Help, I'm out of parts to replace! -- Electrical

rdnkjdi · Oct 7, 2007

My car died and wouldn't start. I figured it was the alternator or the battery, so I went to my local parts store and got them both tested. Alternator showed bad and the battery showed good, so I replaced the alternator. The next day, took the car on a long drive and it died again and refused to start. Had to charge the battery every twenty miles just to get it home.

Brought the car back to the parts store, they gave me a different alternator & I got a new battery just in case. I was told I could check the new alternator & electrical system by disconnecting one of the battery terminals after the car was started. The car should continue to run off the alternator. I tried this with my new alternator and new battery, and my alternator started smoking and the car died.

Next part I replaced was the voltage regulator. I figured it was worth a shot. After replacing it, I did the test again, (took the positive wire off the battery). Same thing happened, car died, alternator smoked, & this time the voltage regulator smoked too.

I'm kinda at a dead end. If I can't figure anything out by Monday I'm gonna call a mechanic. Any ideas?

P.S. It's a 66 Mustang w the 200...

Rusty67 · Oct 7, 2007

As far as I know, that test doesn't work on our classics. My charging system is just find and it dies when I try that test on my car.

First things first. Lets not go doing a buckshot/shotgun approach. Do you have a multimeter ?

rdnkjdi · Oct 7, 2007

Do you have a multimeter ?

Yes

wicked93gs · Oct 7, 2007

whats your voltage at idle then?

Rusty67 · Oct 7, 2007

Also, check the resistence of your battery cables in ohms (the Omega symbol).

p0prcksandc0ke · Oct 7, 2007

you might want to check to make sure your alternator is grounded right and there arnt any burns though your ground wire, and to just check all the grounds

CraigMBA · Oct 7, 2007

I'm thinking the wire from the charge post of the alternator to the solenoid has gone bad and shorted to ground.

p0prcksandc0ke · Oct 7, 2007

CraigMBA said:
I'm thinking the wire from the charge post of the alternator to the solenoid has gone bad and shorted to ground.

ya what he said

CraigMBA · Oct 7, 2007

I had a solderless crimp connector go bad on one once. It got moisture intrusion into the cable and the cable just fell off. I was lucky and it was right on the back of the alternator post and I had it zip tied off so it didn't short out.

All I did was shorten the wire 2" and recrimp it, but it could of been a lot worse if it had failed different. I had the wire get compromised on my truck and it wrecked an alternator.

p0prcksandc0ke · Oct 7, 2007

your lucky, my battery cable was too long and the alternator ripped it open while it was running and it shorted everything and burned through some wires

rdnkjdi · Oct 7, 2007

I'm thinking the wire from the charge post of the alternator to the solenoid has gone bad and shorted to ground.

I visually inspected the wire, and it looks ok.

whats your voltage at idle then?

I can't tell if it's 8 amps or .008 amps. It's the same as in my 96 F-150. If there was a short, wouldn't in be pulling wayyy more amps?

I drove my car around tonight to make sure replacing the voltage regulator didn't fix it...and sure enough after about 30 min of driving with the lights on, it wouldn't start.

StangDreamin' · Oct 7, 2007

rdnkjdi said:
I visually inspected the wire, and it looks ok.

I can't tell if it's 8 amps or .008 amps. It's the same as in my 96 F-150. If there was a short, wouldn't in be pulling wayyy more amps?

I drove my car around tonight to make sure replacing the voltage regulator didn't fix it...and sure enough after about 30 min of driving with the lights on, it wouldn't start.

If you're talking about amperes, you're talking about current; and that sure doesn't sound like much current unless the enigine's been running long enough to recharge the battery! The original question was about voltage; which should be around 13-13.5 volts at idle RPMs (unless you've got some serious audio amplifiers driving the speakers enough to vibrate the car). 8 volts (or even 8 Amps right after starting) just isn't close to enough! Early Mustang alternators were rated at something like 40-45 amperes; and again, a good voltage regulator should hold "engine running" voltage at 13-13.5 volts.

Wiring and connections! One of the three wires going to the alternator is the "excitor" wire. I forget which one right now (somebody help me out with the abbreviation stamped/cast into the alternator body next to the appropriate terminal); but one of those wires is the "Field" or "excitor" wire. Whichever it is, check to see if it's burnt or shorted to ground or (more likely) has a corroded connector - at either end. The alternator is trying to maintain good voltage/current without enough "Excitation" voltage; and smoke starts pouring out.
One "simplified" theory is that electrical items run on smoke; and when you let all the smoke out of something like an alternator or regulator, or radio or amplifier; it quits working.

Rusty67 · Oct 7, 2007

Just put a 3G alternator in it an ditch the dumb externally regulated setup.... once you figure out what the problem is anyways.

JDS68Stang · Oct 8, 2007

I've got a 68 with an I6 and had electrical problems that kept me busy for weeks inbetween working on the POS engineered front end and other areas that needed attention.

My battery tested bad (looked fairly new), alternator tested bad also (looked like new) so I replaced everything including the regulator. At first I believe we had to flash the stator to the Alt. on the alternator to start finally getting a charge. After I shut off and restarted car, no charge again. I burned out one regulator while trouble shooting as well, I'm assuming you fried yours to.

Finally I just by passed all the old wiring and made up a new harness according to the diagram on the sheet that came with the alternator and no problems since.

I to had wires smoking and frying when they were hooked up original, that's why I just made my own harness. If my friggin scanner worked I'd scan the diagrams for you (two choices) and that may have helped. If you still have the problem in a day or so I can look my car over in the daylight and tell you what I ran to what.

If my memory is right I think my stator wire needed to be hooked up on the I terminal on the solenoid and it started charging after that. (not 100% sure about that though without checking tomorrow) Good luck, these electrical problems are a pain in the a** .

rdnkjdi · Oct 11, 2007

Ok, I'm still fighting with this. I think I've figured at least *part* of the problem. I used my meter to test the ohms between the wires @ my voltage regulator & my alternator. The wire that is supposed to be to field, (middle wire) reads to ground. Another wire reads to ground as well, & the third wire, (top wire) reads to field.

Plug to regulator...

o - Field.
o - Ground
o - Ground (This one is grounded better than the other one. Needle jumps faster)

o - Wire that isn't used.

According to the diagram in my mustang book, the wire that doesn't go to the alternator goes to the field relay. Can somebody tell me where this is?

Also, testing the voltage on idle w a digital meter

- 9.5 to 10.5 between alternator field & ground.
- 11 to 12 between my battery posts.
- 20 to 21 MV between my alternator battery terminal & ground.

I think I've got the field from my regulator hooked straight up to ground. I could've sworn I put it back together right, but I guess I didn't. Can anybody tell me how I can

A.) Test the regulator to make sure it isn't shot, & that I've got it hooked up right? (I know I killed my first one, working on my second now).

B.) Test my alternator after I know my reg is hooked up right?

D.) Test my battery after all that?

E.) Rewire my car if that doesn't fix it

Finally I just by passed all the old wiring and made up a new harness according to the diagram on the sheet that came with the alternator and no problems since.

I to had wires smoking and frying when they were hooked up original, that's why I just made my own harness. If my friggin scanner worked I'd scan the diagrams for you (two choices) and that may have helped. If you still have the problem in a day or so I can look my car over in the daylight and tell you what I ran to what.

Yes! I'd be very interested in knowing what you ran to what. I do have a diagram from my mustang book that I may be able to use. Did you replace all the wiring? (Ignition switch, field relay, ampmeter, ect?)

Sorry for the long post, it's guys like me who should never be allowed to own old cars The guy I use for a mechanic is out of commission for the next few weeks, & I really wanna get it fixed before the warm weather goes away, so any help is greatly appreciated!

JDS68Stang · Oct 11, 2007

rdnkjdi said:
........Yes! I'd be very interested in knowing what you ran to what. I do have a diagram from my mustang book that I may be able to use. Did you replace all the wiring? (Ignition switch, field relay, ampmeter, ect?)...............

I only made a new harness from the regulator over to the alt. then up to the solenoid. Also I made new ground wires then added a new manufactured one from the firewall to the engine (heavy gage braided type).

I marked with masking tape the old wires and their hookup locations then clipped them off since I believed they were shorting out somewhere, do the same if you decide to clip off any of the old stuff. I will get out and check, and get back with you later today sometime. I only replaced the regulator (a second time) after I smoked the first new one during my trouble shooting.

Tim65GT · Oct 11, 2007

Maybe this basic diagram will help:

JDS68Stang · Oct 11, 2007

OK, first off I can't find my diagrams anywhere now but here's what I've got under the hood.

Assuming your starting with all parts in working order start by making up a temporary harness, you'll need a few female ends that will go over the male ends on the regulator, and connector ends to hook onto the alternator (one large)

Hook up the temporay wires so you can drive the car on a good test drive without them winding up in the fan. (an old 14-16 gage extention cord you can cut up for the test and use) Unhook your neg. battery post first before you start.
The regulator has the letters, A, S, F and I on it.

OK, from regulator:
"F" (field) terminal, run a "field" wire to "field" on the alternator.

"S", run your "stator" wire from the regulator to "I" terminal on your solenoid.

"A" terminal on the regulator, run to the "Alt" on the alternator. (use 8-10 gage wire)

I went beyond the diagram specs and ran a heavy gage wire from the "Alt" on alternator right up to battery + post also.
Splice and connect the resistor wire (right next to regulator) in with the connector for the "A" regulator teminal then crimp together (not nessesary for just a test).

From here I made a 14 gage ground wire, hooked to "GRND" on alternator then connected to fenderwell and grounded. I ground every "ground point" down to bare metal including under the regulator mount.
From the alternator long bolt I ran heavy gage ground wire over to fenderwell again. I also added a new braided ground firewall to engine.

After finishing I cut, taped and marked the wires that fried a bit prior, comming off my solenoid and going to my alternator. Leave a few inches if you cut any wires incase you ever need to rehook them up. You may want to test the charging system now first before you cut any possible trouble wires. In the spring I intend to install a new factory harness since mines finally charging again.

Now take a test light and see if you have any draw from your neg. terminal to your neg. battery cable, I had none. (I have no working radio or clock to draw any power) Prior to cutting my old wires, I had a bright test light then it would dim and pulse

Start the car, test the voltage between the posts on the battery, it should be reading about 14 volts or up.

I explained everything as easy as I could, if you still have problems, and you know your charging system parts are all working then start trouble shooting the other areas you mentioned. In those areas I have no experience. Good luck.

Edit: I noticed yours is a 1966, mines a 68, I'm not sure if there are any differences in the regulators. I can't faintly remember (we're talking 30 years ago) of some regulators that weren't grounded, anyone here familiar with those?
If your regulator is grounded (the body of it) then this info should work for you.

JDS68Stang · Oct 11, 2007

Sorry, double post.

tredd1 · Oct 11, 2007

definately the voltage regulator. mine went in the same fashion, I changed it out, good as new

Help, I'm out of parts to replace! -- Electrical

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