when is a stock alternator not enough?

[chappy]

I am having issues with a stock alternator on my truck. I had the batteries tested and they tested fine. I got another stock alternator from autozone and still won't put out enough volts. I have hids in fogs and headlights and a fass 95 fuel pump. If I turn the heater on also the voltage drops to 11.8 on my cts. The fass must not be getting enough juice either because I can look at my rr fuel pressure gauge and it drops from 72psi to 58-60. If I shut the lights off or leave the lights on and shut the heat off the volts come back up to 13.8v at an idle and the fuel pressure comes back up to 72.Going down the road it stays at 13.8 with everything on till I come to a stop and then it drops again unless I shut something off. Its kind of annoying. I'm just wondering if this is normal or what? Do I need one of gogo's underdrive pulleys maybe?Does HIDs? really draw that much more juice then normal headlights?

 

[Dustball8504]

Did you check to see what the alternator that was on it put out? I had it rebuilt by a local shop and it put out around 15 or 16 volts if I remember right.

 

[kyle43335]

check your block grounds. seen lots of issues there.

 

[chappy]

yeh same thing 11.8-12.3 at idle with everything on. I knew that was low so I tried a new one and same results so I then had the batteries tested and they were good except the voltage was low since I had been running my lights and heat on .

 

[chappy]

Block grounds hmm? worth a shot

 

[jdc753]

Maybe I am wrong but I thought 11.8-12.3 would be perfectly normal for an idle system, where as when the alternator is charging it will be putting out in the 14-18v range. Remember this is a 12v system, so when idle it should be close to that but to recharge the batteries it will kick up sum till the storage capacity is reached.

I don't have HID's or an aftermarket pump but a fairly large stereo 1500w sub amp and 400w speaker amp and I never have an issue with voltage drop.

I would certainly look into the grounds, and you can check the voltage at the alternator yourself with a DMM, but the amperage is more what you want to know.

 

[chappy]

yeh I did check the voltage at the alt myself. I just checked the ground and it was fine but I wire wheeled tverything anyway since there was a start of corrosion. I know my wifes 05 f150 puts out 14.4v at idle with lights on,aftermarket stereo bumping and heater on high at an idle.I know its a gasser but seems voltage should be the same . It bothers me since the fuel pressure is even dropping from the low voltage at idle.Obviousley the pumps are starving for juice.

 

[CCRICE]

I run 13.8-14 at idle, granted I have nothin but the ordinary stuff drawing power I wouldn't think that having hid's and a fuel pump would even put a strain on the alternator..


Sent from my iPhone using Tapatalk

 

[chappy]

hmm well maybe my last alternator was weak and this one is weak out of the box.Is that with lights and heater on? I didn't think hids, and a fuel pump would put to much of a draw either but I don't know.

 

[CCRICE]

Yeah with lights and heater on full blast.


Sent from my iPhone using Tapatalk

 

[CCRICE]

Well I was off a little, 13.8-14.2 running speed, 13.6 at idle just a minute ago with lights and heater on full blast.


Sent from my iPhone using Tapatalk

 

[Bustedknuckles]

Autozone alternator eh? I'm a tech and our shop wont install Autozone parts unless the customer demands it and supplys the part and then there is no warranty whatsoever. We install Napa or Carquest parts with a 2 yr 24k mile parts and labour warranty btw....

 

[dasboot]

how many amps does all your gadgets need? that includes interior gadgets ie stero etc. It's not as much sometimes the volts as much as the amp. I'm not sure what is standard amps for the truck alt. but you may have to up it. In some rv motorhomes you need 95 + amps depends on all the electronics amps pulling off the chassis battery.
looking at my truck stats on the Napa Dealer Prolink, it could be a 110amp to 140 amp alt.

 

[2wd-fire]

You need a bigger alternator to run any thing but stock equipment. Stock one are bearly big enough to run just the truck

 

[chappy]

110amp because crapzone says that thats the only one available for a single alternator system on these trucks. Only thing extra on my truck is hids instead of halogen heads and fogs and a 95 gph fass lift pump. Nothing else. I have had such bad luck with napa alternators and startors being bad right out of the box I quit running them. That and there warranty is never that good and there prices are usually higher.

 

[chappy]

You need a bigger alternator to run any thing but stock equipment. Stock one are bearly big enough to run just the truck

Great

 

[2wd-fire]

I can't remember the company that makes 170 amp alt someone on here has to have one

 

[CCRICE]

You need a bigger alternator to run any thing but stock equipment. Stock one are bearly big enough to run just the truck

I find this hard to believe... But with they way things are made now a days I guess it's not so far fetched of a statement..


Sent from my iPhone using Tapatalk

 

[Snake]

110a alternator can't even keep up with the glow plugs after the truck is started. Forget about it keeping up with any aftermarket electronic stuff.

Large case upgraded single alternators, up to 300a, can be bought at alternatorparts.com, DB Electric, or DC Power. If you want the best, go with DC Power. I've tried all three.

 

[Extended Power]

I just replaced my stock alternator with a 200amp unit from Mean Green.

Even though the old alternator was still working, (With an overdrive pulley on it) I have Flex-a-lite fans which pull 30-40 amps all the time...and the stock alternator is in no way ment to be on our trucks...they are a POS.

New alternator on...I got 14.2vdc right after the truck starts, and is at idle. NEVER going back to stock alternator again...even if someone paid me to take one...