RPM gage....

[mrcaptainbob]

I have one of those little, two inch long rpm gages on my LGT. It's the kind that has one wire to ground, the other that has four wraps around the spark plug wire. So...the main wire back to the display cut mushed through it's jacket on to the center conductor. Reluctantly I removed the bad sections and spliced the good ends together. All I get now is the hour display, no rpm's. Is it because I disturbed the length of the wire?

[Speedbump]

It sounds like shielded cable. If so, breaking the shield could be the problem.

What's an LGT?

[mrcaptainbob]

Shielded cable...

Yes, Speedbump, it is shielded. A very small diameter one. LGT is Lawn and Garden Tractor. A step up from a tractor with just a mower deck, an LGT can do some pretty hefty work in the garden and operate some ground engagement toy...er-uh....tools. So, does breaking the shield mean the unit is now useless?

[HayZee518]

the shield is a ground. take a look at some tv cable sometimes. some of it is a very close knit weave some of it is more open. its purpose is one to serve as a ground, and two - to contain the energy within the center conductor AND as speedbump said "shield" the conductor from outside influences.

[Speedbump]

Lawn and garden tractor. I'de have never guessed that one; although I should have.

to contain the energy within the center conductor AND as speedbump said "shield" the conductor from outside influences.

That and keep the energy in the center conductor within the shield. Generally used on audio cables.

[HayZee518]

I just read in a web site about installing a tachometer on a lawn tractor. I'm assuming yours is similar. They speak of two wires. One is white, the other is red. They both feed through a "tube" but don't say this tube is grounded. the red wire goes to the plug wire and is wrapped securely around the plug wire near to the boot and secured with a wire tye and tape. the white wire they say just fasten securely to an engine ground [any bolt will do] the thing receives a jolt everytime the plug fires. a voltage is induced into the red wire [don't ask me how much] and is monitored by the gauge with reference to ground.

[mrcaptainbob]

tachometer....

You described it exactly, HayZee. Is there a way I can 'save' this wire? The darn thing runs just shy of forty beans and I hate to think I can't use it for the sake of a small diameter wire like that. Are there super mini connectors like are on the tv coax cables?
And, in keeping with this whole tachometer thing, I do have an automotive tach. It's one of those chrome housing jobs that got attached to the column or a bracket or something. I found it among some parts in a box. It's 0 to 6,000. It has a black, orange and yellow wire from the underside. No idea if it's for a six or eight cylinder, or if it makes a difference. How does that get hooked up? I expect the black to go to ground, but what about the other two? Would one go to the coil +? To the points? Where would the other go?

[HayZee518]

don't even think of it! it's meant for a car not a lawn tractor. your tractor has a magneto that provides a charging circuit for the battery and maybe a light or two. two wires off the timing light go to battery - plus and minus. one lead goes to ground. the big fat wire connected in series with a plug wire so when it fires you get a flash in the xenon strobe light inside. for the tach, use a piece of stranded tw wire and keep away from metal if you can. use a couple of pieces of shrink tubing. should insulate it enough against the high voltage

[mrcaptainbob]

RPM gage....

No xenon bulbs here, HayZee. It's just a plain 0-6000 tach in a chrome housing. Black, ornage and yellow wires coming out of it. I'll look for the tw wire and see if it fits the problem I'm having. Not sure if this is salvageable.....looks like the wire goes into the molded-in-place filler behind the housing.