Need help with MSD

[brent65 10]

Fitted MSD ready to run dizzy today and had to run a relay to get 12v to the dizzy due to the factory resistor wire would not running the MSD but problem now is the factory tacho no longer has a signal. Until the msd was put in car was a stock 69 mach 1 390 running the standard ford resistor wire, the resistor wire wouldn't run the MSD so that's why I used it to switch a relay from the battery however by doing so I have lost my tacho signal. Has anyone encountered this before and which is the best fix or way around it? Any help would be greatly appreciated.

[69gmachine 15]

One way around it is to make a jumper that takes the tach output to a non resistor wire instead of using the rely. Somewhere under the dash you can cut the brown 262 wire that is tied to the resistor wire at the gauge feed disconnect. This wire originates from the starter relay "I" terminal. Tie the tach out signal to the side that goes to the coil.

 

The current going through the tach will be marginally greater than it was designed for but I ran that way for years with no problems. However, my tach recently failed (would not read above 1100 rpm). I don't think it had anything to do with the wiring, but anything is possible.

[danno 128]

Actually, the relay idea should also work fine. The resistor wire going from the tach to the coil will have enough voltage to turn on a relay, but it will have a small effect on the tach reading. With the ignition on and the motor not running, you might see the tack read some RPM as if the motor is running. The amount of RPM, if any, depends on the resistor used.

 

The downside of this is that it is one more part (the relay) to eventually fail. When it does, you are stopped cold, so carry a spare.

 

You could also go with the method 69gmachine suggested. His method involves some digging under the dash, which can be difficult. The wire he mentioned should be available right on the back of the ignition switch.

[388C 10]

I am using the Msd tach adapter on my 1969 mustang with a msd dist. and 6al box. Dont remeber the part number. The Tach adapter solved my tach issue. Will look it up later when I get home. I am using part number 8920. http://www.msdignition.com/Products/Accessories/Tach_Adapters/8920_-_Tach_Adapter,_Magnetic_Trigger.aspx

Edited July 28, 2012 by 388C

[brent65 10]

Thanks guys, 388C I'm using the ready to run dizzy which I'm told by the local distributor here is Australia can't be used in conjunction with the 6AL, I'll give the tach adapter a go and see where I go from there I guess

[1969vert 55]

Msd boxes will fire off any electronic pick up or points check there web page for wireing instructions...i have a 6al2 with a stock dizzy and a tack adapt...works fine..

 

 

No stock coil...aftermarket also

 

Sorry i read the post wrong...I guess no aftermarket box for that dizzy... give MSD a call

Edited July 30, 2012 by 1969vert

[danno 128]

I have a question for 1969vert and the MSD module. Are you using the factory coil with that? If you are, then you should not need the tach adapter. Maybe I am missing something?

[69gmachine 15]

The tach adapter is designed to work with the 6AL or 7AL boxes, not a ready to run distributor.

 

You MUST remove the relay in order to provide a signal to the tach. The relay does not have a signal that varies current draw with rpm, so it will not provide a useable signal to the tach as you have already found out.

 

Before ordering more parts, at least give MSD a call and ask them for technical help. Otherwise you'll just end up with more parts you can't use.