I'am pulling the 305 out of my 91 Formula to replace it with the 357 I have sitting on the stand. The drivers side head has the coolant temp sensor while the passenger side head has a sensor in the same hole as on the drivers side. This sensor has the same type of connector (flared top, single conductor, push on, squeeze sides and pull to remove) that is used on the knock sensor located below it on the block. Does anyone know what this sensor is used for. I tried to remove it but it is frozen tight in the head. Since the heads are mirror images of each other I assume it projects into the water jacket, therefore it must but used in conjuction somehow with the temp sensor on the other head but here it's just conjucture. Does anyone have a clue because I'am at a loss. Thanks in advance.

 

I think I found the answer to my own question. I believe it is the fan switch. If I'am wrong could you please confirm. Thanks!

 

temp gauge left fan switch right