Need help debugging TACH problems...

RedBarchetta · #1 (**permalink**) 04-18-2004, 09:41 PM

Stock Smith gauges on Superformance.

After having my MSD checked out on a warranty repair (no problems reported by them), I experienced "tach bounce" on the initial shakedown run after reinstalling. I then installed a different connector wire from the MSD box to the SPF harness. I then started getting a sporadic reading while driving and nothing at idle or while stopped.

Over the weekend I went for two drives and now the entire tach has gone dead. I've never had a problem previously.

How do I go about checking where the fault is? I'm not very good at debugging electrical, but it shouldn't be that tough, huh?

-Deano

Mr.Fixit · #2 (**permalink**) 04-19-2004, 02:43 PM

Does your tach have a gang connector with all the wires going into a single connector, or individual connectors for each wire? Used to have to put an MSD tach adapter on the individual connector style of Smith's tach, and sometimes an inline capacitor as well.

RedBarchetta · #3 (**permalink**) 04-19-2004, 02:52 PM

First of all, thank you for responding to my inquiry!

Does your tach have a gang connector with all the wires going into a single connector, or individual connectors for each wire?

I crawled underneath the dash (tough when you're 6'3"

) and I noticed one connector with (I think) four wires going into the back of the tach. EDIT: SPF #747 was built in late '99 or early '00.

The previous owner connected the MSD box by using the dedicated tach output port from the box and splicing in one wire from the SPF harness to that port. No tach problems until I disconnected the box and reinstalled.

I called MSD support this morning and they said that many SPF owners have experienced intermittent tach problems when using an MSD box and that I should insert their PN8920 Tach Adapter. So I just made Jeg's $50 richer....

Is my SPF tach voltage triggered or current triggered? The current triggered wiring instructions from MSD are easier.

Thanks! Drove to Newport Beach yesterday, then up to Huntington Beach, then past Knott's and back to North Orange County. It totally sucked not having a tach working!

Mike Simard · #4 (**permalink**) 04-19-2004, 03:39 PM

This whole Smiths tach thing is confusing. Sounds like most have had good luck with the MSD adapter but I believe that there's a small chance that your tach may not work properly even after the MSD adapter. Dennis Olthoff recommended sending my tach to Nisonger who does a modification. I assume that would do it but if I'm going to r&r the tach it's tempting to put in a chronotronic.

RedBarchetta · #5 (**permalink**) 04-19-2004, 03:42 PM

Mike, if I (ever) have to replace the tach, I will go with one of those Autometer units that looks factory.

Mr.Fixit · #6 (**permalink**) 04-19-2004, 05:22 PM

The tach very well could have failed. It used to work with your current setup, now it doesn't. Do you know any other SPF owners in the area that would let you try your tach on their car for a minute? Maybe at the Knott's show.

RedBarchetta · #7 (**permalink**) 04-19-2004, 05:50 PM

I'm going to spend the $55 on the tach adapter unit from MSD and try that route. If it works, problem solved. If it doesn't, then I have the tach checked out. If it's the tach, well it's going to need a replacement. And with running an MSD box, the chances of the new tach needing the adapter unit is good. So, in the end, I'll probably need this @#$@#% tach adapter anyway.... LOL