Gremlins = Alternator?

[shane344]

Hi All,

After a little trouble shooting assistance chasing down an issue I'm having with my wagon.

So I'm losing voltage when I tap the brakes, only on initial application, when the lights get activated.

It's enough to turn my head unit off (basic single din install no amps) which is how I noticed it, and visibly bump my volts gauge down to around 10 volts.

It's only temporary on initial brake application and if i hold my foot on during a normal stop it pops back up and away we go again.

It's really intermittent, its happened three times in about 15 drives, but when its happening it can even drag enough down to cause a cough through the engine as it runs out of voltage to run the coils and ecu.

It has stalled the car at idle when I was playing around in the garage trying to find it..

I have turned off everything feasible (stereo, AC, fan etc) in car when it's playing up, no difference.

Bought a new battery last week after seeing some funny voltages at the battery, was pretty old anyway, happened again today (NS70 suits C34s BTW, skyline stuff isn't tall enough and the battery clamp wont work without adaption).

All 5 brake lights are visibly working, havent inspected the globes or holders yet.

Voltage and resistance through the globes via the brake switch seem reasonable.

Thinking this through I think the brake application is a trigger but not the cause.

If I had a short or something in the brake light circuit it should just blow the fuse in that circuit and not cause any other systems to be affected.

I'm thinking alternator reg isnt keeping up with sharp changes in load and pooing its pants so to speak, but the battery should be able to keep up and maintain.

I guess if alternator is the issue, my new battery is now getting low and not getting charged properly meaning it cant keep up when its having a bad day.

Anyone else got any ideas to look at before I order a replacement alternator?

I know this place is the awesome to access pretty cluey, helpful and experienced people so thanks in advance.

[89CAL]

Have you got a multimeter on the battery and checked the voltages with the car running and stationary? Its a good place to start, especially seen as Stagea batteries are in the engine bay (if I remember correctly?) you should see voltages being output by your Altenator fairly well. If it seems a bit odd you may have a wiring or earth issue.

Just get a multimeter and check battery voltages first before doing anything, you may end up saving yourself alot of money

[Duncan]

I know you said you changed the battery, so I'll assume you are sure the clamps are tight....but I'd also check the chassis and engine earths are grounded properly and the wiring on the alternator is tight too

[66yostagea]

I had issues similar. I redid all the earth leads and put in a couple of extras. Works fine now.

[shane344]

Earths seem feasible to check.

I'll start on the bigguns in the engine bay.

If not them Ill look at the tailgate lights, I reconnected the globe holders after they were hacked for compliance, maybe the tailgate ground aint the best, seems a long shot though....

[KiwiRS4T]

If you don't have a multi meter buy one - they are dirt cheap these days - or else go to an auto electrician tell him you think your alternator is on the way out and he should check the output for you without cost

[533 RYC]

Earths seem feasible to check.

I'll start on the bigguns in the engine bay.

If not them Ill look at the tailgate lights, I reconnected the globe holders after they were hacked for compliance, maybe the tailgate ground aint the best, seems a long shot though....

You mentioned 'reconnecting the bulb holders after they were hacked up for compliance'. Which bulb holders are you talking about exactly & how did you reconnect them?

Was this issue evident BEFORE you reconnected the holders?

I'd check the earths for the brake light circuit, BUT, if it was the tail/brake circuit you reconnected, it COULD be a resistance issue, but not enough to blow the fuse (unless a higher rated fuse has been fitted).

Your alternator output, should be 13.9-14.2v.

Recreating the issue, if you stab the brake pedal very very quick, on & off, is it enough to flicker the batt light on on the dash without stalling?

[shane344]

You mentioned 'reconnecting the bulb holders after they were hacked up for compliance'. Which bulb holders are you talking about exactly & how did you reconnect them?

Was this issue evident BEFORE you reconnected the holders?

I'd check the earths for the brake light circuit, BUT, if it was the tail/brake circuit you reconnected, it COULD be a resistance issue, but not enough to blow the fuse (unless a higher rated fuse has been fitted).

Your alternator output, should be 13.9-14.2v.

Recreating the issue, if you stab the brake pedal very very quick, on & off, is it enough to flicker the batt light on on the dash without stalling?

The brake lights in the center garnish next to the number plate had been disconnected (chopped) in the tailgate when I got the car.

I assume to meet an aus standard of 3 brake lights max.

I reconnected the cut cables, solder tape etc.

I reconnected then for making more niceness a few months ago, only started happening recently.

Fuses all look correct at 10 amp and should theoretically blow if this is the issue.p

have good multimeter.

batt voltage is up at 14ish whilst driving using center stack guauge pod.

was 13,9 last time I checked at idle with proper meter.

haven't seen battery light on dash but gauge shows less than 10.

I haven't had a chance to test since my first post, will check more when back home.

cheers men.

[shane344]

OK, earth tracing sucks, its seem like a wild goose chase that is pretty difficult to test.

So i checked the main battery earth to the body and block and that seemed fine.

Then I got bored and looked for easy alternatives, found a bunch of mess behind the tail lights.

See here:

There were scoth crimps on the brake circuit with tails leading to the bumper, tails untaped (crimps were taped though in a big ball of crap) and just hanging cut in the bumper.

Both sides were the same, I can only think of crazy KITT from night rider LED brake light strips under the bumper..

Crap I removed:

I tidies it up and put it back as it was from Nissan..

The history of this car is weird.

The first photos I got from the yard had a weird nav thing on the drivers side of the tunnel.

Pink diamontes on the dash.

Polish shadow in the paint near the roof rails from tv antennaes.

RS260 nose covnersion with skirts but not the back...

Long story short, didnt fix the voltage problem.

Going to actually have to pull all these sh!t earths off and wire brush underneath aren't I.....

Edited March 19, 2014 by shane344

[shane344]

Anyone got a pointer as to where I can find a body wiring diagram?

Lots of threads on workshop manuals but they seem old...

[shane344]

I got another flat battery after driving the car every day a few weeks back.

So borrowed another alternator off a helpful dude.

Drove for a week with no drama.

Bearings in mine were obviously rooted but wouldnt be causing any electrical fun times.

So I got my original one reconned (Nissan dealer in my area wanted $1500 for the privilege of waiting 6 weeks for a new one) and it only needed brushes.

Mine has been back in for another week, no more dramas.

May have inadvertantly fixed it by tightening a loose alternator connection but meh, fingers crossed, problem theoretically solved.

Edited April 22, 2014 by shane344