Last night on an hour long trip to my parents house i noticed about 20 min into the trip that my coolant temp was above normal. Normally the temp is between 200-220.(no matter what the temperature outside is) It was a beautiful sunny day in the 70s.... the temp of my coolant got as high as 237 and would sometimes come down to 216 when i could get out and get some cool fresh air in front of me. the DIC never prompted an overheating issue nor a check engine or low coolant level.

when i got to the house i checked the coolant and the level was fine but neither fans were running. i shut it off and let it cool down for an hour. Started it back up and watched the temp rise to 200 with out the fans kicking on...

whats my next course of action...? I havent checked the DIC for any codes yet...is there one i should look out for if the fans arent operating normally???

thank you guys...Don

 

Don,

Try putting the a/c on and see if the fans come on. The fan on set point is around 180 when a/c is on and it is something like 220 with a/c off.

 

maybe the fuse, or the relay going out to power the fans?

 

are either of these things hard to find???? thanks

 

Here is a good post with the schematic : http://forums.corvetteforum.com/1570759773-post11.html

I think they are located in the engine fuse box

 

thank you.....

 

Here is the theory of operation from the Service Manual with fan turn on and turn off temps.


Cooling Fan Control

The engine cooling fan system consists of two electrical cooling fans and three fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage and ignition 1 voltage from the underhood electrical center. The ground path is provided at G102.
During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan 3 relay and the right cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the cooling fan 2 relay and the cooling fan 3 relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 3 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan 2 relay coil is energized closing the relay contacts and provides battery positive voltage on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.
The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).

Bill

 

What Bill said. If you are not using your AC, the fans won't come on until 226deg F. Turn on the AC and that drops to 180. So turn on your AC, and then if the fans don't go on with coolant above 180deg, worry about relays and such.

 

FYI, fan grounds go through the ground pack at the right forward top frame rail adjacent to the hood riser.

 

Yuppers

 

What could possibly be the engineering rationale for waiting until 226deg F to turn low speed fans on??? I've had my first Corvette about 2 months and it makes me very nervous to see the temp hand pass 220F. The only way I can keep it under 220F is to run the A/C, which will then keep it down around 185F? (By the way, how are the marks on the temp guage delineated? .. by 5's or 10's?) The other day, in a traffic jam the temp got up to about 230 and I was extremely nervous. I've already checked and both fans are operating on que as should. Also, is it typical for GM engines to rise and fall like this? My 3 Infinitis all will hold a stable temp well below the half mark endlessly while in traffic jams, with the A/C either on or off.

 

The operating temp has to do with overall engine performance emission function. If you are using the proper oil, and the cooling system is fuctioning properly, there is no problem with these temps. My GMC truck doesn't vari, but it isn't a Vette.

Mark