Voltage issue

So start truck voltage goes to 14.6
When warmed up 14.3
My issue when concern if stopped at light idle ,voltage drop to 13.0 to 12.8
Put in park raise to
14.3
Put in neutral 14.3
When driving it 14.3


Alt 2 yr old
Is this normal?

 

No, the voltage should not drop that much at idle, unless you have a lot of accessories turned on, or your idle is below normal, which I believe is 600-750 for a warm engine and depending on ambient temp. Mine drops as low as 13.3 in summer, in idle, and is usually 13.9 give or take a couple points. Resistance affects voltage, so try cleaning all alt/battery contacts and disconnect/connect connectors to see if it helps out.

Note, I see your drop is when in gear. I don't recall what mine is in gear and stopped. Will take note on my next drive. Your numbers look better than mine at idle.

 

What the best way to clean connections?


Only seen with driving in morning with lights on. Stock headlights

 

Many times just disconnecting and reconnecting helps establish a better connection. Look inside the connector and look that the contacts are not corroded. Should be shiny inside. Move over to battery terminals and ground connections. I uses wire brush where I can, then coat everything with dielectric grease to fight corrosion.

I took some readings on my truck for reference. I have an aftermarket 200-amp alt and a two-battery system, but voltage output should behave the same. I also have the diode that bumped up alt voltage output .6 volts.
At start up, 70 degrees ambient; 14.5v at 1300 rpm.
Warmed up; 14v at 800 rpm, idle in gear; same voltage in neutral, at 600 rpm.
No electrical loads. Correction, I had a light e load: DRLs, radio and fan on 2nd setting.

 

Spec is 13.2V-14.8V. You aren't far off. I bet everything is ok. How did you measure volts? It's normal for output voltage to drop at idle (in gear) as the alternator output is based on RPM (more RPM = more voltage, see image below which is for amps but volts also drop at low rpm). If you are measuring at a poor ground or using a cheap meter or cheap leads you can see a small voltage drop which may account for the slightly low voltage at idle or maybe your idle is too low.

One reason auto manufacturers switched from analog oil pressure gauges and voltmeters to idiot lights is people got confused when oil pressure dropped at idle and volts dropped at idle and never bothered to read the provided owner's manual and brought cars in for unneeded warranty service.

It's worth checking/cleaning your connections but I bet nothing is wrong.

 

Get yourself a battery brush for the battery terminals and posts. Any auto parts store should have cheap ones for about 5 bucks. To save your tools from arc marks, disconnect the negative terminal FIRST without touching the positive. To help keep your new battery brush from smashing, brush the positive post and positive terminal first, then the negative post and terminal next.

Sometimes autozone will have noco products on the shelf. Their corrosion prevention felt pads are top notch. Their spray on cleaner & protector are ok. Coke a cola works best if you have caked on acid on the terminals. Take the battery out, put a little container where the battery was, soak them.

A really good way to check battery health is a starter voltage drop test. If your meter has peak high and low hold, set it for peak low dc volts. Start the engine, see what it says.

 

Please don't use coke on battery corrosion, it just makes a sticky mess and it's an acid so it doesn't do well to neutralize battery acid.

Baking soda mixed with water is a much better way to clean batteries and neutralize the battery acid, it's cheap and readily available.

 

Where get the grease from?

 

Been using a stinger voltmeter it connected to 2 battery. I'll try clean all connections and the big 3 I did. Also going to alt. If make any difference

 

Any auto parts store. Walmart has them and I bet also Home Depot and Lowes. It is very similar to silicone grease but silicone is designed as a lubricant and dielectric grease is designed as an insulator and designed for electrical connections. I also put dielectric grease on my AC electrical/cords extensions.

So, I wanted to see how low of a voltage I could get with a warmed up engine in gear last night. I got down to 12.9 volts by turning on everything I could think of (but I forgot the fog lights) - lights on and with high beams, hazards, wipers on high, fan on high, interior lights, brake light, auxiliary Ridgid Hyperspot driving light, and I was charging my iPhone. RPMs were around 600-650. As soon as I put it in neutral, voltage shot up to 13.9 and 800’ish RPMs. Ambient temp was 62.

 

Yes only thing on though is my headlights

 

I know. I was pointing out when 12.9v might be normal. In your case, your alt is going bad or you have build up resistance in your charging system at or beyond the alt.

 

$15 NOCO NCP2 A202 12.25 Oz Oil-Based Battery Corrosion Preventative, Corrosion Inhibitor, and Battery Terminal Protector Grease Spray

https://www.amazon.com/NOCO-A202S-B...2172255&sprefix=Noco+corr,aps,191&sr=8-3&th=1

 

How I fix the buildup resistance???

 

I take pucof both batteries they look ok. No corrosion

 

That’s what we’ve discussed - removing the wiring and cleaning the contact points. Degrease as needed. Use fine sandpaper as needed. Start at alternator, work to the fuse box. Clean battery cables, terminals and ground points. Apply dielectric grease to all contact points.

 

Why would you apply a insulating grease between electrical contact points?

Maybe brush some on over the external part of the connections, but never between.

 

It squishes out when you tighten things up. That’s how I’ve always done it. Faux pas? But, it has worked and contacts stay corrosion free.

 

1. Aren’t these from factory set to charge lower than other cars to reduce parasitic loss?

2. isnt there also a mod out there to up the charging voltage

I don’t know if it’s the diode mode and if that’s only for AGM batteries. If it would be a problem used with regular lead acid or not.

could be pass/fail. Either it works or doesn’t. Either battery is good or dies.

you can run a test on it as well. If you want more confirmation before condemning part and buying replacement.

 

May be, but it isn't intended for that purpose and subtracts from a good electrical connection.

My advise is to clean both surfaces well.
Mate them making sure there is good contact between the two surfaces.
Tighten the retaining bolt(s) to specification.
Coat the exposed surfaces with a corrosion preventative of your choice to seal out moisture and prevent corrosion.

This would be a better choice as it conducts prevents corrosion and seals.

https://www.sanchem.com/electrical-contact-lubricant.html

PDF Document: https://www.sanchem.com/docs/NO-OX-ID A-Special Electrical Grade.pdf

NO-OX-ID electrical contact lubricant (electrical contact grease) is an electrically conductive grease that keeps metals free from rust and corrosion.