Low Voltage

[fastd]

I was getting a low voltage reading at low rpm after the car was running for a few minutes; it was kind of OK on start up; high 12v low 13v. After about 10 minutes voltage decreases to low 12s high 11s. Subsequently, my battery died.

Today I replaced the voltage regulator, alternator, and battery (battery was confirmed bad at AutoZone).

Better on start up, mid 13s but after 10-15 minutes high 11s low 12s again. Any ideas?

[MOTORHEAD]

Check all grounds, batt to frame (neg) reg & alt to ground, don't just look at them, ck them for corrosion and tightness.
Are the voltages you are seeing on the panel gauge,? if so, do you have a multi-meter ?

Ted

[patrickt]

It has to be a broken wire or bad connection. When you replace your alternator, voltage regulator, and battery there's nothing else left but the wiring and connections.

[fastd]

thanks gents. will check all the connections tomorrow.

[fastd]

follow up:
there was no dedicated ground wire directly on the alternator (was grounded through the bracket); adding the ground wire definitely helped improve the voltage but it still drops down to 12.2-12.7 for like 20% of the time at idle after it gets warm. The regulator and battery grounds seem good.

I have 4 wires going to the Alternator: White to Battery; Brown to FLD and Black to unlabelled, Black to Ground; no wire to the "STA" post.

On the regulator: Brown to the "F" post (continuity to Brown on ALT); Red to "S" and red jumper wire from "S" to "A"; "I" is unused. The was continuity from the ALT to the unlabelled wire also).

Wondering how the regulator is supposed to be wired; presumably 14.2 Vs or so comes from the Alternator to the Regulator via the Brown FLD wire and enters the regulator via the "F" post? then the regulated voltage exits the regulator via the "S" post?

Does that all sound right?

Seems like the wires for all but the "BAT" are kind of skinny, like 12 or 14 gauge...seems like they should be heavier, no?

Thanks again.

[patrickt]

Resolving a bad charging issue is easier than you think. First, when you're only getting 12.2 to 12.7, presumably on a dash volt gauge, you should get out of the car, open the hood, put your VOM on the output at the alternator, or on the wire as close as you can get to the alternator output, and measure the voltage there. Then, go here Alternator wiring..... and read the testing protocol. It could easily be something as simple as voltage drop between the alternator and the load.

[fastd]

i did measure voltage at the alternator. was getting 14ish on the BAT and it was jumping around on the FLD to mimic my cockpit gauge. it seems like it starts getting jumpy after it gets warm... that mean anything to you?

[patrickt]

Originally Posted by fastd

i did measure voltage at the alternator. was getting 14ish on the BAT and it was jumping around on the FLD to mimic my cockpit gauge. it seems like it starts getting jumpy after it gets warm... that mean anything to you?

Somewhere between the alternator which is measuring 14v, and the cockpit, which is measuring 12v, you're losing two volts. That's the text book scenario for a "voltage drop" test. With the car running, and with a nice electric load on it, like your fan that probably pulls close to 20 amps, you "walk the charging wire" and measure for voltage along it, especially at connections, crimps, and the like, and search for the "drop." Somewhere between the alternator and your cockpit there will be some sort of resistance, like a bad wire, or a bad connection, and that added resistance will not only create heat, but will rob you of two volts in the process. If you use your VOM and "bracket" that bad connection, or partially broken wire, it will actually read two volts on the meter.

[fastd]

i probably should have mentioned this at the outset: i added an electric fuel pump, distributor and holley sniper to my system. the alternator i recently replaced is rated at 37 amps at 2000 and 58 at 6000 rpms. it would also explain why it gets worse when it gets warm (after the fan kicks in). will replace with larger alternator and report back.

sorry i didnt mention it sooner. thanks.

[Ron61]

That seems like a rather low amp alternator, especially when the fan and fuel pump are running. I had a 100 amp one on mine and it stayed just on the upper side of the 14 volt mark on my cockpit gauge and that is with the battery in the back and the fan and air running.

Ron

[cycleguy55]

Originally Posted by fastd

i probably should have mentioned this at the outset: i added an electric fuel pump, distributor and holley sniper to my system. the alternator i recently replaced is rated at 37 amps at 2000 and 58 at 6000 rpms. it would also explain why it gets worse when it gets warm (after the fan kicks in). will replace with larger alternator and report back.

sorry i didnt mention it sooner. thanks.

Unless you're hung up on the 'period correct' look, I'd strongly suggest converting to a Ford 3G alternator. They're capable of much higher output at idle and low RPM than 1G alternators, and they're not only internally regulated but the fans are internal as well.

I probably have less electrical load than you do, but I switched from a large case 1G 100 amp alternator to a 3G 130 amp alternator and haven't looked back. One of the best changes I made. BTW, you may find your system is more prone to belt slippage with a 3G due to the extra load at low engine speeds. Some people have gone to double V-belts or serpentine, but I found that using an aluminum pulley, properly adjusted, gave me enough belt grip to avoid slippage and squeal. Aluminum pulleys aren't as slick as steel pulleys, so they do a better job of grabbing the belt. I also went to a turnbuckle style adjuster that allows for easier and more precise adjustment than the old slotted bracket adjusters. Not period correct, but very functional.

[fastd]

I ordered a 100 amp powermaster v-belt alternator (part # 8-47101); I assume it's 1G; it's internally regulator "1 wire". I guess I could cancel it...

do you have a part number for the 3G?

[cycleguy55]

Originally Posted by fastd

I ordered a 100 amp powermaster v-belt alternator (part # 8-47101); I assume it's 1G; it's internally regulator "1 wire". I guess I could cancel it...

do you have a part number for the 3G?

Mine was a junkyard pull from a 1995 Mustang V6. I also got about 2' of the wiring harness and the mega-fuse at the same time (N/C). I bought a fuse holder for the mega-fuse from a local battery / starter shop. The 3G will eliminate your external voltage regulator. There are lots of wiring diagrams available on the Internet.

[spdbrake]

That powermaster should work fine for you. Its rated at 75amps at idle.
See page 95 of the catalog POWERMASTER PERFORMANCE

Hook up is easy.
FAQ-Alternators

[strictlypersonl]

Originally Posted by fastd

follow up:
there was no dedicated ground wire directly on the alternator (was grounded through the bracket); adding the ground wire definitely helped improve the voltage but it still drops down to 12.2-12.7 for like 20% of the time at idle after it gets warm. The regulator and battery grounds seem good.

The black wire to the alternator (as all black wires in the harness) are grounds. That particular wire is grounded at the firewall near the starter solenoid. That is where I would check first. The voltage regulator is also grounded to the same connection. A lack of ground at the regulator might give your symptoms.

[fastd]

Strictly,

Thanks.

My alternator has 3 wires; the BAT, the FLD and one black one that went to the unlabelled post on the alternator...that must be the ground that you are referring to. There is one post labelled GROUND but that one wasn't hooked up...

I spoke with the Powermaster tech that was patient enough to answer some basic electrical questions. Based on this conversations, I thought I might summarize the main 2 points to see if you all agree and to help the electrically challenged like myself:
1. The increase from a 61 amp to 100 amp alternator does not necessarily mean I will have to increase the gauge of the wires that I current have in my 2044 ERA FIA. #8 or #10 wire from the BAT post to BATTERY should be sufficient for my amp draw. I added an electrical fuel pump, electronic distributor and Holley Sniper EFI.
2. I wasn't aware of this: the regulator doesn't really carry much amp load at all - electronics aren't driven through the regulator; seems like that wire is #12 or #14 so I was worried that my added EFI electronics would create an issue.

[Large Arbor]

I had a similar issue and it turned out to be a broken fusible link in the charging wire from the alternator.

Phil

[Ron61]

You have added some things that will pull a little more load than was originally pulled. I think your stock wires would be enough for that load but watch them for a while and after running everything for a time check and see if any of them are getting more warm than normal.

Ron

[fastd]

To close this out:
I installed the 100 amp alternator and that seems to work. I get 14.0+ to the starter solenoid (so I assume pretty much the same to the battery).

I get 13.8-13.9 to the gauge in the cockpit. 13.7ish with the lights on and 13.5ish with the lights and the fan on.

I bought an amps mini clamp detector. I see about 16 amps drawn right after start up, about 26 with the lights on and around 46 with the lights and the fan on. The 61 amp alternator kind of keeps up at idle when the draw is 16 amps, but can't do it with any additional draw.

The old 61 amp alternator says it puts out 37 amps at 2000 rpm...it much only put out about 20ish at 800 rpm.

Thanks to everyone for their input.

[Ron61]

I am glad that you have the problem solved.Now you can drive without worrying.

Ron