Lennox MPB012S4S

117
Error Code: P1
Description: Highpressureswitchopen.
General Note: Ifthesamplingvoltageisnot5V,theLEDwilldisplaythefailure.
HighPressureProtection
Checkwiringconnectionsbetweenhighpres-
sureswitchandmainPCB.
Yes
DetermineifHighpressureswitchisfaulty.
Method:Disconnecttheplug.Measurethe
resistanceofthehighpressureprotector,ifthe
protectorisnormalthevalueis0.
Yes
Makenecessarycorrections.
No
Replacehighpressureprotection
switch.
No
Checktheoutdoorambienttemperature.The
outdoorambienttemperatureshouldnotbe
higherthan50°Cor122°F.
No
Stoptheunit.
Yes
Checkiftheoutdoorunitventilationisgood
Yes
Makecorrectionstoallowforproper
ventilation
No
Checkiftheoutdoorfanrunsproperly
See Error code E8 to properly diag-
nose outdoor fan motor.
No
Yes
Checkoutdoorcoils.Theoutdoorunitcoils
shouldbecleanandfreeofanydebris.
Clean outdoor coils.
Yes
No
Replaceoutdoormainboard.
No
CheckwhethertherefrigerantsystemisOK.