Voltage drop

[Michael Starbuck]

Hey guys having some problems with my system. All my lights dim when the bass hits. I upgraded my alternator from the stock 105 amp to a 145 amp alternator without any difference. If anything it got worse, it’s a 1000w system in my 03 gmc 1500hd. I believe it to be more of a problem outside of the system as when the truck reaches high rpm getting on the freeway the lights all dim until I let off the gas. What do you guys think it can be. The truck has the big 3 upgrade as well. Don’t know what would cause such huge voltage drops in my truck as I have run systems about this size in other vehicles with no dimming like this. Should probably put this on a car forum as well but would like to see if you guys have any intake on this as well. Is the alternator still not big enough? Or is it something else? 

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[Boomin_tahoe 5,000+ posts]

A poor connection, corrosion, the type of wire being used, the diameter or gauge of the wire, and the distance between the source and the load can all cause resistance in wiring.

If it were me, I'd go over every single nut/bolt and make sure everything is tight. 90% of time voltage drop is caused by a lose/poor connection somewhere...and can lead to further troubles such as melting of fuse holders, and wiring.

Also make sure the battery is in good condition. Have it load tested too if you can or if it's new within a few to several months.

 

[ckeeler11]

Is the voltage regulator separate from the alternator on that vehicle? If so I would look there.

 

[Michael Starbuck]

Voltage regulator is on the new alt. I’ve gone through all my wiring to the amp multiple times. I’ve tried many different grounds on the amp with no success. I believe it to possibly a ground somewhere else but am not sure where to look. My battery already has 3 grounds on it with 2 of zero gauge wire. All grounds are on bare metal. I’ve been dealing with this for quite some time now. Battery is getting a little old but not sure if that would cause the problem, as it hasn’t shown any sign of going and has had this problem since being new. 

 

[Boomin_tahoe 5,000+ posts]

What does your battery read for voltage when the vehicle is running?

 

[THATpurpleKUSH 5,000+ posts]

Was the 145a alt used? Pull it and have it tested by a reputable shop. Sounds like the alt is slowly failing. 

 

[Michael Starbuck]

The alternator was a refurbished 145a. Didn’t see a difference when changed from the 105a. Truck had big 3 upgrade with 0 gauge wire. A new alternator ground, engine ground and hood ground. Can’t figure this one out. Like I said I believe it to be a wiring problem outside of the system itself because engine quickly drops in voltage above 4000-5000 rpm. Voltage reads about 14v at idle so no problem there until accelerating or bass drops. 

 

[THATpurpleKUSH 5,000+ posts]

Sounds like the belt is slipping if higher rpms are giving you trouble. Check the belt tension.