Aftermarket Tach ? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

69C10@16 · 11-14-2007, 10:29 PM

Picked up a tach off a friend. He had it in his 88 Chevy w/a 350 all stock. It worked great. I hook it up to mine, 12V, GND, Neg on Coil, and it doesn't read at all until I rev the engine and then it seems like it's reading too low. Maybe by 750 to 1000 Rpm's. But I may just be misjudging the RPM's. It may read fine. But why doesn't it register at idle. I realize that his 88 is going to be HEI and therefore be higher voltage on the coil but I figured the tach would still work on mine. Oh, number of piston switch is in the correct spot,8 (I have a 307 btw). I know I hooked it up right or I wouldn't have gotten anything.

ANY ideas?????????

corn · 11-14-2007, 10:55 PM

What brand is it?

69C10@16 · 11-15-2007, 08:33 PM

Honestly, I can't answer that question, though I would love to know for myself. There is an odd emblem in the middles of the face that makes out to an MW. It goes up to 8K RPM. Is a four wire tach:

Green - Neg on Coil
Red - 12V +
Black - Grnd
White - Backlight

That is all the info I have on it. Any help would be greatly appreciated!

rodnok1 · 11-15-2007, 08:42 PM

did you try moving the switch around, i had one that evrey now and then the damn switch would act up and i think it defaulted to 4 banger...

69C10@16 · 11-15-2007, 08:50 PM

wouldn't that make it read high?? B/c it's seeing twice the spark for what it thinks is less cylinders? I would think it t o read twice as high. I'll try it later tonight. just to see.

11-14-2007, 10:29 PM	#1
69C10@16 Registered User Join Date: Aug 2007 Location: Greenfield, MO Posts: 215	Aftermarket Tach ? Picked up a tach off a friend. He had it in his 88 Chevy w/a 350 all stock. It worked great. I hook it up to mine, 12V, GND, Neg on Coil, and it doesn't read at all until I rev the engine and then it seems like it's reading too low. Maybe by 750 to 1000 Rpm's. But I may just be misjudging the RPM's. It may read fine. But why doesn't it register at idle. I realize that his 88 is going to be HEI and therefore be higher voltage on the coil but I figured the tach would still work on mine. Oh, number of piston switch is in the correct spot,8 (I have a 307 btw). I know I hooked it up right or I wouldn't have gotten anything. ANY ideas????????? Last edited by 69C10@16; 11-14-2007 at 10:30 PM. Reason: Typo, stupid me. :)

11-14-2007, 10:55 PM	#2
corn Registered User Join Date: Dec 2003 Location: here Posts: 5,789	Re: Aftermarket Tach ? What brand is it?

11-15-2007, 08:33 PM	#3
69C10@16 Registered User Join Date: Aug 2007 Location: Greenfield, MO Posts: 215	Re: Aftermarket Tach ? Honestly, I can't answer that question, though I would love to know for myself. There is an odd emblem in the middles of the face that makes out to an MW. It goes up to 8K RPM. Is a four wire tach: Green - Neg on Coil Red - 12V + Black - Grnd White - Backlight That is all the info I have on it. Any help would be greatly appreciated!

11-15-2007, 08:42 PM	#4
rodnok1 Registered User Join Date: Jun 2003 Location: Linden, North Carolina Posts: 617	Re: Aftermarket Tach ? did you try moving the switch around, i had one that evrey now and then the damn switch would act up and i think it defaulted to 4 banger... __________________ 64 Panel Rebuild Pics Clutch Replacement and Borg Warner T10 Trans Rebuild 64 Panel 1/2 Ton 350cubes/400hp BorgWarner t-10 3:73 Auburn Posi

11-15-2007, 08:50 PM	#5
69C10@16 Registered User Join Date: Aug 2007 Location: Greenfield, MO Posts: 215	Re: Aftermarket Tach ? wouldn't that make it read high?? B/c it's seeing twice the spark for what it thinks is less cylinders? I would think it t o read twice as high. I'll try it later tonight. just to see.



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