Failing alt./ 1 wire alt. replacement

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RedBird64
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Failing alt./ 1 wire alt. replacement

Post by RedBird64 » Thu Dec 20, 2018 10:52 pm

Last time I drove in the dark I noticed the ammeter showing discharge at stops even worse than usuall over the years.
So today I decided to test it (after verifying battery was fully charged) and found that even at higher RPM, the alt would not keep up with hi-beam headlights and heater motor on high. At idle with headlights and heater it showed 12.3VDC and dropping and that was without brake lights on. Turning everything off would get the voltage back up to 14.3VDC.
Next I installed a 10 awg jumper between the alt "Batt" connection and the pos lead of the battery to bypass any resistance in the cars wiring. There was no change at all.
So it looks like the V reg is working and the alt is weak.
I plan on installing EFI and I have already installed an MSD ign box and aux cooling fan - all of which is pushing the limits of even a healthy charging system from that era. I noticed the charge wire from the alt looks like it's only a 10 awg wire which is really only good for around 30A. Even if it's an 8 awg it would only be good for 40ish amps.

As much as I hate to change any more of the wiring, I'm going to install this alt: https://www.summitracing.com/parts/tff-7078nf
It's a one wire, self exciting unit - turn on is at 880 RPM. I will have install a 4 awg wire between the output of it and the battery but otherwise no other wiring is impacted. This configuration will take much of the load off the cars wiring since it will not have to carry the battery charging current and the EFI, Ign and fan will be powered directly from the alt/bat andnot thorugh the cars orig wiring.
It should provide plenty of power.

I'l post some pics and details of the install when I get it.

Feel free to hit me up with any comments or questions.

Cheers,
Scott
Last edited by RedBird64 on Sun Dec 30, 2018 1:37 am, edited 2 times in total.
1964 Coupe Wimbledon white/Rangoon Red w/black int. Owned for 41 years. It was my folks car before that (second owners). VTCI # 12013.

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sseebart
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Re: Failing alt.

Post by sseebart » Sun Dec 23, 2018 1:00 pm

I'll be watching with interest.

I looked through the product information available on Summit and didn't see the spec for the "turn-on" point--880 RPM. Wondering if that's 880 RPM's at the crank or the alt?

Saw that the instructions warn that a solid state voltage regulator is required. Are you going with the one they offer?

~Steve

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RedBird64
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Re: Failing alt.

Post by RedBird64 » Sun Dec 23, 2018 1:06 pm

Hey Steve, I had to dig for the "Specs" but was they also had an attached video where they call out the 880 RPM spec - which is eng/crank RPM. After it turns on, they say it charges all the way down to stall. I just went back and tried to view the video but now it's all about a starter.... And, I can't seem to find it anyplace else.

I actually got it installed yesterday but I need to get parts to make up the charge cable.

Scott
1964 Coupe Wimbledon white/Rangoon Red w/black int. Owned for 41 years. It was my folks car before that (second owners). VTCI # 12013.

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RedBird64
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Re: Failing alt.

Post by RedBird64 » Sun Dec 23, 2018 1:49 pm

I went ahead and started it without installing the new heavy charge cable. After all, the battery is fully charged and the alt shouldn't need to put out a ton of current.
It works! Started engine and right away it idled to about 700 RPM at which point the alt seemed to already be "turned on" and charging fine at 14.4~14.5 VDC.
Now the tests.. Turned on headlights, brake lights and heater fan on high. Voltage at idle was 13.8~13.95. Even when I raised the RPM's the voltage didn't change much.
Also found that with 13.8VDC inside (lighter receptacle) I have 14.49VDC at the back of the alt. and battery. Crap. Not sure if that's an excessive voltage drop (probably not) or not. The ADD side of me wants those voltages to match but in reality, getting them within a few hundred mV is probably all one can hope for.
Some good news though, the way the ammeter is swired into the circuit, it will still function when I add the larger, direct charge line.

Scott

EDIT:
Upon calculating the voltage drop (14.49VDC @35A & 15' = 13.44VDC) my interior voltage is actually very good.

BTW, Steve, I did not see where a solid state Vreg is required. That wouldn't really make sense because it has one built in and the whole idea of this alt is that you don't need any external components. They do offer a direct replacement 1st gen alt like ours that still uses the external Reg. Maybe that's what you saw?
1964 Coupe Wimbledon white/Rangoon Red w/black int. Owned for 41 years. It was my folks car before that (second owners). VTCI # 12013.

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RedBird64
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Re: Failing alt./ 1 wire alt. replacement

Post by RedBird64 » Wed Jan 16, 2019 11:02 pm

A little update; After driving around some the 1 wire alt is working great.
Because the OEM charge wire is so small, I installed a 6awg charge wire from the alt ouput to the POS battery connection at the solenoid (as suggested by the alt mfgr). The down side of this is that the charge current is no longer going through the ammeter so the ammeter doesn't work quite right. With the eng off, it works normally but with the eng running, any load you introduce shows as a DIScharge on the ammeter. It never shows a positive charge anymore.
So if the ammeter operation is important to you, don't hook up the extra, direct charge wire.

For me, the extra charging capacity and the rock solid voltage output of the 1 wire alt is worth it.

Its performance will be crucial when I add the EFI. It's also great to power my Electronic Ign and pusher fan without worrying about stressing the cars original wiring.

One final thing, there doesn't seem to be a turn on RPM for this alt like some require. Just the fact that it's spinning causes it to work and it works immediately and no matter how long it's been sitting (Some other 1 wire alt's require an ign hot or jump from + to enrgize after sitting a long time).

Scott

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1964 Coupe Wimbledon white/Rangoon Red w/black int. Owned for 41 years. It was my folks car before that (second owners). VTCI # 12013.

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