Alternator Not Turning On/Charging, No CEL, Oil Pressure or Battery Light at Gauge Cluster. Pls Help

Question

2000 Honda Prelude. ELD and Internal Voltage Regulator equipped. Ok guys, need your help. The car starts, runs good. I have pulled DTCs from the ECU and ABS CU. Only one persistent DTC comes up from the ECM and that's for a P1459 (evap incorrect purge flow) and 3 come up in the ABS CU, one is a 61-01 which is for Battery Voltage Failure. One of my issues is that I have No Charging. Alternator is not turning on. Car runs good and everything, while the battery has some juice to keep it running lol 😆 I have been trying to figure this out and I'm still a bit stuck. I get the following readings on the 4 terminals of the C101 green plug connector that plugs up to the alternator .03v at #1, 12v at #2, 5v at #3 and 0.00v at #4 with the Ignition Switch @ On. Idk if these are normal readings or not I've been running thru diag tests for the Alternator, and also removed it off the car and went to get it Tested and was told it's good 🤷‍♂️ After that, I re-installed it making sure the belt tension was set If you look at the photos/video which can be seen at the Links at bottom of post, you will see that the Check Engine, Oil Pressure, and Battery Light Do Not Light Up like the others at the gauge cluster. I have already ruled out the bulbs being burnt out I'm thinking that something in the wiring is causing these lights to not turn on? Idk if that would cause the Alternator to not kick on or not. Been seeing that apparently on some cars, the alternator will not kick on if the Charging Indicator Light on the cluster is not lighting up 🤷‍♂️ Lastly, today I did some Voltage Drop testing on the Alt and the last time I did them I got the following readings: 12.55v at the battery posts with the Car Off4.22v with the leads on the battery + post and alternator B+ stud with Car Off-3.77v with Car On & Idling I checked all the fuses, they all had normal 12vI checked the starter & engine wire harness cables at the fuse box and they had 12v too. I checked voltage at the Alt. with the Car Idling and got 15.85 up to 16.06v there, but when I checked the battery voltage after this, the car was still running off just battery power, 12.14v, so even though I saw up to 16V at the Alt., it wasn't sending anything over to the battery I tested the rectifier of the Alt. by checking how much AC Voltage was there and also in Diode mode, seems to check out Major TIA if you can help me out, have done just about everything up to this point, myself, and don't really want to take it to an auto mechanic or electrical guy #projectprelude #projectcar #h22 https://drive.google.com/file/d/13T-aWWpxZeGFJs03GT5tyRo_B4f1mJWK/view?usp=drivesdk https://drive.google.com/file/d/13izkELIN4aSjZQTFXLG3JvVG9EpzkKjX/view?usp=drivesdk https://drive.google.com/file/d/12pchgB2B_PTsGgfKSp0hOtvRCizrov6d/view?usp=drivesdk https://drive.google.com/file/d/1384fC31e5IXF0y_G0Z3KXJOf7dAHsavT/view?usp=drivesdk https://drive.google.com/file/d/1321Dweb4DxfHoUUsUu90wt6GzBr1o5fY/view?usp=drivesdk https://drive.google.com/file/d/13kqepWxaN8OatBdMQidIT1mAYQNVfoFd/view?usp=drivesdk https://drive.google.com/file/d/13B81HcGCjlCd97dvCg39RPdacG2i7Fw4/view?usp=drivesdk

BruceREE · Accepted Answer

So. Its been a while and IDK if your issue is the same as a honda that rolled into my shop, but first check fuse 15 under dash again in then in the engine compartment, check to see if the 90A fuse in the engine compartment box is blown. If those two are not any issue, if I remember correctly, look real close at that wiring and follow the black/yellow from the alt 4 pin. After snaking around the engine compartment there should be a bracket that I think was under the intake manifold. In that general area see if the harness was rubbing on anything causing a short. That is apparently a problem on older honda's that was a bitch and a half to find out lol

fernandobb6 · Answer

@BruceREE First off, thanks for taking the time to view the question 👍. So, for my Prelude, it's Fuse No.14 (15A) under the dash and Fuse No. 32 (100A). They seem to be good. They read out 12V and the filaments look fine

I'm getting 12V at the Blk/Yel wire at the Alt plug

i know exactly what bracket you're talking about lol. I think it's a support for the intake mani, and yea it's right under the intake mani. I saw a video on YT the other day and the 15A fuse was blown on that Honda so he replaced it, thought he was done. But nope, some cable was rubbing on that bracket causing the wire to be a little rough-looking, and a Short, which was what caused the Fuse to blow probably

I'm going to check that out in a bit and see what's going on there. Also going to go over some grounds. I think it's going to be that I, too have a wire rubbing on that bracket, Or my Internal Voltage Regulator on the Alternator is bad.

I tested the voltage at the Alt just a bit ago, and I got 12V at the B+ of Alt with engine off. But with the engine on, same location gave me ~15.7 all the way up to 16.4V and it seemed like the reading would change erratically on my Meter. I think it's too much V and the ECM is shutting off Battery Charging to protect the systems

Also, with the green Alt harness plug connected, there seemed to be ~3.85 Voltage Drop. But, if I unplugged it, the reading would drop way down to like 0.15V {black}:surprised: