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Username Post: Not charging        (Topic#359485)
leknaw 
Newbie
Posts: 26

Age: 59
Loc: SE USA
Reg: 01-02-15
01-16-20 01:26 PM - Post#2784487    

I have a 1990 K1500, with a 98 Vortec, Edelbrock intake and carb. Also have a 1991 needles cluster. Had a short on the engine harness due to it making contact with hot exhaust manifold. Replaced the harness, replaced battery cables, replaced alternator, cleaned all contact surface for ground, still not charging. New battery was also added. Truck was charging just fine before replacing the harness. I have taking everything off and put it back on. Replaced the ECU, traced just about every wire I can think off. So I am begging for some assistance with this issue.I done research online and followed the different advice given and no luck



 
bobb 
Super Senior Member
Posts: 5530

Loc: paradise
Reg: 09-05-03
01-17-20 08:56 PM - Post#2784573    
    In response to leknaw

voltage must be checked at the alt terminal post and at the battery post. not on anything else. repeat must be checked at the post. also, does the alt light stay on? are there fusable links?

70 L camino, grampa engine, g-force 5 spd, road rage suspension. Pray first before all else fails.


 
leknaw 
Newbie
Posts: 26

Age: 59
Loc: SE USA
Reg: 01-02-15
01-18-20 10:17 AM - Post#2784592    
    In response to bobb

Thanks for the reply! Voltage at the terminal and alt the same, 11.6*. No lights inside. Checked bulbs, the were good replaced anyhow. Yes fusible links wires, which I have replaced already. Good continuity on them. Charged the battery again this morning and it showed 11.65 after one hour. Is only 3Months old at the most. Will replaced today and go from there! Once again, Thanks!



 
leknaw 
Newbie
Posts: 26

Age: 59
Loc: SE USA
Reg: 01-02-15
01-18-20 10:29 AM - Post#2784594    
    In response to leknaw

Changed battery with a good known battery, 12.** volts, no change. Truly pizzle and frustrated.




Edited by leknaw on 01-18-20 07:43 PM. Reason for edit: No reason given.

 
YOUNG57 
Frequent Contributor
Posts: 1181

Loc: Tennessee
Reg: 12-06-10
01-19-20 08:28 AM - Post#2784653    
    In response to leknaw

Quote,

“replaced alternator,” “was charging just fine before replacing” “Voltage at the terminal and alt the same, 11.6”

If you are only getting 11.6 volts at the alternator terminal you are probably only seeing what’s left in the battery. I would suspect the new alternator. Try another new one or your old one.




 
bobb 
Super Senior Member
Posts: 5530

Loc: paradise
Reg: 09-05-03
01-19-20 09:58 AM - Post#2784662    
    In response to leknaw

how many wires on your alt? get a schematic and start testing voltages

70 L camino, grampa engine, g-force 5 spd, road rage suspension. Pray first before all else fails.


 
leknaw 
Newbie
Posts: 26

Age: 59
Loc: SE USA
Reg: 01-02-15
01-20-20 04:43 AM - Post#2784704    
    In response to YOUNG57

  • YOUNG57 Said:
Quote,

“replaced alternator,” “was charging just fine before replacing” “Voltage at the terminal and alt the same, 11.6”

If you are only getting 11.6 volts at the alternator terminal you are probably only seeing what’s left in the battery. I would suspect the new alternator. Try another new one or your old one.




Thanks for replying! I have changed the alternator to the previous one and back, not luck!




 
leknaw 
Newbie
Posts: 26

Age: 59
Loc: SE USA
Reg: 01-02-15
01-20-20 04:45 AM - Post#2784706    
    In response to bobb

  • bobb Said:
how many wires on your alt? get a schematic and start testing voltages



Two wires! I already follow the schematic! part by part individually. Checked the wires with the fusible links and they all test ok. Replaced the gauge cluster to ensure the problem came from there, nothing.






 
scrambldcj8 
Silver Supporting Member
Posts: 2542
scrambldcj8
Loc: Belchertown, MA
Reg: 04-06-03
01-20-20 06:35 AM - Post#2784711    
    In response to leknaw

IDK....
is the alt energized, magnetic force production at back of alt? I am under the impression that an alt needs to be "excited" to begin producing current......I hate auto electrics...LOL



 
bobb 
Super Senior Member
Posts: 5530

Loc: paradise
Reg: 09-05-03
01-20-20 07:29 AM - Post#2784716    
    In response to leknaw

2? 3 is typical. 2 to battery. 1 to light in dash.

70 L camino, grampa engine, g-force 5 spd, road rage suspension. Pray first before all else fails.


 
YOUNG57 
Frequent Contributor
Posts: 1181

Loc: Tennessee
Reg: 12-06-10
01-20-20 08:17 AM - Post#2784718    
    In response to leknaw

You may try running a jumper from the BAT terminal on the back of the alternator to the #2 terminal of the two-wire plug on the side of the alternator to excite the alternator directly from battery voltage.

The #2 terminal tells the alternator how much voltage to produce by sensing voltage in the battery charging circuit from a common buss junction in the harness or the horn relay terminal. Installing a jumper just insures there is a direct connection from the charging circuit to the #2 terminal and not an open circuit or bad connection anywhere.

The #1 terminal applies alternator voltage to one side of the telltale light in the dash and the ignition switch applies battery voltage to the other side of the telltale light. If the two voltages are equal, or nearly so, the light does not burn. Engine not running or alternator not charging light burns. One-wire alternators do not use this circuit.




 
Bad56Sedan 
"13th Year" Gold Supporting Member
Posts: 1223
Bad56Sedan
Loc: Pasadena, Texas
Reg: 04-29-04
01-20-20 01:26 PM - Post#2784742    
    In response to leknaw

I'm just asking,
If you have the two smaller wires to the alt. only one should have voltage?
This is what "excites" the alt.
If this is correct, and I'm just asking,
Is it possible to disconnect the main wire on the back of the alt,
Start vehicle and check for 13.8 volts on the back of the alt?
Will this work?
It won't hurt to try.
Someone on CT has the wiring schematic for that truck.
Like the post above mine, geez I hate electrical issues!

VC56S 2 door Sedan, 39 Years



 
YOUNG57 
Frequent Contributor
Posts: 1181

Loc: Tennessee
Reg: 12-06-10
01-20-20 03:27 PM - Post#2784758    
    In response to Bad56Sedan

There should be voltage on both the small wires of the two-wire plug, voltage on terminal #2 from the remote connection on the charging wire to the battery and voltage on terminal #1 back feeding from the telltale light in the dash (unless the bulb is blown or missing).

I don’t think it wise to energize or run the alternator with an open circuit to the battery (the wire removed from the BAT terminal). And it would not serve any purpose because if the alternator is charging that voltage can be measure at the BAT terminal with the charging wire connected.




 
Bad56Sedan 
"13th Year" Gold Supporting Member
Posts: 1223
Bad56Sedan
Loc: Pasadena, Texas
Reg: 04-29-04
01-20-20 03:40 PM - Post#2784760    
    In response to YOUNG57

Yeah, just thinking it would prove if the alt was any good to start with,
Like OP said he has replaced some wiring

VC56S 2 door Sedan, 39 Years



 
leknaw 
Newbie
Posts: 26

Age: 59
Loc: SE USA
Reg: 01-02-15
01-21-20 05:51 AM - Post#2784794    
    In response to bobb

  • bobb Said:
2? 3 is typical. 2 to battery. 1 to light in dash.


Only two, always had the two! The red to the distribution block and the brown for the light!




 
leknaw 
Newbie
Posts: 26

Age: 59
Loc: SE USA
Reg: 01-02-15
01-21-20 05:54 AM - Post#2784795    
    In response to YOUNG57

  • YOUNG57 Said:
You may try running a jumper from the BAT terminal on the back of the alternator to the #2 terminal of the two-wire plug on the side of the alternator to excite the alternator directly from battery voltage.

The #2 terminal tells the alternator how much voltage to produce by sensing voltage in the battery charging circuit from a common buss junction in the harness or the horn relay terminal. Installing a jumper just insures there is a direct connection from the charging circuit to the #2 terminal and not an open circuit or bad connection anywhere.

The #1 terminal applies alternator voltage to one side of the telltale light in the dash and the ignition switch applies battery voltage to the other side of the telltale light. If the two voltages are equal, or nearly so, the light does not burn. Engine not running or alternator not charging light burns. One-wire alternators do not use this circuit.




Very insightful, Will try this today!



 
leknaw 
Newbie
Posts: 26

Age: 59
Loc: SE USA
Reg: 01-02-15
01-21-20 05:57 AM - Post#2784796    
    In response to Bad56Sedan

  • Bad56Sedan Said:
I'm just asking,
If you have the two smaller wires to the alt. only one should have voltage?
This is what "excites" the alt.
If this is correct, and I'm just asking,
Is it possible to disconnect the main wire on the back of the alt,
Start vehicle and check for 13.8 volts on the back of the alt?
Will this work?
It won't hurt to try.
Someone on CT has the wiring schematic for that truck.
Like the post above mine, geez I hate electrical issues!



I have disconnect the one brown wire to the alternator and tested for voltage with zero volts. Will do the additional wire as mentioned by Young57 and see the results. Thanks!



 
Bad56Sedan 
"13th Year" Gold Supporting Member
Posts: 1223
Bad56Sedan
Loc: Pasadena, Texas
Reg: 04-29-04
01-21-20 01:10 PM - Post#2784823    
    In response to leknaw

1989 GM


Attachment: image.jpg (157.58 KB) 3 View(s)




Attachment: image.jpg (169.7 KB) 9 View(s)




Attachment: image.jpg (193.41 KB) 5 View(s)




VC56S 2 door Sedan, 39 Years



 
Bad56Sedan 
"13th Year" Gold Supporting Member
Posts: 1223
Bad56Sedan
Loc: Pasadena, Texas
Reg: 04-29-04
01-21-20 01:13 PM - Post#2784824    
    In response to Bad56Sedan

Chart


Attachment: image.jpg (203.19 KB) 4 View(s)




VC56S 2 door Sedan, 39 Years



 
leknaw 
Newbie
Posts: 26

Age: 59
Loc: SE USA
Reg: 01-02-15
01-23-20 08:57 AM - Post#2784967    
    In response to Bad56Sedan

Awesome, Thanks Bad56Sedan!






 
leknaw 
Newbie
Posts: 26

Age: 59
Loc: SE USA
Reg: 01-02-15
01-24-20 08:40 AM - Post#2785062    
    In response to leknaw

After a couple of weeks trying to figure out what is going with the truck, I think I came to a conclusion. Following the different diagrams presented here and searching the different years of the 88-98 trucks diagrams, I believe the culprit is the harness itself. 88-89 are the same, 90-93 are the same. 94 stands alone and I did no go further than that. The signal to the dash from the alternator on the brown wire, changes position on the firewall plug, so the circuit is not completed, therefore no charge or light on the instrument cluster. Working on piecing together a harness now and see if it works. If not to the junkyard tomorrow to pulled one from a 90-93 truck! Thanks to everyone that has contributed.




 
bobb 
Super Senior Member
Posts: 5530

Loc: paradise
Reg: 09-05-03
01-26-20 11:47 AM - Post#2785218    
    In response to leknaw

just switch the wire at the firewall connector. they can be unplugged from the connector individualy

70 L camino, grampa engine, g-force 5 spd, road rage suspension. Pray first before all else fails.


 
leknaw 
Newbie
Posts: 26

Age: 59
Loc: SE USA
Reg: 01-02-15
01-26-20 12:52 PM - Post#2785221    
    In response to bobb

I went and replaced the harness altogether. Needed to insulated the spot closer to the manifold with anti-heat shrink anyhow. Got it started a while ago and it charges as it needs to. Thanks, everyone for all your help and assistance.



 
scrambldcj8 
Silver Supporting Member
Posts: 2542
scrambldcj8
Loc: Belchertown, MA
Reg: 04-06-03
01-27-20 09:09 AM - Post#2785281    
    In response to leknaw

Thanks for updating your post/findings!! It helps others in the future if/when they run across this in a search for help.



 
leknaw 
Newbie
Posts: 26

Age: 59
Loc: SE USA
Reg: 01-02-15
01-27-20 01:09 PM - Post#2785291    
    In response to scrambldcj8

Sure, No problem! When I can not figure out what is going on in my truck, this is where I searched the most information!



 
leknaw 
Newbie
Posts: 26

Age: 59
Loc: SE USA
Reg: 01-02-15
02-05-20 04:31 AM - Post#2785927    
    In response to leknaw

So yesterday I went looking for a more complete, un-cut harness and found out a couple of things. I mentioned earlier on the differences and similarities of the harness throughout the years and here is something else. Even though the 88-89 are different than the later years, the harness cover/grommet on the passenger side firewall is the same, square with one screw. The 91-93 are the same as far as the diagram connections, but the above-mentioned cover on the 91-93 is rectangular with two screws. Just figure tis will come in handy!



 
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