (B) - Rheem 64DV Troubleshooting Manual

56 | P a g e S V C 8 2 0 ( P ) P o c k e t M a n u a l
Explanation: Heat exchanger temperature too low
for more than 3 minutes.
Diagnostic Checks:

Inlet & heat exchanger thermistors

Gas control valve

Water volume control valve
Inlet thermistor Diagnostics:
Go to 31 – Error Code.
Heat Exchanger thermistor Diagnostics:
Go to 32 – Error Code.
measure resistance across #1 wire (Red)
Remove connector K . Using the BLACK WIRE
as the common – Individually check resistance for
Continue to diagnostic chart
on next page.
56
29 – Error Code (B)
HINT: ALWAYS diagnose thermistors before
continuing to next steps.
Turn power OFF.
Remove connector R and
and #2 wire (Black):
40-80 OHMS
Yellow, White, Red, & Blue wires:
0.8K – 2.4K OHMS
Replace gas control valve.