Truck not shutting off after alt swap

[kansasc10]

stumped and need some help....I installed a new wiring harness from painless performance a while ago and when I got it all installed the truck didnt shut off. So I installed the diode from radio shack that Painless recommended if the problem arose and it fixed the issue...truck shuts right off and has worked fine great ever since.

Fast foward 6-8 months and my battery starts dying everytime I drive it for more than for 10 or 15 minutes. So I stop by the parts store by my house and had my alt and battery tested and they tell me my alternator is bad. So out comes the wallet and I buy a new alt. they had in stock. I get the thing put in, connections made and take it for a drive. Everything seems to be working fine but when I get home, the truck refuses to shut off, just like it did before. I have to pull the alt connector to get it to shut off now. I made sure the connector was connected right and not backwards and all is good there.

The old alt has a amperage sticker on it that says 85 amps (even though the web lists it at 108 amps?) and the new alt says 63. Would the amperage difference of the two make a difference in whether it will shut off or not? Are there more differences than just amperage that Im not seeing? Is the diode now doing the opposite of what it was doing before and actually preventing shutdown?

The old alt that worked till this week was a Duralast alternator part #DL-70897. I called Autozone who carries Duralast and they said they no longer make or carry that alternator. Otherwise Id buy the same one.

http://www.autozone.com/1/products/4...t-dl70897.html

The new alt that I installed is from Advanced auto part#7127-3A.

http://shop.advanceautoparts.com/p/c...7-3a/5210100-P.

Im hoping someone here is the end all be all of alternators and knows exactly what I need to do to fix it. Whether it be buying another alt, removing the diode, chasing unicorns etc. I just want to get it fixed.
I called Painless today but they were closed. Ill try them again tomorrow but figured someone here may have a solution. Thanks all!

[Jrainman]

In theory the charging system is separate from the ignition system , I don't know anything about painless harnesses .

The only place were the 2 systems meet are at the ignition switch . if all your wiring was done correctly , I would be looking at the ignition switch wiring ,confirming the ignition switch is in working order and also the correct one with the correct terminals. if the ignition switch is the original it could be just worn out and having internal problems.

[sduckworth13]

Here is a thread for you.
http://67-72chevytrucks.com/vboard/s...d.php?t=604881

Might want this moved to the electrical gurus side to better assist you.

[cooperhw]

There are a few really great electrical guys on here who have probably already covered this type scenario over and over. Run a search.
You might want to check Mad Electrical web site. the guy is really smart on this stuff and the tech tips on his site are helpful.

[leftybass209]

That link will give you the low down on it. It's feedback causing it, but fortunately it's an easy and cheap fix! Best of luck!

[kansasc10]

Thanks for the feedback guys. The first thing I see is that I need to wire the #2 terminal of the alt, directly to the junction instead of jumping to the batt post of the alt like it is now. If that doesnt work Ill try installing another diode in case the one already installed is bad. Hopefully one of the two will fix my issue. Ill let you know what happens once I get a chance to make the changes. Thanks again for the great suggestions!