4 replies to this topic

[df13]

hey people i'm wanting to wire up my amp and temp gauges they are sun pro from hudd mini spares but i really want a picture of where they should be connecting to people have tryed to explain but i'd understand it with pics plz post thanx alot

David.

[dklawson]

Ammeters are discussed here frequently. Use them if you dare. I consider them dangerous (unless they are a shunt type). A safer alternative is a volt gauge. The search button at the top right of this screen will help you find old threads.

As for the temperature gauge... it's quite unlikely that the SunPro gauge will work with the stock Mini sending unit. Plan on installing the SunPro sending unit and using it. As for wiring, you need to find a switched 12V supply wire (typically green) behind the dash. Most aftermarket gauges use a RED wire for switched power. DO NOT hook the gauge up to the Mini's voltage stabilizer unless the instruction with the gauge tell you to do so. Most aftermarket gauges have their own internal stabilizer. Lastly, connect the SunPro case (and/or black wire) to chassis ground and its light/lamp to a red/white wire (illumination) behind the dash. Obviously hook the gauge's sender input to the wire coming from the sending unit on the engine.

[strebblo]

Ammeters are discussed here frequently. Use them if you dare. I consider them dangerous (unless they are a shunt type). A safer alternative is a volt gauge. ...

Without wanting to hijack the thread - why are they dangerous, and what's a shunt type ammeter?
Ta.

[dklawson]

A traditional ammeter requires that ALL the power flowing to and from the car's battery must pass through the gauge. (EXCLUDING current flowing to the starter during cranking). This was OK when cars had 22 amp generators/dynamos. For the past 30 years most cars have had alternators with at least 35 Amp output... frequently MUCH higher.

The amount of current flowing through the wires to the battery is dependant on the condition of the battery... NOT the rating of the alternator. However, let's consider a dead or weak battery that is continually asking for ALL the power the alternator can send it. If you have a 50 Amp alternator it will be supplying nearly that amount (less what it takes to keep the engine running) to the battery. ALL this current has to be flowing through the ammeter.

So... first off, you need an ammeter sized with a range HIGHER than the output of your alternator. Second, the wiring to and from the ammeter has to be sized to safely pass ALL the current you alternator can produce. Lastly, all this high current wiring has to pass safely through the firewall to the gauge and back out again. It's dangerous and unnecessary to do this. When was the last time you saw an ammeter on the dash of a new car? You can tell as much about an alternator based charging system from a much safer and easier to install volt meter.

You asked about a shunt-type ammeter. Think of the shunt as a VERY large resistor. It's really a chunk of copper with known electrical characteristics. When current flows through this chunk of copper, its internal resistance produces a voltage drop (end to end) that can be measured with a high-resolution volt meter. This shunt is typically placed in series with the wiring to the battery (excluding the starter motor power). Very light gauge wire connects the gauge to the shunt since it is not carrying the current... only measuring the voltage drop across the shunt. If you must have an ammeter, this is a safer (but more expensive) way to do it.

[strebblo]

Cool thanks!