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E5/6 ECU – Pin21 Polarity Check.

926 views 2 replies 2 participants last post by  AndyH 
#1 ·
A quick question for the mapping peeps, to confirm the below..
According to the wiring diagrams, I have access to, the ‘Rad Fan Low’ (Pin21) wire in the EVO5/6 cars produces a 12v negative output when activated.

The trigger then completes a relay circuit with a positive value from the ignition switch, to relay/switch on the fan.

Reason for asking:
I have an E2 based car, with a remapped 5/6 ECU, but the ignition feed mentioned above was previously cut by a sparky, not long afterwards as it was blowing fuses.

I’ve been running a secondary fan switch, until now as its only really come round to the high priorities list compared to other projects.
 
#3 ·
Thanks Grants,

I think my explanation was wrong, but that's what I was expecting.

Playing it back another way:-

Ignition switched 12V [positive 12v] > relay coil > ECU pin 21 [Neg/ground],

(As you say when the ignition is ON and the ECU is reading the required temp, wire 21 sends a negative to the coil of the relay).

Said coil, when activated connects:-

Fused 12V > relay contact(s) > fan [The other side of the fan is connected to ]> ground

I just wanted to be sure it was a -ve trigger from wire 21.
 
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