Heat Controller SMA Service Manual page 48

Be sure all the wires(including power wires and connection wires)
Check if AC 115V (or 208-230V) power supply outputs to outdoor
Check if AC 115V (or 208-230V) exists at primary coil of
Check if AC 12V and AC 35V (+5%) exist at second coil of
transformer in the outdoor PCB
Yes
Take off the secondary plug of transformer, and then check if AC
12V and AC 35V (+5%) exist at secondary coil of transformer
Check if DC 35V exists at CN6 and 12V at CN3
Uncertain problem on indoor PCB, change it and
is OK
Yes
PCB
Yes
transformer
Yes
No
No
Transformer is defective
Check if DC 35V exists between 2 and 3 on the indoor
terminal and DC 12V between 3 and 4
Yes
Yes
check again
Heat Controller, Inc. Jackson, MI 49203
- 43 -
No
Change good ones
No
Outdoor PCB is defective
Yes
Outdoor PCB is defective
No
Indoor PCB is defective
No