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EFV-8 Club Forum / General Ford Discussion / Polarity check

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Discussion Topic: Polarity check -- page: 1 2

flatcreeker

12-05-2021 @ 2:39 PM

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I have a digital voltmeter which resembles the traditional continuity tester (type with battery/light in plastic handled ice pick with lead and small alligator clip0). This voltmeter has LED voltage display in handle and also has two LEDs indicating polarity: green=pos ground, red=neg ground. Can someone out there in EV8F land tell me if and how I might use to read polarity of generator polarity without removing either either lead from a two wire generator (thereby eliminating need to polarize if already correct polarity)?

40 Coupe

12-06-2021 @ 4:50 AM

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Starting with your voltmeter. Does it have a switch that will allow the voltmeter to read DC or AC? Typically digital voltmeters do not like the DC produced by generators and our running cars, due to the amount of static produced by the generator brushes and the high voltage in the plugs plus arcing in the distributor. The best way to determine if the generator is working is to connect a analog DC voltmeter to a good source of battery - and ground+ Discharge the battery slightly by turning on the headlights for several minutes. Then start the car and read the voltage at idle and then increase engine RPM watching the voltmeter and the voltage should increase to about 7. volts and stop even if RPM is increased further. If so the generator is charging and the regulator is limiting properly. It is best to give more information when asking questions. Info such as vehicle year and voltage of the battery can be helpful in a reply.

flatcreeker

12-06-2021 @ 8:14 AM

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Thank you for your timely and considered response.

I am new to early Fords and haven’t pulled wrenches in 35 years. I’m learning a lot but not fast enough.

Mine is a 39 Mercury fordor survivor with 169K on the clock.

The “icepick” volt meter was intended for automotive use and I have used on both 6v pos ground and 12v neg ground. There are no switches. I have used with engine running and off at battery and regulator. I have checked against my Fluke multimeter and vintage analog volt/tach/dwell meter and they are all in agreement (to a surprising degree).

I disconnect the battery whenever I work on the Merc and figured there must be a way to use the polarity feature to verify polarity of generator after reconnecting the battery. I’m wrestling with a solid-running engine stumbling once engine is fully warmed (after 15+/- miles of moderate driving from stone cold in 55-70F ambient) so I’m under the hood a bit.

I’m not confident in my electrical skills enough to just start poking connections with the pick.

Thanks!

flatcreeker

12-06-2021 @ 8:40 AM

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Better photo, engine off battery 6.4 volts, max charging measured at battery is 7.0 volts. Would prefer about 7.4 but will accept 7.0 rating than start tweaking regulator.

TomO

12-06-2021 @ 8:51 AM

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If your battery is connected with POS post grounded and your generator is charging it, the generator is the correct polarity. If your battery is discharged after a short drive, your generator might have polarity reversed and you would have to polarize it.

Did you get your voltage regulator situation resolved?

Please expand on your stumbling issue. Does the engine have a miss at constant speed above idle? Does the engine miss only when you try to accelerate? Does it seem that the engine is starved for fuel when you try to accelerate?

Tom

flatcreeker

12-06-2021 @ 10:16 AM

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Greetings TomO!

My regulator matter is resolved. I went through 2 new "blue top" regulators without success, destroying them in the process. I found a N.O.S. P&D regulator and after installing and polarizing generator had nothing, cutout not closing at any engine speed. After removing cover and tweaking achieved 7 volt max charging and proper "cutout" function. Would like to have 7.3v - 7.4v max but unwilling to keep live-running tweaking. The P&D regulator was much easier to tweak due to the heavy gauge construction resulting in more force required to bend spring tab so "over-bending" less problematic. Not the best way to do generator/regulator I know but it's what I had. I tried engine off, battery disconnected method but after two days I went "live". After two tweaks I had 7.0v and I said: "good enough". It's been enough to keep battery charged fully charged to 6.4v with surface charge removed.

Just immediately prior to the regulator problem (in fact, it could have happened simultaneously and I just didn't notice change in batt dash gauge), I had an engine stutter develop. It was what I shall characterize as a "snap" stutter which would occur repeatedly 1 - 2 seconds apart upon acceleration in 2nd and 3rd. I went through a litany of ground connection verification, spark cks, plug replacement, etc.. The overwhelming body of forums says suspect coil. I installed my spare coil (Skip Haney rebuild). I had a n.o.s. in the box (believed to be good) NAPA Echlin condenser I used . No change in condition. I have since acquired a vintage FoMoCo N.O.S. in orig box condenser which I intend to install next, absent any other good advice.

The engine runs strong from cold until stutter occurs. From stone cold, it generally takes 2o miles of calm driving in ambient 55-70F for the stutter to begin. If I let it sit for 3-4 hours and then drive, it starts within a 2-3 miles. Sometimes under hard acceleration in the upper rpm range in 2nd or 3rd it doesn't do it.

It has experienced several high voltage events in the 9v range during the blue top regulator attempts.

I do think I have a weak fuel pump due to slow to start sometimes. I have not done any fuel pump testing. I have a N.O.S. fuel pump push rod which I intend to install (after verifying length) if and when I remove the pump. I have experienced no low fuel fades during road running. Did experience some difficulty stalling at idle while working on regulator.

I have a spare Skip Haney distributor/coil with Skip supplied condenser which I have considered installing.

Whatcha think?

37RAGTOPMAN

12-06-2021 @ 10:27 AM

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missing in engine,
did you clean the spark plug;s and what heat range ?
seems to me it is a spark plug problem , or sticking valves,
has the engine been rebuilt , new valve guides,? maybe fitted to tight,ok when cold, but with heat not so good
block expands and tighten the valve so they do not more fast enough and case a stutter,?
do you hear any noises , from the air cleaner or the tailpipes ?
let us know, could use more information to dianois the problem
my 2 cents 37Ragtopman ,Maine,

40 Coupe

12-07-2021 @ 5:26 AM

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I do not believe you engine miss is from the generator. If you have just over 7V charge your good with electrical charging. Do check out the fuel pump and fuel lines especially the pump input flex line. Make sure there are no air leaks or pin holes in the fuel line.

flatcreeker

12-07-2021 @ 6:57 AM

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Thanks 40Coupe.

Didn't mean to throw a curve ball re the generator. I have no problems with the generator, I'm just trying to learn if I can (and if so how) use my device (since it indicate polarity when used) to determine generator polarity. I am electrically challenged but have this nice little instrument I want to exploit.

marko39

12-07-2021 @ 10:29 AM

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Don't assume a condenser is good just because it's new. Especially nos. or nors. ones that are decades old. Have them tested to be sure. I tested about 10 nos. and Nors. And found most of them bad.

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