Carrier 58MVP Troubleshooting Manual page 9

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
1.
hold switch closed. 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 con-
2.
nected, jumper across 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
5.
furnace, or the Y/Y2 thermostat terminal is not wired to thermostat.
6. Fix problem.
Go to page number indicated in Index for CLEANUP AND START-UP
7.
INSTRUCTIONS.
Are air conditioning select switches A/C set to proper tonnage as required by
8.
condensing unit? (See Table 1.)
Set air conditioning select switches A/C for proper tonnage as required by con-
9.
densing unit. (See 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
15.
on an intermittent basis, replace furnace control board. If problem still persists
after replacing furnace control board, contact your distributor.
Does furnace abruptly go through a self-test sequence as blower comes up to
16.
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
19.
wire size specification 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 recommended that AWG No. 18 color-coded copper ther-
23.
mostat 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 fur-
24.
nace control board. If it is, replace furnace control board.
Table 1—Air Conditioning (A/C) Airflow Setup Switch Position
AIR CONDITIONER AIRFLOW
(TONS) (CFM)
1200 or
Default
1-1/2
2
2-1/2
3
3-1/2
4
5
X—Indicates allowable selection.
A/C SWITCH POSITION
A/C-1 A/C-2
OFF OFF
2000
600 ON OFF
800 OFF ON
1000 ON ON
1200 OFF OFF
1400 ON OFF
1600 OFF ON
2000 ON ON
ALLOWABLE FURNACE MODEL SETUP
A/C-3 040-14 060-14
3 Tons 3 Tons
OFF
1200 CFM 1200 CFM
OFF X
OFF X
OFF X
ON X
ON X
ON —
ON —
9
YES NO GO TO
— —
— —
— —
8 5
— —
— —
— — INDEX
10 9
— —
— —
12 13
— —
— —
15 16
— — INDEX
17 24
18 24
19 20
— —
— —
22 23
— —
— —
— —
080-14 100-20
3 Tons 5 Tons
1200 CFM 2000 CFM
X X
X X
X X
X X
X X
— —
— —
2
3
4
—
6
7
—
7
11
—
7
14
—
—
—
—
6
21
—
7
6
6
—
X
X
X
X
X
X