Car tach on kz 700

yes i have tryed 4 6 and the 8 seting no luck on 4 it reads 500 on 8 it reads 250

My point was that in your earlier post you said you were using a 470k resistor. That will not work. It needs to be a 470 ohm resistor (without the "k").

But if you also tried a 470 ohm resistor, then I would try a lower one next. Try a 300 ohm, then try a 100 ohm.

do i need to conect it to power?? my diagram for the tach showes no power going to that wire ?

here is my radio shak list


100 ohm no k
300 ohm no k
470 ohm no k


im gona get diodes to

1n4007

100k ohm resistors

276-1114

so far so good???

.

ready2ryde1985 wrote: do i need to conect it to power?? my diagram for the tach showes no power going to that wire ?

here is my radio shak list


100 ohm no k
300 ohm no k
470 ohm no k


im gona get diodes to

1n4007

100k ohm resistors

276-1114

so far so good???

Yes. That resistor must get 12v when running.
The tach wire normally gets 12v from the coils, but using the diodes blocks that 12v, so the resistor to 12v is added to provide what's known as a "pull-up" voltage.

A "pull-up" provides a source of voltage. The ignition produces the "pull-down" signal on each coil, which pulls down the voltage that the tach wire is sensing. The diodes isolate the 2 pull-down signals from each other, so one ignition circuit won't pull down the other. So the tach signal gets a 12v signal that gets pulled down each time any coil fires. This creates a pulse chain of high and low voltage. That's what the tach uses to sense the RPM.

By the way, it's 12v, but it's not power, really. The tach is just sensing voltage, but not really using any power through that wire.

Also, the highest resistance resistor that works is the one you want to use. Lower resistance will work, but will use more power, and create heat-related problems in the adapter.

EDIT: THat shopping list looks good, but make sure the 300 and 470 are 1/2 watt resistors or higher. The 100 needs to be 2 watt. Under certain conditions, the resistors can get warm and you want them to handle the heat.

If you have the wrong wattage resistors, don't worry, you can combine 4 of them to make the same resistance, but higher wattage. I assume you have like 5 of each.

Ok i ended up with one pac of each i only have 5 of each

if i read this corect i need 4 470 ohm in the power line? they are 1/4 wat

the diodes i have are 1 amp..

the 100k resistors are 1/4 watt

the 100 ohm are 1/8 wat..

ready2ryde1985 wrote: Ok i ended up with one pac of each i only have 5 of each

if i read this corect i need 4 470 ohm in the power line? they are 1/4 wat

Yes, two in parallel, then another two in parallel, then both sets in series with each other.
For a quick test you can use one temporarily, but only use it for a few seconds.

ready2ryde1985 wrote: the diodes i have are 1 amp..

That's more than enough, as long as they are 600v to 1000v.
1N4007 should be fine.

ready2ryde1985 wrote: the 100 ohm are 1/8 wat..

1/8 watt is too small, even when using 4. They will likely burn up over time.

At any time during the rotation of the crank, one or both of the coil negative posts are grounded. When does the pull up resistor get a chance to bring the tach sense input up to 12 volts?

DiamondSkyBlue1000 wrote: At any time during the rotation of the crank, one or both of the coil negative posts are grounded. When does the pull up resistor get a chance to bring the tach sense input up to 12 volts?

With a stock electronic ignition, it should never be both. The dwell is at most about 120 degrees for each coil.
360 - 120 - 120 = 120.
120/2 = 60. There is about 60 degrees of crank rotation for each pullup time. This equates to 1 millisecond at 10,000RPM, and 10 milliseconds at 1000 RPM.

wow this is so deep!!!

sorry guys i just cant get it right so i twisted all 4 of the 470ohm resistors togther was that wrong?

i will cut two out and try it today if no luck i will try with 2 of the 100 ohm resistors even tho they are half wat it only has to work to show me what i need .. anyone wana make a cuple bucks i could so use a hand..

Here is the way to make 4 resistors of the same value equal the same value, but handel 4 times more power. This is four 1/4 watt, 470 ohm resistors to make one 1 watt, 470 ohm resistor.

Here's the whole thing.