Tachometer connection problem

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Dumindu
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Tachometer connection problem

Post by Dumindu » Sat May 30, 2020 8:15 am

My car is a Toyota Tercel 1987 DX Wagon.

I wanted to connect a digital tachometer to measure the RPM of the engine.

I connected the Battery terminals to the battery.

I Connected the signal wire to the -ve end of the Starter coil (Coil Pack).

Reading appears as 8888. Some times it shows 97,85, 100, 90 ... like changing values.

It is mentioned RPM value is x10 on the top of the tachometer.

I am sure RPM value should be more than 500 according to the sound of the car. I dont have a analog one to compare with.

Is it correct the way I connected the tachometer? Do I need to add a signal amplifier to use a digital tachometer in 87 Tercels?
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Last edited by Dumindu on Sun May 31, 2020 2:03 am, edited 2 times in total.

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marlinh
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Re: Tachometer connection problem

Post by marlinh » Sat May 30, 2020 9:27 am

It needs to get its signal from the distributor, so I don't think your connection will work. There is a small unused plug near the distributor that I think may provide a signal but I have never tried. Worth a shot.

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Dumindu
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Re: Tachometer connection problem

Post by Dumindu » Sat May 30, 2020 7:33 pm

Thank you for valuable advice.

Please can you mention in which aspect the plug is located?

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Petros
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Re: Tachometer connection problem

Post by Petros » Sat May 30, 2020 9:01 pm

In al North American Tercels, the connector to the distributor has a two wire connector, one is for 12v when running, the other is for the factory tack signal when equipped with a factory tachometer. that should work. the unused plug that is also present I suspect is for factory diagnostics, and may also have the tach signal.

not sure what you mean by "starter coil", but there would not be a good tachometer signal off the starter.

good luck.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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Dumindu
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My tercel:: 1987 Toyota tercle 4wd DX Wagon 1452CC
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Re: Tachometer connection problem

Post by Dumindu » Sun May 31, 2020 2:06 am

The coil pack I mentioned as starter coil.

In a distributor, In where these located? Whether in the Distributor cap or in its metal body?

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Petros
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Re: Tachometer connection problem

Post by Petros » Tue Jun 02, 2020 6:26 pm

I do not know which of the internal distributor wire it would be. it is possible you have a different distributor. in North America all of the distributors have the coil built into the distributor, and I have seen pictures of those in Australia that use a separate coil and smaller distributor.

You might look in the FSM and study the wire diagrams, to see were in the system the factory signal tach wire goes, and see if you can locate the same spot of your own system. Many decades ago when all cars used points and coil, I used to know where to attach the tach wire, but the modern systems are very different, so I am not familiar with them as much. I never have to mess with them because they are very reliable and very seldom need service.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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Dumindu
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Posts: 215
Joined: Wed Aug 02, 2017 12:34 pm
My tercel:: 1987 Toyota tercle 4wd DX Wagon 1452CC
Location: Sri Lanka
Contact:

Re: Tachometer connection problem

Post by Dumindu » Tue Jun 02, 2020 10:47 pm

Sorry.

According to a electricians advice my connection was correct. There would have been a problem in the tachometer.

When try to disassemble the tachometer to check, its display was broken.

So I will buy a new one. Advice was to by a analog one in which reading is clear.

My car have a separate coil and a distributor as in following diagram.
Untitled-11.jpg
I connected the tacho signal wire to the place indicated in red circle
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marlinh
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My tercel:: 'Everett' Blue mint 4WD wagon and 'Rocky' 86 4WD Wagon
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Re: Tachometer connection problem

Post by marlinh » Sun Jun 07, 2020 8:57 am

You have a different set up than North American cars. That looks correct according to your diagram. I think it's the negative terminal that gives the signal. Any luck yet?

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Petros
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Re: Tachometer connection problem

Post by Petros » Wed Jun 10, 2020 11:19 pm

that is the traditional older set up, common in Europe, Australian and japan. still works, just have to pick the correct wire.

from my childhood as I recall, that is the correct terminal for a tach signal. I install a tach in several of the old beater cars I bought in high school.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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