Hi all,

Let me start by saying I have read every single post there is on this subject multiple times, I have made great progress but have unable to get it over the finish line. I hope you all can help.

I am aware that the voltage gauge in our cars can be inaccurate at best. I have found my gauge to reliably be showing me within .5v of actual read voltage at the battery with DMM. The issues I have are present beyond the gauge, I see lights dimming, and at worst slight engine stumbling due to low voltage when taking off from a stop. For these purposes, all voltage readings are at idle since I did not have issues at speeds.

I am aware that there is a lot of people who like to say "this is how GM engineered the car, its only a 104amp alternator and idle speed is slowest". While that may have some basis in reality, I have owned two other Thirdgen and none have had issues that were presentable to the driver like these, so I don't really want this thread to turn into one of those. Unless you want to help me understand how to find a bolt in CS144 replacement, save it!!

The car starts easily, always, and does not die while driving.

Vehicle: 1989 Camaro RS 305 TBI Vin E

Original Issue:

• Car would start, and be at around 13-13.5v max.
• Once the coolant fan kicked on, it would drop to around 12-12.5v. Very much running off battery power.
• Readings would be 13-13.5v when driving at speed.
• Every so often, idle reading would also be 13-13.5v with coolant fan on
• Signal light on causes the voltage gauge to bounce with it, and a corresponding voltage drop of around .5 volts can be seen at the battery with a DMM so its actually dropping and not just the drop from the wiring to the gauge, or PCB, etc.

What I did:

• Replaced alternator with New not reman, GM Genuine replacement part.
• Replaced belt and tensioner at the same time just in case

Current Status:

• Car now starts at 14.5 volts
• When coolant fan kicks on, there is a brief dip but voltage holds at around 14.3-14.5v
• Signal lights still have a .5v affect when blinking, read by gauge bounce and a DMM at battery.
• If you turn on any other accessories, voltage begins to dip little by little until you are back to 12.5v and on battery
• Worst offender seems to be the blower fan for the HVAC, but you can run any one thing no problem, its the combination that gets you

What I have tried, in order to try to fix without success:

• Replaced the wire that goes from Alternator BAT+ output, to the junction block with new, 4 gauge wire. I found the original to have open insulation in it, as well as corrosion. Thought for sure this would fix it all, but it had near 0 effect on it.
• The thick black ground wire that comes off the battery, it splits to the inside fender for chassis ground, and then goes to the front passneger side of my engine block(behind the AC compressor) for block ground. I removed the screw at the block, removed the wire, and used a wire brush to clean both the cable end and the area where it screws to the block and reassembled.
• Located G200 under the steering column and cleaned it up (for gauge)

I am starting to think that my issue could be a bad new alternator that does work, but just can't seem to support the amps when asked, or less likely based on the symptoms, but i read on some other posts it potentially could have to do with my ignition switch having extra resistance, however I would think that if that was the problem changing alternators would have had no effect. Thoughts?

Should I upgrade the battery to engine ground, and battery to fender frame wires with 4 gauge and complete the "big 3 upgrade"? As you've read, having upgraded the Bat+ has not helped.

There is a ground strap at the back passenger side head. Should I replace this with a new 4 gauge ground? How does this differ from the ground in the fender by the battery?

Any unmentioned grounds to check?

Thanks

 

Do u have an actual ground wire from the block to the chassis/subframe? With my 1984 Trans AM 305v8, I had to have my alternator rebuilt. Once installed & problems with alternator noise, voltage drop to 12+ when driving with headlights on, alt getting extremely hot.
I owned a 1972 Buicks GS that had a separate ground wire from the engine to the frame but the T/A had none.
I installed that ground in the T/A. All problems solved.
How did this car had run for 40+ years with no alt / grounding problems?
The alt, when rebuilt, was painted by rebuilder. I determined that the paint was thick enough to have broken the grounding of the alt to the block.
Make sense? It worked for me. Try it.

 

there is a ground running from the battery to the inner fender well.

There is a ground running from the battery to a bolt on the front LH side (when looking from the engine bay) of engine, behind the AC compressor.

there is a ground strap at the back LH side of engine to the firewall (G112?)

there is a group of smaller ground wires on the back RH side of engine (G118)

all of these grounds, and the alternator case, have continuity to battery negative and all are 0.1 ohms resistance.

I’m starting to lean towards a bad new GM Genuine alternator or that CS130 alternators really cannot support the amps @ idle RPM. Replacing the old, what appeared to be original alternator did help somewhat, but I’m still searching for amps that seem unavailable.

I am going to warranty the alternator, and speak with Mechman alternators on Monday about their drop in replacements for our cars. 140 amp alternators that say they deliver 120 amps at 800 rpm, at 200 degrees too

 

You've probably already got a replacement but I installed a 220amp drop in alternator from new Silverados. It defaults to 13.8v at the post when configured without anything else hooked to it. Can purchase a PWM controller to make it output around11-15.5V.

https://www.thirdgen.org/forums/alte...ml#post6544333

 

I hate a thread without a resolution so:

I went with a mechman alternator. The 170 amp one they sell as drop in for our cars. It fit perfectly. It used the original size belt, and it makes over 100 of those 170 amps, at 500rpm.

This alternator has me at 14.5 at all times in all load/rpm conditions.

This thread is solved at this point.