Service manual

06/2010
1. Remove the wire ties, metal tape, and old thermister. Clean off the old heat sink and be sure
copper is wiped clean.
Note : T-in thermistor position changed on newer models. Current location is on the same tube
forward of the PRV where the pipe makes a 90 degree vertical at the copper heat exchanger.
2. Apply heat sink compound to copper tube.
3. Place the thermister into the heat sink compound. Wrap metal tape around the tube and
thermister.
4. Take the two wire ties. One goes around the wires as a strain relief. The other goes near the
thermister (about 3/8” away from the head) to hold the thermister against the tube. CAUTION:
Do not place the tie wrap over the thermister tip as this may crack the thermister, and Do
not over-tighten the wire ties.
5. Check the resistance across the thermister leads. Under room temperature conditions the value
should be between 700 - 1100 ohms. A further check may be to compare the resistance
measurement to the other two thermisters. If all thermisters have been exposed to the same
temperature they should be within 50 ohms.
6. Route the blue wire leads over the modulating valve keeping the wires away from the burner.
Wrap the harness together and connect into the thermister harness that goes back to the control
board.
7. Perform a test of the unit. Refer to SM500-16 ‘Testing the RV500’.
Kit Parts List:
1436 T-in thermister assembly
Figures:
none
Model: RV500-F-L / RV501-F-L
SM500-08 T-mid Thermister Change Procedure
Other service documents required:
SM500-16 Testing the RV500
Tools Required:
14 mm open end wrench (or adjustable)
9/16” open end wrench
1. Remove old thermister. CAUTION: Use two wrenches: one on the hex (9/16”) of the thermister
and one on the hex (14 mm) located on the heat exchanger fitting. Failure to do so may damage
the heat exchanger.