Alternator/voltage reg question

[bassjack]

Greetings,

My 85 has been exhibiting signs of alternator/voltage regulator failure (dimming and brightening of head/dash lights) over the past couple of months. I don't put many miles on it and most are during the daylight.

I've been reading up on the symptom/cure and plan to check the voltage at the battery this weekend to see what's what, and am working up the courage to pull the alternator for a rebuild (assuming that's the issue).

I'm a little concerned about boiling over the battery. Does driving in the daylight (i.e. w/o using the headlights) lessen the risk of this happening? Are there any telltale signs of battery boil? I'll obviously do a thorough check of the battery this weekend when I check for voltage.

Thanks,
Jack

[JJ 911SC]

Originally Posted by bassjack

...

I'm a little concerned about boiling over the battery. Does driving in the daylight (i.e. w/o using the headlights) lessen the risk of this happening? Are there any telltale signs of battery boil? I'll obviously do a thorough check of the battery this weekend when I check for voltage.

Thanks,
Jack

Jack

BTDT Another Boiling Battery Story

My VR when bad after a few minutes of driving, from 14 volts to 17 volts.

Yeah the battery boiled over. It does give out a foul smell that you should smell it in the cabin (even in a Cab). Also the battery wil be hot to touch and you should have sign of spewed acid unless you got a vent tube.

I only find out when I monitored the voltage while riding (voltmeter via the the cigarette lighter).

I picking up a new VR (from PP) tonight.

The battery still shows 12.4 volts but I will either have it load tested or buy a new one.

[Joe Bob]

The usual suspects claim spikes over 14.2 while driving will tend to damage a battery. You would need to wire in a volt meter to see the spikes.....unless two wires to the nipples sounds good to you....and you can tell the difference between 14v and higher....

[86 911 Targa]

Originally Posted by bassjack

Greetings,

My 85 has been exhibiting signs of alternator/voltage regulator failure (dimming and brightening of head/dash lights) over the past couple of months. I don't put many miles on it and most are during the daylight.

I've been reading up on the symptom/cure and plan to check the voltage at the battery this weekend to see what's what, and am working up the courage to pull the alternator for a rebuild (assuming that's the issue).

I'm a little concerned about boiling over the battery. Does driving in the daylight (i.e. w/o using the headlights) lessen the risk of this happening? Are there any telltale signs of battery boil? I'll obviously do a thorough check of the battery this weekend when I check for voltage.

Thanks,
Jack

I would not drive the car under the described conditions as over-voltage can damage your electronic units.

And, the 3.2 alternator have a well deserved history of intermittent over charging.

pm sent.

Gerry

[na2ub]

Just swap out the VR and you will be fine. Sooner rather than later. Not a big job, so don't fret it. Order one from PP today and get er done before it kills your battery.

[Driver_X]

Taking out an alternator is not a big deal, really. Read through the procedure a couple of times, print out a copy and have it with you. Take your time, take pictures so you can remember what went where.

[bassjack]

I had the opportunity this afternoon to put a voltmeter on my battery and this is what I found.
With the engine off a reading of 12.6
With the engine running @ 2k rpm a reading of 14.2

Right within spec according to Wayne's 101 Projects article. The battery shows absolutely no sign of leakage (looks as good as the day I installed it 18 months ago). The alternator dash light is working properly and does not exhibit any of the things mentioned in Wayne's article.

So why the dimming/brightening routine! :confused

I think I'll check the ground strap at the tranny....any other suggestions? Fan belt slipping? It doesn't feel loose...

Greer, what is the source of that page you posted?

TIA,
Jack

[na2ub]

Let the engine run. Watch the volts closely for 10 minutes, then tell us what you see.