Under heavy load or when in passing gear, the voltage gauge drops and the headlights dim. This started after I replaced a battery that would no longer hold a charge. The battery, alternator and belt tensioner have all been replaced. When tested at a chevy dealer or parts store this system load test @ 2000 RPM is fine. Also have 12 volts between the ground cable when disconnected and the battery ground terminal.
An expert who has achieved level 3 by getting 1000 points
An expert that got 20 achievements.
An expert that got 10 achievements.
An expert that got 5 achievements.
Re: Charging system malfunction under load
If the condition is present for short times only it will not affect
anything. It's possible that the crank pulley is glazed and slipping
slightly on a hard pull (everything else depends upon that pulley to be
properly driven) You can't really duplicate that on a static test.
It's also possible that the battery was a bit low when you bought it
and needs to have the charge level topped off with an external charger.
Otherwise, the only option I can think of offhand would be to obtain an
alternator designed for heavy duty service (police version etc) which
may be able to deal with the demand.
As your vehicle gets older, resistance in all circuits increases,
making little difference during normal operation but can also influence
how your vehicle charges. Cleaning / adding additional ground points
can help with this.
If it seems that I'm jumping around a bit, I am, but since the charging
system is pretty much operational except at that one point, I'm trying
to give you some ideas that either in combination, or one alone will be
of some help to you.
a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need. goodluck!
- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
the voltage should remain at 14.5 volts at all engine speeds above idle 13.9 volts at idle indicates that the alternator is charging but not at set voltage
head lights are the biggest drain that affects charge rate rate and it it maintains and from you description that is not a problem
when you select a gear it indicates a heavy drain which is a high resistance or a dead short in that circuit that is taking out more power than the alternator is charging
There there is nothing in the gear selection that draws such power
the other thing is that when selection a gear the engine rpm is tool low and the alternator stops charging
for auto vehicles , the idle rpm should be at 800-900 rpm dropping to 750-800 in drive
DIM fuse #38 10amp in the rear fuse block .this is for battery sense for voltage regulator . The other two wires in that connector are to the PCM - engine computer .
Fuse Block - Rear
In the passenger compartment, under the left side of the rear seat cushion
Did you check the heavier gage wire on the back of the alternator for Batt. + voltage ? This wire comes from the fuse block under the hood an has a fusible link .
This is a computer controlled charging system.
Electrical Load Management
Electrical load management is designed to maintain battery voltage and covers more than load-shed. The dash integration module (DIM) will request increases in idle speed from the powertrain control module (PCM), when the vehicle is in park or neutral, as well as turn off loads in order to manage the electrical system and preserve the vehicle electrical power availability. The DIM calculates the battery temperature, voltage and charging rate at all times while the engine is running.
You may need a shop manual to get the wiring diagrams and test procedures. The alternator output should be around 14 volts unless you have a heavy load such as headlights or the heater blower on high. If voltage goes above 14 the regulator could be faulty even tho you say the alternator checked out ok on a bench test. The regulator gets a power signal from the gauge on the dash to energize it. There could be a loose connection somewhere in the charging system, or something in the instrument cluster. Even the key switch could be a factor.
Yes this can be a normal condition caused by load being applied to the headlights and that lowers the voltage, the lites dim, then the load is removed and the lights brighten. Typical loads that cause this are AC climate control related. Have the Alternator load tested to confirm there is no problem in the charging system. Also have the battery tested, a battery that is starting to fail can cause this problem as well, a failing battery takes a huge amount of charging system power to keep it up, so that makes the lighting see higher spikes in voltage
A battery's voltage is properly tested under load. This sounds like your battery is low on fluid or has not been charging properly. Not charging properly could be from low battery fluid, poor cable connections or a failing alternator. You did not state whether you tested this voltage issue with the vehicle running or not. If the vehicle was running when you observed this change in voltage upon turning on the headlights, then a bad alternator is most certainly suspect.
PNP park neutral safety switch . Try moving gear selector to neutral . If it starts the switch is bad .
Voltage drop test starter circuit .
fusible relay ??? Now thats funny ! It's just a relay , not fusible relay ! A fusible link is a kind of fuse ,will melt with a short circuit. TEST ,TEST DON'T GUESS and if you can't test ,take it to a qualified repair shop.
How to voltage drop test starter motor circuit Starter Voltage Drop
The computer has nothing to do with it .
http://www.bbbind.com/free_tsb.html Free wiring diagrams ! Suggest you view a wiring diagram to see what all is involved in the starter circuit . NO starter relay ! Enter vehicle info. under system click engine, then under subsystem click starting . You will when you turn the key to start it send's B+ voltage to the PNP switch ,from there it goes to the S terminal on the starter solenoid . Very simple . Get a volt meter an test B+ voltage .
It takes very little voltage and amperage to operate dash gauges. You cannot rely on "seems" when it comes to the battery. A good battery should have standing voltage of at least 12v and be able to "snap back" from a fifteen second 200 amp load. Under load, the voltage should not drop lower than 9.5 volts. Have the battery charged and load tested before going anywhere else with this. then make sure connections are clean and tight. After you get it started, if battery was good, check starter draw and charging system operation. If it does not start, check power flow from key through neutral safety switch and starter relay to starter.