All right. For those of you following all of my alternator problem threads: I ran a ground wire directly from the battery negative cable and the alternator case, as suggested by NO DOUBT, in case I had a "floating ground". I also checked the battery cells with a hydrometer to see if my battery had a dead cell. Battery checked out okay. Also checked out the 3-wire plug wires that go on the alterator, with the ignition switched on, as suggested by my auto electric guy. He said two of the wires should light up a test light bright, and one would light it up dim. I checked this out. All was as he said. On a side note: One thing puzzled me (I am not real electronically literate, mind you) when I checked the voltage of these 3 wires with a volt meter, the two that lit up bright were 12.0 and 12.5 volts, but the one that lit real dim was 12.3 volts! I told the auto electric guy that, and he said that that was normal, and he couldn't explain it to me without getting into stuff I wouldn't understand. Anyway, I thought that the wire that lit the test light dim would have been around 6 volts or so. Anyway, went for a test drive, monitoring the voltage again with a voltmeter in the cigarette lighter socket. Start up.....14.4 volts.......settling down slowly......drive for a couple of miles........voltage settles in at 13.5.....just as before.........all is well. Then after about 7 miles or so.........the voltage starts creeping up slowly AGAIN!.....just as before..........once over 14, the battery light starts to flicker brightly.........when approaching 15 volts, the battery light stays solid on, bright! Pull off freeway exit ramp, slow down to stop light. Voltage drops back down. Make u-turn, get back on Freeway. Voltage is 13.5 and steady........after about 7 more miles............voltage starts creeping up and the same thing happens as above. Everytime I slow down, voltage comes back to the 13.5 for another 7 miles or so. Any more ideas????
The bad ground/floating ground issue would be something could kill your voltage regulator. However, running the extra cable from a bad alternator to the ground terminal of the battery wouldn't fix a voltage regulator that had already been damaged, though in some circumstances it might protect a good v-reg from being killed by a floating ground/bad ground. When a v-reg is failing, it can work for a bit, then fail, work for a bit, then fail, then just fail... So, the first question would be: did you try this fix using good parts? If yes, then you've isolated the problem somewhat (i.e. it's not a grounding issue if you used new/good parts as well as ran the ground cable from the alternator directly to the battery ground).
The alternator that I just put on was a newly rebuilt one with a brand new VR. The alternator that I took off, just before I installed this one was a brand new Nippon Denso Ferrari stock alternator. I believe that all the components of both alternators were good.
Have you taken any of the supposedly "bad" alternators and had them tested for 20 to 30 minutes on a bench? Actually spun up for that long? And voltage and draw tested?
It sounds to me like there is a voltage supply issue, more likely on a + circuit (since you have helped to eliminate any possible issues on the ground circuit). Generally the way the hitachi and denso 3 wire voltage reg works is as follows: First is a Ign + wire. It switches the alternator (regulator) on when you turn on the Ign. (Probably your 12.0V wire, often marked "I") Second is a battery sense wire. This is the one the regulator uses to sense the true battery voltage and regulate the alternators output voltage. (Probably your 12.5V wire. Often marked "B" or "S"...No joke) Third wire is your warning light wire. (Normally marked "L") This is the one that tricks people often. Unloaded it may measure 12V per say, but when you connect a test light, the light seems to glow dim. That's because your grounding the warning light on the dash board with your test light. ie, 2 bulbs in series. The warning light is turned on and off by the regulator. When the alternator starts charging it applies an equal 12V+ potential to the L wire, extinguishing the light. If there's a V potential difference, the lamp can glow, flicker or turn on fully. A few things come to mind that could be happening in your car. 1. An Intermittent short circuit in warning light wire between the dash and the alternator. (Unlikely) 2. Battery sensing wire has an intermittent connection issue. (Possible) 3. Ign wire "I" has intermittent connection to the alternator. This could be anywhere in the fuses, fuse box, relays, or wiring. (Quite Possible) 4. Battery sensing wire "S" has an open or itermittant connection issue. (Quite Possible) 5. Main alternator output wire (14 gauge~ wire on 6mm stud) has intermittant open or hi-resisatnce circuit problem. (Quite Possible) 6. Warning light circuit (to or in the dash and connectors) has an open or itermittant connection issue. (Quite Possible) 7. Combination of 2,3,4,5, 0r 6. (Ign or simliar relay?? I need to look at a wiring diagram for the car) 8. No other suggestions of the top of my head without going over the car with a mulitmeter, but will think about it some more and post what comes to mind. Cheers Br
Nice work above! His measured circuit voltage (@ cig lighter) begins increasing after about 7 miles of driving. That should rule out option #3 above, yes? Ditto for #1, 2 (well, it's a duplicate of #4), 6, 7, and 8, I'd think. If so, that leaves options #4 and #5 above, as he's already ruled out any potential grounding issue.
I re-read your post.. (AZFerrari) Next test I'd perform is to check if the battery is seeing the same voltage as your ciagrette lighter when the w/light comes on after a short (no pun intended) drive. You might need to run a piece of (fused!) twin core cable from the battery to your voltmeter inside the car to get some idea of true battery Voltage readings. Br
Yes quite possibly, but the cig lighter voltage may not represent true Alt. output or battery Voltage. VD testing (Thats Voltage Drop :-O) is the best and fastest way to find these issues, but kinda complex to describe without the car in front of you. These fault finding problems can be really tricky to fix by remote ;-) but I'm all ears for ideas too!
Can he safely short his sensing wire to his output wire to test to see if he has a problem in the circuit connecting to the sensor wire?
That's good thinking, but I wouldn't short the wires together in (the unlikely) case there is something odd going on further down one of those 2 circuits. (All though at the end of the day they are common connections, I would be cautious in advising to back feed either one.) However, providing he has less than 0.25V drop on the main output wire, he could make up a small jumper wire to connect directly to the sensing terminal (Remove the current sense wire from the alt connector and plug the jumper into it). The only thing about doing it this way is it's kinda taking shots in the dark at finding the problem, rather than performing systematic testing and visibly seeing (with a voltmeter/multimeter) where a true fault is. What I would do is perform voltage drop test with the car off and then idling between each terminal of the alternator and the battery + terminal, and various ground points. B - and engine, chassis and dash. If at this point no problem is found, I'd take the next step of running 4 wires from the alternator and 2 from the battery (they only need to be 22 gauge or lighter wire, phone cord?.., as we're only testing Vdrop, there will be no load on these test wires) to the passengers seat and perform voltage drop tests on each of those circuits, while driving AND when the problem is occuring. The good thing about the the fault in this car is it isn't completely intermittent so should be relatively easily traced. To measure for true loaded Voltage drop or bad intermittent connections, test with a multimeter directly between the Battery + terminal and various alternator input wires, not between ground and measured voltage at each wire. Please ask if any of this doens't make sense! Cheers br
