Topic: Tach no-worky

[Angela]

I (finally) fired up the 390 for the first time after installing the tach cluster that the "tachman" rebuilt for me. The car starts and runs, but the tach doesn't work. I need some education as to what this means and what might be the root cause of the freshly rebuilt but dead tach.

I thought, but perhaps am wrong, that in order for the car to start, the tach wire at the dash had to be plugged in. Since my 390 runs, I am assuming that I correctly plugged in the tach when I installed the cluster. If true, what other problem should I be looking for?

Help?

[67gtasanjose]

...Since my 390 runs, I am assuming that I correctly plugged in the tach when I installed the cluster. If true, what other problem should I be looking for?

Help?

There is only ONE way to plug those tach wires in, and YES, the only way it would RUN would be either you DO have it hooked up correctly and the the tach is poop or if you had the wires for the tach looped together on the underdash main harness side, with the tach completely disconnected.

Bummer, but if you do NOT have it looped, your tach is NFG

[Bob Gaines]

I (finally) fired up the 390 for the first time after installing the tach cluster that the "tachman" rebuilt for me. The car starts and runs, but the tach doesn't work. I need some education as to what this means and what might be the root cause of the freshly rebuilt but dead tach.

I thought, but perhaps am wrong, that in order for the car to start, the tach wire at the dash had to be plugged in. Since my 390 runs, I am assuming that I correctly plugged in the tach when I installed the cluster. If true, what other problem should I be looking for?

Help?

It would be prudent to bring the tachman into your assessment  since he rebuilt the tach. Do you have a factory dist or is it MSD or some other?

[Angela]

Factory distributor and coil. Yes, I'll have to contact the tachman. This stinks. I cannot even see behind the cluster to inspect what's going on. Pulling the cluster is worse than going to the dentist.

[Angela]

Using an inspection camera I was able to see the two tach wires but I cannot fish the camera in behind the dash well enough to see if the tach wires are plugged into anything. I spent a half-hour at it...frustrating.

What is the best way to regain access to the tach wires after all things interior have been installed (console, seats, radio, everything in the dash, etc)? Is it possible to plug/unplug the tach wires by removing the ashtray/cig lighter panel? Would removing the radio (in the console) allow one access?

In short, I recall NOT being able to access the tach wires during the installation of the instrument cluster, hence I fear that attempting to unscrew and wiggle the cluster back out isn't going to help me to get in there and make sure the tach wires are plugged in. I want to check and see if I really did connect the tach correctly or if the reason the car runs is because through limited visibility and access I accidentally bypassed the tach.

 

[67gtasanjose]

No short cut I know of :/  Best to place a towel over the column and get started unscewing the cluster. If you have it wrong, you may be able to access a view to the problem without whole removal (unscrewing the speedo cable will allow for an easier slight rotation of the cluster without full removal but PLEASE protect the finishes of the cluster and column so you do not scratch them. Possibly lower the column a tad, a 1/4 inch more room is like a mile in this zone)

If they are correct, you are along the awy of pulling it to inspect/pull the tach anyways.

Sorry

[Angela]

Thanks for the comments. IIRC, I couldn't plug the tach wires into the dash harness while installing the cluster. I think, rather, I could only plug the tach in by reaching around through the opening where the radio and center console go..... both of which are now installed. That's why I am wondering if I should focus on trying to remove the cluster, -or- the radio and console. Ugh.

[Bob Gaines]

Thanks for the comments. IIRC, I couldn't plug the tach wires into the dash harness while installing the cluster. I think, rather, I could only plug the tach in by reaching around through the opening where the radio and center console go..... both of which are now installed. That's why I am wondering if I should focus on trying to remove the cluster, -or- the radio and console. Ugh.

Not much that it could be other then the tach if all is plugged in. With that said the first question he will probably ask is if it is plugged in properly. I would access through the radio bezel for now and if you have a inspection camera that will make the process easier although you should be able to see the pink resistor wires with the camera by looking under the dash while laying down. If you are "husky  " or not very flexible the radio bezel way is probably easier. I assume that this not something that has been on the shelf for a year or more and is something you just had done. If has been a long time since rebuild that fact might complicate your warranty. I would talk to the tachman and only follow his diagnose steps so as first off- to confirm to him that the problem is in the tach and second so as not to possibly voiding the warranty he provides by not making some kind of mistake. Contact him ASAP IMO.

[midlife]

The engine runs, right?  If it does, then the tach wires are either tied together (bypassing the tach) or installed into the tach.  Either way, you'll have to pull the dash to inspect and determine if the tach is bad or simply unplugged.  It's one or the other, unless you bypassed the factory coil wiring with something directly from the battery or starter solenoid.

[Angela]

Well, it turns out one CAN access the tach wires withOUT removing the instrument cluster! Yee ha! I removed all of the instrument cluster screws and then remebered there is still a 10-24 (I think) stud at the upper right corner of the cluster, which meant I was going to have to remove something else first, before I could yank the cluster. So, I took a gamble and removed the cigarette light/ash-tray panel and there they were.... the tach wires. See picture below. I didn't have to remove the cluster.

Turns out when I was installing the restored cluster, I thought I was plugging in the tach wires, but in reality all I had done is reconnected (bypassed) the dash harness wires such that the tach wires were unplugged. I plugged them in, re-fired the 390 and the tach works. Awesome.

Perhaps this will help someone else in the future.... you don't need to pull the cluster to gain access to the tach wires. :-)

[mikelj5S230]

That's fantastic!  Good job, I will have to remember it too, as my tach is very bouncy and will need some rebuilding before long I am afraid.

[67gtasanjose]

then remebered there is still a 10-24 (I think) stud at the upper right corner of the cluster, which meant I was going to have to remove something else first, before I could yank the cluster.

First, I am happy it was easy enough fixed. I really had to wonder what else could be wrong since you mentioned having the tacky sent to the Tachman. (heard nothing but good reports about him)

2nd, noting that NUT mentioned, my example NEVER had that nut installed onto it at least under my watch. I replaced the bezel with a NEW FORD part in 1979, pulling it out for what I thought was it's first time...No nut there so no nut ever went back on there.

Maybe it needs to be there Maybe some never got one