lights oscillate bright and dim whats going on

[highflyer]

i find that the car starts fine,but if i watch the emergency brake light on the dash while idling it goes bright and dim rapidly and faster if i rev it..i pulled the headlights on and they are doing the same thing..iv got grounds on the alt block frame batt dash and regulator case..any one have a cure or know why..diodes maybe or alt ...help please...j

 

[67Dart273]

What are we workin on? Year model?

There are a few things that can cause this

Most common is a bad regulator on the older 69/ earlier systems

On any year or newer systems, this can be caused by a poor ground at the regulator, or by voltage drop in the harness supplying battery power to the regulator IGN terminal. You can set up an "oscillation" of sorts -- the bad connection in the harness is "just right" so that the regulator "thinks" the voltage is low, it ramps the voltage up, and the connection gets "made" so now the regulator "thinks" the voltage is high, and drops back down, thus repeating.

In rare cases, some high output ignition systems can generate enough EMI (electrical interference) to affect regulator operation.

This can also be caused by problems in the alternator, poor brush conditions, and sometimes stator insulation becomes bare from vibration---Sometimes you can SEE this. With the car in the dark, raise the hood and rev the engine while watching the alternator. If the stator windings look like a miniature lightning storm in there, the windings are shorting against each other.

 

[highflyer]

73 duster with 74 harness thats been gone thru unwrwpped checked and cleaned..took the dash meter out of the loop ..new regulator..with heat sink and pressed in studs for ground..any way to jumper to bypass connections to eliminate a poor harness connection..ill have to try another alt also...

 

[jos51700]

Mine did that and it drove me knuts. Replaced all the wiring and alternator, regulator, all of it. Nothing fixed.

Ammeter bypass and bulkhead bypass. No dice.

Replaced the instrument module regulator. Fixed!!

 

[67Dart273]

I would make the same checks as posted in this thread, especially harness drop and regulator ground

http://www.forabodiesonly.com/mopar/showthread.php?t=235311

A temporary test for feedback loop problems might be to

1--add a no12 or larger ground between engine and regulator. I actually like to use a no4 starter cable. Buy one a foot or so, and look at your passenger side front of the head. Those bolt holes for the alternator are UNUSED on the REAR of the driver side. Bolt the starter cable to the rear of the head, and either a substantial bolt through the firewall or to something like the master cylinder studs. Clean and remount the regulator, using star washers, and or add a jumper ground wire to one of the regulator bolts

2--As a purely temporary test, get yourself a male and female push on spade connector like on your alternator field. "TEE" a long about no14 or larger wire into the male and female spade. Hook this up to your alternator field which the blue is hooked to, and hook the blue back up, so you have the (( alternator field---blue field wire -- the test wire )) all wired together.

Devise a way to solidly hook this to the battery---vise grip, battery clip, etc, or to the big starter relay stud, and BE CAREFUL with the bare end. Start the car, and with the headlights on and "cycling" hook/ unhook this test wire to a battery source, and notice whether or not this stops the problem. Again, be CAREFUL with this lashup, because that wire is hot anytime the key is in "run."

If this DOES stop the problem, you have a voltage supply problem from the battery, through the harness, the key, etc, and to the regulator IGN terminal.

 

[KitCarlson]

My guess is one or more bad diodes in alternator. This often results when using car to jump a stalled vehicle and running engine when they try to start. The alternator is a 3 phase generator, loss of one phase results in bumpy waveform the regulator cannot deal with. The flicker varies with engine speed.

 

[highflyer]

thank you all..i will try all avenues you all described and write back on this thread wqhen finished..j

 

[highflyer]

ok...did it..tested the system ..what i found were good grounds..but the test volt drop in the reg test i came up with .8 ..i checked my grounds and made a new one even..i already had it bolted to the back of the head.my grounde were .1 or .2.my next test was checking batt voltage.12.6 motor off..while running 14.6..the next one said something..pulled off blue at the alt stuck in jumper with lead to the batt...all the pulsing went away and motor ran better..just like instructed[aint fabo members great] to..now if its a harness prob or maybe connector prob where is the likely culprit..i have eliminated the ammeter by going direct to the batt from alt so can i now try connections at the ballast res forward from there and back from there..any help PLEASE TX..J

 

[67Dart273]

OK sounds to me the issue is the voltage supply to the regulator, which is the same line as your ignition

The path for the "dark blue" ignition run is thus for a factory harness:

Battery -- starter relay -- fuse link -- bulkhead connector -- ammeter -- in harness splice -- ignition switch connector -- through the switch -- back out the switch connector on the dark blue -- back out the bulkhead on the dark blue -- and then to

alternator field (blue)

ignition system

idle solenoid if used

electric choke if used

smog doo dads on some cars

and most important, the regulator IGN terminal. You show you have nearly 1 whole volt drop (.8v) and this is very likely the culprit.

You need to go through, and your most likely suspects in probable order are

fuse link line (red) bulkhead connector terminal

dark blue bulkhead terminal coming back out

ignition switch connector

the switch itself

more rare but sometimes the ammeter connections or.........

the ammeter itself

more rare but does happen is a loose "in harness splice"

Here:

is a good article, and the simplified diagram shows most of this, except for ignition switch and ignition run buss (dark blue)

http://www.madelectrical.com/electricaltech/amp-gauges.shtml


The ignition switch is fed off the "welded splice" which is a factory splice, taped up in the under --dash harness in the black ammeter wire a few inches away from the ammeter

One way to fix this is to cut the dark blue after it comes into the engine bay and use it ONLY to trigger a relay, then use the relay to feed the regulator/ alternator field/ ignition under the hood

 

[/6 Matt]

67Dart273, that wiring diagram needs to be made a sticky cause I swear I've seen you a maybe a few others post that thing like ten times in just this month a lone.

 

[mcnoople]

There should just be a locked charging system sticky at the top of this page. It should cover all the common basic issue that get asked every few days. It would go real good with a sticky about dash gauge operation and repair.

 

[highflyer]

ok ill have to try the blue wire coming out..not running amp meter and wired to both wires at the gauge.with new links and wire..from batt...switch and connector at end of switch are new..harness was stripped and splice[junction] bared and checked for loose and broken wires deemed good..no smog choke solenoid or ammeter conn.no ammeter new links [2] i like the idea blue wire somewhere is causing it..i remember the blue and a few others wernt as clean as they coulda been when we put it in..ill ohm that connection tomorrow and see what it looks like.ill make a connection up and compare it to each other..my tomorrows job..tx..j