I just finished an engine swap (305 to 350). The whole project lasted about 2 years, so that's how long the car has sat idle in my garage. Almost everything went smoothly at startup - the car started immediately, all the panel instruments are working ok. However, the very first think I noticed is that the fan goes on as soon as the key is moved into the "on" position and the fan stays on until the car is completely shut off. I pulled the fan switch cable from the block mounted fan switch, but the fan stays running just the same.

Anybody have a clue?

 

Did you cange the prom chip during the engine swap process?

 

nope - didn't touch it.

 

Relay might be shorted then

 

that makes sense. I didn't realize there was one, but now that you mention it -

do you know where it is located?

 

Not for your year car, no, on mine it is located right by the radiator on the passenger side.

 

check your temp sensor, is the computer giving you an error code for the temp senosr, is it connected. The fan relay is up by the master cylinder on the fire wall. Will be the one with the BIG red wire coming out of it, also do you have your A/C on when you start the car. The computer controls all fan fuctions on a 305 with one fan setup. check the temp sensor and engine grounds.

 

woops missed it in your post, ""fan switch cable from the block mounted fan switch"" I think you pulled the wrong sensor or something. Either way the computer is turning your fan on because it's a fail safe mode because it doesn't know the temp of the engine or you hooked up a "fan switch" to the temp sensor wire.

 

my car does the same thing but unsted of being on all the time mine only comes on when i turn the air on. i put a 350 in my also. and im getting a code 15 witch is low temp at the coolent temp sensor. i replaced the sensor and the same thing happens.

 

Now I know on a 350 there are 2 sensors 1 on each head i believe, one is fan switch for what would be fan #1 in a 2 fan setup and the other sensor is the TEMP sensor, SWAP sensors and unplug your battery then recoonnect and start. Maybe the temp sensor ground is bad, you might want to check for that. You know everything works because the computer turns the fan on for the A/C.

 

https://www.thirdgen.org/newdesign/tech/cool.shtml

This is the tech articale on mods and how it works.

 

Did you remove the AC? If you did you will need to ground one of the connectors. If it still hooked up are all the AC connectors hooked up? One of the pressure switches for the AC is a normally closed switch. If it's removed or unplugged the ECM will think the AC is on and turn on the fan as soon as you hit the key.

 

Sorry about not getting back to anyone sooner.

Hmmmm - now there's a distinct possibility! Yes, the AC is currently not connected, although I plan to reinstall it when things look stable in the engine bay.

Let me check into this one.

thanks!

 

I think if they were reversed, my temperature gauge wouldn't work. It seems to be working just fine.

 

Nope sorry I THINK your temp guage I belive runs off ANOTHER sensor on one of the heads.