Well I think I might have noticed a problem that I want to nip in the rear before it leaves me stranded with a dead battery (amp gauge doesn't work and haven't had the time to pull mine out and have it converted to volts)

But anyways few years ago when I was doing a bunch of math for auxiliary lighting to figure out what my options were with my current 75A 1G alternator (states 75A on the case), well at that time I had at around 800RPM or so 14.3 or 14.4v at idle with no load. With load like headlights on I was dropping to around 13.5v at idle (I thought voltage regulators were supposed to kick it up to maintain fairly constant output).

Well with my CB whine issue I was dealing with I noticed when I was doing testing on my truck it was 13.2-13.3v at idle with no load on. I just did a test after work today and I am seeing 13.75 - 13.76v at idle with no load. Headlights switched on highbeam with my KC Apollo 100w driving lights (one pair) switched on my voltage was at 12.31 - 12.32v at idle.

The alternator as far as I know has never been replaced and the voltage regulator is original to the truck as its embossed with "Motorcraft".

I also read about bad grounding on the regulator so I jumpered to the negative side of the battery to see if any difference. My multimeter showed a slow steady climb on voltage from 12.4v to 13.6 to 13.7 volts.

So I want to ask should I consider picking up a new Motorcraft voltage regulator and pick up a rebuilt alternator? I know my headlights would dim at idle in gear slightly not a whole lot but enough for me to notice but that was back when I had 14.3v at idle in park and around 13v in gear.

I would do a 3G conversion but I just cant afford to purchase a new 3G alternator and do it right to convert it over at this point. I can pick up a reman 1G alternator for considerably less. I know I could go the junkyard route but being my only vehicle capable of being driven at this point I kind of need dependable for work so I cant justify trusting a used alternator.

 

You want to ask? I'd say go ahead and officially ask your question. Do you even need permission? I don't think so, but if required, how should we handle it? Maybe a general vote by all FTE members? Unfortunately, that might be a little unwieldy. Would it be more practical to abide by a moderator's decision?

 

All seriousness aside, go back and read your paragraph quoted above. It sounds like you've identified and corrected the problem, but didn't realize it. 13.7v at idle with a 1G is pretty good. I don't have my manuals handy (the cat refuses to let me up from my recliner), but I think testing is supposed to be done at a higher RPM anyway. The value you've recorded at idle isn't a true test.

Make a permanent ground jumper to the regulator base and call it good. I'll split the money you've saved by not buying a new alternator and regulator.

 

But the thing is how did I have almost 14.5v at idle few years ago. That is what is confusing me. I could see you know 1/2 volt difference due to weather but a whole volt just seems odd. I know the voltage regulator is the original one to the truck its quite rusty so that's why I am just curious I guess if its something that needs to be replaced. I don't want to replace it if its not going to make a difference. Just part of me feels that it should as the voltage regulator should regulate the voltage to a set value.

I did hook up the jumper wire to ground and it didn't change at all if anything my peak voltage went down to 13.68v with the ground added.

 

Rule #1 when troubleshooting a charging system: Start with a fully charged battery.

Now I've been guilty many a time of skipping that step, but I've also been very careful not to condemn likely good parts just because I didn't do the full-blown checkout. I'm as lazy as the next guy, but am generally careful not to make more work for myself when troubleshooting from the hip.

Your variation from a few years ago could be due to many variables. I wouldn't consider that a fault at all. Your battery may have had a full charge back then, even if you didn't realize it, versus who knows what now. (Read rule #1 again, see above) The general condition of the battery has no doubt changed. If it's the same battery, it's now several years old. If replaced since then, you'd get a variation due to brand, capacity, etc.

The voltage regulator is really a very crude device. Compare it to a smart battery charger, for example. A charger constantly senses the battery voltage, compares the amperage going in, calculates an approximate state of charge, and adjusts itself accordingly for precise charging perfection. A voltage regulator, on the other hand, just blasts out a bunch of electrons, only throttling back as it approaches a predetermined value that should hopefully recharge the battery without going too high. A charger is like a scientist with calibrated measuring equipment and a clipboard. A voltage regulator is like a kid playing with the floodgates on a dam.

What I'm trying to get at is don't read much at all into the voltage at idle, as it honestly isn't part of the test of the charging system. It's a gee-whiz number that is a crude guesstimate at best.

Another way to look at it is imagine you've got an air hose to inflate a giant thick-walled balloon. Your air hose has a gauge on the side. As you start inflating the balloon, the gauge will read fairly low. That's comparable to a battery that isn't fully charged yet. The air compressor (with pressure regulator) is working fine, but isn't going to show much pressure in the hose yet. As the balloon fills, the gauge reading increases. That's like a battery with a higher state of charge. Same perfectly good compressor, but different pressure readings based on how full the balloon is. You can't condemn the compressor solely on the pressure reading when the inflation state is unknown. Heck, the balloon could have a hole it (comparable to a tired battery that won't accept a full charge) and the pressure gauge will always be low. That's a crude example to show how important it is to always start with a fully charged battery (in good condition) for accurate troubleshooting of a charging system.

Here's an excerpt from an '84 service manual. Start at the green dot, read through to the red dot. If these simple tests pass, your charging system is good. Note how none of the readings are taken at idle, so don't get sidetracked by going down that rabbit hole:



I really need some safety rails for when I'm up on my soapbox...

 

Neither of the 1G's I tried on Big Blue will hold over 12.8 volts at 700 rpm. But, if I bring it up to 1200 rpm the voltage will come up to 14+. So, to me your 13.68 at idle is very good. Or, maybe you've adjusted your idle speed?

 

Well there is a difference because when I did the test last time it was with a Diehard Gold battery same as I have now but I replaced it last year as it was 8 years old and started giving me no crank issues.

So its the same battery but a couple years ago it was putting out 14 volts at idle with a battery that was at least 5 - 6 years old. Now with a new battery not even 1 year old and its showing less voltage at idle than it did with the other battery.

 

I'm guessing on the idle speed. The factory tach in gear is set a needle width above 500 rpm which should be around 550 - 650 rpm, about 2 to 3 needles width below 1000 rpm in park which I would figure is around 750 - 850 rpm.

I'm sure at idle in park the voltage output is pure battery voltage I wouldn't be surprised by that I know my headlights dim faintly when I am idling at a light.

 

Old batteries show a voltage rise easier than new batteries. That's because a new battery will convert more of a voltage rise into a chemical reaction. In other words, it takes more current to get the same voltage rise out of a new battery than an old one.

 

So there should be nothing to worry about if I am sitting idling with my headlights on with the voltage being almost straight battery voltage then?

That is my main concern is that I don't want this to go out and strand me. We never replaced the alternator since we've had the truck since '92 or so and we never replaced the voltage regulator either and considering its a rusty motorcraft embossed one I figure its 1982 vintage. So I was concern of something failing due to it not being replaced by us. Guess I will just say screw it and leave it be till I get around to doing a 90A 3G conversion.

 

That means the alternator/regulator are supporting both the headlights and the ignition, so they are working. And probably as well as a new one would. These 1G's didn't throw much at idle. But the redesign for the 3G fixed that. In fact, one web site claimed that the 3G's are so much better that they throw as much current at idle as the 1G's did at full tilt.

 

If you can afford to do it twice, you can afford to do it right the first time. Test the charging system rather than randomly throw parts at a problem. It sounds like you already fixed it though, in that the primary issue was a bad ground at the voltage regulator.

Quick and dirty test of the alternator is jump +12v from the battery to field, this puts the alternator at full field for max output. Check voltage at idle and as you slowly increase RPM. By 1000 RPM voltage should be above battery voltage, should increase to ~14v, and will likely keep increasing to around 16-17v. If you observe this, the alternator is fine, or at least good enough.

Technically if you're really poor and the regulator fails you could jump this with a wire under the hood or switch in the cab and cycle full field on/off periodically to keep the battery charged, keeping it off enough to avoid boiling the battery or overheating the alternator. The less ghetto way of doing a ghetto rig would be a rheostat under the dash and constantly adjusting to maintain 14v-14.5v.

Save your pennies and swap to a 3g later or when the alternator or regulator fail.

 

Well i want to make the 3g swap. I just keep losing my paperwork on what vehicles to buy the alternator for. I know i kneed a 7" pivot to pivot 3G (measured the 3g off the 302 removed from the 82 f150 we did the 5.0 coyote swap) and im perfectly fine with the 90-95 amp version 3G as im fine with the 70A 1G, battery stays charged just fine.

 

I recently did the 3G swap with my 1986 F-150. Instead of going to the box store (who didn't know anything), I went to a local alternator shop. They sold me one for only $80, swapped my pulley, and gave me a new connector pigtail to wire up to the existing solenoid wire.

 

Thats what i was going to do. Where i got the rebuilt 6v starter he reocmmended to me for my 12v '56 they do alternators as well. I might be able to give him this 70A 1g alternatoras a partial trade for a 3G.

I know i want to get that plastic leg for the battery connection to make life easier on me.

Only thing that gets me is the ford bronco forums states any v belt 302-351 engine from 66-86 needs the 8.25" ear spacing and says some trucks can get away with a 7" spacing but now im not too sure, the 7" alternator that came off another f150 of the same year has smog pump and bracket and its 7" but not sure if his brackets were modified or not plus he didnt have a smog pump installed.