the diodes are ez to overload and over heat and blows one usually then you only get 11-12 volts out put. It will just keep your vehicle running until you turn on your head light or heat any heavy load can kill the motor out until you turn off any pull on the battery. It's sound like the ones at the auto parts store have a bad diode with that low voltage out put. I'd have them check the out put so you know it putting out 13.2-14. I think it's time you buy a test meter so you'll not have to guess as is it good or not..
orich

 

The guy at the parts store wanted to check the output since they had bad ones from sitting on the shelf for so long. By test meter are you talking voltage meter or something different, thanks.

 

Yeah a little digital multiple funtion auto test meter you can find them in auto parts stores..
orich

 

I've had a similar experience with Autozone Alternators in my 01 Mitsubishi Montero Sport. I went through 4 alternators in 6 months until I got a good one that has lasted.

Good thing they have a lifetime warranty! LOL That's probably the reason for the lifetime warranty.

 

Unforunately I don't it will be that easy. Got a new alternation from parts and hooked it up this morning. They checked it the parts store pass 13.5 output but failed a dc response test. Neither I or the parts store guy know what the DC response test was but guessed it was because no internal regulator? Hooked up on truck battery fully charged start right. Ran for about 20 minutes shut it off won't start cranked like low battery. Checked battery with meter showed 12 volts.

Got home tried to start it cranked slow won't start. Checked battery with meter shows 12 volts. Hooked up a battery charger show about 7 volts. Did DC reponse test mean the alternator was bad from the beginning?

I did find a blk/red wire inside the cab the was slightly hot. There is a 4 prong connector under the dash that has a red/blue (goes to starter relay) and the blk/red wire. I need to figure out what is going on with that wire, was cut and rewired. So any idea's would be help. I will let you know what I find out about the blk/red wire. Off to look at wiring diagram again.

 

Blk/red wire goes to backup switch is this located in the engine compartment on the steering column? Thanks.

 

The best way to test the alternator at home is with a multi-meter. Set the meter to the DC setting and use the 20 or 50 volt range. You should have 13 -14.5 volts at the battery with the engine running. Pulling the battery cable off while the engine is running won't prove anything. I can pull my negative cable and my engine quits immediately. There is NOTHING wrong with my charging system. I'm getting 14.45 volts at idle. Thats with an electro-MECHANICAL regulator (I prefer mechanical regulators). Just for curiosity I installed a spare electronic regulator I had laying around and the engine WILL run with the battery disconnected. Same alternator different regulators. My point is just because the engine won't run with the battery disconnected doesn't prove that charging system is bad.

 

It could be. Some trucks with "3-on the tree" had the back-up light switch on the column in the engine compartment.

 

http://www.fordification.com/tech/wiring/68-22.jpg

If you look in the center of the engine compartment it says back up switch. Looks like it is mounted on an arm om the steering column. I have an arm but no switch if it goes there. If anyone knows exactly where this is suppose to be mount let me know please. I might as well fix what ever I come across till I get alternator problem fixed.

Got a new alternator last nite going to do some voltage checks in a little while I will post what I find.

 

Had a friend that started having troubles with the alternator not charging. He got a 2nd one tested before leaving the auto parts store. Then every time he mounted it the new rebuilt alternator it would blow cook it. He called me,after getting a 3rd one.
I went over and started looking the whole thing over looking for what may be the troubles wires and all . With in 5 minutes, I saw what was going on. The field rubberised terminal cap that fits over the alternator terminal that worn through the back side that was causing the shorting to the block/head. It seem on all the replacement alternators had a little longer field-terminal causing it to short. Pull the alternator off cut off about 1/8" or so so it cleared the block enough not to tough and short to the block that fixed it. So you may be have something going on like this guy had.. my2cent
orich

 

Actually though about that noticed the back of alt. was close to engine. Just did a qucik visual check looked ok but I will double check tomorrw. My connector havs an open end so maybe the new alt. has a longer terminal than the old one.

Did a voltage check on the new alternator and I'm getting 12. 79 volts
without engine running. Had a full charge since I left it charging while at work. Start it up jumps to 12 .82 stead even with the engine rev. up
Strange thing is I hooked the battery charge after running for about 10 minutes and it showed 6 amps dc. I hooked the charged back up about an hour ago I'm going to check it right now.

Battery was fully charged checked voltage around 13.8 started truck and the voltage dropped stead from 13.8 to13.2 shut off checked voltage was down to 12.8 started truck stayed around 12.8. Hooked up battery charger back down to 6 amps dc but was charging back up fast.

Battery is not that old and had it checked before this problem started and was fine. Should I get the battery checked again. Seems like a drain some where could the voltage regulator have something to do with it. Any thoughs.

Oh I checked the connections on the alternator and they look fine except the blk fat part of the connector is touching the engine not sure if that is a problem. Here is what my connector looks like. http://www.fordification.com/tech/wi...350_master.jpg

Not a real pic but if you look at the alternator you can see the connector.
I will have to check it tomorrow.

 

It''s morning I checked the voltaged at 14.13 and charger shows full charge. Starts right up check voltage at battery 12.8 shut off truck hook up charger shows 6 amps dc. Try to crank it starts up but I can tell by sound it cranks a little slower. Looks like a big dain or the battery is meessed up. Battery cables are new and have a good connection any thoughs? I will get the battery alt. check tonight when I get home from work.

I would like to do this test by my voltage regulator is this safe to do. Not trying to insult just trying to be safe and not blow anything. Thanks.

With the engine running, try unplugging the connector from the voltage regulator and using a jumper wire 'full field' the alternator. This should cause the alternator to jump to 15+ volts. If it doesn't, give it a little revv. If it does go up to 15 by revving it a bit, you may have one of the diodes going bad.
If it doesn't move at all (above your initial readings) then the alternator is most likely toast. Doubble check your wiring and grounds (broken and whatnot) to be sure.
Now if it does shoot up to 15+ volts, then you have a good alternator, and now I'd be suspect to your voltage regulator. Be sure you have it grounded well. I don't have any tests for it other than swapping out and 'testing' your skill at hitting the trashcan from afar. (if another new one fixes the problem of course)

Here's a pic to explain which terminals to jump-
<TABLE id=ncode_imageresizer_warning_2 class=ncode_imageresizer_warning width=400><TBODY><TR><TD class=td1 width=20></TD><TD class=td2 unselectable="on">Click this bar to view the full image.</TD></TR></TBODY></TABLE>
<!-- / message -->

 

That test is listed in most older motor manuals for the ford trouble shooting. Jumper should be on (F) & (A) by my book listing for doing this.
If you have the old style reg. you can remover cover cap by the two screws or drilling the rivets out. Then start motor then try closing the field coil points. If the alternator is good then by closing the reg. points it will then start charging battery. Okay but care in removing reg. cover cap BEST to "disconnect BATT" while doing this, as it's so ez to cook it okay. If it's the newer solidstate one maybe a parts store can test it.. PS If you closed the points on the reg. it may stay closed after turning off the motor and will drain the battery
orich

 

You don't happen to have an idiot light instead of a gauge do you? On those, if the bulb is burnt out, it will not charge. Just covering all the bases.

 

Checked voltage a few minutes ago and the battery reads 13.07 so I'm thinking there is no drain. I'm guessing the second alt. was bad from get go, it did fali a DC response test what ever that is. I have a fair new regulator so I geuss I will try this test without drilling out the rivets at least at this point. I'm still a little concerned about the connections on the back of the alternator I can see one is real close and the other I can not see so maybe that one is touching.

Just got home from work it's dark and I'm a little tired so i may not get to it till tomorrow. But thanks for the ideas once I do some of the checks I will report back. Tomorrow afternoon I will have some time so if I don't figure anything out by then I will take an extra battery and get an alternator and battery check.

Oh using 2 different meters an analog and a ditigal not a test probe but a good idea anyway.