So how exactly do your cooling fans know when to kick on? Because mine apparently dont know... I replaced all 3 relays and the cars temp will just steady go up when Im sitting still, does fine when Im moving. I know there are 2 coolant sensors, one in the head and one in the water pump. Is it one of those?

 

Is this a LT1 car?

if yes, the fans are controlled by the PCM, which monitors temp via the sensor in the water pump

 

Same thing happened to me, I changed all 3 relays and both fan motors thinking they were drawing to much current, wrong. Do some simple tests, do either of the fans come on? Turn on the a/c or defrost and see if it turns one on. First thing is first though, check for blown fuse, if it is blown and you replace it and it blows again check for poor connections or corroded connectors. Corrosion will cause resistence in the circuit so it will start to draw more current therefore blowing the fuse.

 

Ya sorry, I forgot to mention the car....Its a 96 LT1. Im pretty sure the AC fan comes on when I turn it on, the rpm drop about 100 or so for a split second when I turn the AC on, and then it goes back to normal idle. No blown fuse it was the first thing I checked, and I went ahead and replace all the relays, but that temp still just climbs. So if I pull the sensor at the water pump out will it just look really bad or do I need to do some kind of test? What does the temp sensor at the head monitor?

 

This happened on my 95 Formula and again on my 97 WS6..

You have a coolant temperature sensor, and a coolant temperature sending unit. The coolant temperature sensor tells the PCM the (obvious) temperature of the coolant, and the sending unit simply tells your gauge the proper temperature to display.

The coolant temperature sensor went out on both of my cars and was about $11 at Autozone. It's the one below the driver's side head and comes out fairly easily. I couldn't really tell if it was bad or not by looking at it, I just bought a new one anyways and it worked. They go out after awhile. That sounds like your problem.

 

So then the computer knows when to kick the fans on by the sensor from under the head, not the one in the water pump? And thats the one I should replace?

 

The sensor in the water pump give the PCM temp info. You can read about the cooling system here .

 

My mistake Rob. I switched the two, you're right. I haven't been around an LT1 in awhile..

 

my 94 does this too..if u turn the heater on it runs at 185 if im moving 185 if ac on 185 if sittin still with nothin on 220...the fans are stock programmed to come on at 225 and 232 so from wat ive heard theres no way to get it to run cooler and the normal operatin temp is 210...so it will steadily climb to almost the red the fans will come on and it will drop to 210...then repeat...that wat i understand if some1 else has an opinion on this i would like it to run about 185 without the heater on...without putting the fans on a switch...and without changing thermostat...thanks
Daniel

 

Great page for reference! Ok so let me make sure I have this understood...
Water pump sensor = For the PCM
Block sensor = For the gauges

So assuming all else is well I should change the one at the pump?

 

Correct.

Another common failure of these cooling systems is the radiator cap. It's cheap, and you can eliminate it as the problem. They usually either lose rigidity, or become too stiff and lock up. Pick up one of those and change your water temperature sensor (the one on the water pump).

 

OK guys thanks for your help and Im gonna get on that sometime this week and Ill chceck back and let you know if that was the problem. Thanks.

 

OK..replaced the sensor today, no effect.. Any other possible solutions before I hard wire the fans somehow?

 

Are you actually overheating? Have you monitored coolant temps with a scanner?

 

No, I dont have a scanner at my disposal, but the car does become sluggish when it starts getting hot, so I assume the gauge is correct. I guess I could change the other sensor (since it only cost me $3) too, just to be sure, but then I dont know what else it could be. But then the decision becomes to put the fans on a switch or to wire them to the ignition and they will always be on.