Here is what's up...On my just barely O/T '66 Dodge, I've been having a series of electrical woes. I fixed the voltage regulator problem I had earlier, and the alternator is putting out 12.88 VDC at idle, with 13.65 VDC @ 2,000 RPM. So far, so good... Today, I drove the car a little over 260 miles, round trip. The car started just fine, with no apparent issues. Once on the road, things were good...sorta. At speed, the ammeter showed a good charge. Once I got off the highway and the RPMs dropped, the headlights dimmed almost completely off at idle! Fortunately, I kicked the car into Neutral at the stop sign, and drove home fine. Once I got to the shop door, the car stalled and all of the lights went out completely!. I was able to restart the car, but barely. I've checked the grounds, the alternator output, battery voltage, and the other electrical connections. I have not checked the cables for resistance yet. I have new ground cables (x2). The car has been difficult to start when warmed up. So...here is where I'm at... I'm thinking the positive battery cable (original 1966 part) might finally have gone tits-up on me. I have nice, bright lights and working heater fan at speed, but it all goes away at idle; especially after a 10-mile or longer drive. I have good battery connections. Something is happening somewhere that just isn't right. Am I on track here, or do you guys have other ideas for troubleshooting this PITA problem???
No, I got rid of the constant-output unit - it was putting out nearly 18VDC @ 2,000 RPM! Blew out my low beams! I have installed two different stock voltage regulators, and both have had the results I experienced today. One was a factory stocker from a '67 Coronet parts car I parted years ago, and the other was a brand new Chinese POS. Both show the system charging, though barely, at just over 13VDC. The voltage drop theory in the cables, seems to agree with what I have diagnosed so far. The ground cables are brand new - I have one from batt - engine, and the other from batt - radiator cowl. There is an engine to firewall ground cable, too. One other symptom - my factory transistorized console-mounted tach works fine for a few minutes, then zooms up to 5,700 RPM and stays there, until the car is at idle.
Very common Mo Par problem is the amp gauge. The amp gauge has to carry the charge load and the power to run all the systems and will give the symptoms described. On all my mo pars I run a bypass wire from the Alternator to the starter relay, this takes most the load off the amp gauge. My friends Dart had the same problem and this fixed it Van
Belts good, bone-stock alternator w/original pulley. 440, I'll look at that and see what's up. I plan on pulling the instrument cluster this week to see if there is any damage at the ammeter gauge itself - I've seen those melt down before! Fire is not my friend here! I've owned the '66 for 30 years now. I'm not real concerned about "concours" anything on my Coronet! LOL!
Patrick I PMed you, hope I helped. 440 is right if you see any damage replace the dash circuit also but still do the bypass. Van
What is it with Mopar's and electrical problems? Don't get me wrong, I love all Mopar's but Damn! Sorry, I think I just had a flash back.
English cars from the fiftys were a lot worse with Lucas electricals... they even released a service fix for smoking wires........
Check the wiring bulkhead at the firewall as I had a 68 newport that it looked like the main charging wire going to the amp gauge got hot and melted some and a PO did a poor job of bypassing it,I also ran a wire from the back of the alternator to the starter relay which helped a bunch and if the amp guage goes bad it will still charge.
Dont pull the dash. Do what 440 says. Most common problem. EWMN problems with mopar electricals? I dont think so. Very reliable straight forward uncomplicated system. As to the ammeter giving trouble. On a 66 and even a 63 you can feel the back of the ameter with you hand by reaching up underneath. (Dont use your ring hand though. ZZZZZZZZZZZZZ) Turn the headlights on for a few minutes and then go looking for warm spots. If the ammeter is a the problem it will be hot to the touch at the back. In 90% of the cases it is just a lose nut and can be tightend without removal but DISCONNECT the battery first! Do not over tighten! Just not loose. Same goes for the bulkhead connector . Often pulling it apart will reveal of it is defective as it will show signs of heat. A simple bypass through the same hole is a great reliable repair. However. Remember an early Mopar has a 20 amp alternator not a 70 amp or 100 Amp. Since general wiring uses up 7 of those that leaves 14 to keep the battery up so lights going at idle verses cruising is somewhat normal with these cars. (yes i have one) Most commonly overlooked is fan belt too loose. It takes about 5 hp to run a alternator at full clip. If you can move the pulley on any alternator by hand against the belt it is clearly too loose as a human cannot generate 5 HP. From your description if it came to my shop (or was my 63 Dodge) that is the first thing I would be checking. Belt tension? Good rule of thumb is belt should be able to be twisted 1/2 turn when tension is right. Fan blades is another quick way to check since Mopar alt pulleys are not easy to grasp. Don
The lights weren't just dimming, they were damn near OFF, as in "no light was coming from them" at idle, plus there was barely enough current going to keep the car running. When the car stalled and died in front of my shop, the lights had faded completely. That, of course, is NOT "normal" Mopar flickering of the lights. Belt tension and condition have not been an issue here. I am running a 35-amp alternator. I've been around Mopars since 1972, and have never heard of a 20-amp alternator. A 35, yes. Twenty, no. I've never had a Mopar do what my Coronet has been doing, ever. The back of the ammeter is fine. No scorch marks that I can see, anyway. I guess I'm going to try the method outlined in 440s link and see what happens. Thanks for the input!
Patrick, your output voltages at idle and rpm, both sound about a volt low to me. If original reg. was putting out 18 volts then it sounds like you alternator is capable. You have stated a time or two that the pulley is org. and alright and the belt tension is good. Have you actually put hands on the pulley and see if it will slip, sometimes looks are deceiving. If your pulley is really good, then I say probably still a reg problem, or high resistance in the circuit somewhere.
I didnt read the whole thread so sorry if this is a repeat answer but check the connection on the firewall where the engine harness plugs in. May have a loose connection or some burned or corroded terminals.
I'm going to do a thorough check on everything this weekend - this is my goal, with no distractions. It's good to have goals, right??? LOL! The son's truck is all good, the wife's Chrysler is good to go, minus a noisy lifter, so my attention is now to the Coronet. Gotta have it ready for a nice drive on our 30th anniversary - me and the car - on April 1st!
With lites and everything else working okay at rpm it would appear the alternator is working okay. So it would seem then that the battery is either not receiving the charge or is not taking the charge. You stated that you were at one time charging a 18 volts. Is it possible you have boiled the water out of the battery? Have you had the battery tested? How old is the battery? Have you had the alternator tested? May be it is not putting out rated amps, enough to keep lites lit etc. but not enough recharge battery with said lites on.
I couldn't tell ya',..... My Wife and Son's have banned me from wiring cars years ago,... When my son's were little they called my box with electrical stuff in it, "Dad's fire starting kit". I have wired 3 cars,... two smoked the harness and the other caught on fire,... I trade out for wiring now.
I hear ya! I really don't mind wiring so much, it's the stinkin' troubleshooting. Because with this problem, there really are several possible problems, and it could be one or all as a part of it. I'll know for sure once I get back under the hood...and either fix it, or set it ablaze!
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