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Lights dim/flicker at idle #1323489 10/20/12 06:28 PM 10/20/12 06:28 PM
Joined: Jan 2011 Posts: 15,822 Central Florida larrymopar360 OP Stud Muffin
larrymopar360 OP Stud Muffin Joined: Jan 2011 Posts: 15,822 Central Florida	The lights (headlights, dash lights) dim greatly at idle, and then brighten back with any increase in idle on my mostly stock '89 Diplomat police car. There is a bit of flickering too. When I first got the car I immediately had the alternator rebuilt because car had sat so long and I didn't want to chance it. I also have replaced the voltage regulator. I really don't know if it was doing this before I replaced these things because I didn't drive it at night prior. The battery cables look fine, and I cleaned the ground cable to the block real well. Seems to be charging ok, but continues to dim and flicker. It is the 100 amp police alternator, and it does this even when the only thing turned on is the headlights. My others don't do this. It is a very noticable dimming/brightening/flickering. What to I try next? Thanks. Facts are stubborn things.

Re: Lights dim at idle [Re: larrymopar360] #1323490 10/20/12 06:47 PM 10/20/12 06:47 PM
Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska	I'd clean the bulkhead halves thoroughly along with the rest of the charging circuit and grounds. That solved my dim at idle/brightening when speeded up issue live every 24 hour block of time like it's your last day on earth

Re: Lights dim at idle [Re: RapidRobert] #1323491 10/20/12 07:04 PM 10/20/12 07:04 PM
Joined: May 2003 Posts: 15,487 Florida S scratchnfotraction I Live Here
scratchnfotraction I Live Here S Joined: May 2003 Posts: 15,487 Florida	run a ground wire from - side of Batt to the VR mounting bolt. might have a good look at the fuseable links while you are at it. any of it soft or discolored. if it has the dimmer on the floor,check those wires at the plug,the will brake and cuase trouble with the headlight. it could be as simple as adjusting the curb idle up on the carb. both my trucks dim at idle but it is from a low curb idle setting of 650rpm. the flicker part could be a problem. resitance in the wires or bad grounds. my buddys 85 fury had a charging issue and poped 2 set of headlights. not sure if he got it fixed though he did park it. it was a regular 65 amp alt set up. my 85 poped 2 set of headlight till I patch up the fusable links for headlights and ign. IIRC my radio smoked it or got smoked on the 2nd set of bulbs. got any spare bulbs just in case?

Re: Lights dim at idle [Re: scratchnfotraction] #1323492 11/17/12 09:26 PM 11/17/12 09:26 PM
Joined: Jan 2011 Posts: 15,822 Central Florida larrymopar360 OP Stud Muffin
larrymopar360 OP Stud Muffin Joined: Jan 2011 Posts: 15,822 Central Florida	Still have this problem. I cleaned up all the grounds I can see. Ran another ground wire from VR too (also has factory ground straps all over the place including from VR to hood). The fusable link along the drivers side underhood looks ok...if that means anything. The problem is definetly more than just a low idle. The clock on the radio is flashing dimmer and brighter with the turn signals too. Stopped by a good auto electric shop in town. He suggested it could be the ignition switch. Anybody have any thoughts on that? He said he would spend a little time checking it out one day, but it is at $85 an hour. Wondering, could it be the connections at the starter, or is that not likely? Thanks. Facts are stubborn things.

Re: Lights dim at idle [Re: larrymopar360] #1323493 11/17/12 10:05 PM 11/17/12 10:05 PM
Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska	Quote: What to I try next? All that is left is the alt even tho it was rebuilt. If any of your other non flickering cars have an 100 alt alt I would sub it into the dippy & see if that solves it which'd ID the problem as the alt live every 24 hour block of time like it's your last day on earth

Re: Lights dim at idle [Re: RapidRobert] #1323494 11/17/12 10:10 PM 11/17/12 10:10 PM
Joined: Jan 2011 Posts: 15,822 Central Florida larrymopar360 OP Stud Muffin
larrymopar360 OP Stud Muffin Joined: Jan 2011 Posts: 15,822 Central Florida	I could give that a shot (the other cars are fine). I did swap one of the other Voltage Regulators but same issue. I was wondering if the battery could actually cause this issue too...was thinking about swapping that out too. Thanks. Facts are stubborn things.

Re: Lights dim at idle [Re: larrymopar360] #1323495 11/17/12 11:14 PM 11/17/12 11:14 PM
Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska	To me I think the flickering means that there's a variation on the demand side (accessories/devices being fed) & I dont think that's the case or a variation on the supply side (the alt). Yes if you have another 100 amper I would swap it & see what comes of that live every 24 hour block of time like it's your last day on earth

Re: Lights dim at idle [Re: RapidRobert] #1323496 11/18/12 12:22 AM 11/18/12 12:22 AM
Joined: Jan 2011 Posts: 15,822 Central Florida larrymopar360 OP Stud Muffin
larrymopar360 OP Stud Muffin Joined: Jan 2011 Posts: 15,822 Central Florida	I am going to try swapping the alternators asap (hopefully get a chance in the next day or two). It's driving me nuts! Facts are stubborn things.

Re: Lights dim at idle [Re: larrymopar360] #1323497 11/18/12 12:43 AM 11/18/12 12:43 AM
Joined: Jan 2004 Posts: 27,347 Today? Who Knows? 1_WILD_RT Management Trainee
1_WILD_RT Management Trainee Joined: Jan 2004 Posts: 27,347 Today? Who Knows?	Quit wasting time & just add relays for high & low beams.. "The Armies of our ancestors were lucky, in that they were not trailed by a second army of pencil pushers."

Re: Lights dim at idle [Re: 1_WILD_RT] #1323498 11/18/12 10:14 AM 11/18/12 10:14 AM
Joined: Jan 2007 Posts: 7,664 IN A ahy master
ahy master A Joined: Jan 2007 Posts: 7,664 IN	Dimming is normal for cars with the small case alternator but the big one you have should not have that problem. I'm running the big one on a mostly stock wired car. Even with a big fuel pump and lots of electronics idle voltage is rock steady. Lights, brights, AC it doesn't matter. In addition to the suggestions so far, make sure the alternator case has a heavy ground wire. The 100A alternators are mounted in rubber bushings and need the wire to head or block to get a good ground. There should be a stud on the case for this purpose. On the ignition switch, I guess you could have a problem, but if the alternator was putting out enough juice, it shouldn't matter if its at idle or not. I would start with the alternator/regulator/associated wiring first. Also, are you running a standard diameter crank pulley? A samll pulley could cause the problem.

Re: Lights dim at idle [Re: 1_WILD_RT] #1323499 11/18/12 11:14 AM 11/18/12 11:14 AM
Joined: May 2005 Posts: 4,705 Florida BDW master
BDW master Joined: May 2005 Posts: 4,705 Florida	Quote: Quit wasting time & just add relays for high & low beams.. What he said, x2

Re: Lights dim at idle [Re: ahy] #1323500 11/18/12 02:38 PM 11/18/12 02:38 PM
Joined: Jan 2011 Posts: 15,822 Central Florida larrymopar360 OP Stud Muffin
larrymopar360 OP Stud Muffin Joined: Jan 2011 Posts: 15,822 Central Florida	I really appreciate the input here because I am stuck. Ahy: yes, stock pulleys. I have two other ex police cars with the 100 amp alts and no dimming. It does have the same heavy gauge wire on the alternator like the other cars and I have cleaned it up real well too. The flickering now has me much more concerned than the dimming. The dash lights, clock on radio, etc. flicker and especially when I have a turn signal on. If I can at least try a few things first then maybe take it to the $85/hr guy to check it out. Thanks! Facts are stubborn things.

Re: Lights dim at idle [Re: larrymopar360] #1323501 11/18/12 03:56 PM 11/18/12 03:56 PM
Joined: Feb 2003 Posts: 21,318 Manitoba, Canada DaytonaTurbo Too Many Posts
DaytonaTurbo Too Many Posts Joined: Feb 2003 Posts: 21,318 Manitoba, Canada	Replace/run a new heavy gauge wire from the alternator output straight to the battery +. I don't know how your diplomat is wired as the older mopars ran this wire through the firewall to the ammeter, then to the battery. Sometimes the old wires can get all corroded inside and lose conductivity even though they visually look fine.

Re: Lights dim at idle [Re: DaytonaTurbo] #1323502 11/18/12 07:41 PM 11/18/12 07:41 PM
Joined: Sep 2007 Posts: 14,889 up yours Supercuda About to go away
Supercuda About to go away Joined: Sep 2007 Posts: 14,889 up yours	Quote: Replace/run a new heavy gauge wire from the alternator output straight to the battery +. I don't know how your diplomat is wired as the older mopars ran this wire through the firewall to the ammeter, then to the battery. Sometimes the old wires can get all corroded inside and lose conductivity even though they visually look fine. Not applicable to the Diplomat, it uses a shunt resistor to drive the ammeter. So the current never passes thru the bulkhead connection. Sounds like the alternator is flaky to me. Possibly a diode issue internal to it. They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.

Re: Lights dim at idle [Re: ahy] #1323503 11/18/12 07:54 PM 11/18/12 07:54 PM
Joined: Apr 2005 Posts: 279 pgh pa C captaindodge enthusiast
captaindodge enthusiast C Joined: Apr 2005 Posts: 279 pgh pa	Yes, Why does everybody think lights should be full brite at idle? To annoy the driver in front of you at the red light? I think it is working the way the engineers designed it to work.

Re: Lights dim at idle [Re: Supercuda] #1323504 11/18/12 08:22 PM 11/18/12 08:22 PM
Joined: Feb 2003 Posts: 21,318 Manitoba, Canada DaytonaTurbo Too Many Posts
DaytonaTurbo Too Many Posts Joined: Feb 2003 Posts: 21,318 Manitoba, Canada	Quote: Quote: Replace/run a new heavy gauge wire from the alternator output straight to the battery +. I don't know how your diplomat is wired as the older mopars ran this wire through the firewall to the ammeter, then to the battery. Sometimes the old wires can get all corroded inside and lose conductivity even though they visually look fine. Not applicable to the Diplomat, it uses a shunt resistor to drive the ammeter. So the current never passes thru the bulkhead connection. Sounds like the alternator is flaky to me. Possibly a diode issue internal to it. Yes but there's nothing to say his stock 30 year old piece of wire going from the alternator to the battery isn't pooched. New connector at the alternator end? New battery terminals? I agree that swapping the alternator is something he should try before mucking around with the wiring.

Re: Lights dim at idle [Re: captaindodge] #1323505 11/18/12 08:55 PM 11/18/12 08:55 PM
Joined: Jan 2011 Posts: 15,822 Central Florida larrymopar360 OP Stud Muffin
larrymopar360 OP Stud Muffin Joined: Jan 2011 Posts: 15,822 Central Florida	Quote: Yes, Why does everybody think lights should be full brite at idle? To annoy the driver in front of you at the red light? I think it is working the way the engineers designed it to work. As I mentioned above it is the flickering of the gauge lights, clock on radio, etc., that have me most concerned. Definelty not normal and gets worse when the turn signals are on. I understand what you are saying about the a little dimming being normal, but it's not just a little and the flickering is definetly indicating a problem. Thanks. Facts are stubborn things.

Re: Lights dim at idle [Re: larrymopar360] #1323506 11/21/12 06:21 PM 11/21/12 06:21 PM
Joined: Jan 2011 Posts: 15,822 Central Florida larrymopar360 OP Stud Muffin
larrymopar360 OP Stud Muffin Joined: Jan 2011 Posts: 15,822 Central Florida	Darn it, not the alternator. I swapped them last night and same flickering of dash lights, radio clock, etc. Don't know why I didn't think of trying this before, but today I turned the key on (not started) and with just the radio on, I turned on a turn signal. The clock on radio flashed with signal bigtime. Does this eliminate anything since the engine wasn't running. Could it be something with the battery? They are a bit of a pain to swap with the Thermoguards, but will gladly try it if it isn't a complete waste of time. Thank you. Facts are stubborn things.

Re: Lights dim at idle [Re: larrymopar360] #1323507 11/21/12 07:35 PM 11/21/12 07:35 PM
Joined: May 2005 Posts: 222 morrisville, pa S skajm enthusiast
skajm enthusiast S Joined: May 2005 Posts: 222 morrisville, pa	I second head light relays. Buy a relay kit or make one. If you make one use good quality wire not cheap stuff. Also ground and reground everything. You headlight switch could be the problem. Post you solution to help others. Joe

Re: Lights dim at idle [Re: larrymopar360] #1323508 11/21/12 08:08 PM 11/21/12 08:08 PM
Joined: Dec 2007 Posts: 1,357 central Florida VL21 pro stock
VL21 pro stock Joined: Dec 2007 Posts: 1,357 central Florida	First, I am an electrical idiot. Just for something to try, and eliminate the switch, try switch off. Lights on. Then pull on the 4 way flashers. Bypasses the ign switch. This will probably still pulsate the clock. I think there is a bad ground somewhere, you may have a bulb filament shorting across or something, or bad firewall connection? The whole dash panel cluster surround is made of plastic on your car, make sure it is functionally grounded. While the lights are flashing, walk around, looking for something that is on or pulsing that shouldn't be. Maybe something is being back fed. Dome lights, trailer wiring? If this is a Fla car and has an aftermarket hitch, it is almost guaranteed that scotch locks or that ilk was used to wire in the trailer plug. OK,ok, I've done it myself too. It takes gasoline to interest me.

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