dash lights and head lights "pulse" slightly - JeepForum.com
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post #1 of 18 Old 02-15-2009, 08:01 PM Thread Starter
CrazyHorse6
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dash lights and head lights "pulse" slightly

I've got a '79 CJ7 with the 258, and I recently noticed that the dash lights and head lights pulse or flicker slighly, but only while driving (i.e. RPMS above idle). Its not much, just barely noticeable. When its idling, there is no pulse and the lights shine smooth. The engine idles nice and even as well - no surges. Additionally you can see this pulse in the voltmeter - it pulses between 14.5 to 15 volts and about as quick as a resting heartbeat, or almost as if it were blinking in conjunction with the turn signal (but thats not the case). I've had the alternator tested by the local autozone, but they said it tests fine. I can't associate this pulse with the addidtion of any new electrical component as nothing has been added and I don't have any huge electrical drains - just a CB, radio, and two hella lamps - thats it. It pulses when this stuff is on or off - doesn't matter. I redid all the wiring when I did the resto last year and to my knowledge, I don't have any loose grounds or bad connections. What's the next logical step?
Thanks!


CJ7, 258, Dana 20 T-case, Dana 30 & AMC 20, TFI Ignition upgrade, MC 2150 carb, YJ tub mod
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post #2 of 18 Old 02-15-2009, 08:03 PM
jatepper
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Maybe you should get your alternator checked???? Could be on its way out????

Too many Jeeps to count....
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post #3 of 18 Old 02-15-2009, 08:08 PM
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Very well could be the voltage regulator. I had an old Trans Am that did the exact same thing.

My friends always knew it was me if they saw me driving at night, because my lights were pulsing. Voltage regulator was the problem with that one. I replaced the alternator (regulator was internal) simply because I had one in good condition and that fixed it. I did drive it that way for a LONG time, though. Never failed, just the lights and volt meter pulsed.
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post #4 of 18 Old 02-15-2009, 08:13 PM Thread Starter
CrazyHorse6
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I had the alternator tested and I believe it has an internal voltage regulator, and I recall them saying it was part of the test - but who knows it might not have been. I'm leaning towards replacing it. If it wasn't the alternator or voltage regulator, what would be the next step?

Thanks Pacfanweb.

CJ7, 258, Dana 20 T-case, Dana 30 & AMC 20, TFI Ignition upgrade, MC 2150 carb, YJ tub mod
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post #5 of 18 Old 02-15-2009, 08:23 PM
scottymac62
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Grounding, Grounding, Grounding.......Make sure your dash has a dedicated ground. While you are at it, make sure you have good grounds to all parts of your Jeep (frame, dash, alternator, starter)

Read this thread

https://www.jeepforum.com/forum/showthread.php?t=693332
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post #6 of 18 Old 02-15-2009, 08:36 PM
Bakunin
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hmm

Does it look anything like this?

http://www.youtube.com/watch?v=hWv8RQZl0Eg


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post #7 of 18 Old 02-15-2009, 08:38 PM
Pacfanweb
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Quote:
Originally Posted by Bakunin View Post
Does it look anything like this?

http://www.youtube.com/watch?v=hWv8RQZl0Eg
That's just wrong.....
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post #8 of 18 Old 02-15-2009, 08:41 PM Thread Starter
CrazyHorse6
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Quote:
Originally Posted by scottymac62 View Post
Grounding, Grounding, Grounding.......Make sure your dash has a dedicated ground. While you are at it, make sure you have good grounds to all parts of your Jeep (frame, dash, alternator, starter)

Read this thread

https://www.jeepforum.com/forum/showthread.php?t=693332
Thanks - Thats what I first thought too - a bad ground at the dash, but the head lights pulse as well, so wouldn't that suggest a problem component that the dash and headlights have in common? Frame ground is good, dash ground is good (straight to battery) alternator grounds through mounting bracket (right?), and starter ground I'll have to check. But I would think if the started is not grounded correctly I'd have other problems than pulsing lights.

CJ7, 258, Dana 20 T-case, Dana 30 & AMC 20, TFI Ignition upgrade, MC 2150 carb, YJ tub mod
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post #9 of 18 Old 02-15-2009, 08:42 PM Thread Starter
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Quote:
Originally Posted by Pacfanweb View Post
That's just wrong.....
No, no not at all. My jeep is GREEN. Jeez.

CJ7, 258, Dana 20 T-case, Dana 30 & AMC 20, TFI Ignition upgrade, MC 2150 carb, YJ tub mod
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post #10 of 18 Old 02-15-2009, 08:50 PM Thread Starter
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Ok, I appreicate the help so far - anything else it could be? I think I can rule out a ground issue as all my grounds are good and when the jeep idles, the pulsing goes away. If it were a bad ground, I'd expect the problem to be constant. So that tells me its something to due with higher rpms - what changes when rpms increase, the alternator's output right? So it could be failing to regulate voltage (even though the alternator tested out fine) thus making my voltmeter run around 14-15 volts and causing the system to pulse?

CJ7, 258, Dana 20 T-case, Dana 30 & AMC 20, TFI Ignition upgrade, MC 2150 carb, YJ tub mod
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post #11 of 18 Old 02-15-2009, 09:16 PM
mcurcio1989
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Quote:
Originally Posted by Pacfanweb View Post
That's just wrong.....
Wow that just made me angry. All of the color was just ridiculous and incredibly gay. I mean if he had done it with all white l.e.d.'s it would have looked okay. It still would be ricey as could be but at least not so gay. That is just a disgrace.

Disregard everything i say

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post #12 of 18 Old 02-16-2009, 02:53 AM
John Strenk
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Quote:
Originally Posted by CrazyHorse6 View Post
Ok, I appreicate the help so far - anything else it could be? I think I can rule out a ground issue as all my grounds are good and when the jeep idles, the pulsing goes away. If it were a bad ground, I'd expect the problem to be constant. So that tells me its something to due with higher rpms - what changes when rpms increase, the alternator's output right? So it could be failing to regulate voltage (even though the alternator tested out fine) thus making my voltmeter run around 14-15 volts and causing the system to pulse?

It's suppose to be around 14-15 volts. 14.7 I think.

I would also check your alternator belt. Make sure you have the right one. I got one that ran on the bottom of the pulley once. There wasn't enough friction to keep it from slipping at hgher RPM.


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post #13 of 18 Old 02-16-2009, 06:47 AM Thread Starter
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Quote:
Originally Posted by John Strenk View Post
It's suppose to be around 14-15 volts. 14.7 I think.

I would also check your alternator belt. Make sure you have the right one. I got one that ran on the bottom of the pulley once. There wasn't enough friction to keep it from slipping at hgher RPM.
Thanks for the clarification regarding the voltage - I'd read somewhere that 14-15 wasn't outside of the expected range but its good to hear a confirmation. I'll take a look at the belt today as well. I think I may just start with pulling the voltage regulator if I can get to it, and if not, try a alternator swap to see if the symptoms change.
Thanks again

CJ7, 258, Dana 20 T-case, Dana 30 & AMC 20, TFI Ignition upgrade, MC 2150 carb, YJ tub mod
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post #14 of 18 Old 02-16-2009, 07:50 AM
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Actually,
The problem is one of two things,
And what's causing the 'Issue' is the voltage regulator cycling from charging to resting state.

1. Lack of ground to the ALTERNATOR.
If you are relying on the rusty steel brackets, loose bolts, ect. to supply the alternator with a reasonable ground, then you will continue to have electrical problems.

2. Alternator REGULATOR on it's way out or alternator BRUSHES are shot.

Many times, the lest enlightened will change the alternator, and the problem goes away... All they did was tighten up loose bolts, or rub the rust off of bolts, and the new alternator was getting a good 'Ground' for a little while.

Bad ground to the alternator housing will RUIN the regulator, and it's VERY HARD on internal brushes!
The bad ground can CAUSE the other two problems...

So it's ALWAYS a good idea to run a dedicated 10 Ga. ground wire to the alternator housing... It will save a TON of problems in the long run...

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post #15 of 18 Old 02-16-2009, 09:12 AM Thread Starter
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Quote:
Originally Posted by JeepHammer View Post
Actually,
The problem is one of two things,
And what's causing the 'Issue' is the voltage regulator cycling from charging to resting state.

1. Lack of ground to the ALTERNATOR.
If you are relying on the rusty steel brackets, loose bolts, ect. to supply the alternator with a reasonable ground, then you will continue to have electrical problems.

2. Alternator REGULATOR on it's way out or alternator BRUSHES are shot.

Many times, the lest enlightened will change the alternator, and the problem goes away... All they did was tighten up loose bolts, or rub the rust off of bolts, and the new alternator was getting a good 'Ground' for a little while.

Bad ground to the alternator housing will RUIN the regulator, and it's VERY HARD on internal brushes!
The bad ground can CAUSE the other two problems...

So it's ALWAYS a good idea to run a dedicated 10 Ga. ground wire to the alternator housing... It will save a TON of problems in the long run...
Thanks JeepHammer. Once I either replace the voltage regulator and/or the alternator itself, I'll ensure it has a good ground directly to the housing. I know for a fact that it does not have one now, and although the housing and brackets are not rusty and appear to provide good contact, I'm out of options and it sounds like the most likely cuplrit anyway.
Thanks again

CJ7, 258, Dana 20 T-case, Dana 30 & AMC 20, TFI Ignition upgrade, MC 2150 carb, YJ tub mod
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