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1979 K10 SWB "Jolly Green Giant"

Sometimes I change things
Overview Gallery Discussion
Please check the voltage directly at the back of the alternator, from the case, to the output post. If the voltage at the post remains high, then the problem is the connections, grounds, etc. If the alt voltage is low, then we are looking at alt, belt tension, rpm, etc. Would you post a pic of the wiring adapter, plugged into the alt.
 
This is the adapter..., actually a brand new that I just picked up.

20180417_110616.jpg 20180417_110623.jpg 15239849414111942128761.jpg

The one place I actually didn't put the DVOM was aternator charge post to alternator case...

I will have to do that later...
 
The connections on your new alt are P-L-I-S. The smaller wire is attached, to the "L" terminal, or LAMP. The L terminal, is what is turning your alternator on and off, with the key. The red wire on the larger terminal is the "S" terminal. This is a voltage "SENSE". If the Sense wire is getting a bad signal, the alt voltage might wander around, and be inconsistent. If you disconnect the Sense wire, the alt will internally sense the voltage. Check the voltage at the back of the alt, first. Then we can go through more stuff.
 
500$k5 said:
The connections on your new alt are P-L-I-S. The smaller wire is attached, to the "L" terminal, or LAMP. The L terminal, is what is turning your alternator on and off, with the key. The red wire on the larger terminal is the "S" terminal. This is a voltage "SENSE". If the Sense wire is getting a bad signal, the alt voltage might wander around, and be inconsistent. If you disconnect the Sense wire, the alt will internally sense the voltage. Check the voltage at the back of the alt, first. Then we can go through more stuff.
Click to expand...
I did run the voltage check from the alternator charge post to the negative battery post. I found numbers consistent with post to post on the battery. I did not go alternator charge post to alternator case however. I WILL do that.

The sense wire:

Would it be safe to jumper a wire from the alternator charge post to the sense wire location in the plug as a test? Sort of remove the 1979 truck wiring from the equation? Or am I misunderstanding how the sense wire works?
 
You aren’t running a deep cycle batterybate you? They make alternators do some silly things... usually it’s nuclear meltdown though.
 
This pic is for you @6872xtc 20180417_200109.jpg

And don't mind the AFR, pic was taken exactly as it switched from 14.0 to 13.9...

HOWEVER, I have good info to share...

It was obviously a cold start, showing 14.1 on the FiTech, while being 77°F one the coolant.

In the 30 seconds it took to get the DVOM out and testing, the voltage on the FTech display went to 13.8...

But immediately going alternator cherge post to alternator case netted 14.64 volts. Went from there to the battery, post to post was 13.8, but FiTech display was 13.7.

Straight back to the alternator charge post to case was again 14.64 volts.

Then I went from alt charge post to battery negative, 13.79.

Back to alt charge to alt case, still 14.6+.
 
Glad that you found something. You are jumping too far with the test leads with some of that. Find out if you have a voltage drop at the alternator case, or the breacket to the block, or where..
@500$k5 taught me somethings!
And I will still put his product up and against a any parts store one, and watch the smoke roll out of the losers!
;)
 
Yep just start working your way from the alt case to the bracket to the block then to the frame where the ground is attached and see if your voltage keeps going down. Probably just a combination of several painted or rusty ground connections all adding up to the drop you are getting. I've had the same with some of our super dutys at work. Like 14.5 at alt and in the ecm or at batteries like 13.9-14.1 volts or less.
 
I never doubted his product, and obviously I am gaining ground on this issue with everyone's help.

So thank you to everyone...

I am going to do more testing when I get time, last night was a rush to get an answer to @500$k5 .
 
Now we're getting somewhere! Let me know what you find, as you work your way through the ground paths. Yes, on your question, about looping the sense wire to the charge post. The original sense wire went all the way down to the starter battery post. On some S-10 pickups, the sense wire was looped to the charge post. The sense wire has no purpose, if the charge wire is a short distance to the battery, and is large enough to carry the current, with very little voltage drop. Most of the time the sense wire was never used, on the newer alt. Was always used on the cars with a remote mounted battery, like under the back seat, or in the trunk.
 
So what did you find out tonight?
And I know that you had a little time, since you were reading about us old guys bickering....
Lol!
 
Justin V said:
I did run the voltage check from the alternator charge post to the negative battery post. I found numbers consistent with post to post on the battery. I did not go alternator charge post to alternator case however. I WILL do that.

The sense wire:

Would it be safe to jumper a wire from the alternator charge post to the sense wire location in the plug as a test? Sort of remove the 1979 truck wiring from the equation? Or am I misunderstanding how the sense wire works?
Click to expand...
FWIW, on both the K5 and the crew cab, I've just done my own wiring for the sensing wire and the main charging wire. Mostly because I was putting in a different alternator with a higher amp rating so I wanted bigger wiring on the charging cable.
 
Bit of investigation today...

Seems to be my driver's side serp backet to block/head that is causing my issues. The alternator is driver's side, and my "block to frame" ground is off of the paasenger side serp bracket to frame.

I have aluminum serp brackets that have been painted, and the block and heads have been painted...

When i dig through the paint the serp bracket holding the alternator, I get the same voltage output as I get testing the alt charge post to case.

When I dig through the paint on the block or head or go straight to intake (unpainted) then I get the same voltage as I get going from alt charge post to batt neg.

Alt charge to alt case has been consistent (from start of testing) to at least 14.6V.

Alt charge post to any other ground location has been at least .4V lower, all the way down to 12.5V, varying depending on something unknown. Temp? Only known variable at this point...

Here soon I will be replacing the power steering pump, which will give me the perfect opportunity to pull the driver's serp bracket and flap disc the mounting points on it and the block...

I also think that I will run a 10ish (8? 6?) gauge wire from the alt case to the frame or neg batt post.
 
I did a junction block for the battery grounds. One 2/0 cable comes in from the battery. Then I have 2ga cables from the junction block to the firewall, engine, and frame. I also added a ground strap from the engine to the frame and another from the firewall to the frame.
 
That's all part of the plan...

Found a damaged bearing when I went install my hubs...

ORD is taking care of it, should have a new bearing and seal in my hands shortly...
 
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