Electical prob.....HELP Please

I have a 93 Mazda B2200. I just put a rebuilt motor in it and now im having problems. While the old motor was in the truck it never had a problem starting or charging........NOW After I drive it for about 20 mins or so it acts like the alt isnt charging....The bat light comes on, the radio cuts in and out, the signals get real slow....etc.... I started it and unhooked the battery and it runs fine, yet the battery is dead.......Can the alt run the truck but not charge the battery? Do these trucks have external regulators on them? Any help would be great.

yes if truck is running you should be able to keep vehicle running by just the alternator,if the truck is running take a voltmeter and hook up to wire coming from alt to see what volatge is more than likely you need a new battery or possibly the voltage regualtor on alternator could be taking a crap just check voltages on disconnected battery which should be 12,5, with vehicle running roughly 13.5 -14.0 hope this helped

I tested it and the alt only shows right at 12v maybe a hair more while running. its an internal regulated alt correct? If so then I am guessing the alt is going bad.

yeah sounds like alternator going bad ,but check voltge on battery with out being hooked up

yup

Make sure all your ground and connections are clean and good. Batttery to body, to chassis, to motor. etc. All those need to be top notch, or your battery and electrical system will not charge properly. I had the same problem with my wife's B2000 and inside the battery negative cable that hooks to the inner fender was rotted out and barely making good contact. I replaced that wire and saved on having to buy a new battery. Also, a bad alternator can ruin a battery and a bad battery can ruin your alternator. you can get both of those checked for free at most autoparts stores.

yeah... my 90 2200 std cab... i had my alternator checked and it was putting out... but there was a diode blown in it... so it wasnt putting out enough.. instead of spending 200 at the parts house for a replacement i bought the 140 mustang cobra alternator and performed the upgrade!

check out the tech section... its in there.. also you could do a gm 100-140 amp swap for cheaper than getting the factory 55amp alternator replaced!

jeremy

also you can check your belt i had one that was tight but still slipped

Thanks for all the help and ideas..... I think I am going to swap alt's and go from there.......Thanks again

have it checked out before you swap unless you have a spare laying around. Otherwise you may be wasting your money.