Test 3: Continuity Check Of High Limit (Eco) - A.O. Smith SERIES 120 Service Handbook

TEST 3: CONTINUITY CHECK OF HIGH LIMIT (ECO)

Conditions:
• Power On – No Hot Water
• Red, heater control "Call for Heat" LED – on
• Red ignition control board diagnostic LED – 4 Flashes
• Note LED Flash Code before resetting water heater control.
• See Ignition Control Board: Error Codes.
• Turn Power OFF.
TEST 3
IF.........
continuity is indicated
(ZERO "0.0" Resistance)
continuity is not present
(meter reads "0.L")
water is less than 120° F
Servicing should only be performed by a Qualifi ed Service Agent
TROUBLESHOOTING
Figure 22
Continuity check of ECO
(energy cut-off, high limit)
Black to Black wires of upper probe.
Power is off.
Then............
opens at 203° F; closes at 193° F. If water is below 193° F, continuity is correct.
replace ECO sensor if water temperature is below 193° F.
• reset status LED should be on.
• replace heater control if control will not manually reset.
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