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How to fit thermo fan bypass switch

nick88

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doesnt the vs have a low/hi speed fan aswell? i think depending on the temp it either spins 'slower' or 'faster'??
correct me if im wrong tho...
Nick
 

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doesnt the vs have a low/hi speed fan aswell? i think depending on the temp it either spins 'slower' or 'faster'??
correct me if im wrong tho...
Nick

yep, again, check the site above for info on the wiring.
 

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I think that's the same with the VN V6 too - fan comes on low speed if you put the air con on, high speed if it's getting hot. Can't remember where I read that...

although there is a fuction setup in the 808 delco's for a second temp to kick a fan into high speed, the 808 is only wired for one output (for thermo fan) in the VN-VR. so unfortuntly it's a one speed setup only. if it was a two speed setup there would need to be 2 relays to switch the power supplies for the different speeds on the fan. in the VN-VR V6 the thermo fan is switched on for the A/C (it's the same output and circuit). for the VN-VR V8's it still switches the same output on the ecu and uses the same circuit as the V6 setup although instead of having a large thermo fan there is an auxillary fan just for the A/C. it would be fairly simple to convert the V8's to an electric thermo fan setup as all the wiring is there(it's just used for the A/C fan which you could remove if you had an electric thermo fan), you would just need to get the tune modified (memcal) to have it switching the thermo on and off at the appropriate temps etc
 

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I think that the ECM does switch the auxilliary electric fan on the VN-VR V8 in response to high(er) engine temperatures so it might be used to directly control a thermo fan if swapped, without a rewritten MemCal if the temperature that it switches at is low enough.

For a thermo fan swap on a V8 or to alter the switch on point of the V6 fan this:

Jaycar Electronics

with the input voltage taken from the coolant temp sensor and wired instead of a manually operated switch would allow whatever switch on temperature is desired. Using it to switch in and out this:

Jaycar Electronics

would allow two speed fan control.

If you want to cut the fan out above a certain road speed, use this:

Jaycar Electronics

with a speed sensor signal.

(No, I don't own shares in Jaycar).
 

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I think that the ECM does switch the auxilliary electric fan on the VN-VR V8 in response to high(er) engine temperatures so it might be used to directly control a thermo fan if swapped, without a rewritten MemCal if the temperature that it switches at is low enough.

i haven't personally tested this theory on a V8, however i have checked the standard V8 memcal which has the same temp settings as the V6(for thermo cooling fan). as both the thermo fan setup for the V6 and aux A/C fan for the V8 use the same circuit from the ecm one could possibly assume that if you were to wire a V8 with thermo fans into the A/C circuit that they would work. (you could probably remove the A/C fan if using thermo fans to cool engine as they are much more efficient then any little A/C fan)

however to test you would possibly need dissable the viscous coupling fan temporarily to check that the A/C fan does come on with elevated engine temps.

you could use an external type controller to change the temps that the thermos activate however there isn't much point unless you run a cooler thermostat otherwise the thermos would be on a lot of the time when there not really required. in the memcal the thermo won't run when the vehicle is moving faster then 40kph because the natural airflow through the radiator is greater then what the thermofan can pull through the radiator, this however is a problem for people entering burnout comps because the vehicle is stationary but the ecm thinks it's moving and doesn't require the thermofan to cool the engine. for those with the ability to alter there own tunes they can set there thermofan on and off temps to suit the thermostat that they run.

i have considered wiring the bypass switch into the relay circuit for the line locker so when doing burnouts i won't have to manually switch the thermo fan on (when i get around to fitting the line locker that i've had sitting in the garage for 6 months)

if i get a chance i may try and test this theory on a mates VN V8 that he's currently fixing from frontal impact damage. if we can confirm this works it would definitly simplify this conversion for others in the future
 
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Cheap6

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i haven't personally tested this theory on a V8, however i have checked the standard V8 memcal which has the same temp settings as the V6 (for thermo cooling fan). As both the thermo fan setup for the V6 and aux A/C fan for the V8 use the same circuit from the ecm one could possibly assume that if you were to wire a V8 with thermo fans into the A/C circuit that they would work.

The V8 runs cooler than the V6 (witness the radiator cap pressure ratings for each), so the switch on point may be too high for the V8 if it is the same in both. What I would like to see if setting up a V8 to run thermo fans would be the normal operating temps under a variety of conditions, with a factory set up, and then match that by setting the thermo fan switch on point or points. Access to a datalogger would help in this; a cable and Winaldl (or similar) would do.

(you could probably remove the A/C fan if using thermo fans to cool engine as they are much more efficient then any little A/C fan)

It may even be better to remove the small fan to help the flow through two bigger fans (Ford/VT/whatever) because the small fan may disturb the airflow through them.

however to test you would possibly need dissable the viscous coupling fan temporarily to check that the A/C fan does come on with elevated engine temps.

Temporarily blocking the radiator with, say, cardboard will work. As will using a spare (wrecker) coolant temp. sensor plugged in and heated. Or, applying a variable voltage potential to the sensor plug or a variable resistance across it.

you could use an external type controller to change the temps that the thermos activate however there isn't much point unless you run a cooler thermostat otherwise the thermos would be on a lot of the time when there not really required.

Or using electric fans on a V8 with the ECM controlled relay being switched at too high a temp.

for those with the ability to alter there own tunes they can set there thermofan on and off temps to suit the thermostat that they run.

That is the neatest way to do it but requires skill/knowledge and the appropriate equipment (or a favour from, or remuneration to, someone who does). ~$65 plus an hour or two of assembly for the kits may be easier/cheaper.

The line locker switch idea is good. Perhaps a latching relay, triggered manually by a momentary switch, with the latching relay disabled by a frequency switch over a set speed would also work.
 
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The V8 runs cooler than the V6 (witness the radiator cap pressure ratings for each), so the switch on point may be too high for the V8 if it is the same in both. What I would like to see if setting up a V8 to run thermo fans would be the normal operating temps under a variety of conditions, with a factory set up, and then match that by setting the thermo fan switch on point or points. Access to a datalogger would help in this; a cable and Winaldl (or similar) would do.

having just checked the standard trident thermostats,

V6 = 195degrees F (90.6 degrees C)
V8 = 190degrees F (87.8 degrees C)

optional cooler thermostat, 180degrees F (82 degrees C)

have just checked the standard settings

V6
on temp = 101.75 degrees C
off temp = 98.75 degrees C

V8
on temp = 107 degrees C
off temp = 101 degrees C

VN-VR only run single speed thermo fan although there is provision in the tune for 2 fan settings (2 speed thermo's) however there is no extra wiring in the loom that i am aware off to use this extra function

VS onwards do use a 2 speed thermo fan setup on the V6 (unsure about the V8 models as i haven't really ever looked at there wiring diagrams to compare to the V6 wiring loom)

so if you were to use the factory circuit from the ECM you would either want to have the memcal altered to switch on at lower temps or use an aftermarket controller.

no doubt Dr bob would alter a memcal to suit for a small fee but then why not spend a little extra and get a tune done by Dr bob also
 
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