Wierd Charging Problem
Thread Starter
Drifting
Joined: Sep 2006
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From: Stillman Valley Illinois
Wierd Charging Problem
I am having a very strange issue with the charging system on my 66. The alternator is 85 amp replacement, externally regulated. The engine is new, as is the rest of the drive train. After completing the engine swap everything was fine for about 2 weeks. Then the wierdness started. The system was OVERCHARGING. Amp gage read +30 - +40. Voltage at the battery was 15.0.
Replaced Voltage Regulator and Condenser, and there was some improvement, but the system is still acting funny. At idle (~850 rpm), it will again overcharge (+ 20 - +30 on the gage) the headlights get brighter etc. Over ~ 1000 rpm everything looks normal.
Any ideas?
Replaced Voltage Regulator and Condenser, and there was some improvement, but the system is still acting funny. At idle (~850 rpm), it will again overcharge (+ 20 - +30 on the gage) the headlights get brighter etc. Over ~ 1000 rpm everything looks normal.
Any ideas?
Race Director
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Well, hmmmmm..... are you sure the regulator is well matched to the high output alternator? If so, and since changing the regulator didn't help, I'd be suspicious of the alternator. There really isn't anything else.
Drifting
Joined: Dec 2002
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From: Long Beach CA
The only thing in the system that is RPM-dependent is the alternator. Everything else is just electrons. Since it was OK for a couple of weeks, I'd say something has gone in the alternator. Probably one or more diodes. My uneducated guess is that the system is seeing more of an AC wave than pure DC, and as the RPM/frequency increases, it is smoothing out -- becoming less of a fluctuation .
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The charging system isn't working properly. There are only two major components and changing one of them didn't solve the problem. Time to do something about the other one.
Le Mans Master
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Here is a couple of things I would try.
I have found that on all external regulators, except Chrysler electronic ones, that a poor ground will create an overcharging condition.
First run a temporary ground wire from the batt - to the frame of the regulator and test.
I would also check the voltage at the Batt post of the alternator, the battery +, the #3 red wire at the regulator plug and the Batt lug of the horn relay when the engine is running.
Write these readings down and post them.
Joe
I have found that on all external regulators, except Chrysler electronic ones, that a poor ground will create an overcharging condition.
First run a temporary ground wire from the batt - to the frame of the regulator and test.
I would also check the voltage at the Batt post of the alternator, the battery +, the #3 red wire at the regulator plug and the Batt lug of the horn relay when the engine is running.
Write these readings down and post them.
Joe
Thread Starter
Drifting
Joined: Sep 2006
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From: Stillman Valley Illinois
Additional ground wire didn't change anything. Voltage at the BAT terminal on the alternator, at the Battery, horn relay and sense terminal at the regulator are all the same.
at ~ 850 RPM ~ 17.5 v
at ~ 950 RPM ~ 15.5 v
at ~ 1000 RPM or over all appears normal @ 14.2V
at ~ 850 RPM ~ 17.5 v
at ~ 950 RPM ~ 15.5 v
at ~ 1000 RPM or over all appears normal @ 14.2V
Le Mans Master
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Good guess, I agree.
Take your DVM, set it to AC volts and measure across the battery. If it reads 300 millivolts or higher, you have one or more failed diodes.
Dan
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Safety Car
Joined: Oct 2001
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From: Coldwater MI
Had an overcharging/high voltage problem on my '65 Chevelle. Went through a couple regulators----still overcharged. Long story short----the alternator had a new stator. When they crimped on the terminal lugs they failed to remove the enamel from one of the solid wires. Kept making/breaking contact. Freaked out the regulator to force it to full charge. Replace the stator and all is well.
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Drifting
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From: Stillman Valley Illinois
The Alternator is a Power Master 65 amp that I had ordered through Summit Racing (April of this year) I just got off of the telephone with customer service. They are shipping a replacement under warranty today! With a little luck, should be back up and running tomorrow!
Safety Car
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From: Homewood Alabama
Not sure if this has been suggested, but check your main lead wire where it connects to the alternator. It is common for the nut to be overtightened and the plastic surround to crack, causing a short. I just had this problem with the power master alternator in my 67 Restomod convertible. It was putting out 16Volts to the battery. I sent it back to power master and they rebuilt it for around half the cost of a new one and upgraded it for free to a 240amp to help power my electric fans and electric fuel pump.
I see you said they are sending a replacement. That's great, but check the surround anyway to see if it is cracked and be careful not to over-tighten the nut on the new unit.
I see you said they are sending a replacement. That's great, but check the surround anyway to see if it is cracked and be careful not to over-tighten the nut on the new unit.
Last edited by 65silververt; Jun 2, 2015 at 03:53 PM.
Thread Starter
Drifting
Joined: Sep 2006
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From: Stillman Valley Illinois
Just want to say THANK YOU to everyone that offered assistance / advice!
I will check the post, and be careful with the replacement. I will also try to post the end result.
I will check the post, and be careful with the replacement. I will also try to post the end result.
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Not sure if this has been suggested, but check your main lead wire where it connects to the alternator. It is common for the nut to be overtightened and the plastic surround to crack, causing a short. I just had this problem with the power master alternator in my 67 Restomod convertible. It was putting out 16Volts to the battery. I sent it back to power master and they rebuilt it for around half the cost of a new one and upgraded it for free to a 240amp to help power my electric fans and electric fuel pump.
I see you said they are sending a replacement. That's great, but check the surround anyway to see if it is cracked and be careful not to over-tighten the nut on the new unit.
I see you said they are sending a replacement. That's great, but check the surround anyway to see if it is cracked and be careful not to over-tighten the nut on the new unit.
Dan
Thread Starter
Drifting
Joined: Sep 2006
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From: Stillman Valley Illinois
As I mentioned, Summit is replacing the alternator. Just for giggles, I swapped it out for the old alternator (35 amp) that was in the car when I bought it 6 years ago. The old unit was working with no issues when I did the engine swap, I only changed it because it looked like azz with the new engine!
Guess what .............................. Same exact issue! 15 - 17 VDC at the battery at anything below ~1000 RPM; 14.5 (ish) VDC at the battery at anything over 1000 RPM. When I checked the VAC at the battery I get 30.1 - 32.5 VAC at any RPM.
2 bad alternators ?!?!
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Are you sure you are measuring 30 Volts AC at the battery???? Or could it be 30 mV (.03 Volts)?
I'm just skeptical that you could get 30 Volts across the battery because the battery represents a very low impedance load. Your alternator would have to be dumping hundreds of Amps into the battery to do that.
I'm just skeptical that you could get 30 Volts across the battery because the battery represents a very low impedance load. Your alternator would have to be dumping hundreds of Amps into the battery to do that.
Last edited by jim lockwood; Jun 2, 2015 at 07:09 PM.
Thread Starter
Drifting
Joined: Sep 2006
Posts: 1,757
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From: Stillman Valley Illinois
Are you sure you are measuring 30 Volts AC at the battery???? Or could it be 30 mV (.03 Volts)?
I'm just skeptical that you could get 30 Volts across the battery because the battery represents a very low impedance load. Your alternator would have to be dumping hundreds of Amps into the battery to do that.
I'm just skeptical that you could get 30 Volts across the battery because the battery represents a very low impedance load. Your alternator would have to be dumping hundreds of Amps into the battery to do that.
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