Pete Whitstone Posted June 19, 2020 Author Share Posted June 19, 2020 Remember in the stock wiring scheme we run a 512 Ohm resistor in parallel to the bulb so the truck will continue to charge if the bulb burns out. Ah, good catch, I did not even notice that resistor until you pointed it out. I found some actual incandescent warning lights on ebay, I'll see if they act different when they get here. Well, I got the incandescent warning lights in the mail. But I'm stumped by the results of my testing with it. I have a quick-disconnect connector set on the LG/R wire that goes into the VR. If I unplug it, I can hear the load on the alternator ease up, and the voltage drops from 14 to 12. A voltmeter on both ends of that wire reveal that, with the truck running, the VR end has no voltage (well, almost none, the meter reads like .01). The truck end of the wire has 12v. So supplying that 12v to the VR is instrumental in getting the alternator to charge. This seems completely backwards to me. I thought when the alternator was spinning, both ends of this wire would read voltage, thus making the "no potential" situation and thus no alternator warning light. But that's not what the meter reads. Then to really confuse myself, with the engine running I hooked one end of the incandescent light to battery +, and the other end to the LG/R wire going into the voltage regulator. The alternator started charging again, indicating that current was being drawn through the light bulb. BUT THE LIGHT BULB DID NOT LIGHT!!! What the heck! Well, I guess it should not be lit if the alternator is charging, so maybe that's normal. Let's turn the engine off and it should start to glow, right? Nope. Nothing. I give up. Guess I'll be ok with a good voltmeter in the dash, which I have. Electricals are not my favorite. As someone once asked, what do you need a ground/return side for? I mean, you send current down a wire, and the energy is used to light a light bulb or whatever. So what the hell comes back on the return side? Good question... Thoughts welcome. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted June 19, 2020 Share Posted June 19, 2020 Well, I got the incandescent warning lights in the mail. But I'm stumped by the results of my testing with it. I have a quick-disconnect connector set on the LG/R wire that goes into the VR. If I unplug it, I can hear the load on the alternator ease up, and the voltage drops from 14 to 12. A voltmeter on both ends of that wire reveal that, with the truck running, the VR end has no voltage (well, almost none, the meter reads like .01). The truck end of the wire has 12v. So supplying that 12v to the VR is instrumental in getting the alternator to charge. This seems completely backwards to me. I thought when the alternator was spinning, both ends of this wire would read voltage, thus making the "no potential" situation and thus no alternator warning light. But that's not what the meter reads. Then to really confuse myself, with the engine running I hooked one end of the incandescent light to battery +, and the other end to the LG/R wire going into the voltage regulator. The alternator started charging again, indicating that current was being drawn through the light bulb. BUT THE LIGHT BULB DID NOT LIGHT!!! What the heck! Well, I guess it should not be lit if the alternator is charging, so maybe that's normal. Let's turn the engine off and it should start to glow, right? Nope. Nothing. I give up. Guess I'll be ok with a good voltmeter in the dash, which I have. Electricals are not my favorite. As someone once asked, what do you need a ground/return side for? I mean, you send current down a wire, and the energy is used to light a light bulb or whatever. So what the hell comes back on the return side? Good question... Thoughts welcome. How many watts/what resistance is the bulb you have? Link to comment Share on other sites More sharing options...
Pete Whitstone Posted June 19, 2020 Author Share Posted June 19, 2020 How many watts/what resistance is the bulb you have? That I do not know. It's a tiny little bulb. Here is what I used. https://www.ebay.com/itm/Pair-Amber-Pilot-Dash-Indicator-Warning-Lights-12V-Vintage-Classic-Hot-Rod/122306778605?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908103841%26meid%3Db180d132574a415eb339c4661c7ca9e0%26pid%3D100227%26rk%3D3%26rkt%3D10%26mehot%3Dpp%26sd%3D123560127545%26itm%3D122306778605%26pmt%3D1%26noa%3D1%26pg%3D2053904%26brand%3DUnited+Pacific&_trksid=p2053904.c100227.m3827 It says each light has about 27 ohms of resistance, but nothing about wattage. Link to comment Share on other sites More sharing options...
FuzzFace2 Posted June 19, 2020 Share Posted June 19, 2020 Let's turn the engine off and it should start to glow, right? Nope. Nothing. If the motor was off AND the key then you are right. What if the motor was off and the key on did the light light? Remember as a test to see if the light is good or not it should light motor off / key on. Dave ---- Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted June 19, 2020 Share Posted June 19, 2020 How many watts/what resistance is the bulb you have? That I do not know. It's a tiny little bulb. Here is what I used. https://www.ebay.com/itm/Pair-Amber-Pilot-Dash-Indicator-Warning-Lights-12V-Vintage-Classic-Hot-Rod/122306778605?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908103841%26meid%3Db180d132574a415eb339c4661c7ca9e0%26pid%3D100227%26rk%3D3%26rkt%3D10%26mehot%3Dpp%26sd%3D123560127545%26itm%3D122306778605%26pmt%3D1%26noa%3D1%26pg%3D2053904%26brand%3DUnited+Pacific&_trksid=p2053904.c100227.m3827 It says each light has about 27 ohms of resistance, but nothing about wattage. Ohms law works in all ways. 😉 I usually assume 14V running. Link to comment Share on other sites More sharing options...
Pete Whitstone Posted June 20, 2020 Author Share Posted June 20, 2020 Ohms law works in all ways. 😉 I usually assume 14V running. So that would be just under 2 watts I guess? What does that tell us? Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted June 20, 2020 Share Posted June 20, 2020 Ohms law works in all ways. 😉 I usually assume 14V running. So that would be just under 2 watts I guess? What does that tell us? That it's using .14A and at 98 ohms resistance is well below the 512 ohm resistor that will excite the alternator. So I don't know why it's not showing when you first turn the key to 'run' Link to comment Share on other sites More sharing options...
Pete Whitstone Posted June 21, 2020 Author Share Posted June 21, 2020 That it's using .14A and at 98 ohms resistance is well below the 512 ohm resistor that will excite the alternator. So I don't know why it's not showing when you first turn the key to 'run' Ah, now I see where you were going with that, but there was no resistor in this scenario, the light bulb was not "the path of least resistance", it was the only path. I'm stumped too. Oh well... I'll watch the voltmeter. Thanks all, for your input. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted June 21, 2020 Share Posted June 21, 2020 That it's using .14A and at 98 ohms resistance is well below the 512 ohm resistor that will excite the alternator. So I don't know why it's not showing when you first turn the key to 'run' Ah, now I see where you were going with that, but there was no resistor in this scenario, the light bulb was not "the path of least resistance", it was the only path. I'm stumped too. Oh well... I'll watch the voltmeter. Thanks all, for your input. I had no idea how much current the amber bulb filament was passing, but I did have a good idea of the threshold current the alternator needs. Link to comment Share on other sites More sharing options...
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