Alternator charging erratically on my 77
Thread Starter
Le Mans Master
Joined: May 2002
Posts: 5,086
Likes: 786
From: Lebanon Township New Jersey
Alternator charging erratically on my 77
My AC Delco 4 year old alternator lately charges normally but at other times does not fully charge, The "Battery" light glows dimly and the volt gage reads around 11 or 12 volts. I put a multimeter on the alternator while the engine was idling, battery light not lit, volt gage reading around 14 and the meter showed 14.6 volts. Using the car yesterday, at times the gage looked good, other times showed a discharging situation with the battery light on. (I wasn't able to check with the meter at those times.) Any ideas on where to look for the problem?
Le Mans Master
Joined: Jun 2019
Posts: 7,658
Likes: 2,470
From: Indiana
maybe double check all cables to battery etc?
also the beginning of this thread has some good advice i tested on alternator.
if battery low, 15.5 is max normal.. i noticed the crap replacement rock auto ac delco limited to 14 something.. around post 100
on post #114 that China alternator dropped RPM 120!!!!! OEM 40 RPM.. some HP loss there..
79 Tachometer erratic voltage regulator output question - CorvetteForum - Chevrolet Corvette Forum Discussion
also the beginning of this thread has some good advice i tested on alternator.
if battery low, 15.5 is max normal.. i noticed the crap replacement rock auto ac delco limited to 14 something.. around post 100
on post #114 that China alternator dropped RPM 120!!!!! OEM 40 RPM.. some HP loss there..
79 Tachometer erratic voltage regulator output question - CorvetteForum - Chevrolet Corvette Forum Discussion
Thread Starter
Le Mans Master
Joined: May 2002
Posts: 5,086
Likes: 786
From: Lebanon Township New Jersey
Le Mans Master
Joined: Jun 2019
Posts: 7,658
Likes: 2,470
From: Indiana
i would get away from the China AC Delco as above.. do you have the original? seems pretty straight up easy to fix replace.. I was shocked dhow much RPM dropped at idle with China AC vs OEM.. and you are in a super power bracket!!!
Melting Slicks
Joined: Sep 2016
Posts: 2,230
Likes: 984
From: Wauconda IL
Thread Starter
Le Mans Master
Joined: May 2002
Posts: 5,086
Likes: 786
From: Lebanon Township New Jersey
maybe double check all cables to battery etc?
also the beginning of this thread has some good advice i tested on alternator.
if battery low, 15.5 is max normal.. i noticed the crap replacement rock auto ac delco limited to 14 something.. around post 100
on post #114 that China alternator dropped RPM 120!!!!! OEM 40 RPM.. some HP loss there..
79 Tachometer erratic voltage regulator output question - CorvetteForum - Chevrolet Corvette Forum Discussion
also the beginning of this thread has some good advice i tested on alternator.
if battery low, 15.5 is max normal.. i noticed the crap replacement rock auto ac delco limited to 14 something.. around post 100
on post #114 that China alternator dropped RPM 120!!!!! OEM 40 RPM.. some HP loss there..
79 Tachometer erratic voltage regulator output question - CorvetteForum - Chevrolet Corvette Forum Discussion
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Thread Starter
Le Mans Master
Joined: May 2002
Posts: 5,086
Likes: 786
From: Lebanon Township New Jersey
BTW - my battery is 9 years old. Starts the engine fine all the time. I have a disconnect which stays in the open mode 95% of the time. Can a battery possibly cause the charging problem?
Le Mans Master
Joined: Jan 2001
Posts: 6,743
Likes: 1,385
Sounds like the perfect opportunity to upgrade to a 140-amp CS144....... for real. It's wonderful. My battery is also old (like 7 years old) and that CS-144 has been great at maintaining voltage for years.
Thread Starter
Le Mans Master
Joined: May 2002
Posts: 5,086
Likes: 786
From: Lebanon Township New Jersey
I don't really need a higher output alternator but I see the term cs144 describing some new alternators. What are the advantages? Also, what is a 1 wire alternator. I have the stock connections on mine and I want to keep them that way.
Le Mans Master
Joined: May 2007
Posts: 5,029
Likes: 1,120
From: North tonawanda NY
I went this route with my cheap china chrome 105amp unit... turns out it didnt need it but the kit I bought from napa was very easy to install and only took about 20minutes.
In my case the battery would drain while sitting overnight but I had the 2 pin connector installed backwards. At least this way I have high quality components in the alternator and it works well, being able to handle my dual fans and other loads at idle.
I used these videos to decide if this was a skill I wanted to learn.. https://www.google.com/search?q=10si...=2344&bih=1287
In my case the battery would drain while sitting overnight but I had the 2 pin connector installed backwards. At least this way I have high quality components in the alternator and it works well, being able to handle my dual fans and other loads at idle.
I used these videos to decide if this was a skill I wanted to learn.. https://www.google.com/search?q=10si...=2344&bih=1287
Last edited by augiedoggy; Aug 10, 2021 at 01:17 PM.
Le Mans Master
Joined: May 2007
Posts: 5,029
Likes: 1,120
From: North tonawanda NY
cs144 is a later model 144amp alternator. its larger and I believe some minor modifications are needed to install it. it is able to stay cooler while providing more amps if needed... Sounds like you dont need more amp capability in your case.
Last edited by augiedoggy; Aug 10, 2021 at 01:24 PM.
Le Mans Master
Joined: Jan 2001
Posts: 6,743
Likes: 1,385
I picked up a 140-amp CS-144, one of the 3-legged units, at a boneyard just to see if (with the larger body) it would fit in the bracketry.
It fit just fine. I got the best looking one I could find and it cost me 22 bucks. I took it to autozone and go it tested and it tested good! So I bought a slightly longer belt and the appropriate SI to CS converter plug (because I'm lazy). Plugged it in and it worked like a dream.
Eventually I lopped off the 3rd ear so it just mounts with the 2 points which are 180° apart. Some of the best 22 bucks I've spend on this thing.
There are THOUSANDS (if not millions) of those 3-eared CS-144s on all the those FWD GM vehicles. Mine came from a Lumina per my car notes below (geez, that was 14 years ago and they're even more common now): {2-24-07: Bought an AC Delco CS-144 Alternator off a 1999 Lumina, VIN K. AC Delco part number 321-1144}
It fit just fine. I got the best looking one I could find and it cost me 22 bucks. I took it to autozone and go it tested and it tested good! So I bought a slightly longer belt and the appropriate SI to CS converter plug (because I'm lazy). Plugged it in and it worked like a dream.
Eventually I lopped off the 3rd ear so it just mounts with the 2 points which are 180° apart. Some of the best 22 bucks I've spend on this thing.
There are THOUSANDS (if not millions) of those 3-eared CS-144s on all the those FWD GM vehicles. Mine came from a Lumina per my car notes below (geez, that was 14 years ago and they're even more common now): {2-24-07: Bought an AC Delco CS-144 Alternator off a 1999 Lumina, VIN K. AC Delco part number 321-1144}
Melting Slicks
Joined: May 2021
Posts: 2,274
Likes: 1,321
From: Fleming Island, FL
lot of those so-called 3 wire DN10 alternator's that has had it's voltage regulator replaced with in the last 20-25 years will self excite without the field/voltage plug. The one wire alternator is sort of marketing hype.
Thread Starter
Le Mans Master
Joined: May 2002
Posts: 5,086
Likes: 786
From: Lebanon Township New Jersey
Thanks guys for all the input. Just a little more background info: the only things using current in my car is (HEI type) ignition and the power windows. No AC, no fan in the ventilation / heat system. Engine cooling fan and water pump are stock type belt driven units. I have a radio with CD but rarely use them. So, I really don't need anything more than the stock output level.
I haven't checked grounds yet, but I will. I will check the old battery too but I believe it will pass that test. So I'm leaning toward getting a NEW alternator this time, 100 amp max. Jegs has these, supposedly for a 77 Vette with stock wiring, with a deep V belt pulley, black powder coated, for $125.
I haven't checked grounds yet, but I will. I will check the old battery too but I believe it will pass that test. So I'm leaning toward getting a NEW alternator this time, 100 amp max. Jegs has these, supposedly for a 77 Vette with stock wiring, with a deep V belt pulley, black powder coated, for $125.
Melting Slicks
Joined: Jul 2005
Posts: 2,649
Likes: 863
And YES - ANY Alternator is going to get hot when putting out real current for any kind of prolonged timeframe. How hot depends on a lot of things including ambient temp, and the RPM the alternator (cooling fan) is spinning. Most of the time - cars are not drawing crazy high current. Figure less than 10 A for the Ignition & EFI, and maybe 15A for battery recharging. The bigger draws are the electric cooling fan (which can pull 40+ Amps, HVAC (blower fans can easily suck up 10A, and rear defrosters can easily eat up that much or more).
Melting Slicks
Joined: Mar 2005
Posts: 2,095
Likes: 299
From: Midlothian VA
This could be the source of your intermittent charging symptom.