Charging Fine Except Nothing at Idle Speed

[Dibbons]

This is a '72 Plymouth Satellite Sebring Plus 318/auto. I have used 3 voltage regulators, the one that came on the car when I purchased it and two aftermarket units. The same thing with any regulator: no charge at idle speed but charges like a champ at any speed above idle.

This change is verified by voltmeter and by watching the dome light, which gets brighter above idle.

I am not going to worry about for now, because it starts and runs down the highway just fine, including some over 3,000 mile road trips.

However, I was wondering if anyone else has experienced this with their own Mopar charging system? P.S. Once in a while, I believe I have found it to charge at idle momentarily.

 

[Nacho-RT74]

maybe bad diode on alt

 

[MoparLeo]

Agree with above. A bad diode will cause your problem.
Here is an article on alternators and calculating charging requirements, loads etc... Written about Chevy's but the info is universal.
https://www.chevyhardcore.com/tech-...ng-system-and-keep-your-battery-at-the-ready/

 

[66 Sat]

I thought that was normal? I notice it at night, the lights get noticeably brighter as soon as the revs rise, even slightly. Mine idles at about 700 rpm, and the ammeter shows not much charge or nothing, but once I get to even 800 rpm the gauge moves to a charge position.

 

[Jerry Hall]

Your picture shows what appears to be a high quality battery. If your battery is fully charged, the regulator may actually be cutting off charge at idle unless a lot of accessories are on. Try turning on your headlights to load the system and see if it starts to charge at idle. I have noticed on many of my cars that the amp gauge just waves back n forth at idle with the battery fully charged.

 

[Dibbons]

I had this same thing happen with an old conventional battery, the Optima is a new addition. I have converted the ammeter to voltmeter.

I read above that 66 Sat in post #4 has experienced the same phenomenon. That is what I was wondering about, not believing I was alone in observing this characteristic. He explained it perfectly.

 

[Nacho-RT74]

I thought that was normal? I notice it at night, the lights get noticeably brighter as soon as the revs rise, even slightly. Mine idles at about 700 rpm, and the ammeter shows not much charge or nothing, but once I get to even 800 rpm the gauge moves to a charge position.

yes but no... there are limits on this. with stock alts you barelly increase the rpms by 100 or 150 and will increase the load able to keep the charge. The OP description sound as a more radical situation.

BTW, trust me, upgrade the alt and your charging system ( alt ) will be safer. The ideal reading is 0 on ammeter

 

[Nacho-RT74]

stock alts are able to feed maybe 18 to 25 amps while iddling, and our cars maybe sucks out 30 amps, so you have a 5 to 12 amps deficiency. That load is being sucked by the car from the bat. When you give RPMs, the alt is able to source the car needs and get back what the bat lost previouslly. Thats why you have the back and forth amm needle.

If your car need to get 30 amps iddling, the best is get an alt able to feed AT LEAST that while iddling. That will cover everything and the amm will be steady at center, and batt will be never sucked out, which also means, the alt will never need to recharge the batt back

 

[Jerry Hall]

stock alts are able to feed maybe 18 to 25 amps while iddling, and our cars maybe sucks out 30 amps, so you have a 5 to 12 amps deficiency. That load is being sucked by the car from the bat. When you give RPMs, the alt is able to source the car needs and get back what the bat lost previouslly. Thats why you have the back and forth amm needle.

If your car need to get 30 amps iddling, the best is get an alt able to feed AT LEAST that while iddling. That will cover everything and the amm will be steady at center, and batt will be never sucked out, which also means, the alt will never need to recharge the batt back

Very good information if a lot of aftermarket accessories are in the mix. I have run across many original cars with stock 36 amp alternators working flawlessly 50-60 years down the road. I tend to keep things stock, but preforming correctly. My next door neighbor has repaired alternators and starters for 50 plus years and has upgraded some for me to around 50 amp. He won't do them any higher due to original wiring, even if it new reproduction.

 

[Nacho-RT74]

wiring can be upgraded too... this is an old discussion here between pro ammeter and pro voltmeters crowd.

Bulkhead conections needs attention too

 

[Nacho-RT74]

some of the charging issues and propper upgrades here:

http://www.dodgecharger.com/forum/index.php/topic,33574.0/all.html

sorry my crude english there, but the thread is 12 years old. My english is a bit better now LOL

 

[Dibbons]

I have "Crackedback" headlight relay upgrade kit already installed, by the way. I did not notice any change in the lights or electrical from how it performed before the installation. Not saying it doesn't work, the brightness and behavior of my particular lights seem to be the same yo me.

 

[Nacho-RT74]

relay upgrade is nothing if you don't have the juice to source it. Relay upgrade will save the bad wiring, switches and terminal conditions thought. It will help, but if the main source is not enough, the gains will be barelly noticeable

 

[RJRENTON]

Do yourself a favor regarding my explanation of how a Mopar alternator works. I'll repeat a brief explanation of the system.
The Mopar alternator uses a 3 phase full wave bridge rectifier circuit which changes the voltage and current generated by the stator windings to DC voltage and current. The rotating field circuit, whose voltage is regulated by the fire wall mounted regulator. The maximum AC current produced by the stator is limited by design (impedance - which is the AC equlivant to resistance) and changed yo DC by the 3 phase full wave bridge rectifier circuit.
If any diode in the bridge rectifier circuit is open, the alternator will only produce HALF of its rated output. This is noticeable at light loads and above idle RPM. At low RPM and high loads, the alternator's output is significantly reduced. If any diode is shorted internally, the battery will be drained usually overnite. The power drain will be thru the shorted diode and stator windings to ground....which is a high resistance ground. This is in addition to the usual advice of badly grounded regulator case or auxiliary grounds or loose or corroded battery terminals. The round back alternators use pressed in diodes that are individually mounted; the square back alternator's diodes are group mounted....all positive diodes on a heat sink and all negative diodes on their own seperste heat sink.
Perhaps you should go back to the other threads about the same issue and review the other suggestions offered.
BOB RENTON

 

[Dibbons]

Like I said in my first post, since above idle I receive of good charge of 13.5 volts to 14 volts I am not worried about anything. Just wondered how other vehicles of my vintage were acting. Thank you.

 

[RJRENTON]

Like I said in my first post, since above idle I receive of good charge of 13.5 volts to 14 volts I am not worried about anything. Just wondered how other vehicles of my vintage were acting. Thank you.

Like I mentioned in my post, the alternator will produce the correct voltage output (under light load) but have low AMP output with an open diode. Only when subjected to a high load, lights on high beam, blower motor on high, foot on brake, transmission in gear will the voltage and current be low (less than 12 - 13 volts). Perhaps you should have the alternator LOAD TESTED. That will show you if you have a real problem. A bad (open) diode can only be detetmined be individual testing of each diode.
BOB RENTON

 

[440+6]

Like I said in my first post, since above idle I receive of good charge of 13.5 volts to 14 volts I am not worried about anything. Just wondered how other vehicles of my vintage were acting. Thank you.

I took mine to a local alternator shop and it tested fine, put a smaller pully on it and it produced 14 volts at 750 rpm.
That was quite a few years ago.

 

[Nacho-RT74]

yeap, the smaller pulley is allways a help.

 

[Nacho-RT74]

Like I said in my first post, since above idle I receive of good charge of 13.5 volts to 14 volts I am not worried about anything. Just wondered how other vehicles of my vintage were acting. Thank you.

Save the low charge status at iddle. Trust me, it will make a huge difference on your wiring and devices health. The goal is get the harder rock steady amm needle at 0 as posible. Yes I know you don't have ammeter at this moment anymore, but still the low charging status ( for whatever reason ) it keeps being a problem for your car. It doesn't need to be like that.

BTW voltage is just a "parallel" reference of the charging status, but not allways a straight reference

 

[RM23M9A]

Agree with above. A bad diode will cause your problem.
Here is an article on alternators and calculating charging requirements, loads etc... Written about Chevy's but the info is universal.
https://www.chevyhardcore.com/tech-...ng-system-and-keep-your-battery-at-the-ready/

Yep, good read there. Just last night I took the A12 out for a deive, ran into my buddy with his 396 SS Camaro. Well? Yeah Drag Racing. About 10 min later, MINE didnt hardly wanna run short of W.O.T., wants to die at a stop. Ran fine before I blew the webs out of it. I dunno if I need a REGULATOR, BATTERY or BOTH! Batt shows 12.8V. But? Runs like crap short of ACCERATION. Help??