Charging system not charging!! help!!

Im pretty new here so please forgive any mistakes. My 91 4.0 is not charging at all. I put a new battery in today and a new altenator, no dice on either truck is still running soly off the battery. Im thinking voltage regulator? I check for voltage from the altenator, one pin read 11.55v the other 1.28v at the fuse box the Alt1 fuse read 11.58v and the alt2 read 11.57v while truck was running, i cleaned and die electric greased all the connections on the altenator and batterys as well. All fuses in the truck are good and of proper amps. PLease help me!! i want to get the heep running before my leave ends.

LCPL wren

From what i understand, it sounds like your alternator is only putting out ~11.5 volts or so. The average alternator on any vehicle (except diesel) puts out at least 14 volts and they normally run at about 14.5. If you purchased your new alternator from an auto supply store, have them test it and see if it's bad. Maybe they can warranty it out or something. Also, check your connections and the solid state ignition switch near the fuse panel in the engine compartment. The entire electrical system is routed through this little device and if anything is shorting out, it could mean trouble. If you measured the voltage from the actual alternator positive output lead and it is still only putting out the 11.5 volts or so, then the alternator (which has a built in, not easily serviceable voltage regulator) is bad.

Don't neglect the grounds when you check wiring - there are two you're going to be worried about for this one. Battery-chassis and battery-engine block.

Clean the dielectric grease off of the connectors - that's not what it's designed for anyhow. If you want to use something, go to your local hardware store's electrical section and get "corrosion inhibitor" - it will inhibit corrision, but not your connection.

After you've checked the wiring, also take a voltage reading (engine OFF and engine RUNNING) directly at the output post on the backside of the alternator, compare that to the reading you're getting in the PDC. That would point up a possible wiring fault in between the alternator and the PDC (readings should be within about .2VDC of each other.)

It's odd that you're getting different readings on the two fuses in the PDC as well - those should be within a couple hundredths of each other, as it's a parallel circuit. May be an unrelated wiring fault (unrelated to the charging issue.)

Also, don't forget to compare engine OFF battery voltage readings to engine RUNNING readings - I didn't see that you had listed the engine OFF value. That can also be instructive.

Checking the wiring is time-consuming, but it's also free. If all the checks fail, you may just be wanting a new alternator - especially since the regulator (1991-up) is in the PDC, and I honestly don't think I've ever heard of a regulator circuit failing in a ChryCo PDC...

I'm not real familiar with the 91 but some slightly later models, they are likely much the same until the mid 90's. What are the wire colors to the back of your alternator?

ok so I'm a huge idiot. My freakin belt tensioner wasnt grabbing and was meting the belt slip. Wow so easyim so stupid errrr