Mystery yellow wire with blue stripe - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

LoSt180 · 06-14-2022, 10:35 AM

The Yellow/Blue wire from behind your alternator is the oil pressure switch that goes directly to the oil light in the cluster. Check and see if it's just not plugged in or what.

If you see a Yellow/Red wire in the same area, then that SR came from a S14 Kouki that was equipped with the triple DIN gauge pod. Y/R is for the oil pressure gauge.

RaidenKing · 06-15-2022, 05:58 AM

Quote:

Originally Posted by LoSt180

The Yellow/Blue wire from behind your alternator is the oil pressure switch that goes directly to the oil light in the cluster. Check and see if it's just not plugged in or what.

If you see a Yellow/Red wire in the same area, then that SR came from a S14 Kouki that was equipped with the triple DIN gauge pod. Y/R is for the oil pressure gauge.

Thank you for the extra input. I'm going to double check on everything you mentioned. That also gives me good reason to look further into the Y/L wire connection.

Took it out for another brief drive the other day and experienced less idle drop. Cold starts have been the best idles so far. Starts up and slowly steps down from about 1200-1500 rpm. I only experience idle issues after warm up. I have a backup P2M alternator to test out also, since the current one is old and beat.

I'm due to change oil as well since the new cams have had time to break in. Will see how the next few test runs go and come back with an update. Strangest part is just how inconsistent this has been, but further testing has confirmed idle will always drop below normal range when I turn on the AC.

I love Zilvia, you guys are awesome and thank you for helping me troubleshoot this thing.

RaidenKing · 06-24-2022, 05:29 PM

Alternator replaced, idle issue resolved. Not without drama of course, as I managed to hit the new alternator with a ratchet on accident when doing my oil afterwards. Sparks flew, and I nuked my 75A fuse. All well after fuse replaced.

Now when it dips in rpms, it recovers very quickly instead of stair stepping down to a stall.

I'm assuming the old alternator wasn't putting out enough to also power accessories, so the fans kicking on after warmup had enough draw to dip the motor for some reason. It would also explain why night drives had consistently bad idling (lights) before changing out the alt.

Also Lost180 - regarding the y/l wire, I think you were right on target with that. I changed the oil and noticed that I'm missing the oil pressure sensor. That cut wire must have gone to my now nonexistant sensor at one point of its life.

Seeing a max of about 185F coolant temps, and a lopey minor bounce off of 850 on idle. The cams are only 258's after all, but it was bizarre that this problem chose to show itself immediately after I upgraded cams and replaced intake manifold gaskets. Maybe the old alternator didn't appreciate getting drenched in coolant when I was doing manifold gaskets.

Thanks guys again, big time.

06-14-2022, 10:35 AM	#1
LoSt180 Zilvia FREAK! Join Date: May 2013 Location: MD Posts: 1,049 Trader Rating: (18) Feedback Score: 18 reviews	The Yellow/Blue wire from behind your alternator is the oil pressure switch that goes directly to the oil light in the cluster. Check and see if it's just not plugged in or what. If you see a Yellow/Red wire in the same area, then that SR came from a S14 Kouki that was equipped with the triple DIN gauge pod. Y/R is for the oil pressure gauge.

06-24-2022, 05:29 PM	#3
RaidenKing Zilvia Member Join Date: Sep 2005 Location: Jacksonville, FL Age: 36 Posts: 169 Trader Rating: (0) Feedback Score: 0 reviews	Alternator replaced, idle issue resolved. Not without drama of course, as I managed to hit the new alternator with a ratchet on accident when doing my oil afterwards. Sparks flew, and I nuked my 75A fuse. All well after fuse replaced. Now when it dips in rpms, it recovers very quickly instead of stair stepping down to a stall. I'm assuming the old alternator wasn't putting out enough to also power accessories, so the fans kicking on after warmup had enough draw to dip the motor for some reason. It would also explain why night drives had consistently bad idling (lights) before changing out the alt. Also Lost180 - regarding the y/l wire, I think you were right on target with that. I changed the oil and noticed that I'm missing the oil pressure sensor. That cut wire must have gone to my now nonexistant sensor at one point of its life. Seeing a max of about 185F coolant temps, and a lopey minor bounce off of 850 on idle. The cams are only 258's after all, but it was bizarre that this problem chose to show itself immediately after I upgraded cams and replaced intake manifold gaskets. Maybe the old alternator didn't appreciate getting drenched in coolant when I was doing manifold gaskets. Thanks guys again, big time.