Does anyone have a tach (factory) for an 8 cylinder out of their car? If you do can you take a resistance reading on the large resistor on the outer edge of the PCB, (it is right by the 3000 mark on the tach and should be either black or a red/brown) and post the reading here?

Thanks,

~M~

 

Anyone?

 

I dont have my tach out, but if it is a physical resistor, it should be color banded and the colors tell you the resistance.
What drives the tach? Is it off of the distributer or ECM? My tach is really screwy... shows the car idling at about 2250 and normal driving at 5,6,7G (but the engine obviously isnt going that fast).

 

I believe it is a power resistor, no color banding. I have a tach from a V6 and that is the only component on the PC board that is different.
The Tach is driven off of the Tach pick up wire at the coil. I looked into getting it repaired but most places want $125+. I'm going to check the dealer and see how badly they want to rape me for one.

~M~

 

Does the circut board look anything like this? This from an S10 but I dont see why GM would make it much different if any different.

 

Sweet i never knew it was that easy to modify 6 cylinder tachs.

 

Well, its close..but the layout is all wrong. If you could post what the capacitor from the V6 says on it (if you know or have one) I can then pinpoint exactly which one it is on the F body tach. I have a V6 F body tach also to comapre them.

Being a capacitor makes more sense , they are more likely to go bad than a resistor is.

~M~

 

I have an S10 4 banger tach laying around and the capacitor that the arrow is pointing at in the picture is red and says .0039 on it in rough letters which means .0039 microfarad is the rating of the capacitor. I dont know the number for a V6. I imagine it would be .0036 or something close something. This is S10 ftuff so I dontknow how much the same they wil be. I belive this tach is from an '87 or 88 S10 Blazer. What happened to your tach? Why are you wondering about capacitors and resistors?

 

Morley I have been having the same problem with my tach for quite some time. I have been asking around on the boards, but have not gotten any solutions. I actually replaced my whole cluster with a different one, and the problem continued.l I do have a tachometer in my garage. I will look at it tomorrow for you. Please keep me informed of what you find out. I will love to figure this one out. Are you running any kind of aftermarket ignition module?

 

Not running any after market ignition, but I did change my ignition module about a year ago, possibly it is defective, but I used an AC Delco one...if all else fails I'll put the ole module back in and see what happens.

~M~