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Tach Leads on 912ULS

  • sharrc10
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5 years 6 months ago #7069 by sharrc10
Tach Leads on 912ULS was created by sharrc10
Guys,
I tried searching but cant find which tach lead is positive or negative coming from engine tach coil.
My wiring diagram for instrument needs the neg and positive from tach leads from engine. Does it matter since it is a coil trigger

Chuck

Flying Wild Texas

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5 years 6 months ago #7070 by billmartin
Replied by billmartin on topic Tach Leads on 912ULS
Charles,

I don't think it matters. (someone correct me if I'm wrong.) I've only hooked up two types, the EIS 4000 and an UMA. The wiring instructions with those two instruments are like the 912 diagrams in that they don't specify a plus or minus wire. They just say to connect the two wires from the trigger coil to the wires from the gauge. I just arbitrarily picked which gauge wire to go with which trigger wire and and it worked.

Bill.
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5 years 6 months ago #7071 by RobSeaton
Replied by RobSeaton on topic Tach Leads on 912ULS
You are correct; it is an AC signal so it does not matter.
Rob
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4 months 4 weeks ago #21231 by Ransdriver
Replied by Ransdriver on topic Tach Leads on 912ULS
Hello everyone, I have a question on the tach wires also. I'm trying to hook up a VDO tachometer. My lead wires are different colors than described by the manual. Mine are red/white and green / white. Which is positive and do I ground one? The DIP switch has been verified but have seen different posts on the setting as well. Mine engine is new but an older model 912 UL any guidance would sure be appreciated.
Thanks, Todd

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2 months 4 days ago #22196 by bnelson79
Replied by bnelson79 on topic Tach Leads on 912ULS
I've got an issue with my tach on a Rans S-12S airplane, flying a Rotax 912 Uls engine. Just got done doing the 5 year rubber replacement, put everything back together and started it up. Got carbs tuned and took it out to taxi. Noticed tach would read normal, then the needle would start swinging back and forth; up to max, back to 0, then back to normal. Stayed there for awhile, then would start again. It's a VDO tach. Any ideas or suggestions?

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2 months 4 days ago #22211 by Roger Lee
Replied by Roger Lee on topic Tach Leads on 912ULS
Since you had your hands up on the engine working the best bet is you loosened a wire. Go to that black insulated wire up on the back of the engine that has two wires inside and follow it to the connector. Many are in the engine compartment. I think you may find your smoking gun there.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell

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2 months 4 days ago #22225 by cap01
Replied by cap01 on topic Tach Leads on 912ULS
trying to install a jpi system to get rpm off a 912. finding it difficult to find information as to how to connect the tach . wondering if any has dealt with that?

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2 months 4 days ago - 2 months 4 days ago #22227 by Roger Lee
Replied by Roger Lee on topic Tach Leads on 912ULS
The tach only has two wires. They are in a black plastic sheath with a connector on the end coming off the back of the engine.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell
Last edit: 2 months 4 days ago by Roger Lee.

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2 months 4 days ago #22234 by cap01
Replied by cap01 on topic Tach Leads on 912ULS
thanks , i am aware of how rotax works. the problem is the jpi. the edm 740 was previously installed in a ac with a rotec radial with some strange type of rpm pickup. the issue is how to connect the jpi to the rotax or what is required to make the connection. its difficult to find info from jpi about the rotax.

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2 months 4 days ago #22235 by Roger Lee
Replied by Roger Lee on topic Tach Leads on 912ULS
Sorry Cap01 I'm not familiar with the JPI to give you a n answer.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell

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2 months 3 days ago - 2 months 3 days ago #22246 by cap01
Replied by cap01 on topic Tach Leads on 912ULS
roger, thanks for the reply. had the jpi been mine , i would have traded it for a grt. with all the wiz bang features of the jpi it still didn't keep a engine from self destructing. the grt has served me well for 1200 hrs in my plane. the jpi surely serves its purpose well in a way more complex plane than we fly.
Last edit: 2 months 3 days ago by cap01.

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