| MGG | -- 08-10-2017 @ 1:47 PM |
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Scenario: 1940 V-8, 6-Volts, positive ground, 2-Brush later generator with ground terminal wired to the base of the voltage regulator, good battery, new voltage regulator, new ignition wiring, new charge system wiring. Test of the generator and it shot up to 30 amps. Voltage across the battery terminals before start = 6.45 with digital meter. Voltage after running 10 minutes and engine shut off = 6.70 Voltage after 20 minutes on the Battery Tender (indicating full charge), engine shut off = 6.64 Voltage 30 minutes later with engine shut off = 6.51 My meter was too jumpy to get anything across the terminals while the engine was running. Question: The original dash volt meter never got fully into the green area while running, only to the very edge of it, yet the battery after starting and running the engine for only 10 minutes appears to be at, or nearly at, full charge. Is this within the accuracy range of the gauge or do I still have a charging problem? I did not run any lights or other accessories. Thanks - Mark G. This message was edited by MGG on 8-10-17 @ 1:48 PM
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| cliftford | -- 08-10-2017 @ 2:22 PM |
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First, an analog meter is much better, doing this type of work. 2nd, I would tend to believe a good quality analog meter over the original guage.
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| sarahcecelia | -- 08-10-2017 @ 3:23 PM |
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30 amps is good for that generator (it's a 30 amp unit); that's what my 1940 6 volt puts out. Did you polarize the system after all of that work? You should have. I had the EXACT same problem your having, and replaced the volt gauge. Now It goes into the green a little at idle and at about 1200 rev's it goes about 1/3 into the green.I found a NOS gauge on Ebay! If you find that that is the problem, to install the gauge isn't too bad, but you have to pull the radio to get to it. Check the volts between the "Batt" terminal on the regulator and a GOOD ground to see if it's getting to the regulator from the generator. Maybe the wire from the generator to that terminal on the regulator is bad? Remove some paint on the generator brackett. to ensure it has a good ground. I hope this is a help to you. Regards, Steve Lee
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| TomO | -- 08-14-2017 @ 9:12 AM |
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The marks on the gauge are : L = 2 volts, line left of the N is 6 volts, the N range is 6.75 volt at the left end to 8.25 volts at the right end, the line marked H is 9 volts. Your voltage regulator should regulate the generator output to 7.2 - 7.6 Volts. This would put it at the left 1/4 of the green area. The gauge should read battery voltage at idle and take some time(about 1 min) at 30mph or higher to move into the green area. You only need to worry when the gauge reads below the unmarked line (voltage is too low due to the generator or voltage regulator limiting the voltage or a bad battery) or above the right 1/4 of the green area, or above 8 volts (voltage regulator not controlling the output of the generator). Tom
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| MGG | -- 08-15-2017 @ 9:44 AM |
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Thanks guys. Yes, I did polarize the system and I have an analog meter on order. All wiring is new and all connections are tight and bright. The metal is bare where the generator mounts. I will do some more testing when the meter arrives.
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| TomO | -- 08-16-2017 @ 6:53 AM |
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The main purpose of the BATT gauge is to let you know that there is an unusual condition, like a bad battery, bad generator or voltage regulator. It is not designed to give you an accurate voltage reading. My description was for the 39 Gauge. The 40 gauge operation is the same, just the markings are different. The 1940 Gauge right end of the first red zone is 6.2 volts, the right end of the yellow zone is 7.1 Volts and the right end of the green zone is 8.25 volts. These readings could be off by 0.2V - 0.4V At 6.35 Volts the gauge should read in the yellow zone. Your gauge should only read in the green zone when you are driving at more than 35mph without any accessories turned on. The regulator should allow the generator to put out 7.2-7.6 volts at engine speeds above 1,200 rpm. This is measured at the BAT terminal of the voltage regulator with all accessories turned off. If your needle gets to the center of the yellow area at 6.8 volts, it is within the tolerance of the gauge. Drive your car for 20 or 30 minutes with no lights, radio or heater and at speeds above 35 mph. If your electrical system is working correctly, your gauge should just enter the green band while driving at speed. It can take as long as 1 minute after idling at a stop light to enter the green area. If your voltage regulator is only allowing 6.8 volts, you may have a problem with charging the battery when you have to drive for more than an hour with the lights on. Tom
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| MGG | -- 08-16-2017 @ 8:03 AM |
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In testing for the voltage at the battery terminal of the V/R do you unhook the other terminals? I assume the negative lead of my meter goes on the terminal and the positive lead touches to a ground spot such as the head? Do you need to re-polarize after the test? Thanks
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| TomO | -- 08-17-2017 @ 7:04 AM |
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You do NOT need to disconnect any wires to make the voltage check. If you do disconnect any of the wires at the voltage regulator, you will not get an usable reading. Connect the black lead of your voltmeter to the Bat terminal of the voltage regulator, the red lead goes to ground, Strt the engine and increase the rpm to around 1,500 and read the meter. You do not have to polarize the generator after making this test. You only have to polarize the generator when it is not charging or charging in the wrong polarity. This can happen when the generator is replaced with one that has spent a long time on the shelf, when the voltage regulator is replaced and when the battery is connected backwards. Tom
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| MGG | -- 08-17-2017 @ 5:48 PM |
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You are very clear. Thanks so much!!
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| MGG | -- 08-18-2017 @ 2:06 PM |
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In the V/R test, do the connections have to be made before starting the engine or does it matter? This message was edited by MGG on 8-20-17 @ 6:30 AM
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| TomO | -- 08-19-2017 @ 7:42 AM |
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It does not matter. Tom
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| MGG | -- 08-24-2017 @ 6:42 PM |
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I tested the V/R output to the battery today as outlined above by TomO. The most I got out of it was 7.0 volts. The volt gauge in the dash never did quite get to the green area. After running for about 15 minutes the battery was nearly at, but not quite full charge. It looks like I need to coax a little more out of the V/R. How is this accomplished or what further test should I do? Thanks - Mark
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| TomO | -- 08-25-2017 @ 7:22 AM |
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You can replace the voltage regulator with a new one, but I would find a shop that re-builds generators and alternators and have them adjust your voltage regulator. It is not a good idea to try to adjust the regulator without the proper equipment. You can destroy your generator. Tom
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| MGG | -- 08-25-2017 @ 7:53 AM |
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The V/R is a new one, Niehoff brand. I have another good used one (Filco), I will install to see if it makes any difference. Thanks
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| TomO | -- 08-26-2017 @ 5:04 PM |
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Be sure to disconnect the battery when you change regulators.b Tom
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| MGG | -- 08-26-2017 @ 9:44 PM |
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This is what I did today: Disconnected the battery, installed the Filco V/R (Anybody know anything about that brand?), hooked up the wires to the new regulator except for the center (field) wire, re-hooked the battery, touched the field wire to the battery terminal to polarize the system, unhooked the battery, attached the field wire to the V/R, re-hooked the battery, and started the engine. There was no change to the results that I had with the other (new Niehoff) V/R. Did I goof-up the polarization process? Not sure what I will do next. I guess I will take the Generator and V/R to a shop that has a Ford Test Bench. Thanks - Mark G.
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| TomO | -- 08-27-2017 @ 5:17 AM |
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No, you did not goof up on the polarization process. Polarization just makes sure that the generator is charging in the same polarity (Positive ground) as the battery. I cannot recommend any further tests, other than bringing the voltage regulator to a generator shop. They do not need a Ford Test Bench to check them out, they already have the precision equipment to use on the alternators and generatord that they service. Tom
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| MGG | -- 08-27-2017 @ 8:50 AM |
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Ok, I will get to it hopefully this week some time. I should mention that the original V/R had 3, now petrified, rubber mounting grommets attached, and its own separate grounding wire. The newer V/Rs did not have either of these features. I mounted the V/Rs directly to the firewall after scratching the paint down to bare metal. Also, I placed a star washer at each mounting screw between the firewall and V/R. As Ford did in later years, I installed a #12 ground wire from the grounding stud on the generator to the closest V/R mounting screw. Questions: 1. Why would I obtain the same charging result with both the Filco and Niehoff regulators. Strange coincidence? 2. Did someone along the line determine that the rubber mounting grommets were unnecessary?
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| 56MarkII | -- 08-27-2017 @ 5:41 PM |
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My digital multimeter is cheap offshore cr*p that jumps around like a rabbit but better meters WILL work and don't jump around. I have one that cost me $75 and it works very well but is unavailable because it is away where I work. An analog is fine as long as it is very accurate. Notice the fractional voltages quoted here by others? If your analog is a volt out plus or minus is the difference between boiling or undercharging the battery. Like you mine is steady when the engine isn't running but on a positive note I have an old Sun carbon pile style battery/electrical meter with an amp and volt meter and I placed both on the battery at the same time to verify accuracy of the Sun and it was spot on so I used it instead. I also test new regulator voltage settings as well and have had to readjust them to the 7.1-7.6 value. Verify your analog and test your new regulators. This should be done with a fully charged good battery for voltage. Voltage regulators are also thermal compensating using bimetallic springs and charge at a higher voltage cold than warm so your test should be done when this charging system has run for a while with the cover of the regulator carefully reinstalled if adjustments are necessary.
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| MGG | -- 09-02-2017 @ 11:33 AM |
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Conclusion: I took my generator and 3 voltage regulators in to an old-time auto electric shop. Two of my three voltage regulators had a problem. The 1 good one was so close in voltage output that they did not recommend trying to adjust it. So, I installed it and ran the engine for 15 minutes this morning, and when I shut it off the battery was at full charge, per my maintainer. The volt meter only got to the edge of the green area and never quite into it. Since the battery is being treated fairly by the charging system, I am not going to mess with it anymore, and now move on to the next phase. Thanks to all for the help. Mark G.
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| TomO | -- 09-03-2017 @ 8:12 AM |
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Mark, your battery gauge is working properly. 7.2 Volts is the beginning of the green zone and that is where the gauge should be when driving. If it goes to the middle of the yellow zone or below, your generator is not charging the battery. If it goes into the right hand red zone, stop the engine and disconnect the generator before it destroys itself. Tom
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| MGG | -- 09-12-2017 @ 7:21 PM |
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Epilogue: I decided to take a chance on a newer generator shop so I stopped in to talk to them. It sounded like they knew what they were talking about so I took in my generator and new Niehoff voltage regulator to see if they could adjust it. They did adjust it to 7.25 volts output and now my dash voltmeter goes up to and stays in the lower 1/3 of the green zone. At the end of my 10 minute runs, the battery has a full charge and I, my battery and voltage regulator are happy campers. Thanks to all and especially to TomO whose advice is always spot on.
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