Amp Gauge Question
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Joined: Apr 2016
Posts: 71
Likes: 8
From: Centreville, VA
Hi...Got some question to ask. Frame off restoration, 71 bb. Old Engine bay wiring looks pretty ugly. Upgrading to dual electric fans, Fuel injection, Vintage air, Hydroboost and serpentine setup (from Vintage Air) which comes with 170AMP powermaster Alternator...
Now I'm planning my wiring on paper. I'm thinking to run a 4 gauge charge wire to one side of a correct "shunt" and connect the other side to starter and let the ammeter reads voltage drop through the shunt. Obviously, all power draws being fed before shunt, so It can show what is going to battery after all or being discharge from the battery... Is there anything wrong with this idea? I'm listening...
Also, I want to do something for those "fusible links"... According to diagram, I have (or used to have) 3 of them. I want to plan my wiring with something newer (like maxi fuse). Again, I'm listening to what you guys thinking...Appreciated.
Now I'm planning my wiring on paper. I'm thinking to run a 4 gauge charge wire to one side of a correct "shunt" and connect the other side to starter and let the ammeter reads voltage drop through the shunt. Obviously, all power draws being fed before shunt, so It can show what is going to battery after all or being discharge from the battery... Is there anything wrong with this idea? I'm listening...
Also, I want to do something for those "fusible links"... According to diagram, I have (or used to have) 3 of them. I want to plan my wiring with something newer (like maxi fuse). Again, I'm listening to what you guys thinking...Appreciated.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Well, your thinking about it in the right way. But, if I understand what you are asking, there is a problem with your strategy.
If you run larger wire as the main electrical path for current flow in your car, retaining the original "shunt" in parallel with the new wire will allow you to get readings on your ammeter. But the scaling will be totally off. That meter must be tapped into the whole line AND the distance between meter connection points on that new wire will be different from what it was with the smaller wire. Essentially, the length of wire between the meter connection points is based on the actual resistance in the wire; and the length chosen is by the 'shunt' resistance needed for the gauge's calibration (to the scale readings) for it to be accurate. If you had a clamp-over D.C. current gauge to put over the new wiring while it was operating with a known current load, you could connect one meter lead to the main line and the other to a sharp pointed probe that you could poke through the wire's insulation. Move that probe closer/farther from the connected meter lead until the gauge reads close to what the actual current load is in the wire. NOW the meter will be calibrated correctly and you can attach the other meter lead to the "shunt" where the probe was last located.
Clear as mud?
If you run larger wire as the main electrical path for current flow in your car, retaining the original "shunt" in parallel with the new wire will allow you to get readings on your ammeter. But the scaling will be totally off. That meter must be tapped into the whole line AND the distance between meter connection points on that new wire will be different from what it was with the smaller wire. Essentially, the length of wire between the meter connection points is based on the actual resistance in the wire; and the length chosen is by the 'shunt' resistance needed for the gauge's calibration (to the scale readings) for it to be accurate. If you had a clamp-over D.C. current gauge to put over the new wiring while it was operating with a known current load, you could connect one meter lead to the main line and the other to a sharp pointed probe that you could poke through the wire's insulation. Move that probe closer/farther from the connected meter lead until the gauge reads close to what the actual current load is in the wire. NOW the meter will be calibrated correctly and you can attach the other meter lead to the "shunt" where the probe was last located.
Clear as mud?
Last edited by 7T1vette; Mar 25, 2017 at 07:18 AM.
