LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

93 Z/28 LT1 alternator and battery probems

Old 05-06-2019, 07:41 PM
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Question 93 Z/28 LT1 alternator and battery probems

I have a 1993,all stock,Z/28 6 speed LT1...I have brand new battery and had it tested at Advance Auto,where I'd purchased it to make sure it wasn't defective or going bad while under warranty. I had purchased and replaced my original alternator with one from a local NAPA parts store (YEAH I HATE AFTERMARKET STUFF>>>BUT>>>>) This was done because I was in a situation where the car broke down on me on the road one day and could get a friend to replace it on the spot as a favor to me so with limited resources in the moment I went with the NAPA alternator.
So,the new alternator don't even have 200 miles on it and every time I leave the car sitting for a few days the battery drains down to ZILCH on me. The stereo in it was put in in 1996,a few months after I'd purchased the car and was professionally installed. All thru the years I have NEVER had an issue from the stereo as far as battery drain. I do know that there seems to be a "short" of sorts in the stereo,tho where sometimes it wants to work and others it is like it's losing connection to power and if I reach behind the center of dash where it's hooked up at and move the harness there around "connection" is back to okay.
First issues of the battery drain started tho after the car had been just sitting in the garage over the Winter,even tho I'd go out and crank it and let it run at least once a week. I do tend to let her sit right much,as I bought a little 96 Honda Civic as my "run around" vehicle in order to keep miles off the Z,but didn't really drive a LOT when I used her as my primary vehicle because I don't drive a lot due to the fact that I work from home.
I guess now,with the threads I've read so far seemingly related to my issue I have come up with a couple of questions:
1- There is the wire/harness connector I've read about on here to the back of the alternator and is it possible my "friend" forgot to plug this in when he installed the new alternator? Would this also cause the new alt NOT to charge a new battery to full charge??
2- What would make the alternator sound like loud,whirring or whistling?CRAZY sounds? It started this the last time I drove it about a month ago one Friday night when it had gotten dark out. (Random,but possibly helpful fact:I hit a patch of loose gravel in the road where the DOT had put down,but no signs to let you know..and literally SHOT off the right hand side of the road,but handled her like a champ,didn't panic and corrected,didn't hit anything nor bottom out in ditch or dirt.I was litereally 15 to 20 feet OFF the road running paralell next to a corn field. Yes, I live in the STICKS lol... A few miles later is when the sound I am referring to began. I thought maybe the "jolt" to car had done something to my clutch because if I pushed it in to engage it the noise would stop and letting pedal back out would then immediately let the sound start again.) LOUD enough I actually thought maybe something had taken up residence in my engine compartment! Now when cranked and idling this sound just goes on constantly and with the hood up I can tell it IS the alternator making this racket.
3- Where is the best place to get another alternator? I do NOT want to go back to NAPA...these guys don't even keep your purchase in their "system" and the blamed receipt with how they fade these days isn't where you can read it now! (and how I WISH I had not let them take my original as a CORE I replaced the 2 pack coil/distributor and all on this car at local GM dealership years ago. I have tried any and every time thru the past 26 years I've owned this car to always put GM and OEM parts on it if there had to be anything done. I worked at a place Camaro Junction for many years selling parts for Gen 1,2 and some Gen 3's and made lots of "connections" to people,so I can usually get wholesale prices for things if they are still available.
4- Is there a possibility that a fuse or something like a relay could be going bad making a lot of "odd" things happen? Oddly as well,now when I turn the steering wheel hard or push on one side of it the horn will blow. Sometimes it blows at will for NO did this in the middle of the night several times and I had to run out and get it to stop. (I'm wondering if flying squirrels/chipmunks/mice have possiblly bit or chewed into a tiny piece of wiring....just enough to cause me a real "PAIN in the BUTT" situation with my car. Especially since it's beautiful weather now I want to get her back in tip top shape and ride her some and all this is just frustrating!
5- Side thought note: My secondary fan was wired to a "toggle switch" by my ex about 4 years ago,so I turn it off and on by that manually. (I still wonder why he didn't just get the replacement relay and put it on when we replaced the radiator for a crack in the top as they took the entire front end off the car to do part of this.I know that by nature some people are "shortcut takers" but if they are doing work for free to help me out I don't complain.)

Sorry for the long,sporadically thought jumping post but I really hope someone here can help me figure this out. I'm planning to do the work this time myself,as the car is here and I have the tools and place to work on it now.

Gotta get this one right and riding so I can start in on the 91 RS,which needs valve cover gasket and correct relay to fan...the previous owner who converted it to the 350 carb engine used the wrong one and causes the fan to stop entirely when the too small guaged wires get hot. Thus the blown head gasket,but thankfully nothing more than just that.

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Old 05-07-2019, 05:30 PM
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Re: 93 Z/28 LT1 alternator and battery probems

When the "stereo" cuts out, do the power windows also cut out? If so, that could be a problem with the retained accessory power module (RAP). If there is a problem with the RAP module, it may also be causing the battery drain, because it is supposed to turn the stereo and interior lights off based on the driver's door opening and closing,

Courtesy of Shoebox:

With regard to the battery draining down, what does the dash gauge show as the voltage when cranking the starter? When the engine starts after a long shutdown, does the voltage climb up as high as 16 volts? That would indicate the alternator is replacing the battery charge. After the engine has been idling for a while, does the voltage gradually drop down to about 13 volts on the gauge? Have you ever measured the battery voltage at the battery terminals BEFORE trying to start the car?

As I mentioned in the PM, the best way to find a current drain is to put an ammeter in the line from the battery to the red battery "+" box. DO NOT ATTEMPT TO START THE ENGINE - you will fry the meter. look for DC amps, and read the current flow. It should be in the less than 1/10th of an amp range. That's what keeps the memory in the PCM, the stereo. HVAC control head, etc. If you have significantly more current flow, start pulling the fuses one at a time to see which circuit is drawing the current. The meter will drop significantly if you pull the right fuse. Replace the fuse and move on the the next one. Remember, there are fuses in the panel at the end of the dash, in the underhood convenience box, and possible inline in new power wires running to any aftermarket audio equipment. And dont forget the 1/.2-dozen or so fusible links that connect directly to the red "+" box. PITA to pull the links one at a time.

Courtesy of Shoebox:

No problem replacing the 124-amp alternator in your 93 with a 140-amp from a later year. Wiring is identical for all years.

There are only two wires attached to the alternator.... a heavy red wire direct from the battery (no connector in the line), and a thin red wire from the instrument cluster (connector C220 inside the car).

From Shoebox:

See if that helps, and then we can work on the alternator screech, fan wiring, etc.
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Old 05-07-2019, 07:23 PM
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Re: 93 Z/28 LT1 alternator and battery probems

Thanks Fred...I am printing off what you told me and will take it out with me to be sure I follow it closely. As far as the radio it's more like hitting a bump in the road and the connection is lost then reaching behind there and shaking the harness to it fixes that. My interior lights and radio still do the auto shut off if the door opens.

I have a meter...had to get one last yr when power surge in my house caused big issues and also burnt out my AC unit and fried 2 double 60A breakers in my Main Box too. So I know to set it to dif Voltage for the car to test it correctly.

Tks about the 140A alternator too..I noticed there's one for sale on here that is an ACDELCO and will pay the 100$ for it to have another good one. The REMY aftermarket one probably had issues when I first bought it. Car don't have even 200 miles on it since installation and Advance did the battery check for me and confirmed NO issues with the battery,which also is a higher cold cranking amp in their top of the line series. Still warranty on it so I'm good there thank goodness!

Let's get the meter and go play round under the hood now it's cooler here in VA this pm. Will update what I find.
Thanks again!
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