22 replies to this topic

[SmacT]

G'day all, I am getting my memcal done for the 304i I have slotted into my LX four door. It is a VN V8, from a SVLE HSV Commodore. Part of the tune concerns switching on my AU Thermo fans. I want to stagger the fan activation, and after talking to the bloke tuning the memcal, figured we could have one fan come on using the fan condenser pin, and the other switch on (at a higher temp) using the thermo fan pin, which is unused on the VN v8 but still there as the V6 uses it.

Anyone see a problem with this? I figured one fan on at 90 degrees, the second coming on at 95 and both off around 87 (standard VN thermostat).

This way the fans don't draw massive power on start up as they would if they both came in together, and I won't be running both fans when one will do the job.

For the wiring, I was thinking the two trigger wires to separate mini fused relays (30amp), draw power from the starter motor or alt D+ (battery is in the boot). Again, anyone see a problem with this? Seems a logical way to do it, but I can't find anyone else who has done it this way so perhaps there is a reason why... Open to suggestions!

[76lxhatch]

I'm not sure if that's possible directly using the A/C output with a standard program (if it is then not a problem, go with it). There is at least one more modern replacement program that your tuner could use which has flex tables attached to auxiliary outputs, these can be used to trigger relays and others have used them for fans.

As far as power draw for starting two fans at once that shouldn't be an issue, just make sure they each have their own relay.

[SmacT]

Thanks fellas. Yep Viper, it's a big-ass cable back to the battery.

76LXHatch, there is a video floating around here showing these fans drawing over 60 amp for a split second on start-up. You are right, it can be handled, but I figured one fan will do the job most of the time anyway.

I will let you know how I go.

[EunUCh]

You could try leaving the original set up to run one fan, then run another wire from the ecu o/p from the first relay  through another sensor of higher

cut in temp to then trigger a relay for the second fan.

Got no idea how much current the fan switch from ecu can source but high impedance relays would help.

[76lxhatch]

As you use a relay the current draw is no more than is required to energise it, the ECU can handle this on the outputs designed for it without a problem.

Obviously with the fans drawing that much they would either need a relay each, possibly 40A (standard are 30A), or a very big relay. I'd be inclined to run two as it will be cheaper and takes away the single point of failure.

I'm not sure what the issue is with drawing the current all at once, the starter draws a lot more than that so if your electrical system is not up to it then you have bigger problems. I imagine the factory's reason for staging the fans has more to do with refinement and the noise they make.

Did you find a suitable way to trigger the A/C output based on temperature alone?

[EunUCh]

This might work if o/p from ecu goes high and the extra temp.sens. ts2 is normally open.

 

 

[76lxhatch]

The idea is to run a second output from the ECU so the temperature can be programmed (also allows hysteresis), without the need for additional temp sensors.

[SmacT]

Hi guys,

I ended up having the ecu programmed to trigger one fan from the thermo fan pinout and the other from the ac condenser. Problem is, I can't find the ac condenser pin -out in the ecu. I can't get hold of the guy who did the chip for me.

Anyone know which VN v8 ecu pin out is right for the ac condenser fan? Or isn't there one? It looks like the latter.

[76lxhatch]

The output should be pin C2 on a VN, B8 is the request input.

Depending on the car that the loom came from some connectors are missing from the plug, although I would have thought that A/C would be in all of them whether used or not.

[SmacT]

Thanks 76LXHatch, you are a font of knowledge. I will check both input and output are there.

Loving your build thread too.

Thanks again!

[SmacT]

Mmmmm, the car came with air con, but neither B8 or C2 are connected.

Maybe I will just trigger both fans at the same time from the thermo pin out of C1 and see if it works, rather than staggering them.

[76lxhatch]

Seems a shame if you've actually got the program on the memcal switching it. With a tiny screwdriver its not hard to pop the connectors out of the plug, so if you can find another one that's unused you can steal a connector/wire. I don't suppose its a manual so you could use the TCC? It is a proper HSV with a knock sensor, are you using that?

[SmacT]

Hi 76lxhatch,

Yes, having slept on it, it would be better to make it work. I am not sure where the input for the B8 input comes from, I have already changed a few wires, it's pretty easy. I will have a look tonight. And yes, using a knock sensor and yes, it's a manual. What's the TCC?

[76lxhatch]

TCC = Torque Converter Clutch, normally both manual and auto will have the wire/connector in A7 for this, except in manual models it will go to the diagnostic plug and nowhere else since it isn't needed. Since its a manual you could remove that connector/wire and use it for the secondary fan output.

[axistr]

Sam the diagram in Eunuch post unfortunately from my understanding wont work. The ECM fan trigger wire has a constant output of 12v, when the ECU programed temperature is reached the terminal becomes earthed. I have used a separate 30amp relay for each fan. The 86 terminals would need to be connected to the power supply and the manual over ride through a separate relay to earth. The 87 terminal must only have ignition power or the fans will work with the key off.

[SmacT]

Thanks fellas.

76LXHatch, I could use that spare wire for the output, but where does the input for b8 come from?

Lenny, I have gone with the wiring my local auto sparky drummed up for me, using power from the same wire as powering the fusible link. He was ok with that, but I am not sure he understood me as he did the loom off a dummy I made up. Where else should I take the power from?

[76lxhatch]

I would guess that B8 comes from the A/C switch in the dash so the ECU knows it should be on? Presumably your memcal should just switch the output pin on and off without anything else, but I just wondered if there was some electrical requirement that this be high at all times to make it work?

[SmacT]

Ok - I found the B8 wire in a spaghetti ball of old wires, I had removed it as I figured I didn"t need it. Probably should have checked that before having the memcal set up for that. Duhhh.

If I run a wire from the temp sensor in the front of the block to the B8 input in the computer, will that work to trigger the new relay, fed from C2 in the ecu? Or isnt it that simple. Geeze I suck at electrical.

[SmacT]

Sorry mate, we must have posted at the same time.

I assumed B8 needed an input from a sensor to trigger C2 temp-wise. I have connected up C2 to the fan relay and see if it works when I start the car in the near future.

[76lxhatch]

Sounds like you're on to it, can't hurt anything by trying with just the output connected to the fan relay and hopefully that will do it. If no go then ask the the guy that did your memcal for a bit more info

[SmacT]

Thanks for your help fellas, invaluable as usual.