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Old 01-26-2003, 09:24 PM   #1
brunetmj
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Default Tach wire

I have already done a search on this but came up with nothing conclusive. Others have asked the question but there was no definite answer so I thought I would try again.
I need to pick up a tach wire for a remote start. The instructions read: connect the green wire to the cars tach wire under the hood (normally the negative side of the coil or tach output of coil pack). Would anyone have suggestions on how this could be done.
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Old 01-26-2003, 09:36 PM   #2
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There is no place under the hood to connect a tach wire. There are 4 separate coil packs, one for each cylinder, so there is no single connection there with a full engine speed signal.
The only place to pick this up would be on pin C9 of the ECU harness, this is the tach output of the ECU to the instrument panel (green wire). You can try tapping it there, but if after doing so you notice any change in how the tachometer operates or how the car runs you'll have to remove it.
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Old 01-26-2003, 10:26 PM   #3
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Thanks mulder. Just a little confused about where to pick up that wire. Behind the instrument panel or at the ECU? I did read a thread that indicated that the person doing this got an odd voltage readings there. They were not in the range suggested by the manufacturer of his remote starter. Well i could try.
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Old 01-26-2003, 11:07 PM   #4
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You could pick it up at either place. It goes from the ECU connector to the instrument cluster connector.
The signal can't be measured with a voltmeter because it is actually a waveform consisting of pulses that vary in frequency according to engine speed. An oscilloscope would be needed to see it and measure the peak voltages, but according to the factory manual the peaks are 0-13V.
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Old 01-26-2003, 11:12 PM   #5
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Just to add on this since I've had similar questions about where to pick up certain signals in my WRX.

http://www.northursalia.com/index1.html

Under "Tech Docs and Information Pages" on the left frame you'll find a wealth of informations about imprezas.

Especially helpful in your case would be the last item on the following tabled list:

http://www.northursalia.com/m...ng/wiring.html
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Old 01-27-2003, 12:10 AM   #6
brunetmj
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Thanks guys. What a great help this is. I have another thread below that describes my incident with a local remote starter installer. It turns out he missed something. According to the literature provided a manual transmission must use the tach method to work. The other option is non tach which uses engine voltage and that is what he used.. Anyway after my research and your help I might be able to fire this puppy up.
p.s. for his benefit he did do a lot of work and never charged me. Hood pin switch, bypassed the alarm system, clutch switch., neutral wire, e brake. Looks like he just overlooked this one thing.
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Old 01-27-2003, 04:35 PM   #7
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if you happen to have a decent multimeter, you can set it to AC and test the tach wire. some remote start systems can learn off the fuel injector wire as well.

netZ

Quote:
Originally posted by mulder
You could pick it up at either place. It goes from the ECU connector to the instrument cluster connector.
The signal can't be measured with a voltmeter because it is actually a waveform consisting of pulses that vary in frequency according to engine speed. An oscilloscope would be needed to see it and measure the peak voltages, but according to the factory manual the peaks are 0-13V.
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Old 01-28-2003, 08:51 PM   #8
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Netz. I read another thread where you suggested using a fuel injection wire and their location as I (we) may have to try that. This remote starter is giving us a diagnostic code of no tach signal. I tried tapping the ECU tach wire and that dint work.
I do have one question about your other post. Can you or someone else tell me what the term "uncommon wire" means.
I am working with a professional installer who did the bulk of the wiring. This car is giving him fits. He states he will never do another standard again. As I am still learning i cannot give a full description of what was already done.
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Old 01-29-2003, 01:09 AM   #9
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have your installer look at the fuel injectors, find the wire that's not common to the 4. that's your uncommon wire. i'm surprised you just didn't grab the tach off the dash.

netZ

Quote:
Originally posted by brunetmj
Netz. I read another thread where you suggested using a fuel injection wire and their location as I (we) may have to try that. This remote starter is giving us a diagnostic code of no tach signal. I tried tapping the ECU tach wire and that dint work.
I do have one question about your other post. Can you or someone else tell me what the term "uncommon wire" means.
I am working with a professional installer who did the bulk of the wiring. This car is giving him fits. He states he will never do another standard again. As I am still learning i cannot give a full description of what was already done.
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Old 01-29-2003, 08:41 AM   #10
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Netz,
I am going to try picking up the tach wire behind the dash tonight. At the time it seemed easier to pick it up at the ECU. I also will try to tap into those injector wires. So there is one wire common to all four injectors and four wires that are not? I would have to pick up one of those that are not? I want to find these wires and vampire clip into them and run some wires to the remote unit before I go back there. Sorry i am still learning.
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Old 01-29-2003, 09:15 AM   #11
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If the tach wire didn't work at the ECU it won't work at the dash either since it's just the other end of the same wire. Apparently this tach signal is not compatible with the unit you are installing.
Be very, very careful if you are working with the injector wiring. As with the tach wire, if there is any change in how the car runs after tapping the injector harness disconnect your wiring immediately. If the added wiring is incorrect or somehow loads the injector circuit improperly the ECU can be damaged.
Also vampire or clip-on type taps are not a good idea on wires that are critical, carry a high current, or are exposed to the outside. The tap works by breaking the insulation and usually cuts some of the strands in the wire reducing its capacity. If the tap is later removed there is a gap in the insulation that must be covered with tape or tubing to protect it.
You might want to try first inserting the stripped end of your wire into the connector pin at the injector to do a test, before actually cutting or tapping into the wire. This way if it doesn't work you haven't done any unnecessary harm to the wiring.
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Old 01-29-2003, 04:01 PM   #12
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Mulder thanks. I guess I wanted to tap the green wire at the Tach itself to insure I had the correct wire out of the ECU to begin with. I did test the wire I tapped coming out of the ECU to make sure it would do no harm to the remote but i cant be absolutely sure I had the right green wire. Despite all the diagrams the actual unit is a wire nightmare and I was tired and cold. I will be careful with the injector wires. Thanks for that advice. I will be getting more garage time in tonight and hope we can get this thing working.
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Old 01-30-2003, 12:41 PM   #13
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Just for the record some remote starters can learn off the negative side of the coil as well. This is a black wire with a stripe (green or yellow can't remember-but it's the only black there). I think the fuel injector wires do not give enough current for my model starter. If I get this going i will give some kind of step by step on this remote.
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Old 02-05-2003, 05:42 PM   #14
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Default Tach wire

im trying to install a autometer tach and shift light and i cant find the tach WIRE!!! i called subaru and they were being ******** about it. the mechanc told me i need to buy a wireing diagram then hung up on me. ive done a search and coudn't really find anything. someone please help.
thanks
till then
-calvin
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Old 02-05-2003, 05:51 PM   #15
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go to www.northursalia.com

find the ECU pinouts he has hosted on the page.

You will find the wire you are looking for. It is called Engine Speed or something to that effect.

J
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Old 02-05-2003, 07:19 PM   #16
awd=OWNAGE
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there is no solid green wire for my 2000 subaru rs
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Old 02-05-2003, 07:36 PM   #17
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Old 02-05-2003, 08:14 PM   #18
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that would be it.

J
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Old 02-05-2003, 10:11 PM   #19
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I ended up using an uncommon wire from the coil to act as tach.
It turns out that the directions i was using were incomplete. It is possible other wires I tried might have worked.
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Old 02-06-2003, 02:06 AM   #20
awd=OWNAGE
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well, what color was it.. the wire from the wiring diagram in 134 30 is blue..
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Old 02-06-2003, 02:07 AM   #21
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now all i do is trace it form the ecu to back of gauge cluster and splice in there... right ok.. will do it tomorrow let you guys kno
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Old 02-06-2003, 07:18 PM   #22
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I just noticed that a moderator merged two threads. For future readers I wanted to clarify a point. The original thread involved finding a wire that acts as a tach wire for a remote starter.
The remote starter brain has to know when the car is running. Almost any wire that has some variation in voltage when the car is running can be used. The second poster (merged thread) is asking about a suitable wire to run an after market tachometer as is asking about a true tach wire. These are two different things.
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Old 02-06-2003, 11:39 PM   #23
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the tach wire is b134 30 which is ablue wire witha light teal line on it..
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