Why are my headlights dimming when braking?
#23
i think i would take some measurements around the car, see what the voltage is in the car when putting on the brake. they might have had to small a circuit somewhere. might be beneficial to put the sense wire in the car where the loads are
you may have some water in some of the light housings. or water getting into the harness some were or the wire partially shorting to ground due to vibration chafing the insulation
you may have some water in some of the light housings. or water getting into the harness some were or the wire partially shorting to ground due to vibration chafing the insulation
#24
Thread Starter
Senior Member
Posts like a 4 Banger
Joined: Oct 2009
Posts: 143
Likes: 0
From: Minnesota
i think i would take some measurements around the car, see what the voltage is in the car when putting on the brake. they might have had to small a circuit somewhere. might be beneficial to put the sense wire in the car where the loads are
you may have some water in some of the light housings. or water getting into the harness some were or the wire partially shorting to ground due to vibration chafing the insulation
you may have some water in some of the light housings. or water getting into the harness some were or the wire partially shorting to ground due to vibration chafing the insulation
So where would you suggest moving the sensing wire too? I would think the greatest load would be right where it'* at, where all the maxi fuses and relays are located.
#25
I believe the main issue is, the alternator is not strong enough at idle RPM to provide enough power to maintain a sufficient charge on the battery. Though your alternator may pass the bench test at Autozone, but they also ramp up the RPM beyond your normal engine RPM of 600-700. Usually this is due to a failing rectifier bridge. Just my 2 cents.
__________________
Retired Administrator
Retired Administrator
#26
Thread Starter
Senior Member
Posts like a 4 Banger
Joined: Oct 2009
Posts: 143
Likes: 0
From: Minnesota
I believe the main issue is, the alternator is not strong enough at idle RPM to provide enough power to maintain a sufficient charge on the battery. Though your alternator may pass the bench test at Autozone, but they also ramp up the RPM beyond your normal engine RPM of 600-700. Usually this is due to a failing rectifier bridge. Just my 2 cents.
Is there any way to test the rectifier bridge? Or does that mean it'* off to buy a whole new alternator?
#27
If the cables and battery are truly in good condition, it may be possible to do a amp draw test on while a load was placed on the alternator. Basically, measure the amount of amps being drawn on the battery engine off lights on etc, say if its, 50 amps, start car up, allow to reach operating temp or 600ish RPM whichever comes first, then measure the amp draw with the same electrical load except, connect the clamp onto the alternator cable. If the value is the same or higher, and if you increase the RPM and the value goes down, then, yes, your alternator is dying.
I hope that made sense. Or you can read this one, but its using voltage which isn't a very good test. How to Test a Car Alternator
I hope that made sense. Or you can read this one, but its using voltage which isn't a very good test. How to Test a Car Alternator
__________________
Retired Administrator
Retired Administrator
#28
Thread Starter
Senior Member
Posts like a 4 Banger
Joined: Oct 2009
Posts: 143
Likes: 0
From: Minnesota
If the cables and battery are truly in good condition, it may be possible to do a amp draw test on while a load was placed on the alternator. Basically, measure the amount of amps being drawn on the battery engine off lights on etc, say if its, 50 amps, start car up, allow to reach operating temp or 600ish RPM whichever comes first, then measure the amp draw with the same electrical load except, connect the clamp onto the alternator cable. If the value is the same or higher, and if you increase the RPM and the value goes down, then, yes, your alternator is dying.
I hope that made sense. Or you can read this one, but its using voltage which isn't a very good test. How to Test a Car Alternator
I hope that made sense. Or you can read this one, but its using voltage which isn't a very good test. How to Test a Car Alternator
#30
__________________
Retired Administrator
Retired Administrator