Tach install help?

[Speed Kills]

Hi guys, I'm Ian, and yes, I'm a n00b here, but give me a helping hand if you wouldn't mind. You guys are my last resort!

I recently bought a '79 Corona wagon 20R/5 Speed (yes, I know, not a Corolla. Please excuse me that I couldn't figure out whether this should go in here or in the Cressida forum. Please help regardless. ) as a fun little beater to drive around, but it kinda irks me that the car doesn't have a tach. So I scooped up an Autometer Autogage unit from a buddy of mine and mounted it up just as I know how to (Red to switched 12V, white to parking lights, black to the engine ground, green to the neg. side of the coil). Well, click the key, tach powers up to set the shift light, start the car, and the tach stays at the RPM indicated for the shift pointer. What gives? Autometer's website says it's becuase the tach is not receiiving proper signal, reccomends a weird hookup for Toyota trucks (i was told because of the ignitor box on the coil?), and I'm guessing it's probably the same for the Corona.

All help is appreciated guys!!!!

-Ian

[DoubleEdgedWomb]

I believe you have an engine that was also used in Toyota trucks, so try the method he suggested.

[Speed Kills]

Originally Posted by DoubleEdgedWomb

I believe you have an engine that was also used in Toyota trucks, so try the method he suggested.

Hmmm, well here's the direct quote from Autometer's website for an '84 Toyota truck (22R)......

Tachometer Signal Wire Installation
for 22R engine(s)
Black wire at ignition ignitor. 4 cylinder, 2 pulse signal.

(BTW, pulses do not matter, I don't have a pulse reading tach. I have the one that you clip on the back)

For an '85......

Tachometer Signal Wire Installation
for 2.4L engine(s)
Black wire at igniter.


I'm guessing the ignitor is the box that sits on top of the coil? and which pin is number 4? I can't find squat for a 20R, but I'd assume it's the same. Someone PLEASE help, it kills me to see this thing sitting there not hooked up!

Thanks!

-Ian

[Speed Kills]

Now I'm being told to hook the signal wire to the POSITIVE side of the coil? That doesn't sound right at all.


Please someone help! This is driving me crazy......

[thespud]

No. Tach Always goes at negative side of coil.

General Rule of thumb in Japanese cars: Sensor Earth is Brown, General Earth is White with Black Strip. Sometimes, and only Sometimes will you find a Solid black as negative..

[Speed Kills]

Originally Posted by thespud

No. Tach Always goes at negative side of coil.

General Rule of thumb in Japanese cars: Sensor Earth is Brown, General Earth is White with Black Strip. Sometimes, and only Sometimes will you find a Solid black as negative..

Alright, well negative side of the coil for sure did not work. I know the tach is in perfect operating condition, my ground/power is good if it was not, the tach would not power up for the shift light setting, so where on earth does this signal wire go to???


For reference, my wiring goes as follows:

Power (red wire on tach): Switched 12V for the radio (I chose this since it was fused right where I spliced it in)

Ground (black wire on tach) : Ran through the firewall, grounded to valve cover.

Lights (white wire on tach): Parking lights

Signal wire (Green wire on tach):

[TheOtherCarolla]

I ran my green signal wire to my diagnostic port. Its in the very front on the right hand side.

[Speed Kills]

I've got a new one for you guys.......

I tried hooking this thing to EVER SINGLE WIRE off the ignitor, and put it on both sides of the coil and got NOTHING. I tested the tach on two other cars to make sure it wasn't a junk tach, but it works fine. Please help! I've got a $60 paperweight sitting here....

[thespud]

Sounds like you got a dud car, not a dud tach!

Sorry, i'm fresh out of thoughts. Generally the wiring is a cinch to me - but this one has really got me stumped...

[Speed Kills]

Yeah, no kiddin'! I'm REALLY good with wiring, and this one is really messing with me.


I'm this close to putting it on my truck and saying forget it......

[thespud]

Actually, just a thought... Is there a tach wire on the dash? There might be one behind the instrument panel in the wiring harness that you could use. We actually had to do that for my mates car.