All this might be worth the hassle if the ammeter produced reliable information. But the ammeter can only measure the amount of current output to the battery for recharging purposes. When the alternator recharges a "low" battery, the ammeter indicates a high charge rate. With a fully charged battery the voltage regulator reduces alternator output, and the ammeter is supposed to indicate a very low charge rate. But how can you really tell the regulator has reduced alternator output because the battery is fully charged? Maybe a diode in the alternator rectifier failed, or the alternator belt slipped after it warmed up, just as if the battery were fully charged. Or maybe the meter indicates a medium charge rate most of the time. Does the battery need this much or could the voltage regulator be overcharging the battery?

On the other hand, a voltmeter works like a fuel pressure gauge. Instead of measuring fluid in psi, the voltmeter measures electrical system pressure in volts. just like a fuel pressure gauge, a voltmeter only needs to tap into a circuit; all the fuel (or electricity) does not have to detour through the gauge itself. Voltmeter installation is easy, quick and safe: It hooks up to a fused, ignition-switched "ON/OFF" source and does not require any modification of the circuit used to recharge the battery or any part of the alternator/regulator system. In short, the voltmeter installed at the dash will be a stand-alone circuit.

The voltmeter directly measures the result of charging-system performance. With normal alternator/voltage-regulator function, battery voltage is maintained at 14.0 to 14.5 voltsand this is reported directly by the voltmeter. In the event of alternator-system failure, voltage will be low and continue to drop as the battery discharges. In the event of an "overcharge" condition, the voltmeter will climb above its normal zone. In summary, there is no chance for misinterpreting a voltmeter's readings as can happen with an ammeter.

When installing one of our mechanical temperature gauges, you should first be aware of the fact that you will need to drill or cut a 7/8" hole in your firewall to route the capillary tubing. This is done because you cannot remove the line from the back of the gauge and the sealing nut cannot be removed from the capillary tubing line without damaging the line itself. We include a grommet to fill th~ hole you drill, so there is not extra space left in your firewall.
Once you have determined where the gauge will be mounted, you will need to carefully route the capillary tubing. The capillary tubing needs to be routed away from any excessive heat sources, such as headers or the exhaust manifold.This is done for a couple of reasons:

1) Prevents damage to the line.
2) The line does not absorb the extra heat
     and reflect a higher temp than what you
     are actually trying to monitor.

Also, be sure to keep the tubing routed away from any moving components, such as any suspension parts or fan blades. Obviously you will have to bend the tubing somewhere down the line, or you may have some excess line you will need to coil up, and this is where some people start to cringe. No worry though, the capillary is quite flexible, and with this in mind you can, if need be, coil the line to a diameter as small as 11/2" without concern of damaging the gauge or capillary. It is also a good idea to help absorb any vibration that the line may be subjected to.The smaller coiling actually helps to "deaden" any excess vibration that may be transmitted to the gauge. This also extends the life of the tubing.

HOWEVER, these bends cannot take place at either the steel crimp end for the sender bulb or right off the back of the gauge. The ends of the capillary are very sensitive to severe bends.To be safe, leave at least 8" unbent; or, if a bend must be made, be sure it is as large a diameter as possible. Keep in mind you do not want to double-up the line, where a possible kink may form. A kink can cause the gauge to become inoperative.

Now, we can briefly discuss how the gauge itself works. A hollow copper tube is run from the end of the line (commonly referred to as the sender "bulb") all the way into the gauge. It is then covered with a protective plastic/rubber-like covering.This line is filled with ether gas. So if you have ever broken one or cut one and get a funny smell or some clear fluid on you, don't worry, it is not .harmful.When the sender is in the intake, head, trans or oil pan (or whatever you are monitoring) the temperature heats the ether gas inside the tubing. This makes the gas expand and "push" the meter that is inside the gauge.This "push" moves the pointer and shows you the temperature. However, if this hollow copper tube is kinked or doubledover itself, the line will be shut and the pressure will not reach the gauge. This means you will never see the gauge reflect any temp readings at all.This is also true if the line is ever cut or the sender bulb is removed; once the ether gas escapes the line, there is nothing to "push" against the meter to register any temperature readings.
For the latest information on these and other topics, visit Autometers website at: www.autometercom/hp/techtips