Ammeter Pegging after Installing Add'l Electrics--Help!
11-04-2003, 08:18 AM
#21
Le Mans Master
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Re: Ammeter Pegging after Installing Add'l Electrics--Help! (Tom Piper)
:iagree: :iagree: :iagree:
IMO most of tthe people who can handle fixing a C2 can handle the news. Discussions about cam overlap, static compression ratios, and heat transfer rates aren't much easier to swallow.:p:
I get my belief system reorganized on this forum every once in a while, and I'm just another opinionated c2 owner. :jester
IMO most of tthe people who can handle fixing a C2 can handle the news. Discussions about cam overlap, static compression ratios, and heat transfer rates aren't much easier to swallow.:p:
I get my belief system reorganized on this forum every once in a while, and I'm just another opinionated c2 owner. :jester
11-07-2003, 11:38 PM
#22
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Re: Ammeter Pegging after Installing Add'l Electrics--Help! (thorin)
Some additional info that might be helpful. The ammeter shows the rate of charge or discharge of the battery, not the load. During periods of light electrical load the alternator can supply all of the current needed. During a heavy load the battery supplies the extra needed current. If this was not the case, as pointed out earlier, a heavy load would not only fry the ammeter but also the windings in the alternator. The ammeter only shows the charge going back into or out of the battery. This is why after a heavy load is supplied, such as during starting or leaving your lights on with the car turned off, the ammeter will read a high charge rate. As the car runs and the battery gets back to a fully charged state the ammeter will show less and less of a charge. It is not that the load is decreasing but rather that the battery is near a full charge again so the alternator is required to provide less current to it. The same thing goes for engine speed. If you have a heavy load and the car is idling the ammeter will show a negative reading or a discharge because the battery is supplying current back into the system to make up for the shortage. When you increase the engine speed alternater output increases and the ammeter will move back into the positive range. The load didn't change but the output from the alternator to the battery did. During normal use the ammeter should read near zero to a slight positive charge. The alternator will only supply current up to it's maximum rating be that 35 amps, 65 amps or whatever. The battery is required to make up the rest. When you greatly increase the load you should upgrade not only the alternator but the battery as well. Another thing to consider is that when connecting additional loads to the horn relay as was pointed out earlier, the wire from the battery to the relay will have to be rated carry all of the load that the battery is required to make up. Also things connected there can be subject to certain kinds of electrical noise. The battery acts as a kind of filter buffering out some of the interference. This is why devices that are sensitive to these problems or require lots of current, such as MSD ignitions, are connected directly to the battery. I would go down to a trustworthy electrical shop and have them run a diagnostic on the car. Hope this might be of some help to you.
[Modified by hermit, 10:41 PM 11/7/2003]
[Modified by hermit, 10:44 PM 11/7/2003]
[Modified by hermit, 10:46 PM 11/7/2003]
[Modified by hermit, 10:41 PM 11/7/2003]
[Modified by hermit, 10:44 PM 11/7/2003]
[Modified by hermit, 10:46 PM 11/7/2003]
11-08-2003, 07:40 PM
#23
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Re: Ammeter Pegging after Installing Add'l Electrics--Help! (hermit)
thanks so much for taking the time to write all of that, it's very easy to follow and understand. as i told the thread listers, i'll post the resolution. i got sucked into work worse than i thought i would this past week and haven't touched the car....but monday i swear the detective work begins....err, at the very latest tuesday! you great guys have given me so many leads to track down i'm sure i'll get it fixed. thanks again!
:seeya
:seeya
06-02-2017, 03:42 PM
#24
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Additional Question on this for you!
thorin
I think I have it figured out from your symptoms.
Here is the short version:
Don't connect any new loads/accessories to the battery positive (+) cable at either end. This cable is connected at the batter plus side and goes to the starter. If you connect anything on this cable, the ammeter doesn't see it to measure the current drawn for it.
The place you want to connect additional loads/accessories is at the horn relay where all the positive wires are connected together. If you connect them at the horn relay, the ammeter will be aware they are there and how much current they are drawing.
Here is the long version:
From the factory, the only load the ammeter doesn't see is the starter current. If the starter current (about 300 amps) was going through the ammeter and wiring, it would last about one start and go up in smoke.
If you connect any loads at either end of the battery plus cable to the starter, the ammeter won't see these loads either. But, the ammeter will see the alternator output that is supplying these loads.
The ammeter calculates the sum of the current going to the battery. For a given load, if the load is drawing 10 amps from the battery to function (that's 10 amps of negative current to the battery) and the alternator is supplying 10 to the battery to supply that load (that's 10 amps of positive current to the battery), the ammeter will measure 10 amps minus 10 amps, which is zero.
By connecting loads at the positive battery cable, the negative current for that particular load is not known to the ammeter. So, for a 10 amp load, you will see 10 amps of positive battery charge when there is really zero.
When I look at my '64, I see a problem when trying to connect additional very heavy loads. The wiring in my car from the plus side of the starter to the horn relay is about a 10 gauge wire -- good for about 30 amps total. An extremely heavy load may be too much for this wire -- when you consider the loads already on it.
The easiest solution might be to do what a previous post said -- don't use an ammeter, go to a volt meter (like most modern vehicles use). This way, you can connect the load right at the battery cable and the volt meter will still be correct.
Tom Piper
I think I have it figured out from your symptoms.
Here is the short version:
Don't connect any new loads/accessories to the battery positive (+) cable at either end. This cable is connected at the batter plus side and goes to the starter. If you connect anything on this cable, the ammeter doesn't see it to measure the current drawn for it.
The place you want to connect additional loads/accessories is at the horn relay where all the positive wires are connected together. If you connect them at the horn relay, the ammeter will be aware they are there and how much current they are drawing.
Here is the long version:
From the factory, the only load the ammeter doesn't see is the starter current. If the starter current (about 300 amps) was going through the ammeter and wiring, it would last about one start and go up in smoke.
If you connect any loads at either end of the battery plus cable to the starter, the ammeter won't see these loads either. But, the ammeter will see the alternator output that is supplying these loads.
The ammeter calculates the sum of the current going to the battery. For a given load, if the load is drawing 10 amps from the battery to function (that's 10 amps of negative current to the battery) and the alternator is supplying 10 to the battery to supply that load (that's 10 amps of positive current to the battery), the ammeter will measure 10 amps minus 10 amps, which is zero.
By connecting loads at the positive battery cable, the negative current for that particular load is not known to the ammeter. So, for a 10 amp load, you will see 10 amps of positive battery charge when there is really zero.
When I look at my '64, I see a problem when trying to connect additional very heavy loads. The wiring in my car from the plus side of the starter to the horn relay is about a 10 gauge wire -- good for about 30 amps total. An extremely heavy load may be too much for this wire -- when you consider the loads already on it.
The easiest solution might be to do what a previous post said -- don't use an ammeter, go to a volt meter (like most modern vehicles use). This way, you can connect the load right at the battery cable and the volt meter will still be correct.
Tom Piper
06-02-2017, 03:46 PM
#25
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2023 C2 of the Year Finalist - Unmodified
St. Jude Donor '20-'21-'22-'23-'24
It's a 14-year old thread. You may not get an answer. Try starting a new thread with your problem.
Steve
Steve
73, alternator, ammeter, amp, corvette, guage, installing, pegged, pegging, peggingafter, positive, shunt, thunderbird, trip
