Moparts
Lights dim/flicker at idle
Posted By: larrymopar360
Lights dim/flicker at idle - 10/20/12 10:28 PM
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.
Posted By: RapidRobert
Re: Lights dim at idle - 10/20/12 10:47 PM
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
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?
Posted By: larrymopar360
Re: Lights dim at idle - 11/18/12 01:26 AM
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.
Posted By: RapidRobert
Re: Lights dim at idle - 11/18/12 02:05 AM
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
Posted By: larrymopar360
Re: Lights dim at idle - 11/18/12 02:10 AM
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.
Posted By: RapidRobert
Re: Lights dim at idle - 11/18/12 03:14 AM
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
Posted By: larrymopar360
Re: Lights dim at idle - 11/18/12 04:22 AM
I am going to try swapping the alternators asap (hopefully get a chance in the next day or two). It's driving me nuts!
Posted By: 1_WILD_RT
Re: Lights dim at idle - 11/18/12 04:43 AM
Quit wasting time & just add relays for high & low beams..
Posted By: ahy
Re: Lights dim at idle - 11/18/12 02:14 PM
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.
Posted By: BDW
Re: Lights dim at idle - 11/18/12 03:14 PM
Quote:
Quit wasting time & just add relays for high & low beams..
What he said, x2
Posted By: larrymopar360
Re: Lights dim at idle - 11/18/12 06:38 PM
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!
Posted By: DaytonaTurbo
Re: Lights dim at idle - 11/18/12 07:56 PM
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.
Posted By: Supercuda
Re: Lights dim at idle - 11/18/12 11:41 PM
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.
Posted By: captaindodge
Re: Lights dim at idle - 11/18/12 11:54 PM
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.
Posted By: DaytonaTurbo
Re: Lights dim at idle - 11/19/12 12:22 AM
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.
Posted By: larrymopar360
Re: Lights dim at idle - 11/19/12 12:55 AM
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.
Posted By: larrymopar360
Re: Lights dim at idle - 11/21/12 10:21 PM
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.
Posted By: skajm
Re: Lights dim at idle - 11/21/12 11:35 PM
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
Posted By: VL21
Re: Lights dim at idle - 11/22/12 12:08 AM
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.
Posted By: 1_WILD_RT
Re: Lights dim at idle - 11/22/12 01:02 AM
OK I'm gonna waste my time & try to explain this... Your headlights, turn signals, parking lights & dash lights are all fed by the same overloaded wire... When ever your headlights are on they aren't as bright as you'd like because they don't receive as much power as they would like.... Add the drain of turn signals & the headlights get even less power so they dim, the dash lights dim, the heater blower slows down (also fed by the same overloaded wire) All these loads cause the bulkhead connector to overheat which just amplifies the problem.......
Solution Add relays to feed the higher powered circuits such as high & low beam head lights & the blower motor.... Now these items work properly because they receive a dedicated power source, the previously over loaded bulkhead connector suddenly doesn't carry more than a few amps & all the minor loads receive full voltage causing them to work better too...
Oh BTW If you have more options like power windows or a power top on your car the original problem is worse but the solution is still relatively simple & even more effective....
Posted By: larrymopar360
Re: Lights dim at idle - 11/22/12 01:09 AM
Please forget about the dimming of the headlights. I wish I hadn't mentioned that now. IT IS THE FLICKERING that has me most concerned now. The headlights flicker (NOT JUST DIM)when idling, along with dash lights, etc. Everything that is lit is flickering. Put a turn signal on and the clock almost flashes completely off and back on with the signal. This is definetly not normal. I apologize for any confusion, but I have mentioned in several previous posts now that it is the FLICKERING of lights that I am looking to address, NOT THE DIMMING, although my guess is once I figure out what is causing the flickering the excessive (not just a little) dimming will go away. Thanks.
Posted By: 1_WILD_RT
Re: Lights dim at idle - 11/22/12 01:14 AM
Dimming & Flickering are related, they both indicate excessive resistance in the circuit.... The system was poorly designed 40 years ago & now has 40 years worth of corrosion adding to the resistance which is why adding relays is effective... Do what you want, I'm done...
Posted By: larrymopar360
Re: Lights dim at idle - 11/22/12 01:15 AM
Quote:
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.
If I am understanding what you are saying, the clock won't be lit up to see flashing because the key is off.
I have cleaned all the grounds and contacts. The thing I haven't cleaned is the positive cable at the starter, which I planned to do even though I can't see how that would be causing it, but I don't know. No trailer wiring ever. It is an old police car so it did have sirens and lights wired to front, so who knows with that stuff, but I don't see any obvious bare wires or wierdness. So short on time right now that I do a little at a time and then off to work.
Posted By: larrymopar360
Re: Lights dim at idle *DELETED* - 11/22/12 01:28 AM
Post deleted by larrymopar360
Posted By: 1_WILD_RT
Re: Lights dim at idle - 11/22/12 01:39 AM
The deal your electrical guy is pointing toward is a connector coming out of the steering column... It feed to & returns from the ignition switch... Pretty common to have it burned like the picture below... But that feeds switched loads & the headlights aren't....
The thing is once you learn to add relays & see how effective they are as well as how cheap you'll be adding them to vehicles that aren't giving you trouble just because it makes for a better vehicle..
Posted By: mopar_man
Re: Lights dim at idle - 11/22/12 01:58 AM
So whats your idle rpm ? How much do you have to bring the rpm up to loose the flickering? If you only have to increase the rpm a little , just get a smaller pulley put on the alt .
This will not solve a wiring issue or a bad circuit but you may get rid of the flickering ,
Posted By: 383man
Re: Lights dim at idle - 11/22/12 06:33 AM
I would do a charging system voltage drop test first. I would also see if the charging system is putting out the right amout of amps at the right voltage just to start and check the voltage regulator switching voltage. The voltage drop test of the charging system will tell you if you have a bad connection somewhere. If you dont know how to check all that maybe you have a buddy who can do it. Or you may have to pay the tech to check it out but make sure you get a tech who knows what he is doing. Sometimes a problem like this is tuff to fix over the internet and calls for a hands on look at it. Good luck , Ron
Posted By: larrymopar360
Re: Lights dim at idle - 11/28/12 02:07 AM
If I turn the key on but not start the engine, and turn the radio on and a turn signal, the clock light on the radio goes almost completely off and back on with each blink of the signal. Also cuts the radio sound out for a second or two on the first blink of signal, and then just the clock flashes on and off. This happens with no headlights on or anything else. Just key on, radio and a turn signal. So it isn't the idle speed. Thank you.
Posted By: larrymopar360
Re: Lights dim at idle - 11/28/12 02:12 AM
Quote:
I would do a charging system voltage drop test first. I would also see if the charging system is putting out the right amout of amps at the right voltage just to start and check the voltage regulator switching voltage. The voltage drop test of the charging system will tell you if you have a bad connection somewhere. If you dont know how to check all that maybe you have a buddy who can do it. Or you may have to pay the tech to check it out but make sure you get a tech who knows what he is doing. Sometimes a problem like this is tuff to fix over the internet and calls for a hands on look at it. Good luck , Ron
Ya Ron, I think that is where I am now. At least I have tried everything I can do on my own (with my very limited knowledge). At this point I don't mind paying the guy for an hour or two of labor to find out what the problem is. I think I will have the wires behind the dash exposed when I go see him, just in case. Thanks!