Eng. idles good in "drive" but turn on lights and car dies?...UPDATE!!!

[Ghoste]

ECU?

[Pete in NH]

It might be the same issue as 8 years ago or it might be something new. I think I would start by making sure the battery terminal connections are clean and tight and then measuring the battery voltage at idle and then stepping on the brake pedal or turning on the lights. I think those voltage measurements will give us a starting place to do some trouble shooting.

[flyinlow]

You where working with a high resistance in your wiring before.  Lets do some basic elimination troubleshooting.

Hot wire the ignition. If necessary put a spare battery in the car on the passinger side floor and run power wires to the ignition and ground.  Does this fix the problem?

[AKcharger]

- I swapped out the ECU 2 days ago (was missing bad but turned out to be vacuum advance)
- I like the idea of isolating everything and going from there
- might try the alt gauge like ken suggested 8 years ago

[b5blue]

  2 things you can do easy, check volts @ the coil both when running good and crappy. Buy a new replacement ignition switch and don't install it, just plug it in and leave it loose to test if the contacts in the column mounted switch are weak.
  Look for any drop in volts at the coil, one of the unexpected but good things I found when I changed to a 120amp Denso was my ignition got stronger across the board. I think because there was just plenty more juice available @ idle. (The Denso puts out 50-60 amp at idle if needed.)
  The ignition switch could be a choke point for power if not making firm contact inside from oxidization or wear. (At worst you have a backup part, they are not expensive.)
   Poor idle amp output drove me nuts for a long time! You may just have marginal Alt. output.
Do a "pull test" on all connections new or old, I bought a new engine harness for my 70 Charger and when thoroughly checking it the blue wire at the bulkhead just slid right out of the crimp! It was crimped but not tight to the wire. Had I missed it assuming new is must be perfect I'd been chasing my tail after awhile as the connection degraded and ignition starved for voltage/amps. (The loose connection would have built up heat as it ran, much like you are describing.) Use your meter to look for voltage drops. Use OHMs to look for resistance. (With the power off.)

[AKcharger]

Copy all Blue, thanks I'll hit it with the meter

Ignition switch huh? that connector plug has seen better days for sure. Would the ignition switch still be involved in the stumble when turning lights on/off and brake lights??

[b5blue]

My thinking is yes it "could". You have been through so much hunting as I followed your thread I was trying to think of where else to check.
Say your losing 15% capacity to ignition through the switch "generally" and you turn on your lights. Now total Alt. output is taxed (Known to be lowest at idle.) so now your 15% is from a lesser value so greater voltage drop at the coil. Any poor contact in the switch or harness connections would show as resistance electrically and that would relate to less voltage/amps and very importantly would also generate heat. As it heat starts and increases resistance follows to a higher value and that creates more heat so the cycle continues until a maximum value is reached for all the variables involved at that particular time frame.
A switch is one item electrically that could could give random variable readings with each cycle of use depending on wear pattern/corrosion of the contacts. With each cycle setting contacts slightly off you could get 100% effective one time and 85% the next. 
I could be barking at the moon and 100% wrong but if so it at the very least it would eliminate 2 aspects of your problem to look elsewhere for trouble. (With little effort and expense.)   

[Cooter]

How old is battery? What brand? I prefer Interstate. Many of the parts house ( Read CHEAPER) batteries are junk after only 2 years.
I had an import do this to me as it was running off tge alt. Only and when loaded, it would rob from ignition first. Battery was junk.

[AKcharger]

Hmmm I'd better take another look at that switch/wire connector. I recall back in '05/'06 the red power wire actually melted at the connection (remember it well, I had to splice the wire in a bank parking lot) and I had to bypass the connection at the splice with the power wire. I don't recall any issues from the few times I drove it during storage and this past Oct I had the column out for the 4 speed swap...maybe I disturbed something?  does anyone sell new male/female connectors?

Cooter battery is old...same one it went in storage with in 2006, and I think it's the same one since the 2003 restoration...a 10 year old battery? do they last that long? well, it works fine, no problems and cranks OK...so this is same problem you had? I thought batteries that had enough juice to crank a big block meant they were good?

Thanks guys!

P.S. I'm back in Alaska so trouble shooting delayed till I'm back in Florida with the car in 2 weeks...but keep ideas coming!!

[Bob T]

I would lean towards either a faulty alt guage or perhaps the damaged cores ( as detailed by Bryan ) in one of the main looms. If even one of the main looms got a nick or knife slice in it back when it was new, it would wick in moisture to that cable and the cores slowly die bit they increase resistance and opposition to current flow would build. It would become more apparent when more is demanded upon it, like you say when the lights go on.
I had to make some part looms for my car to cure some problems, bit of a mission.

[b5blue]

10 year old battery!  Cooter nailed it! 
   You just described the "melted wire" for the switch.....I can only wonder what the contacts inside the switch look like. 

[AKcharger]

OK next trip down to Florida I have a multi-pronged action plan 

...will keep ya posted

[AKcharger]

I was about to order up the switch but found two types. The 1st one is what I recall seeing last time I had the colum apart but the second one is the one I want to BELEVE is the one I need since it would be easy to swap out...the one with the harness would be a nightmare.

[b5blue]

First one is 70 up, what year car?

[AKcharger]

'70. I think that would explain it, the 2nd one does look 'in dash" doesn't it? It's advertised as '70-'76 non-tilt

[b5blue]

Yea 2nd is "in dash". I got mine from Advance Auto after getting a bad one online. (A.A. has lifetime warranty.) You'll be going in deep to swap that out. Do a search here for what is involved.  (It's worth doing!)

[AKcharger]

Update!

OK I swapped out the  ignition switch, as you can see from the photo the connector was trashed. I was hoping the contacts in the switch were bad but when I opened it up...it looked pretty good    Anyway I put everything together and fired it up and........ (Drum roll)....It's does the same thing! @#$%^&*((&!!!!

My next plan of attack was to disconnect the rear light (which I think I did back in '05) to try and isolate the problem but since disconnecting the lights interrupts the whole light circuit, not just the tail lights...would that do any good??  Also need to do Blue's wire shoot as described above

Suggestions needed...I'm at 7 years and counting    

So if you're just joining us:
- Car starts, runs fine
- If car is "cold" no issues
- after a few minutes if car is at idle and you turn on an electrical item (lights,/brakes/wipers) car dies...keep the RPM's up and it's fine
- Once electrical item is on car is fine, it's just that momentary on
- Headlight relay mod C/W
- New Alt, multiple ECU's, & ballast resistors
- no weird "MODS" done to car

One good note I've developed some pretty fancy foot work when stopping to keep the car from stalling

[b5blue]

Got a pic of the "red wire" ?

[AKcharger]

No, but it was ok, the heat damage was at the connector, that fried back in 2004.

[b5blue]

  Having dealt with poor idle output from the factory type alt. for many years I'm thinking can you rig a meter to read off coil voltage while driving? There is a brief moment when something is turned on that the voltage regulator reacts to the voltage drop. Now that I run a 120amp Denso with plenty of idle output my ALT gauge shows that "bip" and I did notice my engine idle got stronger with the alt. change. 
  Perhaps the coil voltage is minimal for some reason? 

[AKcharger]

Thanks Blue

I'm thinking the cause is some big resistance somewhere in the light circuit. My next plan is to:
- Run dedicated ground to stereo...this will tell me if it's a ground issue or a power surge issue (remember stereo turns off with lights too)
- Cannibalize the 2 month old Battery from my '72 and see if that's the issue per cooters suggestion. I can't see anyway how the battery could do it but I'll leave no stone unturned (and if it works I'll owe him an apology for not believing him months ago)
- I have a new M&H Rear light harness on order and plan to swap that out

If that doesn't work I'm going with the 120amp alt and a new dash gage

[b5blue]

10 years on any battery is highly suspect. However a volts check should show state of condition.  I've a topic on my alt. swap but the complete kit from Mancini is NLA. I'm seeing several upgraded alt. available now that may be even better, anyway look into that before changing anything. 

[MaximRecoil]

I have (#1) my ammeter (alternator gauge) bypassed (the quickest and easiest way to do this is to connect both wires to the same ammeter stud), and (#2) an 8 gauge wire going directly from the starter relay stud to the alternator output stud. Those are two common modifications to improve the charging circuit, taking all of the heavy load off the bulkhead connector in the process, though you do lose the function of your ammeter of course. You could try it to see if it makes a difference; the absolute quickest and easiest way to try it out is to skip #1 and for #2, just use a jumper cable from the starter relay stud to the alternator stud.

Also, if you suspect your ignition switch wiring is faulty, you could try putting the ignition system on a relay. Even if that doesn't fix the problem, it will improve the available voltage to your ignition system, for whatever that's worth (it's worth more in an HEI conversion than in the stock ballast resistor system). For example, mount the relay on the firewall and power it with a 10 gauge wire from the starter relay stud. Once you do that, the juice for the ignition system won't be pulling through your ignition switch anymore, it will be going from the battery or alternator through the factory 8 gauge wire or the 8 gauge alternator-to-starter relay wire you added > through the 10 gauge wire you added to power the relay > to the relay > to your ignition system, which is a very robust path (it skips the bulkhead connector, ignition switch wires and terminals, and ignition switch altogether). This also makes it easy to "hotwire" the car (by jumping the added relay which turns the ignition system on, and then momentarily jumping the starter relay or solenoid), which may or may not be a good thing, depending on your point of view.

[PlainfieldCharger]

Joining this party late. I did read this thread and I did not see any comments on electrical grounds. If your body grounds are poor the current will find another path. For instance when you turn on your lights or other items with heavy electric current use.... if the grounds that support those items are poor the current will find another path. When this happens it draws current from the circuit that has the better ground. (maybe your ignition circuit). Do you tests again with "new ground wires to your lights and body. Might surprise you....I have seen this before

[AKcharger]

Thanks plain. Yup grounds are important, I'm going to tackle it this weekend stand by for up date!