1996 S10 intermittant charging problem

[Land Yacht]

Dad's truck, chevy S10 4.3L. Reman alternator is 6yrs old, 65mo battery 2yrs old. He's been driving some pretty rough roads for the last month prior to having problems, but it doesn't act up then. It has problems on smooth roads, headlights dim, battery light flickers, volt gauge drops to 10-11V. Increasing the rpm does not move the needle at all. Let it sit and cool down, re-starts fine, same problems, still reading 10-11V, battery light flickers, drive 100 feet and everything goes back to normal and stays that way, gauge at 14+ volts, no battery light. The first time I found the cables a little loose at the battery, tightened down, was fine for 2 weeks before it happened again. I'm leaning towards another bad connection somewhere, printed out Wayne's voltage drop test. Has anyone had alternators fail intermittently? I thought they generally worked or did not. Since it's working again having it tested probably won't show anything?

thanks

john

[PeterR]

First guess is worn brushes.

[wayne petty]

since you have the voltage drop test... time to perform it..

Forum members with GM cars and trucks newer than 1993.. .will want to pay close attention..  this may save you days of work.  the voltage drop link again for those who don't have it.. http://i.imgur.com/Mo57rdb.jpg   on S10s.. please perform test 5 to multiple fuses in the underhood fuse block.. some S10s are missing a nut on the stud nearest to the brake master cylinder. if you have a brass strip around the stud and no nut.. put one on . its 6x1.0

i have another test to perform on your dads truck.. this one needs a test light... knee pads..

this is the ignition switch connector for the S10.. its up behind the brake pedal pad..  you may have to remove the underdash cover to get at it. so 7mm nut driver/socket/ratchet.

i am just pasting a link... but there are instructions on it..

http://i.imgur.com/1JNU6q9.jpg

the testing is done as somebody slowly turns the ignition key from the LOCKED position thru run, cranking, run... slowly back to locked..  hint.. pull the Start relay from the underhood fuse box to prevent the truck from cranking..

the white wire in C1 powers the instrument cluster..  also the security system on slightly later versions..  i have found that circuit intermittent.. because the contacts are Silver and there is not a lot of current going thru so the contacts build up carbon/burn marks.. causing intermittent issues..  the C1 white wire may have power when the key is in the OFF, RUN, Cranking. Run, Off positions .. just shuts off in the LOCKED position.. this also turns on the BCM

the Pink wire in C5 is IGN1 on other models..  that powers a bunch of stuff..  engine controls.. transmission controls..


the Orange and the Brown wires in C6 and D6 will usually only have power in the RUN position.. these are important to check also.. using a test light while the key is being rotated slowly.  one will have power all the way the other way in the accessory position. but that is not usually an issue .  again.. worn contacts..  dirty contacts..

there is a huge trick that sometimes helps.. roll the drivers window down.. turn key off,  with  engine off.. disconnect the battery.. get in the truck.. stick the key in the ignition.. turn it from locked to cranking and back to locked about 100 times..     take the key out of the ignition.. put it in your pocket..  close the door.. reconnect the battery..  working the switch with no power flowing across the contacts can clean them enough to make it work again..  tons of GM cars and trucks have this issue including C5 and C6 corvettes..

the ignition switch test should take only a few minutes with a test light..

the voltage drop test also takes about 5 minutes with a volt meter.. try to not use one of the free volt meter versions from HF .. they are not that accurate down at the hundredths of a volt where you will be measuring.

voltage drop testing is like measuring the pressure differences of each end of a flowing garden hose..  with the hose flowing.. you will only have a slight drop in pressure because of resistance inside the hose...  but if you have a kink in the hose.. you will have way different pressures at each end of the hose while its flowing.. pressure drop.. voltage drop.  loose connections.. dirty connections.. are like kinks in the hose.  slow down and limit the flow of electrons..

oh.. and for those with access issues.. look in the owners manual. for the Gauge fuse.. left instrument panel fuse box.. do the C1 white wire test there..  save a boat load of time

i truly agree with peter .. could be a bad alternator.  worn brushes.. but its far better to spend 15 minutes diagnosing than that time changing the alternator only to find you have the same problem. except your wallet is thinner..

diagnosis above is cheap if you have a digital volt meter and a test light..

[Beck]

Unfortunately when some of the shops rebuild alternators they only replace the component that failed. If 1 bearing is bad it gets 1 bearing - nothing else. Worn brushes may be a good call. I rebuild my own alternators when needed. That way I know everything is new inside. I have found on some alternators it makes more financial sense to buy a new one.

[Land Yacht]

There's no underhood fuse box on the '96, all the other voltage drops were 0.02 or below. There are 4 relays that hang from the firewall, 3 more in the glovebox, and a small fuse box on the left side of the dash. Plan on checking the ign switch connector next. Would like to catch it while it's not charging, right now it's working fine.

[tomslik]

look pretty close at the B+ cable at the battery, they get corroded under the plastic, sometimes it's not real obvious..

[wayne petty]

There's no underhood fuse box on the '96, all the other voltage drops were 0.02 or below. There are 4 relays that hang from the firewall, 3 more in the glovebox, and a small fuse box on the left side of the dash. Plan on checking the ign switch connector next. Would like to catch it while it's not charging, right now it's working fine.

1996 S10.. there is a 4 stud terminal block on those... sorry..   its under a cover.. which engine... 2.2... 4.3 Vortec i am taking it.

there is a connector between the positive battery cable and the wiring to the 4 stud buss bar under a plastic cover..

i would want you to photograph the wiring on that stud buss bar... count the wires... one stud at a time take it apart and wire brush the individual ring terminals.

you can perform test 5.. from any of the studs on that buss bar to the battery positive bolt..

you will need to narrow the test locations..    to individual ring terminals on that bus bar to the positive battery post/bolt.

i totally agree with peter.. clean the battery cable ends..   you can dip the end of the battery cables in hot water and the rubber boot might slide off if you have removed the bolt first.  some are glued on ..

perhaps these will help also...


http://imgur.com/a/a9y1f

[Land Yacht]

Thanks for the diagrams, it is the 4.3L. Battery + is clean inside the boot at the battery terminal, the buss bar is clean. Voltage drop from battery + to buss bar studs is 0.12V.

[wayne petty]

Thanks for the diagrams, it is the 4.3L. Battery + is clean inside the boot at the battery terminal, the buss bar is clean. Voltage drop from battery + to buss bar studs is 0.12V.

can you add another 10 gauge wire with ring terminals somehow between the battery post and the buss bar..


see in this diagram 12 and 13.. that is a quick connector... http://i.imgur.com/S73LulV.jpg that could be causing you issues..

[Arnold]

I'ld be trying another known good battery..