Cooling fans stop working when car warms up

[truetrue]

2008 G35X
The fans work when I start the car, when it gets to operating temp and I shut the car car off and turn it back on and the fans will not then back on. It starts to slowly overheat at idle. I’m at a loss on what to do next.

Here’s what I replaced:
Cooling fans
Cooling fan controller module
Cooling fan relay
Coolant temp sensor
Thermostat

Any one have any other suggestions?

[VStar650CL]

Sounds like you need to stop throwing parts at it and break out a voltmeter for some earnest diagnosis. You can find your wiring diagram starting on EC-504 here:
https://www.nicoclub.com/service-manual ... 8%2FEC.pdf

Start by checking for power and ground at the Red and Black wires of the control module when the fans misbehave. If the power is gone the prime suspect would be bad connections in either the relay power path or the relay coil wiring. If it has power, check for signal at the Violet wire. That's a PWM signal from the IPDM and should read something above 0V when the fans are running (5V is top speed). If that has signal, then check for a non-zero voltage across the fan output connectors from the module, if those are zero then your new module is defective. If Violet has no signal then chances are the Violet wire has a problem or the fan driver in your IPDM is going south. If the fans start with an Auto Active IPDM test then you know the problem isn't in the wire or IPDM, so something must be amiss in the ECM or engine temp sensor.

[truetrue]

Sounds like you need to stop throwing parts at it and break out a voltmeter for some earnest diagnosis. You can find your wiring diagram starting on EC-504 here:
https://www.nicoclub.com/service-manual ... 8%2FEC.pdf

Start by checking for power and ground at the Red and Black wires of the control module when the fans misbehave. If the power is gone the prime suspect would be bad connections in either the relay power path or the relay coil wiring. If it has power, check for signal at the Violet wire. That's a PWM signal from the IPDM and should read something above 0V when the fans are running (5V is top speed). If that has signal, then check for a non-zero voltage across the fan output connectors from the module, if those are zero then your new module is defective. If Violet has no signal then chances are the Violet wire has a problem or the fan driver in your IPDM is going south. If the fans start with an Auto Active IPDM test then you know the problem isn't in the wire or IPDM, so something must be amiss in the ECM or engine temp sensor.

Appreciate the quick response and help, I'll tackle this tomorrow through the way you described and report back for others. Thanks again

[truetrue]

Sounds like you need to stop throwing parts at it and break out a voltmeter for some earnest diagnosis. You can find your wiring diagram starting on EC-504 here:
https://www.nicoclub.com/service-manual ... 8%2FEC.pdf

Start by checking for power and ground at the Red and Black wires of the control module when the fans misbehave. If the power is gone the prime suspect would be bad connections in either the relay power path or the relay coil wiring. If it has power, check for signal at the Violet wire. That's a PWM signal from the IPDM and should read something above 0V when the fans are running (5V is top speed). If that has signal, then check for a non-zero voltage across the fan output connectors from the module, if those are zero then your new module is defective. If Violet has no signal then chances are the Violet wire has a problem or the fan driver in your IPDM is going south. If the fans start with an Auto Active IPDM test then you know the problem isn't in the wire or IPDM, so something must be amiss in the ECM or engine temp sensor.

Doing this right now. How exactly do I check the red/black wire and violet wire? Is it through the connector that attaches to the module?

[VStar650CL]

You can check power and ground with the control module disconnected, the power should still be there even when the module isn't. The signal line is just PWM, but the pullup is inside the fan controller and the transistor is inside the IPDM, so you need to back-probe the connector with it in place to get any reading. Use a small safety pin or t-pin and slide it into the back of the connector receptacle alongside the wire.

[truetrue]

You can check power and ground with the control module disconnected, the power should still be there even when the module isn't. The signal line is just PWM, but the pullup is inside the fan controller and the transistor is inside the IPDM, so you need to back-probe the connector with it in place to get any reading. Use a small safety pin or t-pin and slide it into the back of the connector receptacle alongside the wire.

Appreciate it, ran some tests and narrowed it down to a faulty control module on the new assembly I purchased(thanks autozone). Running perfectly now with another new module. Thanks for the help

[VStar650CL]

[jim99]

Is the circuitry the same in my 2005 350z touring, 38k miles? Symptoms are the driver side fan turns on and off after a less than a minute, and the passenger one doesn't come on at all. Do both operate from the coolant temperature sensor, or is one controlled from a/c on or off? The a/c belt broke so, no a/c for awhile. Is low or high speed also a coolant temp function?

[VStar650CL]

Your Z has a relay-controlled fan, not PWM-controlled like the OP. The low speed operates by putting one winding of each fan in series, so one fan being dead will prevent both from operating. The relays are all in the IPDM, you can find the IPDM layout on PG-26 here:
https://www.nicoclub.com/service-manual ... 5%2Fpg.pdf

Run the Auto Active Test as described on PG-23. If one fan works on high but neither operates on low, the fan which doesn't work on high is bad. If both fans work but at different times and speeds, one of the relays is bad.