M35a3 overcharging

[SRB1976]

My original alternator went out on my M35a3 due to bearing failure. Instead of spending over 500.00 for an oem one, I decided to install the AC Delco 27si series alternator using the bracket kit from tmamerica. The first 27si lasted about a week and started way overcharging. I figured I got a defective one and purchased a second one from O'reily auto parts and about an hour later the new one did the same thing Both alternators were very hot, almost too hot to touch. It looks like they might be overheating. I'm not sure what to do or what to look for.

 

[cattlerepairman]

Can you show us how the alternator is wired up to the truck? The alternator has a sensing input that tells the regulator how much charge current is required. Others will chime in but usually it is the wire going to the "S" post on the alternator.
A new out-of-the-box alternator overcharging may mean that the built in regulator has no idea it is supposed to ramp down the charging current. I'd start with the input it gets.

Here is a TSB from Prestolite on alternator wiring: http://www.prestolite.com/literature/tech/alts/TSB-1057_Universal_alternator_wiring.pdf

 

[SRB1976]

Can you show us how the alternator is wired up to the truck? The alternator has a sensing input that tells the regulator how much charge current is required. Others will chime in but usually it is the wire going to the "S" post on the alternator.
A new out-of-the-box alternator overcharging may mean that the built in regulator has no idea it is supposed to ramp down the charging current. I'd start with the input it gets.

Here is a TSB from Prestolite on alternator wiring: http://www.prestolite.com/literature/tech/alts/TSB-1057_Universal_alternator_wiring.pdf

 

[dmetalmiki]

I must be missing a trick here..(as) there should only be one wire from the ignition switch to the sensing terminal on a self regulating alternator. (and the Heavy charging wire to the starter motor input,) or battery positive. Others with more (certain) knowledge hopefully will inform you.

 

[dmetalmiki]

As the unit you chose is self regulating, then this applies. Post up the fix and result of same.

http://www.delcoremy.com/Documents/...I-installation-instructions-10511595?ext=.pdf

 

[Tow4]

That is a one wire alternator that has no provision for external voltage sense. If both alternators failed the same it makes me think either they are not 24 volt alternators (unlikely), there's a B+ or B- connection problem that is causing the alternator to have a series of load dumps which will cause the regulator to fail, or the batteries are discharged. Alternators don't like high output at low rpm because the cooling air air flow will be low.

 

[SRB1976]

I hooked up two wires to the battery side of the alternator. One is hot and one isn't. Only the hot wire connects to the + side correct? The other wire may be a ground but i'm not sure. It has no power at all. I hope I didn't fry something

 

[Tow4]

I hooked up two wires to the battery side of the alternator. One is hot and one isn't. Only the hot wire connects to the + side correct? The other wire may be a ground but i'm not sure. It has no power at all. I hope I didn't fry something

You should stop and figure out what the wires are before you burn up your electrical system. If you don't know how to determine what the wires are, find someone local to help you. Diagnosing problems over the internet is next to impossible if the person asking for help can not accurately describe it.

 

[rustystud]

I hooked up two wires to the battery side of the alternator. One is hot and one isn't. Only the hot wire connects to the + side correct? The other wire may be a ground but i'm not sure. It has no power at all. I hope I didn't fry something

That second wire could be your ignition wire. It has power after you turn on the master switch. Make sure you have a proper ground wire and that the wires you are installing are what you think they are ! If you installed that one wire to ground and it actually is the ignition wire you would fry your system fast !

 

[SRB1976]

That second wire could be your ignition wire. It has power after you turn on the master switch. Make sure you have a proper ground wire and that the wires you are installing are what you think they are ! If you installed that one wire to ground and it actually is the ignition wire you would fry your system fast !

That wire has no power at all, even with the switch on. The truck seems to be running fine except it'll start to overcharge when the engine temp gets about 160

I found out that wire is the STE/ICE power lead. Good ole TMs