Dead tach....need tach filter?

Good information, Hawk.  I've been holding off buying a circuit board for my spare tach conversion until I heard your results.  Appreciate your pioneering work on this. Keep us posted on your progress/results.

I think the issue is probably needing a filter or new board. I hooked up an extra aftermarket tach I had to the distributor and there was no needle movement - which I've read can be an indication of needing a inline resistor or filter. Or the tach was dead but I think it was working before the car was tore apart. When I hooked up the new tach directly to the distributor, the needle moved backwards which also can be caused by a bad board or bad connection on the board.

I ordered a filter and will order a new board to see if a filter is needed or the board that came with the tach was bad.

Got board and wanted to try something to make another tach for cheap.

So I went from this:


With the help of a white face and this:


To this:


Never hurts to have an extra tach. The guts are from a 1979 Corvette tach and I should be able to test it out Labor Day weekend.

My tach from the above post (fuel gauge turned into tach) works good! I miss spoke above, the guts and board are from a 1978 Corvette L82. I'm guessing I need a new board for my other tach I converted using the 1982 Corvette tach guts.

Thanks for the info, Hawk. Now I feel confident in purchasing a new board for the Corvette tach I had bought and, then swap everything onto my G3 tach face.

Just got a 73 tachometer, wired it up and it wont work. I've read through this whole thread. I don't live far from the tachman though so I may just go visit him

Okay...so I pulled this tach gauge cluster out of the '73 El Camino SS. Gauges are in "like new" condition.



The needle sits at about 2200 RPM. When I put 12V to + stud and ground to the - stud, the needle slowly moves toward zero...but, stops at about 500 RPM. Is it normal for a '73 tach's needle with factory circuit board to move that slowly? With the '75 tach conversion using the Corvette circuit board, the needle immediately drops to zero. Just wondering if this is an indication that the '73 tach is in need of repair.

BTW...I was researching how to bench test a tach and found some info referencing using a battery charger as they emit a pulsating voltage that won't damage the pre-HEI tachs. However, I was a little confused at to exactly how they hooked up the tach. Anyone hear of such a technique?

Steve Just send me the printed circuit needed and the this tach I send ya my Vintage Sun Tach with Glass face ?? SE is needing a tach while I have the cluster still apart LOL

Shame on you, Limey...trying to hornswoggle me.  LOL!

Nobody on here running a factory stock '73/'74 tach on points ignition that can tell me how it behaves when you turn the ignition switch on?

[quote="Mcarlo77"]Shame on you, Limey...trying to hornswoggle me.  LOL!quote]

Never know till to you ask right Steve ? Plus I would be taking a chance if it works or not ? LOL

I probably overpaid for this tach cluster; especially, considering that when I got it home, I discovered two copper circuits were chewed thru by mice. Think a section from a donor flex circuit can be easily grafted/soldered onto it to bridge the gap.

Limey...I do have this tach face plate if you can work with it doing the Corvette conversion.

Mcarlo77 wrote:Okay...so I pulled this tach gauge cluster out of the '73 El Camino SS.  Gauges are in "like new" condition.

The needle sits at about 2200 RPM.  When I put 12V to + stud and ground to the - stud, the needle slowly moves toward zero...but, stops at about 500 RPM.  Is it normal for a '73 tach's needle with factory circuit board to move that slowly?  With the '75 tach conversion using the Corvette circuit board, the needle immediately drops to zero.  Just wondering if this is an indication that the '73 tach is in need of repair.  

BTW...I was researching how to bench test a tach and found some info referencing using a battery charger as they emit a pulsating voltage that won't damage the pre-HEI tachs.  However, I was a little confused at to exactly how they hooked up the tach.  Anyone hear of such a technique?  

1973 454 MONTE wrote:40 seconds in is my tach running.
https://www.youtube.com/watch?v=NGyZCSSzJDU

Look at 1973 454 MONTE's video, I think he still has the '73 tach and it shows it at start up.

Good reference video! Looks like his needle drops like I would expect...hmmmm. I've read where the needle pin floats in an oil. Perhaps it has thickened on mine...causing the needle to move slowly? Damn...sure wish there was a sure fire way to test these.

I am chiming in late but here is what my 73 does, the needle drops fast, that said, the tach also doesn't resister when running, stays at zero and doesn't work. When you turn on the key it jumps to zero, you turn of the key and it goes back up to around 1500-2000 (not sure exactly).

Am wondering if, since the only vehicle I have access to with a points ignition is my '67 Cougar, could I just run jumper leads to both battery posts and one to the pos. side of the coil and test it? Any reason to believe these Chevy tachs aren't compatible with a Ford ignition system?

I think that should work Just fine Steve, A tach can tell brand of car just 4 6 or 8cylinder

Well...I tried testing this latest tach ('73) that I picked up on my '67 Cougar w/points ignition. Connected jumper wires to each battery terminal and to designated posts on back of tach. Needle went to near Zero. Ran another jumper wire from + post on coil (one with the lead to the Distributor) to designated post on back of tach and started the car...AND, NOTHING. Assuming this was the correct method to test it, I'm back to having another tach with a faceplate in mint condition that doesn't work. Sumbitch.....

Ok kewl That mean I have another coming my way ?? Its My Birthday today ...... Turned big 50

Anthony, Happy Birthday!! The big 5- oh. I'll be there in 9 short years.

Steve I too have an old Cougar, a std. 1969 H code hardtop rust bucket. But do love the hideaways and sequentials

Happy B-day, Anthony! 50 is a big milestone!

Cougars ARE cool with the hideaways and sequentials!

Happy Birthday Limey!

I just wanted to add some info I received today regarding a couple of questions that were raised in this thread...and, never fully answered.

I had e-mailed a gentleman named Ron today who owns Red Line Gauge and Clock Repair in Humboldt, TN. I asked: 1) about the need for a tach filter and 2) whether a '73 tach with the four post stud coil could be made to work with the new repro circuit boards built for three posts if you cut the fourth post off. Here were his replies:

1) "tach filters were installed to fry tachometers-gm's way to make money in the shops-you don't need them."

2) "you can not use a tach board with 3 holes on a 4 lug meter...the tach must be upgraded to a 3 post meter first." I take this to mean cutting off the fourth post is not going to work.

Just wanted to share my experience with the Tach Man so far.  I called the number last week and got the wife, who was unsure if he does 73 Chevelles, she said she had a file for 67 Chevellles, etc. wasn't sure but said that Gary would be back around 1:30 that afternoon.   So I called back later and got Gary.  Seemed like a good guy over the phone, explained a lot of things, and laid out the plan to fix my tach.  I emailed with him also, and I will say that his emails are very sparse, short, and convey the bare minimum.  After speaking with him on the phone though, I just chalk that up to perhaps an older guy who isn't all that "email savvy".  So with Gary, you're much better off picking up the phone and calling him, he appreciates that as well.

So I sent my tach to him by US mail last week, it got there Friday afternoon, and as of late yesterday it is done and ready to ship back.  He sends you an email with what was done, cost breakdowns, and 3 photographs of the calibration of the tach vs. his machine.  Here's what I got from Gary below.  He prefers PayPal due to the high fees he has to pay if payment is made via credit card.  I do PayPal so it was no issue for me.  I'll install it once I receive it back and report back here.  He told me the tach can now be used either on HEI or points, it doesn't matter since the new board is solid state.   This is good because I'm driving my car with HEI now, but once it's factory restored (if I find one) it will have it's points setup so I'm ready for Pebble Beach (just kidding)

Kevin:
3 pictures or your updated tach calibrated versus our tach calibrator, i will send you a paypal payment request

1. install 3 prong coil and solid state tach board                     250.00  2 yr warranty
2. assemble coil assembly, dial                                                8.00
2. return shipping/handling/insurance                                       29.00

Total                          287.00

Gary

Nice recap, Kevin.

Pricing is about where I was quoted at one time...so, no surprise there.

His statement confirms that the '73/'74 tachs are NOT compatible with HEI ignitions. Likewise, can we then conclude the '75 tach WILL work with ignition points?

Don't know the answer to that one. We need someone here to run an experiment.