Bradford White M-I L6DS electric tanks have upper and lower thermostats. Failure pattern tells you which.
Symptoms
- Upper: no hot water at all
- Lower: hot briefly then lukewarm
- High-limit reset (red button) tripped: reset once; if trips again, thermostat failure
Replacement
- Shut off power, verify
- Remove access panel
- Photograph wiring
- Disconnect 4 wires
- Release retaining clip with flathead screwdriver
- Install new thermostat — firm tank-wall contact is critical
- Reconnect wires per photo
- Reset high-limit, restore power
Bottom line
$30-$45 part, 45-min DIY. For other parts see parts hub.