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I am currently in the process of upgrading some systems on my 1970 Vette. I am replacing the 4 speed with a Tremic 5 speed and also replacing the wiring harnesses and there lies my question. I am upgrading to a 100amp alternator and was wondering if there are any 100 amp ammeter gauges out there with a similar look of the original 40 amp gauge? I see various 100 amp gauges but the face is so different from factory that I think it would stick out like a sore thumb in the center gauge cluster. Any thoughts or suggestions? Also what happened with DR. Rebuild and the wiring diagrams he used to sell?
Thanks for any info on either issue.
My ZZ6 EFI engine came with a CS130 alternator. Along with adding a 6 gauge wire between the alternator and starter and many many other wiring upgrades to modernize the system, I changed out my 1971 ammeter with a voltmeter
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Are you going from the old stock alternator to 100 amp? i had an after market harness with a newer 10S! that was supposed to be a 100 amp alternator but was sub 100 amp. The new harness did quite well, it was about 8-10 gauge but probably only survived due to the 10SI not outputting what it should. it was a 10SI not sure what the exact specs on it were. My new alternator is a power master 12SI 100 amp and they test them and tag it with the actual output. Its 95 amp at idle and 125 at full tilt, they didnt post a cruise amperage. So Now I have a 6 gauge wire in there. That conversion is easy. Just disconnect the alternator output and tape it off. Add a new 8 gauge for a 100 amp top and a 6 gauge for anything above it and run it to the starter lug. the lug will act like a terminal post just like the original routing. Leave the old 10 gauge wire attached at the starter for a positive source for your horn relay and fuse panel power
When I converted from the old 3 wire to the 10SI i bought a voltage regulator bypass adapter since the 10SI is internally regulated. I also bought the old GM square plug conversion adapter to the flat blade. THe 10 SI and 12SI have a rubber plug hiding the flat blade plug slot, but you will need it if you try to use a voltmeter. As stated your done having an amp meter at this point. You can get a voltmeter with the proper gauge color and they look original. You can use either of the old Amp gauge wires, you just have to tape the other one and add a ground.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
Oh and Doc Rebuild has been hanging out at another forum I've read here. Apparently he has toned down his business until the Covid situation clears up a bit. I hope he reopens soon , I wan to get a new wiring diagram. His vacuum hoses are the best as well as his radiator seals
You can use either of the old Amp gauge wires, you just have to tape the other one and add a ground.
Wiring the voltmeter to either ammeter OEM wires- the voltmeter will be "on" all the time. Will result in an unwanted parasitic current draw when the car is sitting.
You can simply tap the "pink"- going to the fuel and water temp gauge.
It's fused AND it on during ignition and start but not in the accessory position.
And then just ground the other negative terminal - right to the cluster is fine
Just tape up the old connector for the ammeter- as those wires are hot all the time.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
Originally Posted by Richard454
Wiring the voltmeter to either ammeter OEM wires- the voltmeter will be "on" all the time. Will result in an unwanted parasitic current draw when the car is sitting.
You can simply tap the "pink"- going to the fuel and water temp gauge.
It's fused AND it on during ignition and start but not in the accessory position.
And then just ground the other negative terminal - right to the cluster is fine
Just tape up the old connector for the ammeter- as those wires are hot all the time.
Richard
Good catch...I have a battery cutoff switch that I kill all power with every time I shut off the engine. Never thought about the parasitic drain
I am currently in the process of upgrading some systems on my 1970 Vette. I am replacing the 4 speed with a Tremic 5 speed and also replacing the wiring harnesses and there lies my question. I am upgrading to a 100amp alternator and was wondering if there are any 100 amp ammeter gauges out there with a similar look of the original 40 amp gauge? I see various 100 amp gauges but the face is so different from factory that I think it would stick out like a sore thumb in the center gauge cluster. Any thoughts or suggestions? Also what happened with DR. Rebuild and the wiring diagrams he used to sell?
Thanks for any info on either issue.
So far as I know, the ammeter doesn't work way you are thinking. On my 69 I traced out the wiring to see just how it was set up. Only a portion of the current being supplied elsewhere goes through the ammeter. Otherwise some seriously heavy wiring would be needed. Instead shunts to the heavy duty stuff supply the ammeter. I didn't spend a lot of time figuring out what was going on, but what I think happens is the wiring itself acts as a current divider. A heavier wire carries the bulk of the current and the lighter wire that goes through the ammeter carries less current. I have to guess that the smaller wire is higher resistance to divide the current.
When you start adding loads, as with my electric fans, if you don't supply an appropriate shunt you don't get an accurate reading at the meter. You need to have some portion of the current going through the meter and when you bypass the meter with a current supply directly to the load, you don't see anything that is part of the load.
Mostly because of all of the add-ons on my car, MSD ignition, audio amp, electric fans, I switched to a volt meter rather than try to accomplish what the GM engineers supplied. The only thing I am missing by switching is noticing that I have left something on like the rear compartment light when I think I've shut everything off. This is because I don't see its trickle of current on what was my ammeter. That has got me a couple of times.
If somebody here has a better take on how the electrical system was designed, I'd love to hear it as this is guesswork on my part.
i would think you would want the volt meter to read in the accessory position. if for nothing else than a reminder of how long you been running the radio at the cruise-in-hangout...
So far as I know, the ammeter doesn't work way you are thinking. On my 69 I traced out the wiring to see just how it was set up. Only a portion of the current being supplied elsewhere goes through the ammeter. Otherwise some seriously heavy wiring would be needed. Instead shunts to the heavy duty stuff supply the ammeter. I didn't spend a lot of time figuring out what was going on, but what I think happens is the wiring itself acts as a current divider. A heavier wire carries the bulk of the current and the lighter wire that goes through the ammeter carries less current. I have to guess that the smaller wire is higher resistance to divide the current.
When you start adding loads, as with my electric fans, if you don't supply an appropriate shunt you don't get an accurate reading at the meter. You need to have some portion of the current going through the meter and when you bypass the meter with a current supply directly to the load, you don't see anything that is part of the load.
Mostly because of all of the add-ons on my car, MSD ignition, audio amp, electric fans, I switched to a volt meter rather than try to accomplish what the GM engineers supplied. The only thing I am missing by switching is noticing that I have left something on like the rear compartment light when I think I've shut everything off. This is because I don't see its trickle of current on what was my ammeter. That has got me a couple of times.
If somebody here has a better take on how the electrical system was designed, I'd love to hear it as this is guesswork on my part.
You are correct. Our ammeters are not true ammeters like the one I added to my Nova back in the day where all the current ran thru it. They are in fact a very sensitive galvanometer that measures very small differences between the alternator output and the battery. It is calibrated relative to the stock wiring. Adding any larger charging wires to support a bigger alternator (which is needed) will throw the calibration off.
While tracing down some wiring this afternoon ran across two relays in the storage compartment for the jack. Thought they might for an alarm syatem and appear to factory installed. Odd thing is this car doesn't appear to ever had the factory alarm system installed. As far as I can tell no alarm system has been installed and again these appear to be factory installed and look as old as the car. Any ideas as to what they may be for? I know it hard to tell with no picture but was wondering if any other folks have seen these while rewiring their C3's. Also have opted for the voltmeter thanks for the advice guys.
You are correct. Our ammeters are not true ammeters like the one I added to my Nova back in the day where all the current ran thru it. They are in fact a very sensitive galvanometer that measures very small differences between the alternator output and the battery. It is calibrated relative to the stock wiring. Adding any larger charging wires to support a bigger alternator (which is needed) will throw the calibration off.
The stock wire is fine between alt and battery at starter, leave stock amp meter alone, you need a higher amp alt for whatever accessories you adding on, let them run the power directly from the alt. out stud through a dedicated inline fuse like I did my fans and many other mods....
Having upgraded from a 40amp to 100 amp alternator myself in my 64 Ford I recommend that you do this carefully.
My ammeter was a "real" one where all the power went through it at the dash. To me that's a fire waiting to happen so I removed all that large gauge wire and modified the gage itself to be a simple volt meter. It tells you more anyway.
The additional amps power my electric cooling fan an a handful of other accessories that were not OE. My alternator now feeds a modern power panel with fuses, breakers and relays for those, along with the headlights and horn. The new panel feeds the original electric panel with a 40 amp fuse. Now the headlight switch just trigger relays so the lights are brighter and the OE switch will last forever.
Lastly the 100 amp alternator with an OE type V-belt squealed badly. I ended up changing out to a serpentine belt kit to make it stop.
Thanks for the info. I booked marked it. I've been thinking about adding an oil temp gauge for a while now. Might be handy if I ever get back to the road course.
C3 Upgrades
