I posted this up in the cooling section and after a day and a 1/2 I haven't garnered a response so hopefully you guys can help me.

I have a '91Z with the 5.0 and dual fans. I have troubleshot different things and they all seem to work. The relay, the fans, some of the wiring.

They even work if I jumper the aldl. I replaced the computer and they still don't come on when they should (at all).

Since they work with the ALDL jumper that tells me that the wiring from the computer to the relay on through to the fan is all good.

I replaced the temp sensor in the head with a new delco part so I know that is good. What wire at the computer can I check to see if its getting the temp signal and what would I check for.

Any help is appreciated. Everything from the computer to the fans seems good, the computer is replaced, and the temp sensor is new. Am I correct (or at least accurate) to assume that it would then be somewhere between the temp sensor and the computer.

 

Check your temp sensor for an infinite resistance reading. If so, it is bad. Basically when checked cold it should read a higher resistance and as it heats up the resistance gets lower. These type of sensors generally work or they don't. They do not work out of calibration. If you are unsure, remove it. Let it get to room temp. Connect your ohm meter and then dip it in hot water. The resistance should immediately begin to decrease. Keep in mind the fans are not supposed to come on until it reaches 210 or so. It may seem as if it is too hot but this is normal. Don't trust your factory gauge for an accurate reading. These F.I. cars are made to run at these temp windows. If you make them run too cool they will drink gas and cause a whole host of other problems.
Good luck

 

And only one of the two fans is under ECM control. The other turns on via the head temperature switch at about 228*F, or when the A/C is run.

RBob.

 

Got it... lol it worked. My gauge is just DRASTICALLY off. It pegs all they way red for a few minutes before they come on.

I had been scared to over heat it and finally said screw it. They work but, like I said, my gauge is WAY off.