Charging system help needed

[tsteiner61]

I am having the following problem, any suggestions are appreciated.

My charge is fluctating between 14-15.5 V. It seems to do this in rhythm with the noise from my electric fuel pump. Has anyone else encountered this issue in a conversion from mechanical to electrical pump? If so, is it normal. I would tend to think this overcharging cannot be good.

Things I know or have already checked.
The following grounds are good: alternator to engine block, alternator to chassis, voltage regulator case to engine block & chassis, ground between engine and chassis.
The regulator has been tested in another vehicle and is working correctly.

Things that have been modified from stock:
I've replaced the stock B+ wire on the alternator with a wire that is routed directly to the B+ battery terminal without passing through the firewall. The alternator itself is stock and has been tested to be functioning correctly.

Any ideas on things to look for are greatly appreciated.

[6 packin]

Have you done the full field test to see your max output from your Altenator? I think you ground the green wire at the voltage regulator.

[ehostler]

The fuel pump is surging due to the voltage fluctuation, not the opposite.

A properly functioning charging system wil run between 14 - 16 VDC. That is not overcharging.

with that much of a fluctuation, you do have an issue. is the engine surging? that could cause this indication. if the engine isn't surging, then I would have to quetion the regulator (or its ground) or the alternator (or its ground).

[tsteiner61]

More details and questions:

Noticed something interesting last night. I can make the fluctuation stop if I turn on every accessory in the car (lights, heater blower on high, wipers). If I do this it stops fluctuating, drops momentarily to about 12.5V, then smoothly goes dead on to 14V and stays there, which is what I would expect from a properly charging system. This would also lead me to assume that the regulator is working, which I already knew anyway because I tested it in my truck and it worked fine.

Retested all continuity between regulator case and alt case and neg. bat terminal and frame and block. Even ran a line from reg. case to neg bat. and an extra ground wire from block to frame.

I wouldn't really be thinking it was overcharging, but I have to assume it is because my battery, which is new, started to swell and leak acid, and when I test the voltage across the terminals after I run the car for awhile it is about 13.5V, which in my experience is higher than normal for my other 70s Dodges which tends to be 12.85V

As for a full field test, what kind of result am I looking for? Is there any chance that the alternator itself is causing this problem, and if so what kind of test would I do to find out?

Thanks.

[Billydelrio]

Sounds like an older points type voltage regulator. The solid state voltage regulator keeps to voltage at close to a constant potential.

Billy

[tsteiner61]

The regulator is the black and yellow one that MPP sells as "OE Muscle Car Voltage Regulator" P4529794. Is this the wrong one for a 71 Dart?

[ehostler]

If that is the thin, rectangular unit with a triangle shapped plug, it is correct for '71 and is solid state.

I would take the car down to a good auto parts store that will run a complete diagnostics of the charging system for free.

[jelsr]

Try another reg! Voltage should be 13.8 to 14.2 with a charged battery. The full field check is to ascertain the alt will reach rated output (amps) but don't do it for any length of time as the voltage is uncontrolled during this test.

[tsteiner61]

I tried the regulator from my truck (76 Power Wagon), which I know to work correctly, and had the same problem when I swapped it in to the dart. Also, I put the one from the dart into the truck and it worked fine. I'm 99% sure the regulator is working and the problem has to do with the wiring or the alternator itself.

When I do the full field test, what reading should I expect on my voltmeter? Thanks.