Proper voltage range

[bucks77ford]

Just wondering what the proper voltage range should be in the charging system. My dual electric fans pull a total of 50 amps when on and with the A/C on my volt gauge drops down to about 12 or slightly above. I do have a 3G 130 amp alternator. Is this OK?

 

[DNFXDLI]

12 is too low although if it is doing it at idle it would be expected as the alternator is not turning fast enough to produce much power.
Once the engine is turning better that around 1500 rpm, you should be getting around 14.4.
If it turns into an issue with constant idleing or running slow, then an AGM (Lifeline, Deka) etc. would help.

 

[primetime]

I agree that 12 volts is to low. Is that at idle? I put a 130 amp 3g on my F-250 and also had electric fans. Just out of curiosity, I put a multimeter on mine. I was showing 12.48 volts at idle with just the heater on low. I was going to have the alternator checked out, but the engine took a dump two days later. It

it always started well, and everything seemed to work like it should, it just seemed low to me. Especially since I`d upgraded my charge wire, and it`s been my understanding that 3gs charge that much better at idle.

 

[DNFXDLI]

Alternators need a minimum rpm to produce electricity, no matter what they are...on a car, truck or a gennny.

 

[bucks77ford]

correction, I have a 120 amp alternator. I may have to step up on my alternator to put out more of a charge to handle the dual fans and the A/C. Those old York compressors sure take a little bit of juice.

 

[DNFXDLI]

The A/C solenoid shouldn't take more than 10 amps Buck, I'm thinking your issue is the low rpm's...you haven't stated, but is this when the issue arises?

 

[bucks77ford]

I was out today again and payed a little more attention and at higher RPMs with A/C on and both fans my volt gauge is just below 13 volts. (without the fans on or A/C, it reads 14). Low RPMs is where the volts drop down to 12 and even below, but quickly jumps up once over 1200-1500 RPMs. Granted I'm not letting it idle at low RPMS for a long time, but my main concern is the 12.5 volts at higher RPMs if I'm driving for an extended period of time. I'm going to have a maiden voyage with the truck with about a 8-9 hour drive at the end of the month. So far right now, I'm not having any signs of low battery issue or any other electrical issues. Thanks so far for the responses.

 

[Evan's f250]

anywhere from 13.4-15 volts is normal. 12.5 volts is simply a fully charged battery by its self, not good. maybe upgrade your wiring?...4 gauge from alt to batt, 4 gauge from negative terminal to engine block, and 4 gauge from negative terminal to the chassis/body.

 

[bucks77ford]

anywhere from 13.4-15 volts is normal. 12.5 volts is simply a fully charged battery by its self, not good. maybe upgrade your wiring?...4 gauge from alt to batt, 4 gauge from negative terminal to engine block, and 4 gauge from negative terminal to the chassis/body.

I thought I put 4 gauge on, but I may have 6 since I originally started out with a 90 amp alternator and mechanical fan setup. So, I will make sure I do that.

 

[bucks77ford]

anywhere from 13.4-15 volts is normal. 12.5 volts is simply a fully charged battery by its self, not good. maybe upgrade your wiring?...4 gauge from alt to batt, 4 gauge from negative terminal to engine block, and 4 gauge from negative terminal to the chassis/body.

I double checked and I only had 8 gauge wire from alt to batt. I do remember on the description of the alt when I received it said use 8 minimum and looking at a chart on a 12 V system for 120 amps is 4 gauge. So, I will replace that and go from there. I'll have to get one of those High Amp circuit breakers too. Hopefully this will cure the problem and I don't have to upgrade to another alt which I shouldn't, 50 amps on the fans plus A/C which as Duncan said shouldn't be no more than 10 amps is only 60 amps for those things so I have another 60 amps for everything else which isn't much.

 

[DNFXDLI]

FWIW Buck, the larger the wire, the better. #1 welding cable makes great battery/alternator cables. Proper connections (as in proper crimping, lugs and bolts) are critical and are often overlooked.

 

[bucks77ford]

FWIW Buck, the larger the wire, the better. #1 welding cable makes great battery/alternator cables. Proper connections (as in proper crimping, lugs and bolts) are critical and are often overlooked.

Right on!!! Do those hammer crimp tools work worth a damn or should I get something else. Chances are I won't be using it too much so I'd hate to spend a ton of money on something else, however, a good tool is priceless sometimes.

 

[DNFXDLI]

Hammer crimps are crap..that is the mildest way I can put it. A compression crimper is needed...end of story. After compression crimp on a commercial lug, you place a piece of thick wall heat shrink over it to seal out moisture.

If you measure what you need and give me the bolt sizes, I will make them for you at cost and ship them from MT.

 

[bucks77ford]

Hammer crimps are crap..that is the mildest way I can put it. A compression crimper is needed...end of story. After compression crimp on a commercial lug, you place a piece of thick wall heat shrink over it to seal out moisture.

If you measure what you need and give me the bolt sizes, I will make them for you at cost and ship them from MT.

Hey thanks for the offer and I will keep that in mind. I did go ahead and got a mega fuse holder and a 150 amp fuse and used some existing cable I had which I don't think turned out too bad. All I really need right now is to put a smaller end on one cable for the alternator stud which right now I'm just using a small lockwasher to tighten the battery cable down to it. I'll try it out and see what is going on. The stud on the alternator must require a 1/4" eyelet.

 

[bucks77ford]

Went out and drove a little bit and with everything on I am now pulling at 1500 RPMs and higher right at or slightly above 13 volts. So there is a big improvement from where I was at before I upgraded the wire.