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Is 12.9-13.3 an acceptable alternator voltage?

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Discussion starter · #61 · (Edited)
I took the high output alternator to get tested and it failed all 3 tests.. they tested the new alternator in the car and said that it was still good (after 1 day) but whenever i go WOT the voltage drops way down like a 2 volt drop.. this is making the maf counts stay the same at high rpm and it goes way lean
 
#63 ·
hardhitter;2374029 but whenever i go WOT the voltage drops way down like a 2 volt drop.. this is making the maf counts stay the same at high rpm and it goes way lean[/QUOTE said:
I bet the FP DC pegs out too, further causing a lean issue. Is your battery in the trunk? I've seen some weird stuff with trunk batteries. I've thought about adding a big ass audio 1F capacitor just before the fuse box under the hood to stop the 0.7v drop i get at wot. Never tried it, but i think it might work. Granted your problem is much worse than the typical voltage drop seen at wot. I've never seen mine drop below about 13.2.
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Discussion starter · #64 ·
Trick Tuners said:
I bet the FP DC pegs out too, further causing a lean issue. Is your battery in the trunk? I've seen some weird stuff with trunk batteries. I've thought about adding a big ass audio 1F capacitor just before the fuse box under the hood to stop the 0.7v drop i get at wot. Never tried it, but i think it might work. Granted your problem is much worse than the typical voltage drop seen at wot. I've never seen mine drop below about 13.2.
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Yeah the fuel pump is pegging too because of the low voltage. It went lean to like 13.5 and scared the hell out of me. I already tried adding a 1F cap and it did help anything. It was only dropping to 13.3V at wot 2 days ago and now with another new alternator its at 11.5V. Battery is in the stock location but I have an amp and the bap wired up in the trunk.
 
#67 ·
Its the gremlins i tell you! I would upgrade the alternator hot wire to at least 4g. Make sure the alternator has a good ground too and the engine to chassis ground is good. Remember that adding additional grounds is a BAD thing and can cause ground loop issues. The OEM accounts for most ground loops already in the car, so try and use the same contact points when you upgrade the wiring. Maybe use a VOM to see the ohms between the battery - and other critical ground points.
 
Discussion starter · #69 ·
Trick Tuners said:
Its the gremlins i tell you! I would upgrade the alternator hot wire to at least 4g. Make sure the alternator has a good ground too and the engine to chassis ground is good. Remember that adding additional grounds is a BAD thing and can cause ground loop issues. The OEM accounts for most ground loops already in the car, so try and use the same contact points when you upgrade the wiring. Maybe use a VOM to see the ohms between the battery - and other critical ground points.
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I already upgraded it to 4g when I put the high output alternator on. I'll check all the grounds again. When Autozone tests the alternator while it's on the car is this a load test?

limited said:
is your bap wired with a hobb's switch?
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No it's on all the time
 
Discussion starter · #70 ·
I replaced a red ground wire from the chassis to the engine because the insulation had worn away exposing about an inch of wire in the middle.. are there any more? The voltage is still dropping below 12.
 
#73 ·
Ya thats the major one i wanted you to check. I think the others are just floating around in the engine bay, and one in trunk (fpdm's ground).
 
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#74 ·
As tricktuners said, you have a gremlin problem...it is weird that it is only happening at WOT...that wire being burned to the point of the shielding being exposed won't always cause problems, since it is a ground wire. Did you swap out ground wires, normally grounds are black and power is red.

My thoughts are that the problem has something to do with the BAP since it happens only during WOT...if it was anywhere else in the system, it should be giving you problems at other times than just WOT.
 
#77 ·
hardhitter said:
bypassed the relay but the problem continues.. about 12 volts at wot, still down over a volt from what it used to be
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I'm not sure how the BAP works, but something is getting loaded down. A relay for the most part will either work or fail, unless heavily corroded.

On the BAP, is it a continuos pump or is only used on demand?

How do the wires to the BAP look? Are they discolored or burnt?

How does the positive lead to the starter look?

Any aftermarket stereo equipment?

How does the positive cable from the batt to the alt look?

All of those are good things to check, but since it only happens under WOT, I can only think of the BAP going bad or something inline with the BAP.

One last question...the day you noticed the problem, did you have any work done on the car that might have affected this?
 
Discussion starter · #78 · (Edited)
dude496 said:
I'm not sure how the BAP works, but something is getting loaded down. A relay for the most part will either work or fail, unless heavily corroded.

On the BAP, is it a continuos pump or is only used on demand?

How do the wires to the BAP look? Are they discolored or burnt?

How does the positive lead to the starter look?

Any aftermarket stereo equipment?

How does the positive cable from the batt to the alt look?

All of those are good things to check, but since it only happens under WOT, I can only think of the BAP going bad or something inline with the BAP.

One last question...the day you noticed the problem, did you have any work done on the car that might have affected this?
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I've been working on the car a lot recently trying to fix the voltage problems. I upgraded the wiring to the bap and it's on all the time. The wires are new. I'm not sure where the lead that goes to the starter is. I have a kenwood amp powering pioneer speakers and a kenwood headunit. The cable from the alt to the batt is brand new 4g cable. Is it possible the alternator is underpowered? The voltage starts to drop at around 4700rpm from 13 volts to 12 volts by 6000rpm.
 
#79 ·
hardhitter said:
I've been working on the car a lot recently trying to fix the voltage problems. I upgraded the wiring to the bap and it's on all the time. The wires are new. I'm not sure where the lead that goes to the starter is. I have a kenwood amp powering pioneer speakers and a kenwood headunit. The cable from the alt to the batt is brand new 4g cable. Is it possible the alternator is underpowered? The voltage starts to drop at around 4700rpm from 13 volts to 12 volts by 6000rpm.
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disconect the amp (both on the batt and on the amp), then check voltage....does it still drop? If not...then either your alt doesn't have enough power to do both, or you have a wiring problem. I thought you said you got a high amp alt though....and yes it is possible to have an under powered amp when adding aftermarket stuff to the car.

The wire going to the starter will be a bitch to follow, ford did a really good job hiding that wire...it might have to come down to disconnecting it and ripping it out...but don't do that until all other ideas have been exhausted.

Let me know how the voltage drops after disconnecting the amp, and then we will go from there on the troubleshooting.
 
Discussion starter · #80 · (Edited)
The amp is disconnected and the voltage drop is exactly the same. I turned the bap down from 50 to 0 and the voltage drop was the same again except it didn't really happen until the ford gt pump pegged (4500rpm). Is this when the bap usually kicks in?
 
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