Hey Guys,

So my 82 F250 has had some issues starting over the last couple of weeks, where if it isn't turned on every day, it won't start, with the battery being "dead". Checked fuses to see if I had a draw, didn't really find anything. Took the battery to get tested, where things got funky. Went to two different auto parts, and while the battery itself checked out as good, just needing a recharge, the charging system test gave me two different results. 1 being "excessive ripple" the ohter reading "phase open". Point is something is killing the battery/not charging, and I have not clue what it could be. Thoughts?

 

Without getting into the fancy explanations of "open phase" or excessive ripple," all that means is you have a diode in the alternator that's ready to be buried.....Your alternator is toast...or nearly so. Did they give you a printout of the wave function or the millivolt AC "ripple" limit?

Have you checked the alternator/engine's charging system?

 

 

Can you post up a picture of the "excessive ripple" test and the "phase open" test?
The voltage is all over the place in the test shown here....but very low. The charge system test shows a lower than normal (14.5 VDC) voltage also.

Not that it matters 'cause yer alternator is history.

To further verify its demise, you could "full field" the alternator to check for a voltage spike.

If you want to do that and don't know how, I'll walk you through it.

 

 

Ok, no problem. But we know there's at least one diode in the alternator that's shot....making the alternator only produce 2/3 of it's power, and rendering the alternator kaput. With that in mind, the other 2 diodes will start to give way, more sooner than later.


Alright, on to cases: Full Fielding the alternator - Attach your DVOM to the BATTERY (+) and (-) posts, set at 20 VDC. AN ASIDE HERE - if you can, remove the regulator plug from the regulator, check its wiring and connections and put it aside. Have a jumper wire handy ..

Have a helper (if you can), fire up your vehicle...once running, attach one end of the jumper wire to the 'F' (Field) or FLD terminal on the alternator and the other to the BATT (+) positive battery post or terminal

Watch your DVOM here! If the meter spikes to around 18 VDC, the alternator tests good. ......and the regulator is bad....or the wiring between them is bad.

No spike? The alternator is junk. AGAIN, you want to see a spike of 18 VDC....not 12, not 14, but 18.

You could always take the alternator to your favorite parts store and have them load test it....but we know from the "open phase" and "ripple" dealies that one diode in the alternator went south......

Let us know your results.

 

Yep, roasted diode sounds like. Recharge battery thoroughly before installation. Do not try to use vehicle alternator for this purpose or you may ruin the new one too.

Maintenance free batteries read 12.80 volts at 77° F. It takes a long time to recharge a heavily discharged automotive start battery. Maybe you know all this already, not trying to beat up on you.

Finally - replace those now 35+ year old ground and start cables! Widely overlooked. Grind down to bright shiny bare metal and tighten securely at block, firewall, and frame. Coat with vaseline or NO-OX.

 

Good call, Tedster9.

 

If one of the diodes is shorted, it will cause a drain on your battery. Of course the alternator will not charge as good either. But if you want to do a quick check, get a testlight and hook it up like the diagram below. With everything off and the door closed, if the light lights up bright you have a drain. Take the wires off the alternator. If the light goes out, then you know the alternator is the reason for the drain.

 

 

Sounds like time for a 3g alternator. 1g is not worth wasting time on anymore and 2g is a fire hazard. 3g is a bolt in swap for only a few bucks more than a 1g.

 

 

You can get by with a 60 amp, which is probably what you have now. Unless you want to upgrade "just because" I would put the stock alt back on it. That is a true "bolt in". With the 3G you will have wiring modifications and there are very few times when the 3G just bolts in. If you carefully research all the different 3G models, you may get one to almost bolt in, but there may be clocking issues with the case, and you will most likely have to swap pulleys. Swapping pulleys can get interesting sometimes if you do not have a impact gun.

 

Not to beat a dead horse just keep in mind old cables and dirty connections will choke off any alternator, no matter how big. A stock alternator is probably fine. But good grounds and wiring means you will get all the juice you paid for.

 

Installing a new 4 gauge charge cable and changing a pulley is still a bolt on deal. Oh, might be getting crazy as you'll have to crimp or solder a wire on the new harness off the alternator as well. Get an alternator already clocked correctly for your application and you won't have to loosen and tighten those 3 case bolts either. 3g is a bolt on swap. heck for that matter a 10si or 12si is a bolt on swap.

To OP, personally I wouldn't bother with the small case 95 amp 3g, the cost difference is negligible and it takes the same time to install either one.

A 42 amp 1g will work and be adequate for the electrical load these trucks have. The advantage of going with a 3g is a simple internally regulated alternator, less wiring, and mainly increased output at idle for full voltage. No more dimming lights or slow defroster at idle, less runtime required to charge battery after starting.