Carrier 58MVP Troubleshooting Manual page 22

STEP
Turn power off and disconnect jumper wire across R, W/W1, and W2 thermo-
51.
stat terminals.
Connect 1 side of a slope manometer with a tee to collector box pressure tap.
52. Connect other side with a tee to gas valve air pressure fitting. Refer to pressure
check diagram in Appendix C.
Turn power on and wait several sec, then jumper R, W/W1, and W2 thermostat
53.
terminals on furnace control board.
Monitor slope manometer. Does pressure reading appear to be stable when
54.
fault occurs?
Replace pressure switch assembly. If problem persists, check wiring for an in-
55.
termittent connection in high-pressure switch HPS circuit.
56. Check for a sag in vent pipe. If problem persists, replace inducer motor.
Fault Code 32
LOW-PRESSURE SWITCH FAULT—This fault can occur under the scenarios shown below. Keep in mind that
whenever the furnace control board shuts unit down, gas shuts off immediately, inducer continues running
for 15 sec, and if blower is running it remains running at low-heat speed or reduces to low-heat speed for
selected off delay.
• CALL FOR HEAT—If low-pressure switch LPS is made when a call for heat is initiated, furnace control board flashes Fault Code 32 until
switch opens, then cycle begins.
• LOW HEAT
1. PREPURGE—If low-pressure switch LPS does not make within 45 sec after call for heat is initiated, furnace control board starts flashing
Fault Code 32, shuts unit down, waits 2 minutes, stops flashing Fault Code 32, and restarts heating cycle.
If low-pressure switch LPS opens before ignition, furnace control board starts flashing Fault Code 32 and ramps inducer RPM up until
low-pressure switch LPS remakes. When low-pressure switch LPS remakes, furnace control board stops flashing Fault Code 32 and
continues heating cycle. If low-pressure switch LPS does not remake within 45 sec after opening, furnace control board continues flashing
Fault Code 32, shuts unit down, waits 2 minutes, stops flashing Fault Code 32, and restarts heating cycle.
2. STEADY-STATE—If low-pressure switch LPS opens during low heat, furnace control board starts flashing Fault Code 32, shuts unit
down, waits 2 minutes, stops flashing Fault Code 32, and restarts heating cycle.
• HIGH HEAT
1. PREPURGE—If low-pressure switch LPS does not make within 45 sec after call for heat is initiated, furnace control board starts flashing
Fault Code 32, shuts unit down, waits 2 minutes, stops flashing Fault Code 32, and restarts heating cycle.
If low-pressure switch LPS opens before ignition, furnace control board starts flashing Fault Code 32, shuts unit down, waits 2 minutes,
stops flashing Fault Code 32, and restarts heating cycle.
2. STEADY-STATE—If low-pressure switch LPS opens during high heat, furnace control board starts flashing Fault Code 32, shuts unit
down, waits 2 minutes, stops flashing Fault Code 32, and restarts heating cycle.
STEP
1. Turn power off, remove blower access panel, and disconnect R thermostat lead.
Turn power on and depress door switch. Use a piece of tape to hold switch
2.
closed.
3. Is inducer motor MTR1 running?
4. Are inducer motor MTR1 and blower motor MTR2 running?
5. Jumper R and W/W1 thermostat terminals on furnace control board.
6. Observe operation of furnace through 1 heating cycle.
7. Does fault occur again?
8. Does a different fault occur?
9. Go to page number indicated in Index for fault code flashed.
Go to page number indicated in Index for CLEANUP AND STARTUP
10.
INSTRUCTIONS.
11. Does fault occur within 5 sec after a call for heat?
Do you have 24v between N.O. (Normally Open) contact on low-pressure
12.
switch LPS and Com on furnace control board?
13. Replace furnace control board.
14. Is low-pressure switch LPS wired correctly?
15. Rewire low-pressure switch LPS per wiring diagram.
16. Replace pressure switch assembly.
22
YES NO GO TO
— — 52
— — 53
— — 54
55 56 —
— — 8
— — 8
YES NO GO TO
— — 2
— — 3
4 5 —
13 49 —
— — 6
— — 7
11 8 —
9 10 —
— — INDEX
— — INDEX
12 17 —
14 47 —
— — 10
16 15 —
— — 10
— — 10