hey guys,

I realize this thread could go several places, but I'm putting here because there are more folks in here running hot FE motors.

I've had a low voltage problem for some time. I run an Optima red top battery, a jeg's chrome 100amp alternator, with a mess of new cables and grounds etc. But I also run a big dual electric fan, electrig ignition (MSD 6al), electric fuel pump etc etc. Once the fans, lights or AC is on, the voltage is below 12 on the gauge and I believe it is real, because i can hear the fuel pump slow down. It is very obvious at idle. but even at speed, with a bunch of accessories on, the voltage seems low.

I installed a new generic brand voltage regulator years ago.

The voltage is low enough now, that the AC clutch can start slipping. I've thought about wiring up a second battery (maybe a deep cycle yellow top). But, that might just be avoiding whatever the real problem is.

any suggestions?

your long lost FE buddy, greg

 

It is either the regulator gone bad again or the alternator is bad. Can't be anything else.

 

Well looky who comes fraggin back !! LOL.. Good to hear from ya Greg...If it was a bad ground your headlights would Pulsate or ficker..and Bear could be right on the regulator ...If your useing a standard Reg..thats only made for say a 60 amp system..

I dont remember off hans what we used in the past...But with a little research it shouldnt be very hard to find an upgrade...also with that 100 amp system are you useing a new set of HD wires to your headlight with a relay inline for them? that helps also..

Also I know Summit sells an alt that puts out high amps even at low rpm..Might check into that..we use to use the 130 amp alts that came on the cop cars to run all there electrical BS...

Dont be such a Stranger

~Russ

 

Welcome back Greg!

Yours sounds like the same issue I have on my race car. After I get it fired up, the alt kicks in I still have problems getting above 12v(I have voltmeter in car). With electric waterpump, electric fan, electric fuel pump, and MSD there is no way to keep it up(even with BIG alt. I have installed). In all the years it hasn't been an issue, but I wish I could get it improved. I had a local shop rebuild the alt and boost it up(I can't recall but I think he made it 130amp?) but still won't keep up.

The one issue I want to address maybe this winter is installing a much larger feed wire to the battery. I think I have maybe a 10ga wire going back to battery(from 1 wire alt), and this might not be big enough to charge the battery enough? Gunno work on that this winter.


On another note, I have the same typical issue with my '69 F100 after I wired up my dual fans on a thermo switch. For 15yrs I had it on a manual switch as I rarely needed any fans, as for as long as you are moving it stayed pretty cool and only when you got stuck in alot of traffic did I need fans. Well, I finally wired them to work automatically and after one long day of driving it it killed the battery!! I stopped for gas and it went "click" when I tried starting it. DOH!! I had watched my voltmeter and noticed it was not going above 12V when the fans were running. The way the thermo switch worked, it would get fans running, but never get low enough after to shut off, so they ran all the time.

I eliminated the issue by only wiring ONE fan to thermo as it keeps things in check for the most part(around 180deg) while driving and only if I really need the second fan I put it back on manual switch. Now it charges great, and rarely dips to 12V on the meter.

You can't imagine how much draw all that fancy electric stuff hits you with.

 

maybe i goofed. This may be a "1 wire" alternator from Jeg's. Maybe I hooked up the regulator and it's not needed? And, I notied, that with all the new wiring I've done, I'm still using the old wire from the alternator to original truck wiring.. probably not good. I'm going to wire the alternator direct with a large cable and see if that helps.

 

The race car has a GM style one wire on it, the truck is still a stock replacement.

"IF" it is a one wire, you can just run one very large wire directly to the battery, no need to run it thru anything else. I'd go for something like #4 or 6 ga wire. I think my car has #10 and I THINK that may be an issue.

 

Yeah, the old wire is certainly causing you fits

I was going to say, get a bigger alternator ...

Long time no type

 

The one thing I dislike about the 1 wire is testing their max output requires a load tester. With a seperate regulator at least checking the alternator for max output is as easy as shorting a couple on contacts in the regulator plug. But the 1 wire sure are a simple swap. I have never had good luck with alternators rewouned for more ampage output, "short" lived is the term I would use. You have to be turning a 2k or 3k rpm for an alternater to get max output. A smaller pulley on the alternator will help this, but of course racers want all that horsepower it takes to run the alternator faster to go faster.

 

Not me!! That's why I run an alt in the first place. ALL the guys I know that WON'T run one cause it slows the car down .01? Huh?? It's a freak'n bracket car, consistency is what matters. They would rather put TWO big ol 20# batteries in the truck then a 4 lb alt. Then have to carry a battery charger around(down to staging lanes alot of times) to charge the batteries as they go deeper in rounds. What a PITA!

 

I attempted the "1 wire" approcah and got no charging as best i could tell (even lower voltage, probably all battery). I think this alternator does require and actuator signal and that appears to be one of the wires in teh original harness (12v with key on). So, I hooked it back up and the alternator appeared to be helping boost the voltage. I then re-hooked the old main wire to the alternator in addition to my new wire. This looks to be the best combinatin so far. I guess it negates anything the regulator was doing, but the voltage is more consistent when all the stuff comes on. I will run this way for a while and see how it goes. the new wire is just 10 gauge, but that will have to do for a bit. knuckles busted, skin burnt grease everywhere....aahhhhhh, it's been a while. kinda feels good.

 

Greg, are you saying the alternator has only one wire and that's it? Or that there are additional wires connected to it?

Because if it's only one wire, there's no way it needs outside power. Or, it should get it from the one wire in the first place. And, the regulator is doing absolutely nothing if the alternator is only one wire.

That "one wire" is connected directly to the battery? Or at least, the starter solenoid on the fender well?

 

the alternator has several connections. One of which is obviously and actuator of sorts. It doesn't work without it. So, I don;t think I bought the one-wire setup. There were also some ground connections (seems redundant to me for a chrome alternator with a big bolt going into the block)

 

so, there appears to be a small improvement to the voltage. I got the AC blowing cold and the heater working again. I had the cables reversed on the heater air valves, so the floor would blow when i pulled defrost and vice versa. I also got the window washer jet unclogged :-) so, the old truck is riding in luxury once again! this is the most old truck wrenching i've done in a while. It felt good.

NOw, to teh track to try and blow it all up.. guess I shouldn't even joke about that given recent events for other members... But I am itching to see if it's got a low 13 in it.. If the future budget allows for paint, I may strip it down to almost nothing and make a track trip just to see if i can post a good number to benchmark by.

greg

 

On my painless wiring kit. It says for a 100amp you require a min of 3 #10 ga wires. I think the orig 55amp used a single #8.

You want to use is cable that has fine strands like Welding Cable...... Amp travel on the surface, more strands, more surface, more amps it can carry.

 

Ive got a one wire set-up on one truck. its a 72 body on a 75 frame,there is lots of evidence of wires bypassed,changed,switched,eliminated due to a previous owner who put this thing together. ive got a relatively low amp alternator,and i replaced the one wire that ran from the alt to the starter relay,its now got a single 8 Ga. wire. at low idle(about 550-600 rpm) it only puts out a bit over 12 volts,but once you go above 800 or so rpm its putting out at least 13 volts,and around 14 over 1200 or so. If i eventually start adding 12V accessories,i will look at a higher amp alternator,with a heavier wire.