QUOTE(jfort @ Jul 14 2008, 08:44 PM)
Rich, I'm looking at the coil, since it is new. The CD box and its wiring haven't changed since before the tach worked fine. There are two wires to a terminal lug on the + side of the coil. I assume one of those goes to the tach since the tach gets its RPM signal from the + side of coil, correct? On the - side of the coil is one brown ground wire that goes a few inches to the fan housing.
I think I'll clean up all the connections and check the ground. Don't know what else to do right now.
My response earlier.
QUOTE
Same one,so here is how its wired.
Looking at the numbers on the box, there are two terminals vertical, then three horizontal at the bottom.
If you are using the part numbers, (our is upside down) but lets use the numbers for reference..I will explain as if the box was mounted on the firewall, with numbers right side up.
So, the connector closest to the face with the numbers.
This wire goes to the ground screw on the distributor that also attaches to the advance plates inside the distributor...so its a direct ground.
Next wire is also a ground.
This goes to the fan housing, and the negative side of the coil also goes to the fan housing...another ground post.
Then we have the plug with three spades.
Bottom connector goes to the postive side of the coil.
Middle connector is the heavy black wire from the ignition switch. (12vdc)
Top connector is the green wire to the condensor AND the little black tach wire (its a double spade connector deal)
That works.
I think the two grounds are important..one to the dizzy and one to the motor...
Remember, its throwing alot of multiple sparks.
Rich
Your initial response that got me going on this thought.
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the thing is, it worked fine until a few months ago. the CD box was looses and hence not grounded. i saw arcing at the coil and i think that's what burned out tach.
I wanted to put all of this together on one page.
You mentioned that the tach dies after you had a grounding issue with the CD box.
Look at how mine is set up.
Lug one , closest to the part number plate is grounded to the motor.
This same lug goes to the negative side of the coil.
Lug two is grounded to the distributor.
Ground is very important here.
the tach gets its signal from negative side of the CD box on my setup, same lug as the condensor.
Tach cannot get a signal from the coil, it will get confused.
Anytime a CD box is used, you can no loger get a valid tach signal from the coil.
IT MUST get its signal from a terminal off the CD box, or an adapter.
The CD box is shooting multiple sparks. This signal is what activates the coil.
So, instead of getting your tach signal from the coil, you gotta get it from the CD box or adapter. This bosch box seems to provide a port for it. Our is hooked up this way, so give it a shot.
Rich