Alternator - Sometimes It's Not The Culprit

9/16/2008

OK, finally got SW9 back on the road couple of weeks ago after almost 2 year haitus. Most of debugging done. Have a slick problem.
I noticed that at greater than legal speed I would get a "winkie" Battery Light. Back off it goes away. Finally, last Saturday boom no start. I charge the battery real quick and get it started. Grab the multi-meter and I'm reading sub 13's for out put. Hmmm not good.

I test the Alt on the 96 and I'm getting 14.2 up to 14.6 - ahh much better. Make the swap last Sunday. Fire it up and all is well.

Driving home from work Monday, I creep up past 80 and damn - winkie again! Check the output when I get home and it's still reasonable - very high 13's.

Come home tonight, decide to mat it in an open stretch of road now that all the components from the 12 or so different engines have had time to meet and greet. North of 100+ I get the winkie again but stays on a little longer. Pick up the kids, get home shut it down in the driveway, do some stuff, come out to put it in the barn and BAM click click click. CRAP!

Charge it up quickly and read the output - remember this is the same alternator that less than 5 days ago was reading 14+. Now - I'm basically running off the battery.

Before we jump on the voltage regulator, I tear off the fender liner, play around with the plug and post wire to the mega and get it back up to mid 13's. Not great but will get me to work.

Now - anybody - anybody ever see this before? It almost sounds like a tiney short. Chaffed wire coming up from the Alt?

I'm not so sure I need to condemn the Alt at this point. In fact I'm thinking I have 2 good alternators and a totally unrelated wiring problem.

Larry Eck
97TR
Mods
Cam Failure #425
96MG
Almost Bone
Webmaster www.v8sho.com
LMIR
___________________________________________________________________________

Bad/dying battery?

Regards,
Jon Heese
____________________________________________________________________________

I had to replace the 2 wire plug at the alternator. The 1st time the alternator was rebuilt.
The sop tested the alternator right in front of me after taking it back about 3 days from paying them to rebuild it.
Cost me like $25 buck IIRC and about 1.5 of my time as that is not the nicest place to solder on a new pigtail.
Clare
______________________________________________________________________________

Where are you measuring the voltage? At the battery posts? a bad cable could cause a voltage drop, so you would not see the alternator voltage at the battery.

Since it improved when you messed with a connection/moved a cable, it moves into the realm of something to check out.

Doug
___________________________________________________________________________

Actually I'm measuring pre battery post by inserting the probes into the wires of the battery cables. Yup I have the joy of tracing a two wire problem from the plug back up to the pcm. Lucky me. :{
Larry Eck
97TR
Mods
96MG
Welds
Webmaster www.v8sho.com
____________________________________________________________________________

I am wondering most about the cable from the alternator to the battery...

Doug
___________________________________________________________________________

Well Clare and Doug are the winners. Upon closer inspection I found that I could wiggle the connector at the alternator. After some minor research I found that NAPA had a pigtail under their part number URC 441 that fit our alternators. After some preliminary testing, and confirming conversation with Paul Nimz to verify voltages, I determined the plug to be the culprit.

Clare was correct - sort of. He chose the manly manner of changing the plug. I chose the wussey way out. Instead of soldering the wires while on my back with solder dripping on my hands, I chose to disconnect the 02 sensor, bring the loom up top to trim, solder and apply liberal heat shrink to the work. You will not need the center wire that comes out of the pigtail so just clip it and apply a liberal amount of heat shrink and crimp the end to insure no voltage jumping.

After reconnecting everything, the multi meter tells the story. I should add that it was also easy to confirm the plug vs the Alternator. I purposely sought out some local washboard road. On every bump I got the battery light to spark up. After the fix, on the same road at the same speed - nada

Of course the final test was pulling the cable off the battery. PERFECT!

Although it's extremely difficult to see in the one picture of the original plug, Paul's observation was correct. The internal connectors had simply separated due to age, and *cough* being connected/disconnected so many times that they just simply opened up.

The Pigtail was under $5.00 and the time was less than one beer to effect the repair and SW9 has been running fine.

On another note, you will see in one of the pictures, what is a fried O ring crimp connector for the ground strap from the surge tank to the fire wall. Not sure how/when that happened, but I caught it and trimmed the braid back to full potential and applied an new connector.

Now, as it is a SHO, we will wait and see what the jury has to say.

Larry Eck
97TR
Mods
96MG
Welds
Webmaster www.v8sho.com

NOTE THE GROUND O RING!

Note how snug the new plug sits in the Alternator!
__________________________________________________________________________
Also see this great write up by Paul Nimz

Blinking Battery Light

Contact Information