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Can anyone offer me some advice about an S100 ECU please? I am using launch control on pin 4 of the 4 key plug of the ECU but when I press the launch button the rad fan pulses. The rad fan is fed by a standard 4 pin relay via pin 4 (aux 2) on the 3 key ECU plug and goes to the negative terminal on the relay. Now you might think that I have the pins wired to the wrong ECU plugs as aux 2 and launch are both pins 4 but I havent. Is there anything in the DTA software on the Aux 2 page or the rad fan operation page that may be causing this? I did not build the loom but it was done professionally and worked on the previous car. I added the rad fan subloom myself. Thanks guys

The rad fan/aux2 grounds the relay, so the other side of the "trigger" (terminal 85 or 86) needs fed with 12v. Is that how you've got it wired?

Hi yes that's how I have it. I'm wondering if a wiring fault with the launch and traction potentiometer could cause it? They have black, pink and yellow wires. Can someone confirm which each is please? I have pink as +12v, black as ground and yellow as %. Thanks

Good morning, connect your pc to dta, so you say there may be a temporary short circuit when you press the button, and the ecu warns by making the fan work, a large red screen appears on the pc screen indicating that there is a short- circuit. to the connector -B- pin 4 there will be a button normally, to pin -10- Ana 1 / Traction Cut% / Launch RPM that must be the potentiometer or a multi-position switch.

Launch is by a momentary switch signal and ground. Launch pot is by a pot so 3 wires 5v, signal & ground. the pink wire is probably 5v.
I think you have a ground problem somewhere from when you moved the loom to a different application.

If rad fan control is selected in Engine Config > Sequential control does the Ana2 /Aux 2 function have to be set to active in Other Map Settings or does it take care of itself?

If Aux2 function is not checked, then the output side of Ana2 really should not operate.

I guess if it is checked...it may override the fan function ?

The Ana/Aux really need to be divorced.

Update - I've found the fault and rectified it. I had a pair if pins in a 4 way Deutsch DTM plug the opposite way round, one of which was an earth. Swapped to correct way round and all working perfectly now Thanks for all the tips. The car was mapped the day before Christmas eve and behaved perfectly once running

Good to hear it's fixed!