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Electrical Oddity In Tucson AZ
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Amskeptic
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PostPosted: Thu Oct 18, 2018 9:26 am    Post subject: Electrical Oddity In Tucson AZ Reply with quote

This car has been so reliable for so long, but here we are with an oddity that I'd like to address before taking off across Texas today.

1977 factory alternator and regulator and two year-old battery

a) ignition on/engine off - headlamps show normal battery-driven brightness

b) engine running - headlamps brighten to normal running intensity

c) engine slowed down with clutch against ebrake- headlamps dim to nothing

d) last night, I stalled engine to see if voltage regulator would decouple alternator from battery and give me headlamps back to (a) above, and everything went dark dead gone.

e) this morning, car started normally.

Question, can voltage regulator keep the battery from the electrical system?
Colin


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PostPosted: Thu Oct 18, 2018 9:37 am    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

Telford is on it
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PostPosted: Thu Oct 18, 2018 9:44 am    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

Amskeptic wrote:
This car has been so reliable for so long, but here we are with an oddity that I'd like to address before taking off across Texas today.

1977 factory alternator and regulator and two year-old battery

a) ignition on/engine off - headlamps show normal battery-driven brightness

b) engine running - headlamps brighten to normal running intensity

c) engine slowed down with clutch against ebrake- headlamps dim to nothing


d) last night, I stalled engine to see if voltage regulator would decouple alternator from battery and give me headlamps back to (a) above, and everything went dark dead gone.

e) this morning, car started normally.

Question, can voltage regulator keep the battery from the electrical system?

In a word, no. Voltage regulators only modulate the rotor current to keep the alternator output voltage constant. Sounds like a connection issue in the main feed wire from the starter to the fuse block, a battery terminal problem, battery wire connection to starter and body ground, the battery itself, or a fuse block problem. (I'm skipping the trannie ground strap, as that affects mainly engine operations.)

"C", above, may be the key: it implies that the battery/related wiring is going intermittently open circuit, and the bus is running strictly off the alternator. When it drops out at low engine speed, the electricity goes away.

The trick is to catch it in failure mode, then probe with a test light and see where the power stops on its way to the front of the bus.
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Last edited by telford dorr on Thu Oct 18, 2018 10:02 am; edited 4 times in total
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PostPosted: Thu Oct 18, 2018 9:56 am    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

There, now I've done my good deed for the day
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PostPosted: Thu Oct 18, 2018 10:48 am    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

telford dorr wrote:

"C" implies that the battery/related wiring is going intermittently open circuit, and the bus is running strictly off the alternator. When it drops out at low engine speed, the electricity goes away.

The trick is to catch it in failure mode, then probe with a test light and see where the power stops on its way to the front of the bus.


I will be investigating further today. I do not experience anything intermittent with this suite of symptoms.
a) I know there is a cut-in in the regulator (thus, it is a cut-out too).

b) I do not understand how the alternator is allowed to run the electrical system at what appears to be 2 or 3 volts with a fully charged battery just waiting to supply the 12 volts it definitely has. If it were a cable issue, I would think that starter draw would test that. Starter operates fine. Red/white main supply wire to fuse box buss is snug and very clean at both ends.

c) I have seen voltage regulator contacts go from one pole to another as engine starts (thanks YouTube!) . . . what if the contact stays stuck "on"?

ColinInTucson
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PostPosted: Thu Oct 18, 2018 10:49 am    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

Colin in Tucson - We are headed to Los Angeles this weekend but will be back Sunday. You are welcome here if you decide to limp along. Pensacola is going to be a mess because of Michael's damage one hour east of there. My brother lived in Pensacola then Panama City Beach many years, and my late parents were in Fort Walton Beach for 35 years. Your failure mirrors the battery failure in the 2006 Acura RL about 5 years ago. One minute it was running, I stopped with the AC running on high on a 110F day, the voltage flared, and 10 seconds later the engine died and everything went dark. A test of the battery the week before said it was very strong but I was having some issues with lights flaring etc. occasionally.

for others who might read this is in the future here are possible places that failure might occur IMHO. (not in any specific order)

Intermittent ground strap
Intermittent power cable from battery (could be rotted internally)
Intermittent connection at the power plug near base of late column
Ignition switch going bad
Failing battery where either + or - side has a failed battery post internally
Loss of 12V+ at the fuse panel

The key is that the dash went dark. Combined with headlight flaring this implies that the 12V+ voltage or grounds are in an unstable state. When the RPM falls low enough the ECU FI system falls out and then the alternator drops out completely.
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PostPosted: Thu Oct 18, 2018 11:33 am    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

I sent you a PM, but here is the public musing:

I, too, had visions of some horrific current draw, but nothing of the sort happened.
Ignition switch is fine. Components upstream of the ignition switch such as parking lights died too!

What does that cut-in contact in the regulator do?
1) It keeps the alternator out of the electrical system if it is not charging, yes? (cut-out)

2) It adds the alternator into the electrical system if it is charging, yes? (cut-in)

So what would happen if the contact keeps the alternator cut-in below threshold (2)? Does it give the whole electrical system to the alternator and tell the battery to stay out? That doesn't even make sense. I have the alternator B+ terminal right against the battery cable end at the starter solenoid.

Do you have any notions that some damn main alternator diode is committing a path to ground only when regulator is allowing alternator into the circuit?
Colin ??
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PostPosted: Thu Oct 18, 2018 11:43 am    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

replied to PM

Generators try to run as a motor when the engine is stopped. The cut out prevents this. Alternators do not have this property.

Likely to be battery internally or one of the power cables from it e.g., ground strap or 12V + power cable.

If there is a second battery it could be the battery switching unit too.
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PostPosted: Thu Oct 18, 2018 12:46 pm    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

Amskeptic wrote:
What does that cut-in contact in the regulator do?
1) It keeps the alternator out of the electrical system if it is not charging, yes? (cut-out)

2) It adds the alternator into the electrical system if it is charging, yes? (cut-in)

No, the diodes inside the alternator do that. Only a generator regulator needs a disconnect relay (which, by the way, can be replaced with a diode...)

The alternator regulator should have only one relay which modulates the alternator rotor current. If yours has two, then something is wrong. Are you sure someone, sometime, didn't install a generator regulator?

Generic alternator wiring:
Image may have been reduced in size. Click image to view fullscreen.

Here's a '73-'74 schematic highlighting the alternator circuit (basically the same in all late bays):
Image may have been reduced in size. Click image to view fullscreen.

Note that (1) there is no regulator between the alternator and the battery, (2) the starter terminal is the mecca point for the battery, the alternator, and the rest of the bus, and (3) either the battery or the alternator or both can power the bus. Therefore, if the bus goes dark, then neither battery power or alternator power is getting to the front of the bus. The loss of alternator can be explained by the RPM being too low. That leaves the battery as at least part of the problem - it's power is not getting through.

What is your voltmeter telling you?

[The fact that the bus starts is just an annoyance created by the bus just to tick you off. Even though it's illogical, in this case don't be distracted by it. Evil or Very Mad ]
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aeromech
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PostPosted: Thu Oct 18, 2018 1:33 pm    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

Seems to me if all else fails go get yourself a spare battery
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PostPosted: Thu Oct 18, 2018 2:45 pm    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

X2 on Aeromech's suggestion, plus cables and a ground strap.

Don't need to be stranded 300 miles from who knows where on Hwy 10 with vultures circling and illegal border hoppers climbing in your bus to hide. Smile
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PostPosted: Thu Oct 18, 2018 3:38 pm    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

Dead cell?
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PostPosted: Thu Oct 18, 2018 6:52 pm    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

Though I will never understand how the starter was able to turn so merrily, with such verve, I do believe the problem has been solved.

Removed entire positive battery cable and the sheath over the cable for a very close inspection, all is factory fresh. Reinstalled it through all factory grommets and harness protectors. Removed alternator B+ wire and performed a similar close inspection, it is fine.

Unbraided the factory cable after removing it from an aftermarket terminal:

Image may have been reduced in size. Click image to view fullscreen.



Straightened and raked each strand with a razor blade, then re-braided:

Image may have been reduced in size. Click image to view fullscreen.



Reinstalled cable to aftermarket terminal and stuck on a little heatshrink tubing where the insulation was stripped back too far (some time back in the eartly 1990's):

Image may have been reduced in size. Click image to view fullscreen.



Car is fine now, and thank you to all who chimed in.
Colin
(p.s. while rummaging for my asiab3 Commemorative New Battery Box Drain Valve, I found my spare regulator (way too late which I am happy about, no hopeful useless parts installation). But the new drain valve kept falling through the replacement battery box drain hole because it is bigger than the oem drain holes. A shifter bushing for a 1993 BMW 5 Series was the perfect hole reducer drain valve support)

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PostPosted: Thu Oct 18, 2018 8:13 pm    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

I strongly recommend using the replacement cable ends for temporary EMERGENCY use only. They are notorious for being installed and then ignored until they have caused problems and often lead to expensive and unnecessary repairs being done. I can buy a battery cable a size or two larger than stock from my local Napa and have them cut it to the length I want and crimp on the end that I desire for very little moola .
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PostPosted: Thu Oct 18, 2018 8:31 pm    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

Wildthings wrote:
I strongly recommend using the replacement cable ends for temporary EMERGENCY use only. They are notorious for being installed and then ignored until they have caused problems and often lead to expensive and unnecessary repairs being done. I can buy a battery cable a size or two larger than stock from my local Napa and have them cut it to the length I want and crimp on the end that I desire for very little moola .


X2

I hate those connectors. They cause more issues than anything.

http://www.wolfsburgwest.com/cart/DetailsList.cfm?ID=211971228A

I had an intermittent start issue on my bus, mainly when the engine was at temperature and the starter was heat soaked. It had cheap, crappy battery cables on it w/those lousy connectors. I replaced both the ground and positive cables with these from WW. Problem gone. I was amazed with how much faster the starter spun after installing the new battery cables.
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PostPosted: Thu Oct 18, 2018 8:43 pm    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

wcfvw69 wrote:
Wildthings wrote:
I strongly recommend using the replacement cable ends for temporary EMERGENCY use only. They are notorious for being installed and then ignored until they have caused problems and often lead to expensive and unnecessary repairs being done. I can buy a battery cable a size or two larger than stock from my local Napa and have them cut it to the length I want and crimp on the end that I desire for very little moola .


X2

I hate those connectors. They cause more issues than anything.

http://www.wolfsburgwest.com/cart/DetailsList.cfm?ID=211971228A

I had an intermittent start issue on my bus, mainly when the engine was at temperature and the starter was heat soaked. It had cheap, crappy battery cables on it w/those lousy connectors. I replaced both the ground and positive cables with these from WW. Problem gone. I was amazed with how much faster the starter spun after installing the new battery cables.


Better connections and larger cables equate to more voltage at the starter, which in turn equates to a faster cranking speed and less current draw, which in turn equates to easier starting and longer starter, battery, and alternator life. Hard to find a down side to spending some funds here.
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PostPosted: Thu Oct 18, 2018 9:19 pm    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

So Colin, if you ever make it to my house in San Diego, we’ll use my bulk welding cable and hydraulic swagger for a couple custom cables. They won’t be stock, just better.
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PostPosted: Fri Oct 19, 2018 4:12 am    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

SGKent wrote:
for others who might read this is in the future here are possible places that failure might occur IMHO. (not in any specific order)

Intermittent ground strap
Intermittent power cable from battery (could be rotted internally)
Intermittent connection at the power plug near base of late column
Ignition switch going bad
Failing battery where either + or - side has a failed battery post internally
Loss of 12V+ at the fuse panel


I've been having an issue where my headlights flare/brighten up for a few seconds randomly and then go back to normal. I'll check these spots out. Thanks!
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PostPosted: Fri Oct 19, 2018 5:16 am    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

Quote:
flare/brighten up for a few seconds randomly and then go back to normal.


probably different cause. That sounds like your VR. You'll need a VOM to watch the voltage when it does it. Also - if you have an older points style VR you can clean the points a little very carefully not to bend them and see if that helps. They may be sticking together.
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PostPosted: Fri Oct 19, 2018 5:17 am    Post subject: Re: Electrical Oddity In Tucson AZ Reply with quote

It always happens when I'm driving and the headlights are on so checking the voltage would be tricky Confused
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