Electrical Troubleshooting / Bad Alternator?

[jw63]

Hello all -- looking for some help diagnosing an electrical issue.

Purchased the car last year and installed a new battery over the winter months.

Recently I've seen some low voltage readings while driving. Voltage appears to be normal after starting the car (14V range) but once returning to idle at a traffic light, voltage drops with a turn signal load (voltmeter ticks/pulses up and down with light) and also drops significantly if the fans kick on while at idle (I'd guess down to 11-12V range). All of this happens more frequently with heavier load on the battery (i.e. lights on, radio on, ac on, fans on, brakes/turn signals on). I doubt this to be normal operation?

Is this sign of a failing alternator, or could it just be a bad ground somewhere? Battery terminals are clean but I believe there are 2 ground points on the back of the engine that should probably be checked. I purchased an ACDELCO rectifier for the alternator but have not installed it yet.

I've also been receiving a INFL REST light (code 26) frequently. I had cleared the code last year but it just now reappeared. Sensor area seems to be pretty dirty and needs to be cleaned up, but not sure if the problems could be related at all.

Thanks in advance for any assistance.

[Ccmano]

As I tell everyone in this circumstance start with the battery new or not. Take it and the alternator to an Autozone (or similar). Have them load test the battery and test the alternator for free. If Im not mistaken they can test both while still in the car. Also be absolutely sure the battery terminals are clean, wire brush thoroughly even if they look clean. If those check out move to the other ends of the battery cables and make sure those connections are clean and secure. Lastly clean an resecure the grounds on the engine/bellhousing with dielectric grease. Your symptoms are not unusual for an aging electrical system. To one degree or another all our cars do this.
H

[Paul Workman]

X 2!

[32valvZ]

I was having a similar issue. I replaced my alternator with one of Jerrys Remy rebuilt units.. For the first 50 or so miles, I noticed the light pulsating was actually worse than with the old one. Now its completely stopped. Im thinking the brushes had to seat in a bit and create the arc shape between them and the copper ring on the stator, making better contact. Just glad it quit though..

[Paul Workman]

Flickering lights, i.e., dash lights dimming with turn signals, etc. is one of two sources: The voltage regulator (module inside the alternator), OR resistance build-up in either the positive source OR in the ground connection.

Note: A highly resistive (film) often forms on the surfaces of connectors - especially those exposed to air/humidity/and SALT (especially), and may even appear clear to the naked eye. Therefore, scrubbing with abrasive paper or wire brush followed by an aerobic barrier like dielectric grease or specially designed electrical sealer will cure a host of erratic electrical gremlins! (Start with the two main ground posts terminals under the MAP sensor. I suggest you tie-wrap the wires before removing the bolt securing the several circuit ground wires to prevent the individual lugs from inadvertently pulling away out of reach...ask me how I know!)

[Corvette95]

I have a never used rebuilt LT5 alternator if you have the correct pulley and spacer you can swap to it.


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