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Charging issue with Grand Vitara

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Offline ebewley

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Charging issue with Grand Vitara
« Reply #1 on: May 14, 2018, 06:05:31 PM »
Friend Stasi recently purchased a GV and has been having charging issues. Here's his saga below:

My affected model: 1st Gen 2002 Grand Vitara,  2.5L V6, 120k miles,  Nippendenso alternator with 2 control inputs (2 wires in one shared 3 terminal connector –see earlier post for diagram) and main charging wire fed directly through 80A fuse to + side of battery (see post #11 for charging system schematic).
Here is the quick Problem / solution statement: Alternator not charging in car; determined by following all known testing / troubleshooting procedures (please read whole story below!).  Alternator then tests fine at auto shop.  Cause: Weak / faulty main charge wire gives good V readings while troubleshooting but cannot induce alternator charging.  Also, determined this alternator has a rare “slow ramp up” which, along with weak circuitry, may add to charging problems (again, see below)  Diagnose: bypass charge wire with appropriate test wire.  Fix: Install new main charge wire.
This is a long story for a simple problem that ended up hard to diagnose.  The *disclaimers*: this happened on my car (with specific circuit mentioned above), your situation may be similar but your root cause may different. If you have similar symptoms read this whole thread, understand the problem and the troubleshooting procedures. I’ll try and re-state my troubleshooting process but may not remember / cover every detail; you should be familiar with basic charging system theory and electrical troubleshooting procedures.  Please refer to earlier posts in the thread: #3 from from Fordem – great charging system troubleshooting write-up, #11 from Darrell has the charging system schematic, and others have posted good info and diagrams.
My problem started with car electrics acting erratic -car eventually died. This went on for several weeks, it can be hard to identify erratic electric stuff, I thought it might be bad gas, old spark plugs (changed), basic tune-up stuff or loose wire somewhere. Charge light (idiot light / batt symbol on dash) NEVER came on while running at low V / not charging, but lights up as it should before starting with key on engine not running.  I even hooked up my OBDII code reader and saw NO errors.  Finally Determined cause -battery dropped below 12V. (NOTE to self: put “Check battery voltage engine off and running sooner on troubleshooting list”). This problem came on very slow and was probably intermittent for several months – just enough to keep car barely charged *most* of the time.  I recall the previous owner saying they installed a new alternator, which it was, very clean and new looking–HMMM.
Determined Alternator not charging by following known testing / troubleshooting procedures (again see Fordem post #3): using DVM (digital volt meter) verify no increase in V measured at battery, also at main output of alternator after starting engine or revving; 12V measured at both locations and it continued to drop as car ran / used electricity; indicating everything is running of battery power and 12v seen at alternator is just the voltage supplied by the battery.  Verified belt is proper tension.  Installed known good battery, cleaned inspected batt terminals, same results.  Continuing with known good battery, checked / cleaned all grounds: body of car and engine (right under alternator); checked wiggling wires while measuring resistance with DVM.  Also, this is a very low mileage well cared for car, never off roaded or abused, all electric terminals were clean / untouched, engine compartment looks like it rolled out of the factory very recently minus some random oil seeping / dust.  At this point I figured the alternator was faulty, removed it and took it to my local trusted alternator “guy” who has been in business many years and knows his stuff.    Alt. guy spins it up as I watch and says: “this thing is putting out plenty of power, proper voltage (~14V) and 60+ amps, nothing wrong here.”  HMMMMMM.  Well not wanting to waste any more of his time I take my “good” alternator back to the scene for more troubleshooting.  Charged good battery for next session and did some internet research for this problem.
This is when I noticed the common thread for 1st gen Grand Vitaras: “I did all known troubleshooting / testing with conclusion that alternator is bad, but alternator tests fine on test bench. People would continue with new batteries and alternators and still end up with same no charging situation HMMMMM.  What am I missing?  I’m willing to throw new parts at the problem but have a funny feeling I’ll end up like others back where I started.
More troubleshooting:  Since common handheld DVM may not be accurate for diagnosing larger current circuit issues I re-tested main charging circuit (all big wires between alternator and battery (+) terminal and body / engine ground and battery (-) terminal) by checking for voltage drops with engine running.  For example: charging wire between alternator and battery should have very little voltage drop measured at both ends, more than a few volts and power is not getting through.  Everything tested fine.  I visually inspected the main charge wire (hard to do it’s buried in a loom which I never completely took apart), terminal ends, and the 80A fuse, everything appeared fine but I cleaned terminals / replaced the 80A fuse anyway.  Started looking at input “control” wires (3 prong connector with only 2 small wires- see earlier diagrams).  .Determined both need 12V (or battery supplied V with key on) for charging.  One wire activates the regulator/rectifier circuit, the other is a signal from the “trouble/charge light” on dash, I am not clear on the full theory of this input other than it’s a safety indicator and needs to be functional to provide 12V to the alternator.  Both wires tested good; 12V present.  Tested both at output (terminal unplugged) and plugged in (I have special insulation piercing probe for this) on the wire itself, with key on engine off AND engine running. Checked/reseated fuse for warning light (#13 I think), was OK.  I remember an old farmer trick “connect jumper cable between battery (-) and body of alternator to eliminate grounding issues during charging.”  No change.  HMMMMM, now what???  Lots of head scratchin’
Finally I go back to the alternator guy, offer to pay for his time, and say “please help me figure out why this alternator works fine on your bench but not in my car.”  Of course we spin it up and it works fine.  I then learned some alternator theory (for this type of application) which is extremely important and not always understood. The alternator “pushes” electricity through the main charge wire to the battery for charging BUT the battery, initially on startup, provides voltage back to the alternator to energize the charging field (I mistakenly thought the small IG input wire did this).  If there is too much loss in this circuit the alternator cannot start charging.  Aha!  Clue #2: Alt. guy says; “this alternator charges fine but comes up slow to full output, there must be a delay logic in the regulator/rectifier circuit, probably to avoid full load on startup as a fuel saving / emission measure.” AH HAH!!!!  How many things have been screwed up in the interest of saving gas?  Digging more through the catalog he found this was the ONLY Nippendenso alternator with “basic” charging circuitry that had this “delay on startup” feature.  (BTW his reference indicated only the V6 2.5L engines have this particular alternator).  At this point we develop the theory (still a theory) that this delayed charge circuit needs the proper signal for a certain amount of time FROM the battery (over main charge wire) before the system will start ramping up the field coil and inducing a charge.  A-HA 3X!!!  This matches the symptoms; battery almost charges but not quite, very intermittent, on the edge.  Alt. guy says “here’s your last test: bypass main charge wire with suitable replacement and see what happens.” Hooked it up, started engine and you guessed it, ZAP! The battery immediately jumped to 14V and climbing…!!!DISCLAIMER!!! Doing this test with anything less than purpose made wire (I confess I used a jumper cable) is clunky and sketchy, one wrong move and you’ve got trouble.  Also, this bypasses the 80A charge fuse.  A more desirable method would be obtain or make a wire (large gauge with ¼” ring terminals or at least jaw style alligator clips) for testing, keep the 80A fuse inline if possible.  Also, the air cleaner box can be removed for much easier access.
I built a new main charge wire from the ALT to the 80A fuse using 6ga wire and soldered ¼” ring terminals at each end.  I covered it with heat resistant wire cover for the first 2’ near the engine and left it external from the original wire’s path inside the wire loom. Old wire is taped up off to the side. Instead of building a new wire from the 80A fuse to the battery (+) I used the existing wire and flowed solder into both connectors.  I’m assuming the problem wire was on the ALT side, and the batt side is easy to access for solder work.  I connected a DVM to 12V in cab so I can monitor V while driving.  As for the “delayed charge” it’s definitely a feature; on startup I only see battery voltage ~12.5V, and then V slowly increases, maybe taking 2min to reach 14V.
I’m Feeling more confident this issue is resolved.  2 weeks now and the car runs / charges as it should.  Although a funny thing happened, after 5 min of driving one morning the CHARGE warning light actually came on.  What now??!!??  The ALT belt broke –haha, finally an idiot light that worked right and an easy fix.  Still running fine.  If you read this far thanks for bearing with me, you probably are having similar trouble and I hope this helps.
Eric L. Bewley                               
Editor, ZUKIWORLD Online                   

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