RS w/Tach or Voltage?

Hello, I am going to install a remote start system (autopage RS-660). I noticed that you can use the Tach/RPM or a crank timer, which I am used to. But I also noticed there is a "Voltage check type" and Im not really sure how this works by looking at the installition manual. I figured I would have it learn the RPM becuase that is what Im used to doing, but it says "No Connection of this wire (Tach. signal wire) is required if you use the voltage or timer checking type mode". Less wires to hook up is good, so Im wondering... What is this Voltage check type? From where does it test the voltage?

The voltage sense mode uses the crank time to start the engine and checks for the increase in voltage when the engine is running. If the engine does not start the voltage will be resting at about 12 volts, instead of the 14 volts or so it will be at when the engine is running. To answer your other question, it is connected to a constant 12 volt source, correct? That's where it checks the voltage.Life moves pretty fast; if you don't stop and look around once in a while; you could miss it.

Thx for the quick reply So it detects from the same power source as teh alarm brain? Ok, this sounds easier than using the tach... What do you think? Any difference between using the tach or the volts? If not ill go for the volts option.

it is easier than using the tach, but the tach is more reliable. Some vehicles don't have enough of a jump in voltage for the alarm to sense it. Life moves pretty fast; if you don't stop and look around once in a while; you could miss it.

I always go with the tach option, being that it's more reliable. Besides, what's one more wire?

Use the tach wire, like you said, only one more wire.  And you will eliminate any combacks, when the car doesn't start on a cold morning, b/c it takes an extra half second to fire. 

Recently I've been having some problems with the tach not being recgonized. I actually now use voltage and set the crank time a little bit longer.

I tried that option, but had an issue with customers coming back worried that the starter would be burned up by cranking an extra quarter/half second each time it started. I tried assuring them that this was not the case, but I ended up going with tach on every remote start I put in. I've never had one come back when I used the tach wire. It's usually not too hard to get to an injector to find a wire. Many newer cars actually have the tach available at the BCM/PCM or diagnostic connector.Life moves pretty fast; if you don't stop and look around once in a while; you could miss it.

Seen where high power amps confuse the voltage sense. You don't even have find the tach wire really. You canuse the wire to the ign coil which usually sticks out like a sore thumb on the engine.