'94 Sierra / 5.7L - Electrical problems

[94Kcode]

Here's my myriad of electrical issues:
1.) Cargo lamp doesnt work
2.) Courtesy light doesn't come on when either door is opened.
3.) Battery idiot light just came on and voltmeter reads ~11 (running)
4.) Alt. is not charging battery, battery is now dead (3 mos old)
5.) Fuseable link that's shared by Alt., battery and fuse block is good.
6.) All fuse block fuses are good
7.) Before #3, the voltmeter would drop and hold when any components were turned on (Radio, lights, cruise, etc.) and rise when turned off.
8.) Voltmeter falls and rises in rythem w/ turn signal flashes.

Any ideas, or information on an accurate schematic for the charging system (I have Haynes but it's, well weak)? Any internet schematics for my truck avaiable (I found sites but all wanted my credit card).

Thanks in advance for any hints, or suggestions.

[swensonb71]

Originally Posted by 94Kcode

Here's my myriad of electrical issues:
1.) Cargo lamp doesnt work
2.) Courtesy light doesn't come on when either door is opened.
3.) Battery idiot light just came on and voltmeter reads ~11 (running)
4.) Alt. is not charging battery, battery is now dead (3 mos old)
5.) Fuseable link that's shared by Alt., battery and fuse block is good.
6.) All fuse block fuses are good
7.) Before #3, the voltmeter would drop and hold when any components were turned on (Radio, lights, cruise, etc.) and rise when turned off.
8.) Voltmeter falls and rises in rythem w/ turn signal flashes.

Any ideas, or information on an accurate schematic for the charging system (I have Haynes but it's, well weak)? Any internet schematics for my truck avaiable (I found sites but all wanted my credit card).

Thanks in advance for any hints, or suggestions.

check all of your ground cables from cab to frame and engine to frame. have you done any mechanical work to the engine?

[Bob B]

Originally Posted by 94Kcode

Here's my myriad of electrical issues:
1.) Cargo lamp doesnt work
2.) Courtesy light doesn't come on when either door is opened.
3.) Battery idiot light just came on and voltmeter reads ~11 (running)
4.) Alt. is not charging battery, battery is now dead (3 mos old)
5.) Fuseable link that's shared by Alt., battery and fuse block is good.
6.) All fuse block fuses are good
7.) Before #3, the voltmeter would drop and hold when any components were turned on (Radio, lights, cruise, etc.) and rise when turned off.
8.) Voltmeter falls and rises in rythem w/ turn signal flashes.

Any ideas, or information on an accurate schematic for the charging system (I have Haynes but it's, well weak)? Any internet schematics for my truck avaiable (I found sites but all wanted my credit card).

Thanks in advance for any hints, or suggestions.

-------------------------------------------------------------
Hi,
I'd get the alternator tested first. Then also the new battery in case it also died.
Next check or replace the cargo light bulb.
Does your truck have the button near the headlight switch for dome light override?
My 97 has this button and it will stop the courtesy lights from lighting.

Bob B

[94Kcode]

Thanks SWENSONB71 and Bob for your replies.

I haven't done any mechanical work in ~1 year. I've clean, checked all ground points (I think anyway). Today I diconnected the Neg battery cable and hooked a test light between the cable and open battery terminal. The light came on. I disconnected the Alt wire and still stayed on. I spent the next 3 hours disconnecting every fuse / breaker / connector I saw --- light still stayed on. So I appear to have a short.
However, when I jump started the truck the other car's Alt WAS charging the battery.
I think your ALT swap / test suggestion is right Bob, regardless of the aforementioned test light results. So, tomorrow I'll pull the Alt and battery and head down to Auto Zone.
I'll post a reply on that outcome.
PS - my '94 model doesn't have a dome light override.
Many thanks, Larry

[Bob B]

Originally Posted by 94Kcode

Thanks SWENSONB71 and Bob for your replies.

I haven't done any mechanical work in ~1 year. I've clean, checked all ground points (I think anyway). Today I diconnected the Neg battery cable and hooked a test light between the cable and open battery terminal. The light came on. I disconnected the Alt wire and still stayed on. I spent the next 3 hours disconnecting every fuse / breaker / connector I saw --- light still stayed on. So I appear to have a short.
However, when I jump started the truck the other car's Alt WAS charging the battery.
I think your ALT swap / test suggestion is right Bob, regardless of the aforementioned test light results. So, tomorrow I'll pull the Alt and battery and head down to Auto Zone.
I'll post a reply on that outcome.
PS - my '94 model doesn't have a dome light override.
Many thanks, Larry

-----------------------------------------------------
Larry,
The radio and computers have a keep alive memory, so will show some battery drain.
Bob B

[94Kcode]

Originally Posted by Bob B

-----------------------------------------------------
Larry,
The radio and computers have a keep alive memory, so will show some battery drain.
Bob B

Good point Bob! I was under the impression that the Test Light had meg ohm input impedence but........

Update: I pulled the Alt and battery yesterday and took them for testing. The battery passed a load test after about an hour's worth of charging. The Alt failed the Diode/Lamp and Regulator tests but passed the Rectifier portion.
I hooked up the new Alt and the truck is back to how it was prior to this issue .... Thanks for your help!
Unfortunately the "quirks" I noted remain. I'm going to pull out the aftermarket alarm system, as it's wired into virtually all of the affected circuits and then redouble the ground checks SWENSONB71 recomended.

Thanks again for taking the time to help me and I'll post a reply on the outcome of my "quirk" troubleshooting.
Larry