Does anyone know why the ECU has an input from the fog light relay? it is pin 1S on the S5 ECU.
the only thing i can think of is BACV adjustment, so it can compensate for the extra load?

 

actually, what i really want to know is why my fog lights are not working, even though the input/output at the relay checks out fine with a multimeter, and the fog light bulbs are not burnt out?

i am not getting any power at the actual fog lights...even though there is power/ground at the relay...??

wiring diagram says the wire goes directly from the relay to the fog lights, so only thing i can think of is somehow that wire got damaged?

i hate wiring on these cars........

 

Hmm, Canadian cars got DRL, not fog lights.
So not sure what you are trying to do.

If it was fog lights, then they only work when the headlights are on.

 

You're right, it's for idle load compensation. That's why the ECU also has inputs for the headlights, rear defroster, interior fan, power steering and A/C.

If you suspect a broken wire, use a DMM to check continuity.

 

yup, i'm aware they are DRL, but they are also fog lights operated by the switch when headlights are on low beam. in any case, i have bypassed the DRL unit so i can turn them on without headlights, and it was working for quite awhile before they just stopped working. i'm getting the proper voltage and ground continuity at the relay, but my lights aren't actually coming on.

i'm not quite sure if there is a difference in checking continuity between fog light and relay, because i checked continuity across the relay (on the N.O-COM side) and it was fine, so that must mean it is grounded properly. oh well, i will check tonight...

 

alright, i've done testing with a multimeter. i will refer to the diagram below of the fog light relay:



with the fog light switch on:

R/Y on the right to R/L is 12V (this is the coil side of relay)

R/Y on the left to R/B is 12V (this is the switch side of the relay, N.O-COM)

R/B to fog light connectors have continuity.


so why the hell aren't my fog lights working? i am getting no power at the connector....

 

Well pull the plug off the relay. Jumper the RY to the RB and the lights should come on If they don't then the bulbs are burnt out.............or the gnd for the lights is kaput..........or you have a open wire b/t the relay RB wire and the lights.

 

yup, i did jumper the wire and lights did not come on. and i'm testing voltage over the actual connector, so it's not an issue of my light being burnt out. however, i found something odd: i tested current accross the R/Y to R/B and it was very low, about 100mA i think. normal current should be well over 10A, should it not?

 

Jumper directly from the battery positive post to the RB wire and the lights should come on. IF they do, then you have a sorry connection somewhere on the RY wire.