Carrier 58MVP Troubleshooting Manual page 10

HIGH-FIRE TEMPERATURE TOO LOW—Generally, this indicates the HIGH/LOW solenoid in gas valve GV has
failed or furnace is extremely underfired.
STEP
Turn power off and remove blower access panel. Make sure thermostat is NOT
1.
calling for heat.
Depress door switch. Use a piece of tape to hold switch closed. Wait a few sec
2.
for self test before proceeding to next step.
3. Set thermostat to call for heat or jumper R and W/W1 thermostat terminals.
When GREEN LED4 is ON solid, clock low-fire gas rate. You have 16 minutes
4.
on this first call for heat. On propane installations, check manifold pressure.
When YELLOW LED3 is ON solid, clock high-fire gas rate. On propane installa-
5.
tions, check manifold pressure.
6. Is high-fire rate approximately same as low-fire rate?
Do you have 24 vac across gas valve terminal HI and Com on furnace control
7.
board during high fire?
You have an open wire or bad terminal on BROWN wire from furnace control
8.
board to gas valve GV. Repair it or replace the harness.
Go to page number indicated in Index for CLEANUP AND START-UP
9.
INSTRUCTIONS.
10. Replace gas valve.
11. Is high-fire rate within 2% of that specified on rating plate?
Ensure gas inlet pressure and burner orifices are correct, then adjust gas valve
12.
to proper rate. If it cannot be adjusted to proper rate, replace gas valve.
13. Check outdoor condensing unit for operation during heating cycle.
Check temperature rise with blower door in place. Temperature rise should be
mid-range or slightly higher than midpoint of range stated on furnace rating
14.
plate. If return temperature is below 60°F, condensation may form on heat ex-
changers. If left uncorrected, failure will result.
15. Check return-air ducts in unheated spaces for leaks.
LEDs 1, 2, 3, or 4 ON SOLID (Solid means on continuously.)
• RED LED1 ON SOLID indicates furnace is operating in emergency heat.
• RED LED2 ON SOLID indicates microprocessor has malfunctioned or secondary voltage to furnace control board is low.
• YELLOW LED3 ON SOLID indicates furnace is operating in high fire.
• GREEN LED4 ON SOLID indicates furnace is operating in low fire.
STEP
1. Turn power off and remove blower access panel.
Turn power on and depress door switch. Use a piece of tape to hold switch
2.
closed.
3. Jumper R and W/W1 thermostat terminals on furnace control board.
4. Is RED LED1 ON?
5. Is setup switch SW-4 labeled EMER. HEAT in ON position?
6. Put setup switch SW-4 labeled EMER. HEAT in OFF position.
7. Replace furnace control board.
Go to page number indicated in Index for CLEANUP AND START-UP
8.
INSTRUCTIONS.
9. Disconnect jumper wire across R and W/W1 thermostat terminals.
10. Is RED LED2 ON?
11. Do you have less than 17 vac between R and Com on furnace control board?
12. Do you have less than 90 vac between P1 and P2 on furnace control board?
Make sure wire gage between main fuse box and furnace complies with wire
13.
size specification in Installation, Start-Up, and Operating Instructions.
14. Fix problem.
15. Disconnect R thermostat lead.
16. Is RED LED2 ON?
17. Replace transformer.
Check thermostat wire gage between furnace and thermostat, and furnace and
outdoor unit. It is recommended that AWG No. 18 color-coded copper thermo-
18.
stat wire be used for lengths up to 100 ft. For wire lengths over 100 ft, use
AWG No. 16 wire.
19. Disconnect all thermostat leads from furnace control board.
Put setup switch SW-1 in ON position and jumper R, W/W1, and Y/Y2 thermo-
20.
stat terminals.
21. Does RED LED2 turn OFF?
22. Put setup switch SW-1 back in OFF position.
10
YES NO GO TO
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7 11 —
10 8 —
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— — INDEX
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13 12 —
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YES NO GO TO
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— — 4
5 9 —
6 7 —
— — 8
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— — INDEX
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11 32 —
12 19 —
13 15 —
— — 14
— — 8
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17 18 —
— — 8
— — 14
— — 20
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22 7 —
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