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vz thermal fans?

henrytad

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hey guys, ive noticed lately that the second fan in my engine bay never turns on? even if the airconditioner is on. can someone please explain too me what triggers the second fan to turn on? also how do i check if the fans ok, electrical wise?
 

richardpalinkas

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Second fan turns on at 110 degrees, when it starts to over heat, the highest temp your car would get to is 108
 

henrytad

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Ok sweet. My car generally hovers around 96 degrees, so it's normal for that fan to be off even if the aircons running at full blast
 

Stewlz

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It should come on with a/c regardless. Check your fuses
 

henrytad

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Both fans?
 

Sabbath'

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Check your fan relays aswell.
 

Luke52

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It should come on with a/c regardless. Check your fuses
Wrong.

Courtesy of Torquative from my thread last year. I always re-quote this when a thread appears regarding VZ thermo fans, because it's excellent info.

Conditions for Stage 1 Fan Operation

1 The Engine Cooling Fan Relay 1 is turned ON when :

- Air Conditioning request indicated (YES) and the vehicle speed is less than 30 km/h
-Air Conditoning pressure is greater then 1 500kPa (so no, it wont turn on just because the AC is on unless the pressure is above 1 500kPa)
-Coolantg temperature is greater than 104 C OR
-An engine coolant temperature sensor failure is detected by the PCM OR
-When the ignition switch is turned from ON to OFF and the engine coolant temperature sensor is above 117Cm the ECM will continue to engergise tyhe Engine Cooling Fan Relay 1 (R7) for approximately four minutes

2 The ECM switches OFF Enging Cooling Fan Relay 1 when the following conditons have been met:

-Air Conditioning request not indicated (NO) and the coolant temperature is less than 99C OR
-Air conditoning request indicated (YES) with pressure less than 1 700kPa, vehcile speed greater than 50 KMh and coolant temperature less than 99 C

Conditons for Stage 2 Fan Operation

The ECM determines when to enable the Engine Cooling Fan Relay 2 based on inputs from the ECT sensor

1 Engine Cooling Fan Relay 2 is turned ON if the Engine Cooling Fan Relay 1 has been energises for one second and the following conditions have been met:

-if there is a ECM message response fault, setting DTC P1258
-an ECT sensor failure is detected by the ECM.
-Engine coolant temperature is above 108C OR
-Air conditioning pressure is greater than 2 000kPa

2 If Stage 2 has been enabled, the ECM reverts to Stage 1 operation when:

-The Engine Coolant Temperature is less than 103C and
Air conditoning request not indicated (NO) OR
Air conditoning request indicated (YES) and the pressure is less than 1500kPA
So basically, the second fan is really only a back-up and kicks in if the engine is getting really hot, the first fan fails, or the A/C needs an extra kick.
 

Torquative

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that info is directly from the genuine Holden workshop manual :idea3:

also - dont mind the typo's - was typing that late at night. Might have been easier to just upload a screenshot of the document

So basically, the second fan is really only a back-up and kicks in if the engine is getting really hot, the first fan fails, or the A/C needs an extra kick
And bingo - old cars like the Ecotec would work in the way everyones mentioned above, ie turn the AC on and it'll kick in, but the alloytec is different. Theres a few threads on here where people have done all sorts of things to turn it on, from changing relays to shorting out relays to removing the fan completely and checking on a test bed.

Ultimately unless your car is overheating or your AC is about to blow its load, that fan aint gonna turn on and in all my time Ive only ever had that fan turn on once, which was in the Adventra after going up a hill towing a 2 tonne load, and that was after we parked for a pie and switched the engine off - I assume it was above 108 degrees as above.
Not even a track day in 40 degree temps got it going in the Acclaim because it never got hot enough to do it, nor in any of the other VZ Alloytecs there on the day
 

henrytad

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Ok thanks heaps guy for the info, especially torquative for the original.. Now I no, lol
 

veetwin4me

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I was having issues with my AC not working when the car was stationary. Turns out the Second fan was not kicking in. Closer investigation found that one of the pins on the 4 pin plug on drivers side of radiator was not making contact and had been arching. Fixed this up and AC works perfectly now :)
 
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