Carrier 58MVP - 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.
10