Sudden voltage drop???????????
Thread Starter
Racer
Joined: Jun 2007
Posts: 459
Likes: 2
From: Hawaii
Sudden voltage drop???????????
Whenever I hit the brake on my 96 LT-1 my main orange LCD screen on the dash dims, is this common, or perhaps a voltage drop from a weak alternator? Regulator?
Does anyone else experiance this problem?
Does anyone else experiance this problem?
Le Mans Master
Joined: Jul 2007
Posts: 5,356
Likes: 2
From: No HOA, New Hampshire
Cruise-In X Veteran
St. Jude Donor '09
Does the volts gauge drop as well? IMO The alt would be the first thing to check, second the battery. Sudden loads on the battery can cause the voltage to drop. Let us know what you find out.
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
Could be several things, loose/corroded wiring at alt/battery, or battery. If it is the alt you should seeing other symptoms as well. I would check alt and battery connections first then go from there.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
You need to determine if the voltage across the battery drops when you put the brake on is due to a failing voltage regulator in the alternator. An easy test is to put the ign sw in the run position without the engine running and then press the brake. If the dash dims, then the alternator is not the fault. If the alternator isn't the problem, I would first remove the battery cables (neg first) and clean the cable lugs, bolts, and the battery terminals and replace the cables (neg last). Try the experiment again and if the dash still dims, you will need to find out where the voltage from the battery to the dash is dropping when you press the brake. First, with a digital voltmeter (Harbor Freight for $7), see if the voltage at the battery drops when pressing the brake, then see if it drops at the brake fuse. Power gets to the fuse block through a fusible link, then through the connector on the firewall, then to a large splice in the wiring harness behind the dash where individual wires go to about 6 individual fuses in the fuse block, one to the brake fuse and one to the dash display. Any unusual resistance in the connections from the battery positive cable, fusible link, firewall connector, or the splice can cause your dash to dim with brake applied.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Do you have a larger pulley on the alternator to reduce parasitic load? The alternator has a limit on how low its rpm is and its ability to supply current. At normal idle speed and without an excessive electrical load, the alternator should be able to maintain 14.3 volts (dash voltmeter) across the battery. You may have a defective voltage regulator in the alternator. You can replace the regulator or the alternator. The regulator is cheaper. You can have the alternator tested for output at low rpm too.
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