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Electrical System Frustration
Quite a regular
Joined:
2014/12/27 9:59
From State College, PA
Posts: 26
Hello folks,

I have questions about the electrical in my Pacific.

I have a 1954 Pacific. We tore a lot of it apart and reassembled it to get it back on the road. Ive been driving it for a few months locally. The problem is the battery seems to drain as I drive and I only get it to crank and start 4 or 5 times before needing to charge the battery.

Using a Volt meter the battery averages at about 6.25v When running the Generator doesn't charge the battery past 6.3x volts if at all.

I had the regulator replaced and checked as well as the generator. The generator on a bench being tested will output over 7 volts. The starter has been rebuilt. The battery is a two year old 6v Optima, also tested and confirmed to be good.

During June I'd drive the car, bring it home and place a battery charger on it so it'd be ready for the next trip. That worked fine.

Recently I realized that if I tried to start it after driving and it would drain enough to not turn over. But if left sit the battery seems to "recharge" after a few hours once the engine is cold and it would start up fairly easy.

I'm not good with electrical so specific instructions are helpful. I'm also thinking to place a 6v fuel pump on the system to help starting, I'm not sure if vapor lock is happening but it's difficult to start when hot and after some reading that seems like it could help just at startup. I understand this is a rabbit trail to my main question.

Any insight is appreciated.
Andy

Posted on: 2017/8/2 14:54
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Re: Electrical System Frustration
Forum Ambassador
Joined:
2007/4/20 17:54
From Fresno CA
Posts: 15988
First thing I would do is re polarize the generator just to make sure that part is OK. With key and engine off, do the polarizing by using a decent size short piece of jumper wire and MOMENTARILY touch the ARM (GEN) and BAT terminals at the regulator together. You will get a small spark when the terminals connect. Once they connect, leave them connected for a couple of seconds and then remove the jumper wire. After that is done test the output again.

6.3v is the nominal battery standing voltage. When the engine is running at a slow idle the generator may not be putting much voltage out and that is all you will read. At a fast idle -- say 1000 rpm or so -- the generator should be delivering approx 7.4 v when measured with the voltmeter across the battery terminals.

If you speed up the engine and still only read 6.3v either the generator or regulator is not functioning properly. To test for which, connect a small jumper wire to the field FLD terminal at the regulator. You can use ordinary wire or a test clip lead which you can usually find at a hardware store in packages of 3 or 4 wires. With the voltmeter connected across the battery and engine running at a fast idle TOUCH the jumper to ground and watch the voltmeter. It should immediately jump up to at least 7.5 v. If it does not change the generator or wiring to the generator has a problem. If it does the regulator has a problem. Be sure the jumper is on the FLD terminal and not the ARM or BAT terminals. Don't leave it grounded any longer than it takes to read the measurement.

At two years the Optima should still be OK but it can fail like other batteries. If it has had issues getting charged and stayed low most of the time or has been overcharged by too much output from the charger the battery can also develop problems and may not be able to hold a charge or deliver the specified output current for very long.

With the hard starting when hot, what size are the battery cables. If they are the originals then no issues unless they are damaged. If they have been changed make sure they are at least a 0 gauge and better yet is 00 gauge. 12v cables are definitely too small and the typical modern 6v cables at the parts store -- even those labeled for 6v use -- are marginal with the large engine. Also if you have one of the battery post disconnect switches make sure it is one capable of carrying the several hundred amps the starter needs in order to turn over a large hot straight 8.

Posted on: 2017/8/2 15:14
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Howard
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Re: Electrical System Frustration
Home away from home
Joined:
2009/9/30 11:25
From Dayton, OH, USA
Posts: 333
Andy,
Agreed with Howard and would add to check not only cables, but their connections to the frame. If the battery to frame connection is loose or dirty at either end, or an undersized or damaged conductor, the result is a voltage drop and current limiter to the engine while cranking and as importantly, back to the battery when charging.

Although I am not familiar with your model, I suspect there is also a frame to engine ground strap, usually the braded wide/thin construction. Check these connections for tightness and cleanliness. Simply, current does not go through air, paint or rust well.

Hope all is well with you and hope to see you again at Hershey this year.

PM

Posted on: 2017/8/3 9:42
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Re: Electrical System Frustration
Quite a regular
Joined:
2014/12/27 9:59
From State College, PA
Posts: 26
Thanks Fellas,

So upon review the generator has been polorized.

The car idling I have 6.16v. When idle is increased I see no change in the volt meter readings.

With a jumper wire I connect the FLD terminal at the regulator to a ground while the idle is running fast. I still see no change in voltage at the battery. That points to the generator or generator wiring as the problem correct?

Being the generator bench tested well. I assume I start replacing wires connected to and from the generator? Does that sound correct?

Thanks again
Andy

Posted on: 2017/8/3 18:33
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Re: Electrical System Frustration
Forum Ambassador
Joined:
2007/4/20 17:54
From Fresno CA
Posts: 15988
Unless there is evidence of damaged wiring or a bad connection I suspect the generator and not the wiring is the problem. It might be worth popping the band over the commutator end off and check the brushes. They might have been marginal when the bench test was done but if they have worn shorter or something happened to a spring one might not be making good contact with the commutator now.

One other wire to check is the ground on the generator. It goes from a screw on the generator case to a mounting screw on the left fender headlight junction terminal strip. Another wire connects at the same terminal strip screw and continues on to the regulator ground or a regulator mounting screw. If there is no ground screw and it is on a mounting screw, make sure the wire is on the side of the rubber insulator so the regulator base gets a good connection. Also make sure the connections are clean and are on bare metal, not over paint. The purpose of that ground is to ensure the regulator and generator are seeing exactly the same ground potential.

The regulator controls by connecting the field to ground thru some resistors. Without the wire, if something happened to the ground and the two pieces are at different potentials due to a rusty bolt or poor connection thru a bracket, the regulator wouldn't know the true value the generator was putting out. That could result in an over or under voltage condition.

Posted on: 2017/8/3 19:23
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Howard
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Re: Electrical System Frustration
Home away from home
Joined:
2013/7/17 6:26
From Clover, SC
Posts: 659
Always check the battery first, put in a known good one or have tested with a drawdown/ampdraw tester. Any parts store that sells batteries should be able to check. It may not be taking a charge.
Wiring, since it was removed, could be incorrectly hooked up, so run down/check against the schematic.
Once battery and wiring confirms, then start and measure the voltage but put the headlights on, and see if V goes down(lights will dim) or starts to charge(lights will go brighter). If it doesn't charge, and generator is good, suspect the regulator is not working/not hooked up right. (to me most likely cause but battery has to be good) It easy to fry the points on one.
Lastly, but not as likely, there maybe an amp gauge or charge/discharge on the dash. It may or may not be working but maybe in series in the charge circuit and causing issues. It can be bypassed to check as a cause if all else checks.
A battery's voltage will recover to a point on sitting, once the amp draw is removed, if it's been pulled down and not recharged, but eventually draws down. Amps are what counts here.

Posted on: 2017/8/4 17:46
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Re: Electrical System Frustration
Quite a regular
Joined:
2014/12/27 9:59
From State College, PA
Posts: 26
Fixed!

Howard, it was the wire connecting the ground screw from the generator. Apparently not a good connection. After disassembly, cleaning the surfaces and reassembly I got my voltmeter to increase with the engine speed. Plus the idiot light on the dash went out for maybe the first time ever.

Thank you all, I learned something.

Andy

Posted on: 2017/8/9 18:15
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Re: Electrical System Frustration
Quite a regular
Joined:
2014/12/27 9:59
From State College, PA
Posts: 26
One more thing,

Howard, you mentioned early on in this thread that it takes a lot of current to turn over a large hot engine.

Why is that the case? The engine definitely starts easier when cold, but when hot it's obviously more difficult.

Andy

Posted on: 2017/8/10 4:52
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Re: Electrical System Frustration
Forum Ambassador
Joined:
2007/4/20 17:54
From Fresno CA
Posts: 15988
I am definitely no expert on the subject but I think it is a combination of things.

Different expansion rates of materials in the engine can cause tighter tolerances in some areas when hot. Hot oil is thinner and may run and not be covering all the surfaces as thoroughly or as evenly as when the engine is cool causing a bit more friction.

The bigger issue is electrical items are generally less efficient when hot. The starter motor, coil, and battery are particularly affected. In order for the starter to do the increased work of turning the engine and cope with its own loss of efficiency it needs to draw more current. If the battery is hot it has a harder time supplying the extra current. An added insult is if the battery cable is marginal in size it may not be able to carry the needed current easily and results in a voltage drop to the entire car. The lower voltage available to the coil makes the spark weaker.

Added all up, a hot engine needs more power to be turned but the items providing and using the power are at their least efficient states. On a 12v car there is extra capacity to help in all the requirements but on a 6v car there is not much room between barely enough and not enough. That is why the 6v electrical needs to be in top notch condition.

Posted on: 2017/8/10 8:07
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Howard
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Re: Electrical System Frustration
Home away from home
Joined:
2009/9/30 11:25
From Dayton, OH, USA
Posts: 333
Matt, HH,
I do not believe there to be an inherent reserve benefit of 12V systems over 6V with today's battery offerings. But there are definitely needs, as HH and the prior posts indicate.

Definitely true that electo-mechanical systems that use copper windings become less efficient. The resistivity of copper goes up with heat...WAY UP. So starter snd generators lose efficiency and reserve margin as temperature goes up. WHen a hot engine is shut off, its heat soaks into the starter.

Speaking of heat, the battery cable, which would carry a few hundred amps during starting, will cause a voltage drop and limit the current able to get to the starter. This is why you want to have the largest battery cable you can. I suggest 00 (double zero) gauge. It costs about $20-25 to get one of these and you'll never regret it. My 39 has the 00 gauge cable and a 700 CCA battery, it cranks very fast no matter what.

As HH indicates other things are also affected by heat, but in general, internal combustion engines are designed to operate at or around the thermostat temperature for best overall efficiency. I had always understood that to mean not just how well the fuel mixture can flame, but also the effectiveness of the oil at the temperature to reduce friction at all the sliding and rolling surfaces like cylinder walls, babbett bearings and roller bearings.

Pat

Posted on: 2017/8/10 13:05
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