Chosen Solution
I have two A1342 Macbooks. One has a fan that spins up like crazy everytime I turn it on and it never shuts off. That one is otherwise normal. The other is fully functional with no issues. The fan thing was really bothering me. I tried swapping the fans between the two macbooks and that didn’t help. I even tried swapping logic boards, superdrives, batteries… everything. No matter what combination of parts I use, the one has a fan that spins like crazy and the other functions normally. How is this possible? I’m pretty much stumped and any insight would appreciated.
Try this, download Temperature Gauge Pro it will tell you what the heat sensors and fans are seeing and doing. Paste a screen snapshot here for us to see whats happening. I suspect the issue is with your heat sink but without any diagnostics its hard to say for sure.
There is a temp sensor on the track pad that sometimes goes bad try replacing it.
Run AHT - you have a hardware failure, could be a blown sensor, failing fan, or overheating CPU. AHT should help you narrow the field of possibilities. By default when EFI detects any of the aforementioned hardware problems the fans switch into high speed to keep you from cooking (destroying) your CPU. If this answer is acceptable please remember to return and mark it.
