Not Enough Cooling Airflow - Carrier 58MVP Troubleshooting Manual

NOT ENOUGH COOLING AIRFLOW—Generally, this indicates the Y/Y2 thermostat lead is not properly
connected.
STEP
Remove blower access panel and depress door switch. Use a piece of tape to hold switch closed.
1.
Wait a few sec for self test before proceeding to next step.
Make sure thermostat is calling for cooling. If thermostat lead G is not connected, jumper across
2.
thermostat terminals R and G.
3. Make sure thermostat fan control is in AUTO position if equipped.
4. Do you have 24v across Y/Y2 and Com on furnace control board?
You have a defective thermostat, or a break in wiring between thermostat and furnace, or the Y/Y2
5.
thermostat terminal is not wired to thermostat.
6. Fix problem.
7. Go to page number indicated in Index for CLEANUP AND START-UP INSTRUCTIONS.
Are air conditioning select switches A/C set to proper tonnage as required by condensing unit? (See
8.
Table 1.)
Set air conditioning select switches A/C for proper tonnage as required by condensing unit. (See
9.
Table 1.)
10. Disconnect the G thermostat lead or jumper if used.
11. Does blower motor turn off in 90 sec when G thermostat lead is disconnected?
12. Replace furnace control board.
13. Observe operation of furnace in cooling mode for 8 minutes.
14. Does furnace operate properly in cooling mode?
Make sure outdoor unit is properly charged. If it is, go to page number indicated in Index for
CLEANUP AND START-UP INSTRUCTIONS. If problem persists on an intermittent basis, replace
15.
furnace control board. If problem still persists after replacing furnace control board, contact your dis-
tributor.
16. Does furnace abruptly go through a self-test sequence as blower comes up to speed?
17. Do you have less than 17 vac between R and Com on furnace control board?
18. Do you have less than 90 vac between P1 and P2 on furnace control board?
Make sure the wire gage between main fuse box and furnace complies with wire size specification
19.
in Installation, Start-Up, and Operating Instructions.
20. Disconnect the R thermostat lead.
21. Do you have less than 17 vac between R and Com on furnace control board?
22. Replace transformer.
Check the thermostat wire gage between furnace and thermostat, and furnace and outdoor unit. It is
23. recommended that AWG No. 18 color-coded copper thermostat wire be used for lengths up to 100
ft. For wire lengths over 100 ft, use AWG No. 16 wire.
Press down on microprocessor chip and make sure it is properly seated to furnace control board. If
24.
it is, replace furnace control board.
AIR CONDITIONER AIRFLOW
(TONS) (CFM)
1200 or
Default
2000
1-1/2 600
2 800
2-1/2 1000
3 1200
3-1/2 1400
4 1600
5 2000
X—Indicates allowable selection.
ACTION
Table 1—Air Conditioning (A/C) Airflow Setup Switch Position
A/C SWITCH POSITION
A/C-1 A/C-2 A/C-3
OFF OFF OFF
ON OFF OFF
OFF ON OFF
ON ON OFF
OFF OFF ON
ON OFF ON
OFF ON ON
ON ON ON
ALLOWABLE FURNACE MODEL SETUP
040 060 080
3 Tons 3 Tons 3 Tons
1200 CFM 1200 CFM 1200 CFM
X X
X X
X X
X X
X X
— — —
— — —
10
YES NO
— —
— —
— —
8
— —
— —
— —
10
— —
— —
12 13
— —
— —
15 16
— —
17 24
18 24
19 20
— —
— —
22 23
— —
— —
— —
080 100
5 Tons 5 Tons
2000 CFM 2000 CFM
X — —
X X X
X X X
X X X
X X X
X X
X X
GO TO
2
3
4
5 —
6
7
INDEX
9 —
7
11
—
7
14
—
INDEX
—
—
—
6
21
—
7
6
6
120
5 Tons
2000 CFM
—
X
X
X
X
X
X