Strange Charging Issue - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 9 Old 07-06-2017, 09:41 AM Thread Starter
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Strange Charging Issue

Basics on the car. 92 GT with a new 3G alternator from PA Performance, all instructions followed when wiring it up. Stock pulley configuration.

Here is the issue. When it had the original alternator on it I noticed that the headlights and everything would dim and the gauge would show a drop in voltage. I thought that I would just upgrade it since I planned on using electric fans in the future. Upgraded it and it was still doing the same thing. Took the new alternator to Advance and had them test it off the car, tested good and I put it back on with the same results. Went there and tested it on the car and it was putting out 14 volts but only 30 amps with nothing on and it dropped to around 10 with a load. I sent it back to manufacturer and they tested it and it was putting out the correct voltage and amps per their specs.

Reinstalled it on the car with the same results as before. Changed the cluster out thinking that the cluster might have a problem in it, same results. Changed the voltage regulator on the back of the cluster and got the same result. Rechecked all of my connections when I installed the supercharger and ignition box, tested again at Advance on the car, no load around 30 amps and no under load it is putting out 0.3 amps.

I'm at a loss now on what to do or what to check. Any suggestions?


92 Mustang Supercharged 302
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post #2 of 9 Old 07-08-2017, 12:31 AM
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your amperage drops with more loads on?


89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #3 of 9 Old 07-08-2017, 10:28 PM
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You didn't mention if your battery was still in the stock location or if relocated to the rear but a friend of mine was having a similar problem when he first got his car together. Brand new 3g alt and it acted like it still had the weak stock alt on it. Turned out his ground from the block to the frame was just snug at the block so making poor contact. Just a thought if you had any main grounds off or anything during the msd or supercharger install. Good luck with it

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post #4 of 9 Old 07-11-2017, 11:28 AM Thread Starter
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Yes any load drops the amperage to almost nothing but the voltage remains high.

The battery is in the stock location and I will add another chassis to motor ground this week and see if it helps any.

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post #5 of 9 Old 07-11-2017, 07:15 PM
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think about that.

you have loads that reduce amperage

your testing is flawed

what do you mean voltage stays high? what voltage is that?

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #6 of 9 Old 07-13-2017, 09:08 AM Thread Starter
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Quote:
Originally Posted by indy2000 View Post
think about that.

you have loads that reduce amperage

your testing is flawed

what do you mean voltage stays high? what voltage is that?
I understand that a load will reduce the amperage but being that the amperage never comes close to the 130 it is supposed to be. Turning on the A/C and the amperage going below 1 amp is very confusing to me. I was testing this with the tester at the local Advance Auto Parts. Other than using the tester there you can clearly see a major drop when running the headlights. If you are watching the voltage at the battery with it running the voltage doesn't drop below 13.5 with everything turned on. At idle and just above idle the voltage is right at 14 volts. Voltage was tested at Advance and with my own multi-meter.

I added another ground to the engine on the passenger side and no change. The ground cable from the battery is a 2AWG cable. Positive side is the same size all the way to the starter.

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post #7 of 9 Old 07-13-2017, 06:36 PM
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amperage goes UP, with increase in LOAD

what are you measuring?

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #8 of 9 Old 07-17-2017, 07:40 AM Thread Starter
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Pretty sure that I found the problem. The back side of the original cluster has a circuit overlay(not sure what it is called) has a few areas that it was coming apart. The copper inside was intact though. I swapped it out with another one and so far with the testing I have done it is working properly. I will be taking it to test the amperage in the next few days.

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post #9 of 9 Old 07-17-2017, 07:44 AM Thread Starter
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Quote:
Originally Posted by indy2000 View Post
amperage goes UP, with increase in LOAD

what are you measuring?
I understand that the amperage will go down with a load on it but under 1 amp is not correct. The alternator should be putting out more than 30 something amps at 2500 rpm with no load, just the normal electronics should be pulling more than 30 something amps. The reason I started down this path trying to figure out the amps and volts is because just turning on the headlights would drop the factory gauge way low. I would notice that the brightness of the lights would change as the gauge would fluctuate up and down. I would expect that with a stock alternator but not a 3g.

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