Triggering/wiring AU Thermos from VN ECU
#1
Posted 12 May 2014 - 09:00 PM
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!
#2 _Viper_
Posted 12 May 2014 - 10:12 PM
If the tuner has the options in the software to turn the condenser pin output on/off at a certain temperature then it will work... And yep its a good way to do it, just depends on the limitations of his software.
And yep no probs taking the power feed from the Starter motor (which im assuming has a large power cable running directly to the battery)
#3
Posted 13 May 2014 - 05:48 AM
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.
#4
Posted 13 May 2014 - 07:32 PM
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.
#5 _Viper_
Posted 13 May 2014 - 08:38 PM
Yea ive set my Twin thermos to be staged for that reason, altho Ive just used a physical switch that is screwed into the radiator and has 2 different switching temps...
#6
Posted 21 May 2014 - 09:16 AM
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.
#7
Posted 21 May 2014 - 10:27 AM
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?
#8
Posted 22 May 2014 - 09:10 AM
This might work if o/p from ecu goes high and the extra temp.sens. ts2 is normally open.
#9
Posted 22 May 2014 - 10:36 AM
#10
Posted 24 July 2014 - 05:43 PM
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.
#11
Posted 24 July 2014 - 08:21 PM
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.
#12
Posted 24 July 2014 - 09:11 PM
Loving your build thread too.
Thanks again!
#13
Posted 24 July 2014 - 09:51 PM
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.
#14
Posted 25 July 2014 - 05:30 AM
#15
Posted 25 July 2014 - 07:48 AM
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?
#16
Posted 25 July 2014 - 08:12 AM
#17
Posted 25 July 2014 - 09:11 AM
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.
#18
Posted 25 July 2014 - 09:24 PM
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?
#19
Posted 25 July 2014 - 10:14 PM
#20
Posted 25 July 2014 - 10:15 PM
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.
#21
Posted 25 July 2014 - 10:32 PM
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.
#22
Posted 26 July 2014 - 07:37 AM
#23
Posted 26 July 2014 - 08:09 AM
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