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Discussion Starter #1
I have a 68 XR7. On the left side of the guage cluster there is a guage that says Amps.
The guage has -60 on the far left side and +60 on the far right side. The needle stays in the middle all the time. How do I know if the this guage is working? If it is working what is information is it telling me?
 

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The needle stays in the middle all the time.
= not working.

The connection for the ammeter is often placed on the wrong side of the solenoid and the result is that the coil inside the meter burns through.
 

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i have had a number of cougars and in most cases if the needle moved it was because of a bad bad short.
the amp meters don't even make a good relitive indicator to me. even my ranchero gt the amp gauge will move but only under a very heavy load.
they just are not sesitive enough.
it might be due to the scaling of the meter after all +or-60amps would melt something.
i prefer a volt meter instead.
 

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Most of us here have been through this "amp meter doesn't work". Some never worked from the beginning. The problem is that the circuit design counts on a positive or negative voltage drop across about a foot of wire to deflect the meter, after a voltage drop through ~20 feet of harness plus connectors. In other words there is not enough voltage at the meter to deflect it. The meter actually works as a volt meter. There have been some past posts here that tell how to check whether the meter or wiring is bad.
 

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The ammeter is in what is called a shunt circuit. It runs in parallel to the charging lead from the alternator. Inside the meter there is a coil of wire wound around an armature. Depending on the direction of current flow the orientation of the magnetic field, and its strength changes. The direction of the magnetic field determines which way the needle will move, and the amount of current flow determines the degree of deflection. Since it is a shunt, and much higher in resistance than the main feed wire, only a very small amount of current passes through the harness. Over time, the connections in the harness increase in resistance resulting in even less current passing through the circuit. I typically see working ammeters only in low mileage original cars that have not been molested. It is very common for people to mistake the ring terminal for the ammeter as the prove out lead for the low fuel light and hook it up on the wrong side of the starter solenoid. This results in the meter being fried internally, or in a few cases the wire to the meter gets burned up.

I think the best solution, although not "correct" is to replace it with one of Rocketman's volt meters. I actually prefer the information given by a properly working ammeter, but the key term is properly working...
 

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Discussion Starter #7
How is the information from the ammeter interpreted tell the health of the electrical system?
How do I repair the ammeter to work properly?
 
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