Cooling fan problems

[Robertsdad]

I came to Virgina to visit my son that's in the Navy, but all we've done is try to figure out what's wrong with his radiator cooling fans. It's a 93 we've replaced the sensor and tested the fans, they work. But not when the cars running. Any suggestion?????

 

[Rob]

Welcome to the Corvette Action Center. I'm going to move your thread into the C4 tech forum for greater exposure...

 

[ecss]

I came to Virgina to visit my son that's in the Navy, but all we've done is try to figure out what's wrong with his radiator cooling fans. It's a 93 we've replaced the sensor and tested the fans, they work. But not when the cars running. Any suggestion?????

The fans are controlled by the ECM.
The Primary fan comes on around 226F and the Secondary at around 235F.
To verify the fans can be controlled by the ECM.
Take a piece of wire and connect pin A to Pin B on the diagnostic connector located above the drivers right knee.
Turn the ignition On. Don't start the engine. This puts the ECM in diagnostic mode.
Both fans should run.

Connector pin out.

 

[Robertsdad]

These things we have checked

The fans are controlled by the ECM.
The Primary fan comes on around 226F and the Secondary at around 235F.
To verify the fans can be controlled by the ECM.
Take a piece of wire and connect pin A to Pin B on the diagnostic connector located above the drivers right knee.
Turn the ignition On. Don't start the engine. This puts the ECM in diagnostic mode.
Both fans should run.

Connector pin out.

We have done the fan test in and out of the car. We checked the fuses, replaced the temperature sensor that controls the fans. The plugs going to the relays are hot. Not sure how to test the relays or what to do next

 

[hcbph]

On the relays, looks like on the primary if you supply power to F and D to ground then A to E could be a complete circuit. Same thing with the secondary as they look to be the same relay based on the shot from the FSM.

 

[ecss]

We have done the fan test in and out of the car. We checked the fuses, replaced the temperature sensor that controls the fans. The plugs going to the relays are hot. Not sure how to test the relays or what to do next

You need to be provide more information.

Is this a new problem?

Why do you say the fans don't work is the engine over heating?

Be more specific on how you tested the fan relays relays.

There is no need to remove the fans or relays to verify their operation.

Do you have a volt meter?

Are you saying you connected Pin A to Pin B on the diagnostic connector and turned the ignition On the fans do not run?

If not you ground the Dark Green/White wire at the relay socket and turn the ignition On.
The Primary fan should run.

For the Secondary fan you ground the Dark Blue/White wire turn the ignition On and the Secondary fan
should run.

If both test pass the ECM is probably bad.

Only other test would be to verify the ECM has a bad ground.
If the engine or transmission have recently been pulled it's possible the ECM ground was not reinstalled.
It's bolted to a transmission to bellhousing stud on the driver side.

Which temperature sensor did you replace? The Engine Coolant Temperature Sensor is located on the water pump driver side.
It has a Yellow and Black wire on the connector.

Other methods to force the fans on.

If you remove the ECT sensor connector and leave it unpluged and jump the Yellow and the Black wires together that will simulate a temperature over 266F. When you start the engine both fans should run.

The ECM will also turn the fans on if the AC high pressure is over reaches 189 psi (shouldn't take more than 20 seconds) no matter what the engine temperature is.

 

[Robertsdad]

You need to be provide more information.

Is this a new problem?

Why do you say the fans don't work is the engine over heating?

Be more specific on how you tested the fan relays relays.

There is no need to remove the fans or relays to verify their operation.

Do you have a volt meter?

Are you saying you connected Pin A to Pin B on the diagnostic connector and turned the ignition On the fans do not run?

If not you ground the Dark Green/White wire at the relay socket and turn the ignition On.
The Primary fan should run.

For the Secondary fan you ground the Dark Blue/White wire turn the ignition On and the Secondary fan
should run.

If both test pass the ECM is probably bad.

Only other test would be to verify the ECM has a bad ground.
If the engine or transmission have recently been pulled it's possible the ECM ground was not reinstalled.
It's bolted to a transmission to bellhousing stud on the driver side.

Which temperature sensor did you replace? The Engine Coolant Temperature Sensor is located on the water pump driver side.
It has a Yellow and Black wire on the connector.

Other methods to force the fans on.

If you remove the ECT sensor connector and leave it unpluged and jump the Yellow and the Black wires together that will simulate a temperature over 266F. When you start the engine both fans should run.

The ECM will also turn the fans on if the AC high pressure is over reaches 189 psi (shouldn't take more than 20 seconds) no matter what the engine temperature is.

This issue has been on going for a while. Took it to the dealership and they didn't fix the issue. We took the fan and radiator out to check and make sure they weren't the cause. Everything seems to work and all the tests we perform go as planned but no different out come. When I turn the car on and drive it or let it sit at idle it overheats. We will check the ECT connectors and after that I am kind of at a lost as to why my fans don't come on when the car hits the right temps?????

 

[Hot Rod Roy]

The plugs going to the relays are hot.

If the relay sockets are hot (temperature), focus on that problem! Check for burned wires to the sockets, or scorched electrical contacts in the sockets. If the relay itself is hot, it may need to be replaced.

 

[ecss]

The temperature of the ECT sensor can be displayed on the dash cluster by repeatedly pressing the Gauges button until you see coolant displayed.

If you monitor that display the primary fan should come on around 219F and the secondary fan around 226F.

When the ECM commands the fans on, it monitors the Dark Green/White wire and the Dark Blue/White wire.
When the relays are commanded on the voltage on the wires should change from 12 volts to 0 volts.

If they don't the ECM sets DTC 28. This does not turn on the Service Engine Soon/ Malfunction indicator.

If you short Pin A to Pin G on the diagnostic connector and turn the ignition On, any DTC's will be displayed on the dash cluster LCD.
Module 1 is the CCM
Module 4 is the ECM
Module 9 is the ABS/TSC

If the ECM does not command the Primary fan on and the digital coolant display is around 219F the ECM is bad.
You could reseat the four connectors at the ECM and see if that makes any difference.

92 and 93 ECM's which are the same are know to have bad solder connections on the circuit board and cause
intermittent problems.