Carrier 58MVP 170 Series - Status Code 24 Continued; Diagnosing Wiring Shorts for Status Code 24

STEP ACTION YES NO GO TO
17 Replace the pressure switch assembly. 7
18 Is the high heat pressure switch HPS wired correctly? 20 19
19 Rewire high heat pressure switch HPS per wiring diagram. 7
20
Replace the pressure switch assembly and replace the vari-
able speed furnace control.
7
21
Check the inducer PWM line. To do this disconnect PL11
from the inducer motor and connect a DC voltmeter across
terminals PL11-2 BROWN (+) and PL11-10 YELLOW (-)
then run COMPONENT TEST by turning setup switch
SW1-6 ON. Does voltage across PL11-2 and PL11-10
change between states as shown below?
- State 1 - OFF (1.0 - 4.0 vdc)
- State 2 - MED (7.0 - 10.0 vdc)
22 15
22 Replace inducer motor or inducer motor assembly. 7
Status Code 24
SECONDARY VOLTAGE FUSE IS OPEN - Indicates fuse is open and there is a short in low-voltage wiring.
STEP ACTION YES NO GO TO
1 Turn power off and remove the blower access panel. 2
2
Is secondary voltage fuse blown? Check continuity to make
sure.
53
3 Replace variable speed furnace control. 4
4
Replace secondary voltage fuse if necessary then go to
page number indicated in Index for CLEANUP AND
START-UP INSTRUCTIONS.
INDEX
5
Disconnect all thermostat leads from the variable speed fur-
nace control (including all wires connected to the HUM ter-
minal) and replace secondary voltage fuse.
6
6
Replace the fuse, turn power on and depress door switch.
Use a piece of tape to hold switch closed.
7
7 Does status code 24 flash? 8 12
8
Turn power off and disconnect PL1 from variable speed fur-
nace control.
9
9
Do you have continuity between either RED wire connected
to the limit circuit and chassis ground?
10 3
10
You have a short circuit in the limit switch circuit. This in-
cludes limit switch LS, and flame roll-out switch FRS.
11
11 Fix problem. 4
12
Disconnect the pressure tube from the collector box and
jumper R and W/W1 thermostat terminals.
13
13
Does status code 24 begin flashing when W/W1 is ener-
gized?
14 21
14
Turn power off and disconnect PL1 from variable speed fur-
nace control.
15
15
Do you have continuity between the YELLOW wire con-
nected to the low heat pressure switch LPS and chassis
ground?
16 3
16
You have a short circuit in the low heat pressure switch cir-
cuit.
11
17
Does status code 24 begin flashing when the HUM terminal
is energized?
Note: On the variable speed furnace control the HUM termi-
nal is energized when the blower turns ON.
318
18
Disconnect jumper wire across R and W/W1 thermostat ter-
minals and wait until inducer stops.
19
19
Disconnect the pressure tube from the collector box and
jumper R, W/W1, and W2 thermostat terminals.
20
20
Does status code 24 begin flashing when W/W1 is ener-
gized?
34 37
21
Reconnect the pressure tube from the pressure switch as-
sembly back to the collector box.
22
22
Does status code 24 begin flashing when the low heat pres-
sure switch LPS is energized?
23 26
23
Turn power off and disconnect PL1 from variable speed fur-
nace control.
24
18