Noticable Electrical Drain when Braking

[MaddCelt]

Something I have been noticing lately on my 98 OBW is that then I brake I notice a drain on the electrical. The lights dim and the blower slows down until I let up on the brake. It happens when the clutch is pressed or when in neutral.

 

Any ideas?

[lmdew]

pull the fuse for the brake lights and see if it still happens. If pulling the fuse fixes it you have a short in the brake lights somewhere.

[doc526]

Could just be a weak alternator. Is it a stock or reman unit?

 

When I come come at night and roll the windows up with the headlights on, the lights get dim. It has been this way since I bought the car and have gone through several "reman" alternators for bearing and rectifier failures. All remans I have used have performed this way.

 

The only reason I keep using the reman units is because I keep getting them for free under warrantee.

Edited June 30, 2011 by doc526

[backwoodsboy]

+1 for an alternator on its way out.

[MaddCelt]

I had thought about that. There was a recall in the past for the alt but it expired so I could not get it replaced. So it's likely the same one from the day it hit the street.

[edrach]

Get a voltmeter and check battery voltage and alternator output. Most likely, the alterntor is no longer up to snuff, but it could also be as simple as a loose alternator belt.

[MilesFox]

Do you have trai,er wiring? sometimes the wrong pigtail (2 wire vs 3 wire0 will be installed, and it crosses the brake and turn circuits.

 

See if the marker lights are coming on with the brake pedal.

[Ricearu]

my forester has done this since I got it... 14k miles strong... rev it to 2200 rpm, it doesn't do it. if you think about it, headlights pull about 10a, blower motor on hi is probably close to that and the brake lights are going to pull about 5a plus a few amps for engine control, and a few for running lights... also, now it's summer and if the a/c is running, you have a small draw at the compressor and the ALWAYS running alternate fan pulling 7-10a. at idle your alternator only makes about half it's rated capacity or so

 

my vote is with normal operation of vehicle unless they dim a crapload or the battery won't stay up.

 

also if you want to check for hokey rectifier, then check for ac voltage at the battery. FSM gives a max spec. this generally will point out leaking diodes in the trio.

 

edit, also if the clutch is in or in neutral, your at idle. think about that. that's the least efficient speed for the alternator

Edited June 30, 2011 by Ricearu

[cagranitz]

Could also be poor/dirty/corroded ground connections. Check/clean/tighten all of the various ground connections to the body and engine.

[CNY_Dave]

You would probably notice the ABS unit running, but when the ABS activates it draws a considerable load.

 

Dave

[Fairtax4me]

It's nothing to worry about. Pretty normal for an old car with an aging alternator. Every car I have EVER owned has done exactly this.

My Lincoln did it from the first day I bought it with 55k miles, sitting at 78k now and the alternator still charges just fine.

My 96 Legacy sedan has been doing it since I bought it at 166k, still doing it now at 187k.

 

There will be other signs before the alternater goes out completely. Slow starting and random lights on the dash coming on (ABS, Battery) are the most common.