MSD Tach Adapter not helping
 

Installed the MSD tach adapter #8910 to my 69T.
Have the MSD 5 and a Blaster 2 coil.

No difference. Tach still doesn't read below 3000.

Any tips?

Jim

You might need to include the diode as shown on the right side of this circuit diagram.

http://forums.pelicanparts.com/uploads/MSD.jpg

What does the diode do?

Had the same thing with my 67s when I put the MSD on ,I bought the tack adapter and it did not work also, sent the tack to North Hollywood Speedometer (818)761-5136 They handle this all the time knew what to do and made it work, Fritz

If you are still using points to trigger the tach, split the signal and send it to the ignition and also the tach. This works with points, pertronix or a Crane optical setup. The tach will read that 12V signal just fine.

I tried a tach adaptor and it never worked for me either.
I ended up sending my tach out for MSD conversion to
North Hollywood.

Can someone comment on how much the "MSD conversion" from North Hollywood cost?

Thanks,

I had mine done recently.

$150.00 + $10.00 shipping

Add $20.00 and you can the face of your tach changed out to 10,000 RPM if you plan to modify your car in the future and need higher rpm's.

Talk to them and ask

I just ran out and split the signal from the points like JPnovak suggested and it worked. One wire plugs into the purple/black tach line the other into the white wire. The Tach adapter is still wired in and strangely the whole thing wouldn't work without it. Thanks, for the advice, Sam

I have a tach out of a 69E that had this MSD mod done (It works cuz I used it). I do not have any use for it now since I upgraded. I will sell it for $100+ shipping if anyone is intrested. Its in good shape.

Can someone alter the wiring diagram above to illustrate what they did to make this work, I have the silly tach adapter sitting on the work bench since it never helped fix the magical bouncing tach.

Please give as many details as you can (my car is a 71)

Thanks,

Spud. That's a diagram that I made to record how I made my system work with the stock (unmodified) tach. It took me a little bit to get there with the help of the MSD people. Sure you can send your tach out for $100+ to get it updated, but I suspect that all that they do is add the diode internally to the tach. I didn't see any reason to waste the money since the diode comes in the bag of little odds and ends that come with either the MSD or the Tach adaptor. So the diode was "free".

As far as what the diode does, I'm no EE, but I believe in this application the diode is used because it only allows current to travel in only one direction. So when you install it, you might need to try it both ways to determine which is the right way.

Yup - that's what diodes do. My guess is that it stops the neg. going pulses from getting thru, while allowing the + going ones (which are half the total)....

Info on my tach for sale with MSD upgrade.
http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/206836-fs-1969-911-e-tach-good-condition-msd-upgrade.html

http://forums.pelicanparts.com/uploa...1108605200.jpg
Here is the altered diagram. This is what I did to my wiring today to make the tach work. Before I had the tach wire hooked up to the positive terminal on the coil and was getting triple readings below 3000rpm. This is exactly what JPnovak recommended. Hope this helps. Sam

If I want to split the points line to lag into the tach, where in the engine compartment do I pick up the tach line?

http://forums.pelicanparts.com/uploa...1108612637.jpg

Instructions for the diode installation. Be sure that the male end is toward the MSD unit and the female connector is toward the tach adapter, tach wire and distributer connections. In my 69E I had two black/purple wires. One went from the CDS unit to the RPM transducer. The other from the Oscillationg SCR to the tach. If you tie into the black/purple going to the Rpm Transducer your tach will never work. You must disconnect the tach wire and tie it into the white wire with the adaptor and diode. Funny, my hand held tach/dwell meter was able to read the tach output of the MSD unit but the car's tach couldn't. The reason you need the tach adaptor is that the white trigger wire for the MSD is just a ground-no voltage to it. The tach adaptor adds 12 volts so the tach can see the signal. Hope this helps.

Jim

I got the MSD and Tach Adapter from another Pelican. I don't have the diode that would have been included.

Does anyone know if I can pick one of these up at Radio Shack?

I'll call my local performance auto store tomorrow.

Jim

You dont need the diode. At least I didn't. Just plug the split line from the points into your blk/purp wire going to the tach. My wire is blk/dashed purp. and the other into the white line with the tach adapter wired as in the schematic. This should work for you. Sam

Thanks Sam

Now to find the tach wire...