Carrier 58MVP User Manual
Page 10
NOT ENOUGH COOLING AIRFLOW—Generally, this indicates the Y/Y2 thermostat lead is not properly
connected.
STEP
ACTION
YES
NO
GO TO
1.
Remove blower access panel and depress door switch. Use a piece of tape to hold switch closed.
Wait a few sec for self test before proceeding to next step.
—
—
2
2.
Make sure thermostat is calling for cooling. If thermostat lead G is not connected, jumper across
thermostat terminals R and G.
—
—
3
3.
Make sure thermostat fan control is in AUTO position if equipped.
—
—
4
4.
Do you have 24v across Y/Y2 and Com on furnace control board?
8
5
—
5.
You have a defective thermostat, or a break in wiring between thermostat and furnace, or the Y/Y2
thermostat terminal is not wired to thermostat.
—
—
6
6.
Fix problem.
—
—
7
7.
Go to page number indicated in Index for CLEANUP AND START-UP INSTRUCTIONS.
—
—
INDEX
8.
Are air conditioning select switches A/C set to proper tonnage as required by condensing unit? (See
Table 1.)
10
9
—
9.
Set air conditioning select switches A/C for proper tonnage as required by condensing unit. (See
Table 1.)
—
—
7
10.
Disconnect the G thermostat lead or jumper if used.
—
—
11
11.
Does blower motor turn off in 90 sec when G thermostat lead is disconnected?
12
13
—
12.
Replace furnace control board.
—
—
7
13.
Observe operation of furnace in cooling mode for 8 minutes.
—
—
14
14.
Does furnace operate properly in cooling mode?
15
16
—
15.
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
furnace control board. If problem still persists after replacing furnace control board, contact your dis-
tributor.
—
—
INDEX
16.
Does furnace abruptly go through a self-test sequence as blower comes up to speed?
17
24
—
17.
Do you have less than 17 vac between R and Com on furnace control board?
18
24
—
18.
Do you have less than 90 vac between P1 and P2 on furnace control board?
19
20
—
19.
Make sure the wire gage between main fuse box and furnace complies with wire size specification
in Installation, Start-Up, and Operating Instructions.
—
—
6
20.
Disconnect the R thermostat lead.
—
—
21
21.
Do you have less than 17 vac between R and Com on furnace control board?
22
23
—
22.
Replace transformer.
—
—
7
23.
Check the thermostat wire gage between furnace and thermostat, and furnace and outdoor unit. It is
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.
—
—
6
24.
Press down on microprocessor chip and make sure it is properly seated to furnace control board. If
it is, replace furnace control board.
—
—
6
Table 1—Air Conditioning (A/C) Airflow Setup Switch Position
AIR CONDITIONER
(TONS)
AIRFLOW
(CFM)
A/C SWITCH POSITION
ALLOWABLE FURNACE MODEL SETUP
A/C-1
A/C-2
A/C-3
040
060
080
080
100
120
Default
1200 or
2000
OFF
OFF
OFF
3 Tons
1200 CFM
3 Tons
1200 CFM
3 Tons
1200 CFM
5 Tons
2000 CFM
5 Tons
2000 CFM
5 Tons
2000 CFM
1-1/2
600
ON
OFF
OFF
X
X
X
—
—
—
2
800
OFF
ON
OFF
X
X
X
X
X
X
2-1/2
1000
ON
ON
OFF
X
X
X
X
X
X
3
1200
OFF
OFF
ON
X
X
X
X
X
X
3-1/2
1400
ON
OFF
ON
X
X
X
X
X
X
4
1600
OFF
ON
ON
—
—
—
X
X
X
5
2000
ON
ON
ON
—
—
—
X
X
X
X—Indicates allowable selection.
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