1987 carbed truck. changed out alt brush and both lights are still on and battery is discharging slowly What else can I check?

 

Well, what did the old brushes look like??? Did they actually need to be changed?? How'd the slip rings look??

Might look to the voltage regulator and the diode bridge.

 

The brushes were about a little less than halfways out compared to the new one. Where are the slip rings? Today it was too low to crank over after work. @ days ago ,I measured voltage at alt stud and it was 12.6. I remember that I had some problem with the big screwed on fuse near the batter but I don't remember what it was for.

 

Slip-rings are what the brushes contact and run on. They conduct the exciter current to the rotating field.

 

I did notice that the area where the brushes ride on was grooved , where the brushes made contact. What else can i check before i take alt out again?

 

And what did you do about that problem? If you want us to help, pls tell us more details. (See signature).

WITH B-WIRE DISCONNECTED, measure resistance from screw terminal to ground. You should get Very high reading. Lots of Meg-ohms (Sorry I forgot how much mine read). If low, suspect bad rectifier (s).

And here: https://www.yotatech.com/forums/f116...s-22re-304868/

 

I think I had to change fuse because my fuel gauge, signals and charge light did not work, something like that I replaced bolt on fuse and all was well. what other info do you need on present problem? '87 22R,stock alt.

 

That's better. It helps when we know what you did.
Next steps:

Grab a multi-meter

WITH B-WIRE DISCONNECTED from screw terminal of alternator, measure resistance from screw terminal to ground. You should get Very high reading. Lots of Meg-ohms (Sorry I forgot how much mine read). If low, suspect bad rectifier (s).

Then do voltage checks described on my thread here: https://www.yotatech.com/forums/f116...s-22re-304868/

 

I ended up putting in a rebuilt alt. The output on alt is around 14.7, at the battery post it's 14.7 also. That fuse for "L" was around 8.8. i checked cable that runs along trans and it looked good. I did an Ohms test on the 3 big fuses all ok. Charge and park lights still on.

 

keep throwing parts at it. you'll get it eventually. maybe you'll get lucky and only spend several hundred dollars.

 

Obviously the alternator was not the problem. See signature.

O.P.
Remove charge fuse and tell us what you see.

REPEAT:
Measure IG, and S voltage as mentioned on my post.

 

Oh sure, several HUNDREDS , when the alternator is probably the most expensive part, which I had a spare one that I used.

 

[QUOTE=RAD4Runner;52419219]Obviously the alternator was not the problem. See signature.

The charge fuse is good, but was reading 8.8 when I checked with voltmeter

 

[QUOTE=sc2dave;52419248]I am not questioning whether charge fuse is good or bad. I am asking you to help us help you by...

(REPEAT)
1) Removing charge fuse, and telling us what you see. then...
2) Measuring IG voltage,
3) Measuring S voltage,

 

[QUOTE=RAD4Runner;52419285]I don't get what you mean by what I will see. do you mean to look at the fuse, to see if it's good, or test with a voltmeter where the fuse goes in to see voltage?

 

When u remove charge fuse, do charge and brake lights stay on?
We need to see what you are seeing, being far away.
Exactly where are you measuring 8.8 V?
I reiterate. Pls put us AT ur vehicle so we can help even from thousands of miles away. repeat; see signature.
A picture paints a thousand words.

Repeat:
Then do voltage measurements I listed several times above.

 

Ok, I messed with it again. The charge fuse previously had the 8.8 volts, befor I replaced the alt.When I removed charge fuse while running, the charge light dimmed and the brake light got brighter.I put wires in between the intermediate harness connector and the white B wire showed 14.25 running.The battery is at 14.25 running. In the link that you provided, you wrote, " WITH B-WIRE DISCONNECTED, measure resistance from screw terminal to ground. Do you mean the whole plug from the back of the alt, and what "screw terminal? Man, this is a weird charging system

 

Show us what u are looking at and well talk.

Also, what is intermediate harness wire?
Repeat:
A picture paints a thousand words.

 

First pic shows alt plug, second is the "intermediate" plug as named by you in the link that you provided. I forgot to mention too, that my idle is higher also.

 

Awesome, Dave!.
14.25V is normal charging.
8.8 V at Charge fuse means alternator "L" fault signal is high enough and not indicating fault condition.

BUT to double-check, because I like to be thorough (like the Japanese/Toyota) please:
1) Double check voltage at "S" and "IG" wires. As in my post, "S" Should be thin white wire on that plastic connector, "IG" is thin red wire. Probe from back of connector with that plug connected. Should reflect very close to battery voltage whether running or not.
2) With engine running, Charge fuse removed, measure voltage at each side of the charge fuse socket. Charge fuse is NOT needed to charge. It is just there to complete indication circuit for fault condition.

Charge light did not completely turn off?
Sounds more like a wiring problem than an alternator fault.

Thick B-Wire should be connected via Screw terminal as shown on my post: