Slant 6 coil

-
Johnny71dusty

Johnny71dusty

Well-Known Member
Joined
Jul 6, 2021
Messages
829
Reaction score
114
Location
Maryland
What voltage should be on positive side of coil when running ? & what voltage on leaving side of coil when running ?

my + side of coil to ground is 9.5 vrf
My - / leaving side going to my distributor is 5 vdc

ive bought 3 different tachs and non move the needle . I'm thinking that 5vdc to ground is not enough signal to move the tach I don't know though . All 3 tachs are different brands and are wired red to battery positive , black to negative , green to coil .


Only wiring under my hood to get idea on my rpms for timing sake I'll remove once dialed in . Why I disnt wire to ignition 12volts .
 
  1. Are the tachs set up for 6 cyl?
  2. Voltages dont seem out of line.
  3. Do you have any MSD boxes or the like.
  4. Points?
  5. Have you contacted the tach manufacturers?
  6. You might have black and green reversed ( don't think so but each wires things different)


Tachs only need to see a on off signal from the coil to work.
 
Last edited:
Many new Tach's have a internal switch that can be set for 4-6-8 cylinders.
Did you check for that ?
 
FIRST thing we MUST know is what type of ignition, AKA is this an MSD, or other capacitive discharge, or a "switched" system like Mopar breakerless, HEI, or breaker points

Desired voltage does not often happen because of wiring voltage drop WHICH ALSO causes over charging

Power to the "key" side of the ballast "should" be exactly same as battery, and when charging/ running, should be nominal 14V

COIL + voltage VARIES because of the ballast resistor, and will vary "running" about 9-12 with the key side of ballast at about 14

Key on/ not running, coil+ will vary about 6-10V with key side of ballast at 12--12.6V

Coil - is NOT measurable with most meters because it is a pulse. The neg side of the coil actually produces some fairly high voltage--over 100V pulses, and is enough to give you a very good tingle.

I have no idea why a tach would not work IF it is not a cap discharge type ignition. On a CDI, the coil - is actually GROUND
 
Make absolutely sure the tach is actually GROUNDED as some columns are NOT well grounded. if it is mounted there. Make sure tach is powered from 12V switched and not from dimmer controlled lighting source or coil + !!!
 
Dana67Dart said:
  1. Are the tachs set up for 6 cyl? It has switch on back and yes all set to 6
  2. Voltages dont seem out of line.
  3. Do you have any MSD boxes or the like.
  4. Points? I have points
  5. Have you contacted the tach manufacturers? One other havr no contact info we're bought through Amazon
  6. You might have black and green reversed ( don't think so but each wires things different) they each come with wiring diagram . But I tried both ways too

Tachs only need to see a on off signal from the coil to work.
Click to expand...
 
List the make and model numbers.


Fyi

if you add text between the leading [q u o t e] and the ending [q u o t e] it becomes part of the quote.
Best to reference the line numbers with answers, or just copy and paste.
 
67Dart273 said:
Make absolutely sure the tach is actually GROUNDED as some columns are NOT well grounded. if it is mounted there. Make sure tach is powered from 12V switched and not from dimmer controlled lighting source or coil + !!!
Click to expand...
It's not on the Column , none are metal all them are plastic housing . I have been wiring them under the hood so I can see what rpms I'm running trying to tune this carb and get my timing better .
 
All use this same wiring for the colors . But none work . They light up thr back light from yellow / white some of them . But none show anything on the needle. It's weird

26D71F5C-3390-4F13-8F2C-0E73AA405AD6.jpeg
 
If you want to pay shipping, send one or two over and I'll have a look at them Can you "get into" them that is get them apart and get into the electronics? Or are they under warrantee?
 
You must log in or register to reply here.
-

Back
Top