Hi everyone, We have a 66 Dart, 225/ with electronic ignition. I replaced broken Alt guage with original guage from parts car. Had guage tested and was in working order. when I turn key just to on it registers slight discharge. When I start car it goes further to discharge and when I turn on lights or heater it points well into discharge side, past 2nd marker. I had alternator tested and was good. Replaced voltage regulator and checked battery. Car runs great but I do notice a very slight drop in rpms when lights are turned on. When I give some gas guage does move a little to charge side. Is this normal for this system. This is my first build with a Mopar and when we bought car it was not in running order nor was guage working when we got her going so I have no reference point. Thanks for any help. Ed & Jeremy

Depending on the provenance of your alternator (is it a parts store "remanufactured" unit?), the tendency of the early Mopar charging systems to be weak at idle can be aggravated to the point where you get no effective charging at idle. Whether your problem is due to a poorly-"remanufactured" alternator or simply a faulty one (open or shorted diode, open or shorted phase in the rotor or stator windings, worn brushes), or due to some other problem (faulty system ground — tie the alternator housing, regulator base, and battery negative together with a 14ga ground wire loop), it should not be difficult to fix. If you took the alternator to a parts store, the "test" they did is not sufficient to rule out alternator faults. Another possibility is a dead cell in the battery. With the engine off, turn the high beam lights on for 60 seconds, then turn them off and measure the voltage across the battery. You should see something in the neighbourhood of 12.6 volts. Significantly lower = faulty battery.

See this thread for more detailed testing procedures, and let us know what results you find.

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Hi Dan, Thanks so much for all the tips and advice. I will try to get to them by tommorrow and will send results in. Thanks again for all of your help now and with past ?'s my son and I have had. Ed & Jeremy

Hi everyone, I ran all tests today as suggested heres the outcome. Going off link Dan posted I started with "headlight test". Turned on at high for 60 sec.Battery reg at 12.6 good test. 2nd ran wire from Volt reg "FLD to Alt "FLD" no difference in guage. 3rd made sure Regulator had best ground possible no difference. Last test ran jumper from "BAT" to "FLD" on Alt. I have a "dual field" so I grounded other "FLD". this test made a slight difference in guage reading. Guage still would not go into charge side but discharge was less and movement to charge side was more. Another thing I noticed, by accident, was I pushed in cig lighter with key off and guage went to discarge side almost to first marker. Is this normal. I know there is juice being pulled but have never seen a guage move like that with key off. My guess is my Alternator is wearing out. Please confirm if you feel the same.Also can anyone tell me the proper output AMPs that should be run, 66 Dart 225/ 1bbl. Once again thanks so much for helping us. Ed & Jeremy

i think i got about 60 amp on my valiant when i tested it at school. you should also get about 14V at batt while engine is running. you can check from B+ to Alt+ to see if theres a volt drop too

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'72 Valiant DD for over a decade-225-Disc brakes, big T-bars, big Sway bars f/r, carter bbd/super six, GM HEI, 2- 12" subs in trunk, 1000w amp...
'77 cherokee cheif widetrack-360-33x12.5 tires-no lift. keeps driveway dry-project/backup DD/mudder

Hi Dank10Fenny, Thanks for info.I have another update. I was able to get a new alternator tonight to use, did not have to buy it, in a test on system. When I installed it I got the exact same results as I had with my original Alt. I am really at a loss now. Could there be a reverse wire somewhere. All aspects of anything electrical on car work. Car runs great. I haven't taken her out for a long ride yet with lights,radio and blower going. Maybe that will show something. Is there a link to a diagram that shows wiring route from electrical block located on firewall. I have 1 wire that appears to be cut off. It is, facing block from front of car, located on top row 2nd from right. thanks for any help. Ed & Jeremy

you got a multimeter? and if your lights are affecting your ignition you got some voltage regulation problems. make sure you do the steps dan told you. these ol voltage regulators are crap. so you really gotta make sure all the eltrical goin to any of this system is in workin order. you can also even add some redundant grounds to body and voltage regulator. i went through this for awhile. i also know those in dash alt meter are crap, i bypassed mine cuz it burnt up and gave me a dead batt condition

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'72 Valiant DD for over a decade-225-Disc brakes, big T-bars, big Sway bars f/r, carter bbd/super six, GM HEI, 2- 12" subs in trunk, 1000w amp...
'77 cherokee cheif widetrack-360-33x12.5 tires-no lift. keeps driveway dry-project/backup DD/mudder

Hi dank10fenny, I have a small multimeter that basically can test voltage, resistance and continuity. I checked I think all wires,WHEW, and found all to be in good shape. I found a wiring diagram and located the missing wire I referenced in my prvious post. It says that wire should go to BAT on alternator. It is cut off at bulkhead. So I traced the wire at BAT connection on alternator and it goes straight to the Bat connection on starter relay. Could this be the problem. Can I run a new wire from bulkhead location to Bat on alt to see if it works. I do not know much about wiring and I am afraid I may blow something big. Please advise and thanks for all of your help. Ed & Jeremy

Someone may have done some re-wiring on your car, it’s almost certain they’ve re-wired it for a dual field alternator that didn’t come on it, but everything you’ve said so far shows that the alternator is connected and working (at least some).

I don’t have a wiring diagram but it sounds like they may have also wired the alternator straight to the battery, by-passing the ammeter, which would make it read low. At one time a wire probably went from the alternator, through the firewall, through the ammeter, and back out to the starter relay. Now, this same wire goes straight to the starter relay and you may not be able to fix it, and could possibly make it worse, by hooking up one loose wire.

If you only want to know if it’s charging, use the multi-meter to check the charging voltage. It should be around 14v with the engine at a fast idle.

Danny

Hi Danny, thank you for tips and advice. Yes the previous owner had bypassed the amp gauge under dash. When I installed my new gauge I traced the mess under dash and believe I tracked all wires going where they should,with the one exception of the bulkhead wire, and rehooked them to proper location. Saturday I went ahead and hooked up wire from Bat on alternator to the "B" slot on bulkhead that I referenced in previous post. I got the same reading. As soon as I turn key just to on it goes to discharge when I start car it sits in discharge but seems to flutter to charge direction at idle. I checked charge at battery at idle as it was 12.4V. Other than wanting car to be in proper working order the main reason I am so set on getting this original gauge to work is I am building the Dart with my 12 yr old and really want to express to him follow through. I am so thankful for this site and the forums as it helps a "first time builder" with so many questions. I'll keep plugging away. Please any advice and tips will be followed to completion. Thanks Ed & Jeremy

That's definitely low; given the 12.6v reading you got with the engine off, it looks like you're getting no charging at idle and low speeds. At this point it's probably time to look at the voltage regulator and the wiring between the alternator and the voltage regulator. Which type of voltage regulator is on the car? Has it got two individual wire connectors, or has it got a single two-wire triangular plug retained at the sides? Perhaps the previous owner didn't do the dual-field conversion correctly.

Have you got at least the factory service manual, and preferably the other two books described in this thread yet? If no factory service manual, what wiring diagram are you working with?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Hi Dan, I will try to be clear on what I did today. I have the factory service manual for 66 Dart. I am using those diagrams. This morning I removed gauge cluster to access wiring. For neg side of Ammeter all wiring is correct. The black wire coming from bulkhead intersects with 3 other wires, a blk tr from light switch a red from ign switch and a red tracer from fuse block in car. These are all correct. The red wire for the positive side comes from bulkhead and is correct but I see on diagram that it also calls for a red tr wire to access circuit breaker. I do not have this one. Is it to be tied into same spot on fuse block as red tr that intersects Blk wire? that is the only discrepancy I see. Moving on to bulkhead in engine bay. previous owner had run wire from Bat on alternator to Bat on starter relay, he cut wire from bulkhead marked "B" top row 2nd from right. I replaced wire and routed to proper location, Bat on alt to "B" on bulkhead. Car started but still has discharge issue. Next to voltage reg. It is a circuit type and has 1 wire from FLD on alt mounted to one spot on top and has another wire looks like from Ballast res cliped on bottom. Last my alt is dual FLD. there is a wire run from FLD to GRD. Then there is wire from Bat on alt to "B" slot on bulkhead other FLD is routed correctly. Sorry such a long message. Hope you can understand my explanation. Please advise. Thanks so much for your time. Ed & Jeremy

OK, so somebody did install a dual-field alternator but leave the original type voltage regulator in place. At this point, I think the voltage regulator is your prime suspect. Go get a Standard-BlueStreak VR-128 or NAPA Echlin VR-1001 premium electronic regulator, which will fit and hook right up to the existing wires. Make sure you've got a good ground loop from the alternator housing to the regulator base to the battery negative.

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Too many people who were born on third base actually believe they've hit a triple.

Hi Dan, I ran 1 more check. I tested voltage across battery with key on it was 12.65. I then tested at IGN of regulator to battery ground it was 11.35. does this indicate a faulty reg? I have checked all wires and they test good. Please advise. Thanks again, Ed & Jeremy

If all the wiring is routed correctly, that suggests high resistance in the circuit between the battery main feed and the regulator's IGN terminal. Could be faulty wire(s), or dirty/corroded connection(s), or high resistance in the ignition switch itself.

But check to make sure someone didn't miswire the system such that the IGN terminal on the regulator is connected to the output end of the ballast resistor.

Nevertheless, if the voltage regulator were working correctly, and it were seeing a reduced line voltage as you measured, you would likely see an overcharging indication as the regulator, falsely sensing low line voltage, ordered the alternator to maximise output. So I still think you need a voltage regulator, but now I also think you've got more wiring and circuit inspection to do.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.