Only 1 Thermo fan working...mostly

[Mr Scorpio]

The drivers side thermofan doesnt activate. When the motors hot the passenger side fans fires up, no action from the drivers side fan, and when it powers off the drivers side fan powers up "briefly" and matches the spin down rate of the passenger fan (get ur head around that if you can). So the drivers fan seems functional, just not activating.
Ideas anyone?

 

[accentstencil]

Do they both come on when A/C is on?

 

[Mr Scorpio]

My AC compressor isnt working, hasnt worked for a long time

 

[rambunctious]

I bought this up and it was discussed at length some time ago, and fwiw this is normal on my VZ

It appears the second fan only comes on when the engine gets really hot, which of course is probably the reason the radiators crack/blow the seal/leak on that side.

You might find more info here https://forums.justcommodores.com.au/threadloom/search?keywords=thermo+fans&tab=0

 

[Mr Scorpio]

Thanks mate

 

[BlackVXGTS]

...It appears the second fan only comes on when the engine gets really hot, which of course is probably the reason the radiators crack/blow the seal/leak on that side...

Unlikely, below are the conditions for fan operation from the Holden VZ Service Manual. The low and high fan temperature starting criteria have been at the same level from the VR/VS.

Conditions for Stage 1 Fan Operation

1. The ECM turns Engine Cooling Fan Relay 1 (R7) ON when:
• Air conditioning request indicated (YES) and the vehicle speed is less than 30 km/h;
• Air conditioning pressure is greater than 1,500 kPa;
• Coolant temperature is greater than 104° C; or
• An ECT sensor failure is detected by the ECM.
or
• When the ignition switch is turned from ON to OFF and the engine coolant temperature is above 117° C, the ECM will continue to energise the Engine Cooling Fan Relay 1 (R7) for approximately four minutes.

2. The ECM turns Engine Cooling Fan Relay 1 (R7) OFF when the following conditions have been met:
• Air conditioning request not indicated (NO) and the coolant temperature is less than 99° C; or
• Air conditioning request indicated (YES) with pressure less than 1,170 kPa, vehicle speed greater than
50 km/h and coolant temperature less than 99° C.

Conditions for Stage 2 Fan Operation

The ECM determines when to enable the Engine Cooling Fan Relay 2 (R5), based on inputs from the ECT sensor.

1. The ECM turns Engine Cooling Fan Relay 2 (R5) ON if the Engine Cooling Fan Relay 1 (R7) has been energised for one second and the following conditions have been met:
• If there is a ECM message response fault, setting a DTC P1258;
• The ECM detects an ECT sensor failure.
• Engine coolant temperature is above 108° C; or
• Air conditioning pressure is greater than 2000 kPa.
NOTE
If the large engine-cooling fan is off when the criteria for turning the small engine-cooling fan on are first met, the small engine-cooling fan will turn on 5 seconds after the large engine-cooling fan is switched on.

2. If both the large and small cooling fans are enabled, the ECM turns the small engine-cooling fan OFF (via Engine Cooling Fan Relay 2) when:
• The engine coolant temperature is less than 103° C; and
• Air conditioning request is not indicated (NO); or
• Air conditioning request is indicated (YES) and the pressure is less than 1500 kPa.

 

[lout]

when the passenger side fan turns off
most likely the fan motor then becomes a generator which then energises the drivers fan through back emf