Okay i got a 95 z lt1.. i finally decided to hook all the fans back up the way they were meant to be. they were hooked up to the batery from the last owner. I got all three relays pluged em all in .. the fans do come on when i put the ac on wich i know is normal... i let the engine idle and it got up to about 235 before i put the air back on to cool it off... what could be causing the fans not to come on.? I was thinking the temp sending unit to the pcm. but i dont have any codes on the dash about it. or maybe the pcm? please help

 

well just replaced the temp sending unit and still the same thing so i dont know what to do now.

 

Anybody??????

 

i believe that if u have the fans hooked up stock, and the stock thermostat, the fans should kick into high at237, my lt1 usually runs between 210 and 245 depending on my speed. sometimes when sitting at a long traffic light or in traffic, it will get somewhat close to the red, but never in it. im guessing this is normal since my fans and thermostat are hooked up stock. i noticed my fans dont kick into high(where u can actually hear them) until almost 240.

 

There are two temp sensors on the engine, one to drive the temp gage, and one that talks to the PCM. You need to replace the one that talks to the PCM.

 

yes i allready replaced the one that goes to the pcm. the one on the front of the engine

 

Unplug the ECT sensor and ground the yellow lead going to the PCM. This will send a false Max high temp signal to the PCM, and the PCM will operate all 3 fan relays and both fans should now run at high speed. Power to the relay coils is through a 10 AMP fuse, power to fan relay contacts is from a fusible link. Being that the fans work with the AC, the circuitry from PCM to fans should be OK. In this case if the fans fail to work there may be a wiring or connector problem between the sensor and the PCM, or a bad PCM
Low speed operation. PCM grounds the DK GRN lead to relay #1 and the fan are connected in series through the contacts of un-operated relay #3 and run at 1/2 speed. Relay #1 provides power to both fans. Relay #2 does nothing.
High speed operation. PCM grounds the DKGRN lead to relay #1, and the DK BLU lead to relays #2 & #3. Relay #3 operates and drops the series connection between the two fans. Relay #1 provided full battery power to the left fan, Relay #2 provides full battery power to the right side fan.

The ECT sensor and the TEMP gage sender are different things, so make sure that when the ECT is changed it is the proper item.

 

will look a little more into it. i'll try the grounding of the yellow wire. however i do get the 5 volts to the sensor .... im allmost thinking the pcm. have to take it to someone that has a scanner and see if the pcm sees the temperature.

 

The scanner would be the ideal tool, it will show what temp the PCM is seeing and wether or not the PCM is ordering the fans ON. The ECT sensor is a varistor between the PCM and ground, and will take the 5 volt from the PCM and cause it to drop, the hotter the engine the lower the voltage on the yellow wire as long as the ECT is working and has a good connection to both the PCM and ground.