I have a 93 Camaro Z28. The cooling fans will not come on. I have taken the relays out and used a jumper to connect the two terminals and the fans power right up. However when i turn the ignition on and the AC on the fans do not come on. Also, when the car heats up they do not come on. I have replaced the relays so its not the relays. Another thing, when this started the other day the Service Engine Soon light comes on about 10 seconds after starting the car. I assume this is related. However, I do not have a code reader. Anyone have any ideas? My buddy from VA sent me some info he had when he had a similar problem, I will attach it.

 

u can get the trouble codes out using a paper clip. this is from the lt1 fax and tech section. has lots of good stuff. do a search on here see what comes up.
1993- Still using the old ECM. Codes can be flashed by shorting the A & B terminals on the diagnostic connector. Turn the key ON, but do not start the engine

 

u might as well replace the temp sensor. i show oem part# 25036979. its in the water pump. make sure they dont give u the temp gage sensor.

 

I am having the same problem and don’t know why my computer won’t turn the fans on (I suspect a lack of motivation). I think I’m going to buy a kit that allows the fans to turn on without the PCM having anything to do with it. Check out these fan wiring kits http://www.jegs.com/c/Cooling_Electric-Fan-Wiring-Kits-Senders/11471/10002/-1

If you prefer to troubleshoot and figure out why the fans aren’t turning on, here are some actions you can take. Like me, you probably don’t own a scan tool that allows you to compare the temperature the PCM is detecting with the temperature that the temp gauge on the dash reads. This would be the best thing if you were able to do it. If you cannot do that, you can try testing the coolant temp sensor (ECT) and the voltage (5 vdc) at its connector harness http://shbox.com/1/temp_sensor1.jpg , the three fan relays, and the temp gauge sender and the voltage at its connector harness http://shbox.com/1/temp_sensor2.jpg.

Here are two helpful links to help you perform these tests:
http://shbox.com/1/4th_gen_tech2.html#ect
http://shbox.com/1/4th_gen_tech2.html#cooling

What I did to test my ECT was to put it in a pot of hot water and compare the resistance values with the temperature of the water. Here are the resistance values and the corresponding temperatures http://shbox.com/1/4th_gen_tech2.html#ect. Keep in mind that the ECT will begin to cool off as soon as you pull it out of the water and try not to burn yourself if you do it. Since you already checked the fuse box, you can check the three fan relays by swapping them out with three others of the same value or perform voltage tests on their leads (repair manuals should say how to do this – the Haynes repair manual does). I think the ABS relay is the only one that is different from the fan relays.

One last thing you can do, and this is purely theoretical and possibly crazy on my part, is to simulate a hot ECT. I don’t know if you could potentially damage your PCM by doing this, but I don’t think so since it would be the same circumstances as an extremely hot ECT. The ECT is a thermistor and its resistance decreases as the heat increases. So, you should be able to fake a super hot ECT that exceeds fan turn on temp by connecting the two leads in the ECT harness connector with something that has close to zero ohms resistance. In fact, if you know the corresponding resistance for the fan start temps, you can hook a resistor of that value to the ECT connector harness. If this action turns the fans on, then you know that the PCM is capable of getting a reading and starting the fans when a certain temp is reached. Again, this is just my theory and not an official test that I know of. Remember, you can always buy a programmer to reset the fan on/off temps or a fan kit like I’m looking at.

I would like to give a shout-out to craby since he like reading my posts.

 

^^^ all good ideas, hay mr x good to see your still here. been a while.

 

Thank you guys so much for you input! After reading Mr. Exacto's post I saw he said 3 relays. I was only messing around with 2 Relays.. after a closer look I found a 10 amp fuse that was marked fans and was blown! This fuse must have blown when i was messing around with the primary fan. Now the secondary fan comes on when i turn the ignition on but the primary doesnt come on... When im driving the temp gauge is below half.. when I idle it goes up to between half and red... Here are some pics.

 

thats pretty normal, second fan should come one when it gets to were its at in the second picture maybe a little sooner. thats how my first camaro was. i have the prom tuned for the 160 thermostat so it hangs around were your first picture is all the time.

 

I forgot to mention the fan fuse. Wouldn't the SES light come on if that fuse is blown? I've pulled my fan fuse out before and I remember my SES light coming on. Anyway, I'm glad you fixed it.