Battery not charging and running proper voltage

[Silver03MM]

Ok so I started by changing the battery that was 7 years old and the voltage on the car gauge reads 12 volts. So I changed out the alternator with a 200 amp DB Electric one and now the voltage on the gauge reads 10 to 11 volts. It has actually gotten worse! Now i checked all the grounds and everything looks pretty secure, do any of you guys think it could be the voltage regulator?

[thathotrodlincn]

You may want to check the voltage with a good hand held DVM (digital volt meter) or other multimeter. The OEM installed volt meter is not a true fully functional meter. The normal voltage across the battery with the engine running at fast idle is in the vicinity of 14 volts. If the voltage is much less then the 14 volts, tou may have a bad alternator or regulator. How old is the battery? Good luck!

[Silver03MM]

I checked it directly on the battery and it is only reading 11-12 volts, the battery is a month old and the alternator is brand new from DB Electric!

[musclemerc]

You are getting that with the car running? Either you got pully's and did'nt compensate for the idle or you got one hell of a draw. If the draw is while the engine is running then an amp proble will help narrow down the circuit. If the car is hard to crank then something is being left on.

[FordNut]

What is the voltage at the alternator terminal? Maybe a blown fusible link?

Is the battery voltage the same with the car running vs not running? Maybe the regulator (which is integral with the alternator).

[Silver03MM]

Ok I have had pulleys on the car for about 25k miles and haven't had any problems. Yes, I am getting 10-11 volts with the car running, it was down to 9 volts for a little bit if I put the A/C on. Do you think I should increase the idle and drive RPM from 700?

[Zack]

Put an OEM alternator back on it.
PA alternators always fail on Cobras. 200a is too much in the size of a stock case anyway.

[Silver03MM]

Problem is it is still doing the voltage thing no matter what alternator is on there, it did it with the stock one and its doing it with the DB Electric one

[Zack]

If it does it with any alternator it sounds like you damaged the connector taking it off and on. Check that first.

[Silver03MM]

ummmm the reason I changed the alternator and battery is because I had this problem to begin with. So I changed the battery, problem still existed, now I changed the alternator and the problem is still there.

[FordNut]

What is the voltage at the alternator terminal? Maybe a blown fusible link?

Is the battery voltage the same with the car running vs not running? Maybe the regulator (which is integral with the alternator).

Did you do these tests?

[Silver03MM]

Started th car just now, at idle the car says 12 volts on the gauge but sometimes goes down to 11 volts. When I give it gas the car goes up to 14 volts and once RPM returns to idle it goes back to 11 volts. Yesterday I checked it at the battery and at idle it reads the same give or take a half of volt. I've had pulleys on the car now about 25 to 30k miles maybe more and never had a problem until a little over a month ago the voltage started to read low in the car. So I decided that since the battery was 7 years old its probably going to die on a long trip so let me get a new one. That didn't change anything so I decided to get a new alternator and I heard good things about a DB Electric 200 amp one so I upgraded to that. Long story short, I'm still having voltage problems :hmmm:

[thathotrodlincn]

With undedrive pulleys and the engine at curb idle, it is quite unlikely that the any alternator will produce its full output. Accordingly, you should establish a repeatable off idle engine speed (say 1500 RPM) and take all engine running voltage readings at that engine speed. Variable electrical loads (lighting, hvac, ect) should be consistant from test to test. Have you checked drive belt tension/tensioner? There might be some belt slippage.

[FordNut]

Started th car just now, at idle the car says 12 volts on the gauge but sometimes goes down to 11 volts. When I give it gas the car goes up to 14 volts and once RPM returns to idle it goes back to 11 volts. ....

Long story short, I'm still having voltage problems :hmmm:

You sure it's a problem? sounds normal to me.

[Silver03MM]

Well I was under the impression a car should idle at 14 volts and everything I read says that, would the pulleys really cause a problem 30k miles later?

[MM2004]

I have had UD's for awhile now, and your scenario is identical to my MM.

Cruising, I will pull 13 - 14 volts.

Idling, I may dip to 11.5 or thereabouts.

As soon as I touch the gas, the volts jump up.

I am waiting for my battery to crap out anyday now as it is over 6 years old.

You may just be a little over-concerned?

The tune I have has the idle near 850 RPM because of the UD's.

Mike.

[hwy73]

I seem to remember a similar discussion previously conerning these alternators. Seems the issue was the fact that the MM alternator was specific in that the PCM controlled the internal voltage regulator as opposed to a similar-appearing Mustang Cobra alternator (with a different internal regulator). Thus the problems with the aftermarket alternators not working.

[FordNut]

I seem to remember a similar discussion previously conerning these alternators. Seems the issue was the fact that the MM alternator was specific in that the PCM controlled the internal voltage regulator as opposed to a similar-appearing Mustang Cobra alternator (with a different internal regulator). Thus the problems with the aftermarket alternators not working.

That can be an issue, but the symptoms are totally different.

[4play]

plus the MM has a clutch on the alt, maybe a corroded ground?

[FordNut]

I have had UD's for awhile now, and your scenario is identical to my MM.

Cruising, I will pull 13 - 14 volts.

Idling, I may dip to 11.5 or thereabouts.

As soon as I touch the gas, the volts jump up.

I am waiting for my battery to crap out anyday now as it is over 6 years old.

You may just be a little over-concerned?

The tune I have has the idle near 850 RPM because of the UD's.

Mike.

Yep, I think that's normal. And if it's night with the lights on, AC running, Jams cranked up, car in drive so the idle is a bit lower... might even drop down to 10 volts or so.

[FordNut]

plus the MM has a clutch on the alt, maybe a corroded ground?

The clutch is only a one-way mechanical clutch which allows the alternator to over-run the belt on sudden decelerations.

[musclemerc]

You need to get a tuner and up the idle and drive rpm's. To answer your question yes, it could take time for the pully's to have a negative effect on the charging system. The low rpm's at idle will eventually take a toll on both the alt and battery.

Time for a tune.

[Silver03MM]

I have an SCT Tuner right now set to 700 RPM's at Idle I guess when I get home I'll up the RPM's to 800 -850 and see what happens, thank you guys. If that doesn't fix it I'll continue posting here ;) I just want to make sure I don't have a big problem or anything....

[Silver03MM]

Ok I increased the RPM's with my tuner but the thing I don't like it how the lights brighten as I step on the gas!

[MM2004]

Ok I increased the RPM's with my tuner but the thing I don't like it how the lights brighten as I step on the gas!

Mine does the same thing.

Mike.

[musclemerc]

Are you also running a sound system?


Ok I increased the RPM's with my tuner but the thing I don't like it how the lights brighten as I step on the gas!

[4play]

well whats all that Liado talk about his tune shutting off the alt at wot? was that all just bull?

[fastblackmerc]

I believe you can program the PCM to "turn off" the alternator.

[Blk Mamba]

with stock pulley's at WOT the clutch takes the alt. off line. When my alt. went, I waited 2 weeks for a rebuilt, from, Calif. only to find that they sent me a Cobra alt., (no core charge) so I took my original to a local re-builder, he fixed it, and it's been perfect since, I don't have UD's though, I feel with the clutched alt. as opposed to UD's at WOT the difference is negligible. BTW what was stated earlier about the internal reg. being controled by the PCM is correct, my problem was a bad reg., and bad clutched pulley.

[PonyUP]

I have had UD's for awhile now, and your scenario is identical to my MM.

Cruising, I will pull 13 - 14 volts.

Idling, I may dip to 11.5 or thereabouts.

As soon as I touch the gas, the volts jump up.

I am waiting for my battery to crap out anyday now as it is over 6 years old.

You may just be a little over-concerned?

The tune I have has the idle near 850 RPM because of the UD's.

Mike.

Mine does the exact same thing with the exact same set up. At low idle I'll drop to 11or 12, and when I accelerate it's back up to 13 or 14. When I had my header gasket fixed and the guy first got into drive it, he was concerned I had an alternator problem. I asked him after the work and he said he checked everything out and it was all good. So I wouldn't worry about it too much

[FordNut]

with stock pulley's at WOT the clutch takes the alt. off line. When my alt. went, I waited 2 weeks for a rebuilt, from, Calif. only to find that they sent me a Cobra alt., (no core charge) so I took my original to a local re-builder, he fixed it, and it's been perfect since, I don't have UD's though, I feel with the clutched alt. as opposed to UD's at WOT the difference is negligible. BTW what was stated earlier about the internal reg. being controled by the PCM is correct, my problem was a bad reg., and bad clutched pulley.

The clutch does not disengage the alternator. The clutch is a one-way mechanical device that allows the alternator to over-run the belt speed when the throttle is suddenly closed.

[MM2004]

The clutch does not disengage the alternator. The clutch is a one-way mechanical device that allows the alternator to over-run the belt speed when the throttle is suddenly closed.

Brian,

Ever get the feeling you're not being heard?

:lol:

;)

Mike.