Well, I'm stumped once again guys. My '66, 240, A/T, had a unique smell on the way home last Thursday. Smelled like roofing tar. Got home, popped the hood just for a weekly checkover of things. The battery was sizzling!!! It was burning up hot, let it cool for a few hrs, and was still sizzling. Later felt brave enough to disconnect it and not risk causing a spark to set it off. The next day I got my DVM. Connected the batt. and started the truck up. Went from 13.4 when off, and started going to over 18 volts. Shut her down after just a couple of minutes, and battery sizzling again. Checked out the batt, and was toast. Got a new one. Same thing. This is with a new regulator replaced about a month ago. Swapped in 2 known good regulators, and still same problem. Pulled alternator off, took it to advance auto, and had it checked. Was charging fine. Came back and checked my grounds, onces I could find, and were clean and good. What am I missing here. I just really need an idea, I've got so much going on, and limited time right now to check out the truck from the start. Thanks again to everyone that makes this site so great. Brian

 

what kind of alt...3 wire, single?

 

When you are saying 13.4 when off does that mean you measured 13.4 volts with the battery just sitting there? Since it is a 12 volt battery that would seem impossible to do. Most fully charged sitting at rest batteries would give you 12.15 - 12.25 volts which is what I got on 6 different batteries.

Now if you mean 13.4v when the truck is idling then that would be about right. The output will go up as the rpm's increase. So what are these regulators that you know are good? The old points type or electronic? Did you use a volt meter to measure 18 volts in the driveway with the rpm around 2000?

Guess work now. If the output measures 18 volts with different regulators then open the regulators as they are adjustable if point type. Electronics are not adjustable and tend to run around 14.8 volts which is a little too high for my tastes. Now there are actualy 4 things you can adjust on a point regulator. Three can be done out of the car and one when in the car and running provided you don't ground yourself. The one in the car is what determines the output level. There is that one contact with a spring on the backside. Increasing spring tension raises the output and decreasing tension decreases the output. Cover off, steady hands and needle nose pliers can manage the task. Do it all the time.

I doubt the alternator would be the problem as the regulator controls how much volts are put out. So the alternator could be almost as high as you want or as low as you want depending on what one did with the regulator.

 

Morning fellas,
Heavy, it is a 3 wire. And Mike, the 13.4 volts was with the first battery, at rest, and truck shut off. That was after sitting over 24 hrs, after the thing had been overcharging on the 35 mile trip from work to home. With the new battery, I've got the proper 12.3 or so. At idle is when the thing will jump up to 18+ volts. I blurped the throttle a few times, and didn't change. It only takes about 2 minutes at idle to go from 12.3 to over 18.5, that's when I shut her down. Don't want to boil another new battery. The regulator that was on it when it started isn't over about a month old. Non-point type I'm guessing since the cover is riveted on. It's a Standard brand. The second one is a Mighty that was working fine on my other truck, and the last is the one that came off the truck originally. A couple months ago, I replaced it, because I was letting it warm up one morning, had the headlights on high beam, and blurped the throttle 1 quick time. Blew both high beam filaments out. Checked everything I could think of, and figured the regulator could be the culprit. Left it for a while, and never happened again, but I changed it anyway, 'cause I didn't know the history of/or how long it'd been there. Still no problems from then, until last week. Hope this helps some more. My cables and grounds all seem good. Thanks again, Brian

 

Something tells me that the wiring going to the voltage reg isn't up to par. For instance if the wire going to the reg that tells it how much the batt voltage is has corrosion it will indicate a low battery and trick the reg into thinking it needs to "charge" the battery. Check over the voltage regulator wiring for bad crimps, broken shielding, melted shielding, or green/white powder in the copper. Also double check the wires to make sure they are connected to the right terminals. External voltage regulator wiring diagrams for alternators, and starters. - Ford Explorer Ranger Photo Gallery at Serious Explorations If this doesn't change anything it could be a fire wall connection or under the dash, idiot light or amp meter.

 

one easy check check is unplug regulator and check voltage

 

Sounds like classic voltage regulator malfunction to me.

Tommy

 

Mark may also be right if you have the old alternator harness in the truck. When I got my '65 and saw the wiring harnesses in the engine compartment I immediately ordered 3 replacements: alternator harness, gauge harness and lighting harness. Not cheap.

As for voltage regulators I am not a fan of electronic ones especially aftermarket. Many Chinese made. If I had a truck that used an electronic regulator from the factory then I would use a Motorcraft replacement only. So instead I look for NOS American made point regulators on ebay to stock up on. Adjust them, put new Autolite covers on and bag them up on a garage shelf.

 

It is not odd for a piece of electronic equip. to fail, right out of the box, or only last a week, month.
I would take the new reg back, get a replacement, and then look in the harness coming from the alt too see if the wire cominf off the feild term, (FLD), is completely isolated from the one coming off the stator, (STA), term.
I've had it happen once before on a vehicle, where the insulation on these two wires had deteriorated to the point that they were touching, and all kinds of weird stuff was happenig, boiled batteries, fried electronics, and finally wrecked alt.
Let me know how it woks out as I am curious to know.

 

OK guys, Spent most of the day trying to troubleshoot this thing. Started with disconnecting the battery and then tracing wiring from the regulator back to the alternator and solenoid. Everything ohmed out fine. Then I took terminals loose. The positive at the starter solenoid was corroded on the stud itself, under the terminals there. Cleaned all that up, reconnected the battery and reg, and started it up. Now instead of 18 volts at idle, I was down to around 16. Shut her off, and started pulling all the other connections loose and cleaned all that I had time for, and got a new solenoid. Tried that, and am now charging at 14 at idle, and 2000 rpms put me about 17. I've never checked these before at the higher rpms, but is that about right? My '74 is parked at my shop 30 miles away, and can't check against what I'm getting on it right now. Probably won't have time tomorrow with Mother's Day and all, but I'll post when I find anything further. Thanks again guys. I am a mechanic by trade, but just don't have the tools here at the house and with the shop so far away, I've already burnt up 1 battery, don't need to do that again. So, I'm just running on limited resources her at home. And it has been an awfully long time since I've had to work on a external regulator type vehicle at all. Thanks again, Brian

 

It shouldn't ever charge that high voltage. You still have a problem if you are getting 17 volts. Why don't you try just converting to a 1 wire alternator.


ROb

 

Well, I still have some wiring and connections to go over before I rule that option into play. Going to take all the grounds loose, and clean everything. That would need to be done anyway, so if that gets it working correctly, no use in spending that on a new alternator. At least I got it off the 18 volts at idle. I will keep posting what I find. Thanks guy.... Brian

 

If all the wireing checks out good, Sounds like a bad regulator,
it should get between 13.5 and 13.9 at 1000 rpm. the highest
you should see is 14.5 if yor battery is low.
If your battery is fully charged it is not unusal to see 13 volts
on the battery with the engine off.
Replace the regulator first, it's whole purpose in life is to take
the DC voltage from the Alt and control it.
Sounds like it has failed at it's purpose.

 

do you know what amp rating the alternator is?
the higher the amp rating the higher the voltage it will put out

 

Not necessarily true. Higher amperage alternators charge with more amps. You don't ever want to see over 15 volts on that battery.


ROb