I have had my truck run the battery down after three days of sitting.
Decided a month ago to put a battery disconnect on the "-" terminal to see if the battery stays charged when not connected and it does. In fact I went as much as 4-5 days in winter and battery still works fine.
Finally had some time to dig around and start trying to find out where it's being pulled down and started with putting meter on alternator and boy was I surprised.
With truck off I was getting 17V on battery terminals. With truck running I was getting a whopping 20.6V. Read through the threads here saying the voltage regulator is built into PCM. Had a buddy of mine tell me that it could still be the alternator that is bad and that he would start there.
I was so surprised, it made me put a new battery in my voltmeter just to be sure it wasn't acting up and got the same thing. Double checked the voltmeter by checking the old 9V battery and it was reading correctly.
Now my question is:
How many think I should bench test alternator and who thinks it's definitely a bad voltage reg. in PCM?

I just want to avoid pulling the alternator unless I know that is the problem.

Thanks guys.

 

Grab your schematic and check for wiring faults -- but don't run the thing because you're risking turning the battery into an automatic hood opener. If the wiring all checks out, test the alternator but expect that it'll pass because in the absence of a wiring fault it's likely a shorted driver in the PCM.

If it is the PCM, the cheap reliable fix is to retrofit an old-style two wire voltage regulator to bypass the PCM's voltage regulator completely. Works fine, lasts a long time, won't rust, bust, or collect dust.

 

thanks and by the way, I like your signature!

 

Honestly i would just pull the alternator out and bench test it anyway. It's really simple to take out, I can have mine out in 10-15 mins tops. The hardest part of the whole thing is getting it around the ac lines. Once its out just bring it into an auto parts store and have them hook it up to their tester. If the alternator checks out, thats one less thing that could be causing the problem

 

Alternator bench tested ok so I went ahead and purchased the voltage regulator and started installing. Stuck in two places.
One: Do I need to connect up the other two ring terminals that are coming off the plastic box back to the alternator along with the two new field wires going to the VR?

Two:
Where in the heck do route a ignition POS wire from to provide switching 12V to the VR? This has made me lose sleep tonight and I'm sure it's a really dumb thing to lose sleep over....
HELP PLEASE!!!!

 

One way is to go to the parts store and get one of those add a fuse pigtails which give you an extra outlet. Get your test light and find a fuse in your fusebox that is hot when switch is on and utilize that fuse holder, you will have to run a wire thru the firewall, usually a place centered under steering wheel where there is already a grommet you can use.

 

Snagged this from another forum, hope the image shows for you:


Snagged from an outfit that sells kits to do the same thing:

 

thanks for diagrams. That helps and I did install it manage to get it installed right and I thought yeah this will fix this bad boy and well it didn't...
I was so puzzled by this that I went back and check out my voltmeter again and that's when "shade tree mechanic" kicked in. Apparently when I was in the kitchen checking out the voltmeter(pc of crap voltmeter) the first time, I flipped the backlight off and was checking some household batteries just to see if it was measuring properly and I confirmed it was. As soon as I stepped into the garage (low light) I flipped the backlight on and guess what? when loads were applied it amplified the voltage. Flip the back light off and everything works fine. It was a variable increase too! I check my alt. with backlight off and she is doing what she's supposed to. flip it on and 20.6volts. Unbelievable!! All that freakin work for nothing but at least I learned something. Get rid of the pc of crap meter and check out my measurement tools a little better!!! jeeesh!! That was a rookie mistake!

 

You are now officially entitled to drown ice cubes in Jack Daniel's. Just don't visit a hangover upon yourself -- you've dealt with enough 5h17 for this week already.

I was wondering how you managed to hit 20V without boiling the battery. Thanks for the follow up!

 

Lmao sorry but that is pretty funny right there