TRAMO

hey guys how much voltage variation come out of the alternator would cause all my lights to pulsate/oscillate? with a digital meter it goes from 14 to 15 back and forth.

pro-tech

Newer vehicles will hold dead on. 14.2.. older vehicles shouldn't be a volt but will have up to a 1/4 to 1/2 volt variance.. Sounds like it might be a voltage regulator problem..If it has one. No year/make/ model given so hard to know....Bill

TRAMO

im sorry bill.its a 67 plymouth satellite with a75 440. and 1972 alternator and regulator.all gronds that i have checked seem good.not sure if i have checked all that i should.you might know others to check.i have a volt meter. it doesn't have a regular ign. switch.it has a toggle on and push button start.if i unplug the regulator lights stop pulsating. ofcourse i know that turns off the alternator. thanx randy

Archer

randy -

I'm going to take a small stab in the dark here.
(OK, not really, let's just say I've been there and done that...)
Replace or rebuild the alternator or borrow one if possible.
Willing to bet one or more of the diodes are missing or blown.

You can check voltage drops between any and every two points on the system, and everything will check out fine, and still have a problem (you'd actually need to be checking amperage, not voltage). Sometimes the quickest test/fix is a simple parts replacement.

Archer

TRAMO

My meter has an amp guage.tell me where to check.im also carrying the alternator and regulator to be checked tommorrow

RacerHog

I agree...Diode is out of it....Or the Idle speed is set a tad low...

TVLynn

Check the connections on the AMP meter

TRAMO

istalled new alt and reg today.all lights still pulsate.haven checked factory amp guage yet.very hard to get to. by the way all lights pulsate at all rpm.

440roadrunner

Pulsating voltage can have a few different causes, or a combination. It is IMPORTANT to check and eliminate as many causes as possible

First it can be an old, out of cal regulator. This is especially true if you have an ACTUALL electro/ mechanical regulator. To find out, look at the bottom. If it has two large wire wound resistors on the bottom it's an old "relay" type. Replace it immediately.

Old style:

http://vintagemoparts.com/img/p/97-396-thickbox.jpg

Now a new REPLACEMENT regulator is MOST likely to be electronic, even though it looks nearly the same. Again, look underneath

See? No resistor

http://i381.photobucket.com/albums/o...tor/bottom.jpg

This one here, with a "short" cover is definately electronic

http://www.classicindustries.com/ima...mg/v/vr706.jpg


Now, Standard Motor Products and NAPA / Echlin sell one which looks like and probably is the same as the Mopar Performance unit. This is an expensive solid state unit, and even though it looks different, it'll hook up the same. The Echlin is VR-1001, the Standard is VR-128

http://i968.photobucket.com/albums/a...ps0d75acd7.jpg

Next, PLEASE read this excellent MAD article. Even if you do not perform this modification, it has a simplified diagram of the main power distribution, and covers the pitfalls of what happens in these old girls..

http://www.madelectrical.com/electri...p-gauges.shtml

Next if you DO decide to replace the alternator DO NOT allow a parts man to sell you a "round back" alternator. "Ask for" an alternator that fits about a 74 pickup, Dart, or B body, makes no difference.

This should get you a "square back" and do NOT accept the older style.

THIS is a mid--late 70's "squareback," what you want

http://www.classicindustries.com/ima.../7/7024_v2.jpg

You will NOTICE that this has TWO field connections. If you want to continue using the 69/ earlier regulator (which is fine) you can just pick one field terminal, make up a little jumper wire, and GROUND it, then hook up just like your old one.

OR you can add one more wire, and wire it up and convert to the 70/ later solid state factory regulator, like this

http://stores.atlaschrys.com/media/0...cdaff217_m.JPG

===================================


Now, with all that under your belt PLEASE make a couple of tests

Get your multimeter, turn the key to "run" but with engine stopped.

With meter set on low DC volts, stab one probe right into the top of the battery positive post. Hook the other probe to the regulator IGN terminal. Don't unhook any wiring, "backprobe" the connections.

What you will be reading is the voltage drop between the battery and the regulator, and the LOWER this reading the BETTER. If you read over .3V (three tenths of one volt) you have a drop problem in the ignition harness.

The circuit path includes the bulkhead connector, the ignition switch connector and switch, and the ammeter circuit.

===================================

Next, start the car, warm it up, and get the battery charged up "and normalized"

Now, with engine running to simulate "medium cruise" RPM, stab one probe of the meter onto the battery NEG post. Stab the other probe onto the regulator mounting flange. Again, you are hoping for a very low reading, the lower the better. Zero volts would be perfect. More than a tenth, you should look into it, more than .2--.3V you should improve the ground between battery, block, and body.

===================================

Now with engine still running, make this check first with accessories off, then with lights heater, etc turned on.

Put one meter probe on battery positive post. Put the other probe onto the alternator output stud. Be careful. This should be an absolute max. of about 2 volts, and the less the better.

====================================

Other causes besides the regulator is a poor connection anywhere in the ground path between the battery and regulator, or the ignition harness feeding the regulator, or the charging line/ bulkhead/ ammeter circuit.

What can happen is, a bad connection "won't make" so to speak, and the regulator keeps ramping up trying to get the alternator voltage up. Suddenly the bad connection "makes," the voltage jumps up, and the regulator says to itself "HEY the voltage is TOO HIGH" and ramps back down. This can then go round and round into this pulsating oscillation.

TRAMO

thanx 440rr. mine is a67ply sat with 75 mod 440 with 1972 alt and 72 reg,it has been wired for 2 fld alterntor and solid state reg.it does not have a normal ign switch.it has a panel with toggle switch on/off and push button start.today i did some tests.with switch on and not running im getting 11 volts fromthe 2 plugs that go to ballast.im getting 11 volts from both wires that go to the reg. what does that indicate?by the way the car was already done like this when i bought.and this car runs perfect but the pulsating lights are very annoying.all further help appreciated 440rr. thanx randy also what is a back probe and a drop problem? with what i have told you do i do these same tests?

TRAMO

also when i got the car it was not charging i had to run a wire directly from alternator to battery and it charges now 14/15 volts.the black wire that is on the alternator has a break some where and does not make connection to battery+. stock ampmeter bounces on the discharge side of the guage when engine is running.

440roadrunner

Much of what I said still stands.


You can of course now disregard the section on regulators. What you are calling "dual field" alternators (properly "isolated field") DO COME in either roundback or squareback. IF YOU buy a replacement DO NOT accept the older "roundback" design.


The 11 volts you are getting at the ballast indicates a harness drop. Read the MAD article

The circuit path from the battery to the regulator/ ignition system is..............

battery.....fuse link.....through bulkead connector.....through ammeter circuit.....ignition switch connector ..........through switch........back out switch connector......back out bulkhead.......to ignition, alternator field, and regulator

Are you saying you have a toggle switch instead of ignition?

You will have to tailor and check out the circuit as modified, so "I'm guessing." the path becomes..........

Battery.........fuse link.......bulkhead.........toggle switch.........back out bulkhead......to ignition/ regulator

The most likely poor connections are in the bulkhead connector and the ignition switch, but depending on what has been changed/ modified, it still could be right at the ammeter / ammeter connections.

When a car has been modified, this gets more difficult, because obviously I cannot look at it.

One approach you could take is to buy a nice heavy duty relay

Disconnect the "ignition run" coming out of the bulkhead and use that wire coming from the ignition switch (toggle?) to key the relay.

Run a big fuse, say, inline 30A from the starter relay stud to one of the normally open relay contacts.

Run the other contact to feed your underhood loads..........the ignition, alternator field, and regulator.

You can check voltage drop two ways. What I detailed gives you the voltage drop reading directly.

You can also measure the ignition line to ground (your 11V) and then measure the battery (12.6??) and subtract.

Whatever that drop is it is ADDED to the charge voltage.

TRAMO

ok.today i unpluged all three bulkhead connectors.flip ignition/toggle switch on and my ammeter hand moves byturning onblinker or dome light in other word how would my ammeter hand show a draw when bulk head is completly unplugged?

TRAMO

ok guys my son and i fixed it, this morn.it was in the bulkhead.the black wire from alternator " p" on the bulk head had melted into the yellow wire" l " that comes out to the start relay.the previous owner had bypassed both wires good enough for car to start and run good but didnot completley fix it.now no light pulse and ammeter showing good steady charge.i know i worried some of you guys to death especially 440ROADRUNNER,BUT WITHOUT HIM AND A FEW OTHERS .i would not have fixed it.thanx very much randy