1994 Pontiac Firebird cooling fan only works when A/C is on

[quote="markrob76"]Other Category problem
1994 Pontiac Firebird 6 cyl Two Wheel Drive Automatic 115000 miles

My son bought this car last summer the cooling system was in real bad shape. I used permatex cooling system flush and flushed it 2 times also replaced 2 frost plugs that were bad also repaced the block drain plugs with t handle drain plugs to make it easy for working on cooling system. The problem that I am having is the coolpng fan will not kick in when the block reaches temp. To turn on fan but if the a/c is on the fan runs with the a/c compressor. I have tried unpluging the coolant temp sensor to get the fan to turn on but nothing happens. I have also checked the fuses and relay and they seem fine. I have found a TSB on alldata #61-65-64 Cooling Fan-Revised Elec. Circuit Diagram. And still nothing. If you have any information on this I sure would be greatful. OK I just spent 2 hours going through test checking out the elec. And have determind that the problem is somewere between the coolant temp sensor plug and the coolant fan relay. I have constant power at the relay and ing on power. When the relay is out I can manually jump it and get the fan to run. Looking at the wiring dia. It shows coolant temp sending unit for the gauge with a single DK green wire and a coolant temp sensor with a yellow wire and a black wire. This sensor I can't find anywhere or the motor. If you have any input I sure could use it. Thanks Bob M. Just sloved the problem. Some one took out temp sensor for the ECM and put a pipe plug in it. I found the wire plug tuck under upper intake manifold. Just shows you that some people should not work on cars thanks for site and hope that I can help others out with their problems.