Just had alternator rebuilt, what voltage should it be putting out at idle?

[moneypit94]

My alternator had a bad diode in so I had it rebuilt. Now the voltage is consistant but at idle its putting out 13.71 volts at the battery. I thought it should be at about 14.2.

Watching the little dumby guage it doesn't move now at all with different rpms so thats good but i still feel its a little low. Or should i just not worry about it?

BTW Im thinking this alternator has cost me about a $1000 so far! !FAIL!

 

[toyman]

My alternator had a bad diode in so I had it rebuilt. Now the voltage is consistant but at idle its putting out 13.71 volts at the battery. I thought it should be at about 14.2.

Watching the little dumby guage it doesn't move now at all with different rpms so thats good but i still feel its a little low. Or should i just not worry about it?

BTW Im thinking this alternator has cost me about a $1000 so far! !FAIL!

A couple of things. The output will vary with battery charging requirements and temperature (higher when cold). In that sense there is no fixed number. 13.7v is good.

 

[revhead347]

13.7v is good. It's charging fine.

Kurt

 

[nmcgrawj]

Why did u spend so much on the alternator?


And is the stock pulley on there? That could explain it running a tad lower. Still, i agree with the others and say 13.7 is fine.

 

[moneypit94]

Why did u spend so much on the alternator?


And is the stock pulley on there? That could explain it running a tad lower. Still, i agree with the others and say 13.7 is fine.

Im thinking that bad diode had been causing mine inconsistant results on the dyno. I figured this all out when i kicked on the high side of the fan and it would kill the motor if the air fuel wasn't below 13.25. Im thinking the different voltages and current were causing the fuel injectors to change up a little.

Soon as i had it rebuilt i had to retune it slightly and its been much more consistant on the street.

So to answer your question i have spent about that much or more in towing, personal time, and dyno time.

 

[toyman]

Now you haven't said what device is being used to tune the car but I would be surprised if there isn't a battery offset table to adjust injector timing based on battery volts. That tuning parameter should deal with the issue you were concerned about with slight voltage changes affecting the injectors.

 

[nmcgrawj]

I thought u meant u spent that much on JUST the alternator. lol, i gotcha now

 

[moneypit94]

Im using a AFM PMS piggy back system. I don't remember seeing anything about voltage changes in it.

 

[ProKiller]

there isn't voltage change tables with the PMS. what was the problem again? I thought you fixed it with the new ECM you bought?

 

[moneypit94]

It did fix a lot of stuff with the new ECM. It helped the drivability in it greatly. I think what it did was make it to were it would idle with a slight load like a normal automatic car will do when you put in in drive and hold the break, as to were the manual computer didn't really like this light load without extra gas which makes sence.

But far as the last dyno trip shows, it made no difference in how it responded to WOT. We ran runs without changing anything and got different fuel/power curves? Im really thinking/hoping it was the alternator bouncing around that caused this. I will find out july 23'd. Its going to the dyno and then up the road for test n tune that night.

 

[ProKiller]

i'm so paranoid now since i finally diagnosed my problem i'm seeing it everywhere in tech now. Have you checked your engine grounds? I had talk to Rick Anderson and he said all kinds of things can get screwy if it isn't grounded. I was having extremely rich conditions. worth the 10 min to check it out and clean it up.

 

[moneypit94]

i'm so paranoid now since i finally diagnosed my problem i'm seeing it everywhere in tech now. Have you checked your engine grounds? I had talk to Rick Anderson and he said all kinds of things can get screwy if it isn't grounded. I was having extremely rich conditions. worth the 10 min to check it out and clean it up.

Funny you should mention that. Because i spent about 40 bucks on 4 guage wire to run to the motor directly from the battery in back. I also went crazy grounding everything including the pms, the injector driver, ignition module, etc.

And the last time i had it tuned at AFM they took a wire and ran it directly from the battery to the block because i guess the modular cars have huge issues with this and the injectors not acting like they should because of it. Unfortunatly it didn't make a difference for me.

I have not had it dynoed since i did all the ground work but it really didn't seem to make a difference as to were fixing my alternator did.

But im hoping/guessing that the alternator was not only screwing with the injectors but also the ignition. I know after i fixed it, i had to richen up all my settings because it was running to lean.

 

[ProKiller]

interesting...i really wouldn't have thought it would be screwing with the injectors. how old is the alt wire? have you ever replaced it? they get hot overtime and heat will eventually add resistance to the copper.

 

[GTA_V6_Mustang]

13.7 sounds great. Mine is usually 13.2 to 12.8 after it gets hot (98* here) cold is 14.2