Simple midyear question.

[67HEAVEN]

Ammeter issue

The new AC Delco ammeter spends most of its time way over at 40+.

I'm running dual electric fans with my Dewitt aluminum rad and they are power hungry. So, I replaced the original 42amp '67 externally-regulated alternator with a newly rebuilt 95amp internally-regulated alternator. I also used the Lectric Limited kit to complete the wiring change without the need for cutting or splicing.

There is no other unusual electrical behaviour.

1. What are the possible causes of this reading?

2. If left unchanged, what will this condition lead to? A cooked battery? A cooked alternator?

3. Is it possible to enjoy driving any more than in a 502/5-speed/'67/red/Corvette? :gap

 

[Mac]

1. What are the possible causes of this reading?

Maybe your problem is... your ammeter itself ie: it isn't reading properly and everything is working normally. I would check the charging system with an engine analyzer.

2. If left unchanged, what will this condition lead to? A cooked battery? A cooked alternator?

If the alternator is producing too much juice (ie: regulator isn't working) things will get ugly sooner rather than later. Electrical componants aren't designed to run at full capacity for extended periods, so your alternator would likely bake your battery and then self-destruct.

Since everything is new and the car isn't daily driven, both might last for weeks or months... or until your first extended drive, at the furthest point away from home, next to the only autoshop in the world that doesn't have a standard GM alternator in stock. Oh, did I mention that your tank is almost empty and you can't find your wallet? :crazy

3. Is it possible to enjoy driving any more than in a 502/5-speed/'67/red/Corvette? :gap

Let's find out, shall we?

-Mac

 

[68Roadster]

67,
I am by no means an expert but I had a problem on my 68 awhile back where the ammeter was heading to 40+ every time I pushed the accelerator. It was staying over about 20+ even after running for awhile. Prior to my last outing I pulled the battery ground and cleaned the POR 15 from the frame where it attached back down to bare metal. Now my ammeter readings are perfect, she shows a slight charge and the needle is steady. Mind you I'm stock alternator/externally regulated.
Cooking the battery was my biggest fear, one it was new and two I could just see it exploding right behind my head.

Please let us know what does the trick.

As for #3, I get a kick outta driving the wifes 2004 )when she lets me!)

 

[Ken Anderson]

It would appear your new alternator does not work correctly or else you've got a short somewhere that's putting a drain on the system. With motor off and key on, how much discharge is shown? If less than 15 amps, then you've probably got alternator problems. Your original unit should handle your system, unless you hang on more stuff like amps, and pumps. You say you have a new gauge? Unless it's one of the new GM resto parts, then the dampning fluid is probably dried out and you will get some needle flicker. If it's been "restored", then the windings may be wrong and you will get readings such as you are experiencing.

 

[67HEAVEN]

It would appear your new alternator does not work correctly or else you've got a short somewhere that's putting a drain on the system. With motor off and key on, how much discharge is shown? If less than 15 amps, then you've probably got alternator problems. Your original unit should handle your system, unless you hang on more stuff like amps, and pumps. You say you have a new gauge? Unless it's one of the new GM resto parts, then the dampning fluid is probably dried out and you will get some needle flicker. If it's been "restored", then the windings may be wrong and you will get readings such as you are experiencing.

I forgot to mention that I'm forced to run an electric fuel pump as the 502 has no provision for a mechanical pump. So, three heavy draw items not normally associated with a midyear car. Twin cooling fans and electric fuel pump.

Ken, I checked the engine off/key on scenario and I'm getting a -05 reading. The ammeter (battery) gauge is pictured below...

Turning headlights, wipers, power windows on or off seems to have no noticeable effect on the +40 reading.

I have noticed a slight dip to +35 after about 10 minutes at highway speed, but then it creeps back up to +40 again.

Tonight, I'll remove the fuses on the cooling fans to observe any possible change in behaviour. I'll do the same with the electric pump.....it'll live for about 30 seconds until the bowls are dry.

Thanks for the comments so far.

 

[67HEAVEN]

68Roadster,

I'll check my ground connection too. Thanks.

 

[67HEAVEN]

Ken, I checked the engine off/key on scenario and I'm getting a -05 reading.

I should have said, in the engine-off/key-on scenario, the ammeter reads as follows:

door open (courtesy lights on) -05 reading
add parking/tail lights -15 reading
add low beam headlights -20 reading

 

[67HEAVEN]

Considering that the twin fans run anywhere from two to five minutes after shutdown, I can understand the ammeter reading high on the + side for a short time after re-starting, but it never seems to return to normal.

 

[67HEAVEN]

In addition to the other tests I mentioned above, tonight I'll check with an analog multimeter as a means of "gauging" the accuracy of the in-dash gauge.

 

[Ken Anderson]

Your in dash gauge is reading correctly.

 

[JohnZ]

Where are your fans (relay-switched, I assume) getting their power - from the screw terminals on the horn relay, or directly from the battery? The "battery" gauge is actually a highly-sensitive voltmeter (galvanometer); its two leads connect to the starter solenoid battery cable stud and to the screw terminal on the horn relay, and it measures the voltage difference between those two points and displays that difference as "amps". If the power source for the fans (or any other major load) are connected to the battery instead of to the horn relay (which is the power distribution center for the whole car), the "battery" gauge won't see that load, and won't read correctly. That's why a simple voltmeter is a better indicator of charging system health for vintage Corvettes that aren't wired EXACTLY as they were originally. Several of the usual instrument restorers/rebuilders can convert the "battery" gauge so it functions as a voltmeter.

 

[67HEAVEN]

Where are your fans (relay-switched, I assume) getting their power - from the screw terminals on the horn relay, or directly from the battery? The "battery" gauge is actually a highly-sensitive voltmeter (galvanometer); its two leads connect to the starter solenoid battery cable stud and to the screw terminal on the horn relay, and it measures the voltage difference between those two points and displays that difference as "amps". If the power source for the fans (or any other major load) are connected to the battery instead of to the horn relay (which is the power distribution center for the whole car), the "battery" gauge won't see that load, and won't read correctly. That's why a simple voltmeter is a better indicator of charging system health for vintage Corvettes that aren't wired EXACTLY as they were originally. Several of the usual instrument restorers/rebuilders can convert the "battery" gauge so it functions as a voltmeter.

Once again, John, you truly amaze me. Yes, the two fans are run from the battery through individual relays (as per their instructions). May I assume that you recommend moving the source to the horn relay?

If yes, to the move, I'll still get juice for the fans with the key in the off position, correct? (necessary for cool down after ignition off).

Ken, thanks for your information and for the private message. It's good to know that the gauge seems correct. I'm trusting that the wiring change will reveal the internal regulator (in the alternator) to be okay as well.

 

[JohnZ]

I'm no expert on this issue, but I've seen it before while trouble-shooting old Corvette charging systems. The M.A.D. site has lots of good information on how to make vintage GM electrical systems work properly with later internally-regulated alternators - here's one article, and there are more:

http://www.madelectrical.com/electricaltech/chevymain1.shtml

 

[67HEAVEN]

Tonight, I'll remove the fuses on the cooling fans to observe any possible change in behaviour. I'll do the same with the electric pump.....it'll live for about 30 seconds until the bowls are dry.

Absolutely no difference after removing all the fuses. :confused

One more item to consider. The MSD ignition box is connected to the battery, not the horn relay. Maybe that's the problem?

 

[67HEAVEN]

Ran some tests with the multimeter today, and it agreed with the dash gauge. When the dash ammeter said +35, the multimeter agreed. When the dash ammeter said +40, the multimeter agreed again. I'm satisfied that the ammeter is good.

Next, I checked charging voltage -- 14.2 volts.

So, the only conclusion left is that the internal regulator in the alternator is doing the hoochy-koochy. It's going back to the dealer on Tuesday. They've already ordered a replacement.

One final question. I understand that overcharging (in terms of voltage) will cause battery problems in short order. What is the likely outcome of the condition described here (constant high amperage reading)?

 

[Ken Anderson]

You've got a bum alternator and it is unlikely you've hurt anything in your battery in the short time you've run the car. I would suggest you buss everything to the horn relay and avoid direct hookups to the battery. I would also suggest your fans cut off with ignition unless you're running an electric water pump. With no coolant moving there is little heat being removed. Also you should NEVER hook up an electric fuel pump direct to the battery, it should be switched with the ignition. Sounds like you're about ready for a long trip, once the gremlins are gone.

 

[Billybeau1]

I'm no expert either, but it occurs to me that possibly your battery could be bad. Have you tried swithching batts to see if this changes anything. If the battery isnt storing enough amps, the regulator will increase to compensate. And with all the electric ad ons is the Amp rating on your battery enough? Just my .02

 

[67HEAVEN]

You've got a bum alternator and it is unlikely you've hurt anything in your battery in the short time you've run the car. I would suggest you buss everything to the horn relay and avoid direct hookups to the battery. I would also suggest your fans cut off with ignition unless you're running an electric water pump. With no coolant moving there is little heat being removed. Also you should NEVER hook up an electric fuel pump direct to the battery, it should be switched with the ignition. Sounds like you're about ready for a long trip, once the gremlins are gone.

Thanks, Ken. If I didn't make it clear before, yes the Holley pump is switched throught the ignition. As you and JohnZ suggested, I'll move the fans from the battery to the horn relay.

Billybeau1,
I purchased the heaviest duty Delco top post that was available, and it seems to be problem free.

Thanks to everyone for their comments and advice. I'll let you know the results of the alternator switch on Tuesday or Wednesday.

 

[KOPBET]

I've just been following this thread. Interesting reading, especially the MAD electrical link from JohnZ. Maybe I missed it in the discussion, but I don't think so, where was the point you measured the charging voltage? I presumed it was at the horn relay. And what kind of internally regulated alternator did you install, a three wire or a one wire? I presumed it was a one wire. If so, wouldn't that disrupt the remote sensing capability original to the GM design? Pardon the intrusion, but I'm just trying to follow along and understand the process.

 

[67HEAVEN]

KOPBET,

I measured the charging voltage at the alternator as well as and at the battery. 14.2 volts both places. The midyears do not have voltmeters on the dash, however. The gauge marked BATTERY is actually an ammeter, and the scale goes as follows:

-40 -20 0 +20 +40 (the 20's are actually just marks) The problem is that the ammeter never returned to a near neutral reading after driving for any distance. It stayed at between +35 and +45. YIKES!

It's a three wire 95-amp alternator.

It seems as though the internal regulator is kaput.