Cooling Fans not working correctly - trying to locate relay switch

[Susan48]

My car is overheating then the second cooling fan will kick on. Parts store told me it was my relay switch. But I can't locate it. Can some one please help me?

Greatly appreciated! 

[BodybyFisher]

Please describe exactly what you mean by overheating.  Boil over?, message on dash?, gage to HOT?  

Do you have a gage or digital temp readout?

What year and model

Does your AIR CONDITIONING work? It mades a difference with how the cooling fans operate

@Susan48

[Susan48]

The temperature goes to 255+, monitoring systems says either to idle engine or stop engine. I have replaced one relay switch and it did not fix the issue.

 

Thanks

[BodybyFisher]

95 Eldorado

Don't parts replace, did the parts store see a code for fan relay?, what was the code. 

I have never replaced a fan relay yet.  

PLEASE check for diagnostic codes that might have been set.  Do you know how?  We need all P codes posted here.  ECT sensor could be a problem, but post codes

Check these items

1) coolant level, 2 inches below the cap

2) check that the coolant concentration is at least 50/50, lesser coolant concentrations boils at a lower temp

3) check that the cooling system holds pressure, it should hold 15 to 16 psi, if it only holds 9 or 10, coolant will boil.  Find the leaks and repair. Check the cap also to be sure it holds the rated pressure.  Replace the cap every few years.

4) check that the cooling fans are running, there are 2.  They run differently when the AC is on vs when it is off.  Believe it or not, you will see more stable temps with the AC on.

5) check the water pump belt for cracks, and check the tensioner for binding and that it applies tension on the belt.  If the belt appears shiny it might be slipping.

6) the thermostat can bind causing overheating, if it has not been changed it should be changed.  We prefer AC Delco stats

7) the air purge line must be clear

This is very important >>>>Buy a NAPA block tester and check the coolant for combustion by products.  If the head gasket is bad, the coolant will contain combustion by products.  You can buy the tester at Napa on line for about $50, it can be used for many many tests on multiple cars.    A bad head gasket should be eliminated before spending any money on the car.  The very first thing I do with overheating is test the head gaskets.

[BodybyFisher]

@Susan48