Hi Forum. Here's the situation:

1994 EX J-vin - built 10/93
Car: california driven (no salt / harsh weather), mostly freeway, 170k, stock sound system / lighting.
Alternator: original OEM Denso. No metallic grinding noises heard when car is running....(haven't put my ear to it though.)
Battery: Good. Car was tested with another known good battery and same charging voltage was found.
Running condiitons: Good gas mileage (28-29mpg). Good starting and running performance. Smooth idle @ both startup and warm.
Weather: Mild - high 70's - 80's. 30% humidity.
Future plans for the car: It's in xlnt condition mechanical & paint so I'd like to keep driving the car for as long as I can.

I have a plug-in cigarette lighter volt-meter that is constantly on whenever the car is running. I've noticed a drop in running voltage from 13.5 or so to 12.6-12.9 after I came back from an extended trip and the car wasn't run/started. That started about 3 months ago.

Recently, I've been noticing a slight dip in charging voltage on start up. Today it was really bad: 8.9 - then to 10.2 - then to 11.3 - then finally to 12.6 (head lights on) 12.9 (headlights off). It took about 10 minutes of mild driving until the voltage hit the 12's; I'm guessing the alternator finally heated up.


My questions are:

1) What charging conditions trigger the charging system light to come on?
2) What is going on with my alternator (i.e. is it dying slow or fast? Is it really dying?)
3) How long can I expect it to last?
4) What is the best option short of changing out the alternator? (are there any?)
5) What is the best option on changing the alternator: A: I.e. take my own to a local rebuilder. B: Or find a used never-rebuilt <100k mile Denso? And ballpark costs on actually having my own rebuilt?

I want to be "as cheap but good" as possible. (not afraid of used parts)

Thanks forum

 

If your alternator is going out they are fairly easy to replace and would only take you about 15 or 20 minutes to do. I would take your car to an auto parts store or battery shop that tests alternators and batteries for free. They can hook up a machine and tell you which one it is that is going bad.

 

It sounds that the alternator is mechanically sound (no bearing noises) but sometimes charges, sometimes doesn't. At your milage, you may be looking at no more than worn Alternator Brushes (They are sevicable seperately) or a lazy voltage regulator.
I am somewhat concerned at the voltage you're seeing at start-up

[QUOTE]
"Today it was really bad: 8.9 - then to 10.2 - then to 11.3 - then finally to 12.6 (head lights on) 12.9 (headlights off)".

12.6 volts is the batteries static state voltage. The voltage recovery was nothing more than the battery recovering from the starter draw. The Alternator was not contributing much of anything during this start cycle.
Traditionally, during a battery test, the voltage should drop no lower than 9.5 volts for a standard applied load. I'm not sure, but I believe that figure is even higher with a gear reduction starter (like Hondas')
I'd get a second opinion on the battery, the Alternator is a given...

P

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by P_Adams &raquo;</TD></TR><TR><TD CLASS="quote">At your milage, you may be looking at no more than worn Alternator Brushes (They are sevicable seperately) or a lazy voltage regulator.
I am somewhat concerned at the voltage you're seeing at start-up

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">
"Today it was really bad: 8.9 - then to 10.2 - then to 11.3 - then finally to 12.6 (head lights on) 12.9 (headlights off)".</TD></TR></TABLE>

12.6 volts is the batteries static state voltage. The voltage recovery was nothing more than the battery recovering from the starter draw. The Alternator was not contributing much of anything during this start cycle.
Traditionally, during a battery test, the voltage should drop no lower than 9.5 volts for a standard applied load. I'm not sure, but I believe that figure is even higher with a gear reduction starter (like Hondas')
I'd get a second opinion on the battery, the Alternator is a given...

P</TD></TR></TABLE>

thanks for everybody's replies. I just put in a brand spanking new costco battery (i'm okay doing this as my old battery came from the corner of my brother's garage) and the same running / charging voltage conditions were seen. So you think the alternator's brushes or regulator might be an issue?

I'm wondering if it's the voltage regulator b/k I've noticed my voltage is rather "lazy" to compensate for a headlamp switch-on. It sometimes takes a few seconds for the voltage to bump up or bump down. But it never goes over 13.0V anymore!

ADDED: Ok...just got off the road after a good 30 minute drive. My voltage never peaked over 11.2V even w/ good steady high-speed highway driving.


Modified by RotaryBzzzz at 2:12 AM 8/20/2005

 

I stand by my first response.

I just realized something while going back thru all the posts....The cig lighter is like the "backwater" of the electrical system, and could see some voltage loss from light gauge wiring a distance from the battery.

Do you have a way of modifying your volt meter so that you can test at the battery? That is the correct place to get an accurate voltage reading; and it should correspond with voltage found at the Alternator.
Normal automotive systems will see 12.6 /12.9 w/engine off depending on battery surface charge and any parasitic voltage draws (like clocks and memory circuits in engine control modules). With the engine running you should see anything between 13.8 and 14.2 volts depending on system loads and battery charge states.

I'd suggest comparing the voltage readings between the two locations

 

If you have a voltmeter you can use DC volts and check your alternator. Start car and place + to + and - to -. Your alternator should be anywhere from 13.7 to 14.4 volts. If it is much lower than this than you have issues.

"Not afraid of rebuilt parts"
If you got 170K out of the 1st one then a new one should get you another 150K+ as well.
You always take some chance with used/rebuilt unless you get a good warranty.

 

I thought I post a data-point as to what I did with my car.

So I bought a used alternator from a 94/95 automatic-equipped Ex w/ ~100k. 160amp never rebuilt unit. Easy job swapping it in...the unit and bracket were exactly the same. The unit designation was slightly diffferent (I assume it being from an automatic) but the rest of the code on the alternator body (Denso) were the same. If anything, the alternator being from a auto-equipped car might suggest there is less sigma spin on the bearings/brushes as auto-equipped cars generally operate at lower RPMS over their lifetime.

Slapped the unit in and now I'm chargning a solid 13.1 V at start-up all the way to ambient temps. No voltage drops.....no wandering voltages. I'm guessing my brushes were going bad on the 1st alternator. Wish I had known about the 'caveman test' before I dumped the first one.

Now I'm back to being ready to: Drive to NYC at a moments notice.