I can NOT figure out why my battery wont read over 12v when on (3800 swap) (Page 2/4)
Threedog AUG 08, 03:23 PM

quote
Originally posted by olejoedad:

If you could provide information on how the alternator is hooked to the PCM it would help.

Where is C500 B3 (brown wire) terminated?
Where is the red wire from the small alternator plug terminated?
Where is the grey wire from the small alternator plug terminated?


C500 B3 (Brown) ---> Pin 16 (white)

Red Wire ---> Pin 35 (white)

Grey Wire ---> Pin 62 (white)


I used sinisters guide. The extra weird thing is that again, this ran for two years and was fine, charging at 13-14vs, now it is not.


The things I can think of are..

Belt too big?
Battery too big?
theogre AUG 08, 04:58 PM
If PCM controlled, maybe a "Dead" PCM. IOW looking at wrong part multiple replacing the alt.

Many sections of ECM and latter PCM can "Die" and a function not working and never set a code.

Example: DIS Dukes ECM can "die" not working the injector because of bad part or solder joint in the injector driver section.
You can test this w/ a noid light to see is not blinking during cranking.

CS130 or whatever case you see is often not same regulator in it when PCM controlled vs "dumb" regulator in old SI or CS. Worse, often can't test by putting 12V on L or I pins on alt side plug. I forget the exact "name" that GM gave this setup... App Specific something something that are "digital regulators."

Think right now my ECM is "dead" because blinking MIL/CEL driving over RR tracking and no codes. Too hot to work or replace the ECM last few days even w/ spare ECM I have. (I replace ECM a few weeks ago looking for a part dying from heat and left it after and now MIL blinks...)

[This message has been edited by theogre (edited 08-08-2022).]

sanderson231 AUG 08, 07:30 PM
Yes, I think I would beg, borrow or steal another PCM for test purposes.

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

olejoedad AUG 09, 10:23 AM
The pinout is correct for a 1996 3800, probably correct for the 97 as well.
98-02 are different.
SERGE144 AUG 09, 02:52 PM
I had a burnt out dash alt light on my 4.9 swap. I used a new bulb and a different dash socket and my alternator started charging again.
Threedog AUG 09, 03:10 PM

quote
Originally posted by theogre:

If PCM controlled, maybe a "Dead" PCM. IOW looking at wrong part multiple replacing the alt.

Many sections of ECM and latter PCM can "Die" and a function not working and never set a code.

Example: DIS Dukes ECM can "die" not working the injector because of bad part or solder joint in the injector driver section.
You can test this w/ a noid light to see is not blinking during cranking.

CS130 or whatever case you see is often not same regulator in it when PCM controlled vs "dumb" regulator in old SI or CS. Worse, often can't test by putting 12V on L or I pins on alt side plug. I forget the exact "name" that GM gave this setup... App Specific something something that are "digital regulators."

Think right now my ECM is "dead" because blinking MIL/CEL driving over RR tracking and no codes. Too hot to work or replace the ECM last few days even w/ spare ECM I have. (I replace ECM a few weeks ago looking for a part dying from heat and left it after and now MIL blinks...)




Shouldnt the PCM be ruled out if I only connected the alternator S peg to 12v power and left the other two wires disconnected?


I do have another ECM, but it was programmed for a 1996 non supercharged. Pinout for alternator is still the same..


Just to verify I have the battery wiring correct(because I am questing everything right now...). I have:

- 0/1 gauge from the positive terminal to the top peg of the starter
- Directly attached to top peg of the starter that is a 4 gauge cable going to the post under the C500 connector.
- 4 gauge cable from the alternator to the peg under c500

[This message has been edited by Threedog (edited 08-09-2022).]

sanderson231 AUG 09, 04:44 PM
Everything points to your alternator defaulting to 12V.. With only the S terminal connected it made 12V. Without it connected it made 10V. So the alternator is working if it has power to it. It works same regardless of whether it is connected to the PCM or not. That says the PCM is not doing anything.

------------------
formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

Threedog AUG 09, 05:38 PM

quote
Originally posted by sanderson231:

Everything points to your alternator defaulting to 12V.. With only the S terminal connected it made 12V. Without it connected it made 10V. So the alternator is working if it has power to it. It works same regardless of whether it is connected to the PCM or not. That says the PCM is not doing anything.




I guess I got two bad alternators? Time for alt #3 then..
sanderson231 AUG 09, 05:47 PM
Not necessarily - we don't know what the normal default mode is for that alternator. I would try plugging in your 3800 N/A PCM and see if the car starts. I think there is a higher probability of a damaged PCM than two bad alternators

------------------
formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

theogre AUG 09, 08:50 PM
⚠️ The battery is "Dead" and why see 11 or less when alt is off etc. Charge the battery. Low/Dead Battery alone can make any CS to stay off. ECM controlled or not. Is done so the Alt won't fry trying to charging a dead battery.


quote
Originally posted by Threedog:
Shouldnt the PCM be ruled out if I only connected the alternator S peg to 12v power and left the other two wires disconnected?

I do have another ECM, but it was programmed for a 1996 non supercharged. Pinout for alternator is still the same..

jump S wire to 12v doesn't matter. In very short... The "Digital" Regulator wants a "signal" on L or I from ECM/PCM to set Output Volts at any given time slice. Other PCM control the Field coil in the alt's resulting in the same. You still can't tell if the CS Reg has I or F setup for sim reason in my Cave, CS Alternator

If you jump "12v" to I/F or L could do nothing or cause bigger problems when a Field Coil have "full power" because the alt can output >15v and fry other parts like ECM, "Radio," and more.

While you likely can't drive w/ non supercharged ECM/PCM... IF both ECM have all pins the same not just alt pins. Should work to test the charging system But likely going to flip because has wrong MAP. If not sure All pins are same then don't use that because need rewiring to and back often causing more problems.