67 Tachometer Adjustment

[DGSOH]

My tach is about 200 rpm off, it actually sits at 200 with the ignition off. Comparing with a DMM confirms the offset.

Many analog meter movements have an adjusting screw, typically located in the front but generally hidden from view in some way. Before I start pulling the dash apart does anyone know if these tachs have a similar adjusting mechanism? Or some other adjustment mechanism like a trimmer or something and how would I identify it?

So much for having the gauge cluster "professionally" restored and calibrated... wish I'd checked it before reinstalling.

Thanks!

DGSOH

[Royce Peterson]

Just to make sure - the meter reads 200 RPM high with the bezel mounted in the car? Or is it 200 RPM high with the dash laying on the work bench?

These tachometers rely on gravity to read zero. If the tach isn't oriented as it sits in the car it reads high because gravity isn't helping.

There is no adjustment screw but they can be adjusted by bending the tang on the movement. Everything else needs to be correct such as the coil resistance and the resistance of the pink resistor wire.

My tach is about 200 rpm off, it actually sits at 200 with the ignition off. Comparing with a DMM confirms the offset.

Many analog meter movements have an adjusting screw, typically located in the front but generally hidden from view in some way. Before I start pulling the dash apart does anyone know if these tachs have a similar adjusting mechanism? Or some other adjustment mechanism like a trimmer or something and how would I identify it?

So much for having the gauge cluster "professionally" restored and calibrated... wish I'd checked it before reinstalling.

Thanks!

DGSOH

[DGSOH]

Just to make sure - the meter reads 200 RPM high with the bezel mounted in the car? Or is it 200 RPM high with the dash laying on the work bench?

These tachometers rely on gravity to read zero. If the tach isn't oriented as it sits in the car it reads high because gravity isn't helping.

There is no adjustment screw but they can be adjusted by bending the tang on the movement. Everything else needs to be correct such as the coil resistance and the resistance of the pink resistor wire.

+200 mounted in the car.

Sorry to hear there's no quick fix. I've adjusted analog meter movements as you describe in years gone by, ruined a few that way too as I recall.

Starting to sound like a next winter kind of project.

Just for the heck of it, would anyone have a photo or 2 of the movement in question? I know it's a long shot but worth asking. I typically like to have an idea of what I'm getting into before starting if I can.

Thanks Royce - and anyone else who may respond.

ps: Just went and looked at a photo of the cluster when I pulled it out before resto, wouldn't you know, almost smack dead on 0.

[DGSOH]

Time to start those winter projects...

So I have the cluster out of the car and on the bench and for the life of me I can't get the needle to settle at 0. Bending the needle either way only makes it worse - which doesn't really make sense.

The small screw in the middle of the movement would typically be an adjuster but previous poster(s) have stated not so with these. But on the off chance I decided to give it a try... that made it worse as well.

Is there some way to rotate the face that I'm not seeing maybe?

Does anyone know of a good (safe) way to simulate the tach signal on the bench? I can live with it off zero when not running but would like it to be as accurate as it can be otherwise.


Thanks!

[DGSOH]

Problem solved. Just had to be a little more aggressive on the bending than I was allowing myself on the first attempt. "Aggressive" being used as a relative term here, it's still a fairly delicate task.

[shelbydoug]

Unless you originally bent the pointer removing the cluster, it's more likely that it is the jewel movement that is screwed up.

I recently had my two tachs serviced and my '68 tach was working but not indicating over about 1,200rpm's.

My Tech found that the jewel movement was clogged with metallic dust and needed to be cleaned.

Before you go "re-alighning" your indicator needle, you need to have the jewel movement looked at for cleaning before you go and destroy the thing, BUT that is entirely up to you as the caretaker.

This is a situation where a little knowledge can be dangerous. I hope it works out well for you though?

[DGSOH]

Unless you originally bent the pointer removing the cluster, it's more likely that it is the jewel movement that is screwed up.

I recently had my two tachs serviced and my '68 tach was working but not indicating over about 1,200rpm's.

My Tech found that the jewel movement was clogged with metallic dust and needed to be cleaned.

Before you go "re-alighning" your indicator needle, you need to have the jewel movement looked at for cleaning before you go and destroy the thing, BUT that is entirely up to you as the caretaker.

This is a situation where a little knowledge can be dangerous. I hope it works out well for you though?

Respectfully, please refer to my original post, this is the state the meter is in AFTER having paid out-the-wazoo for "professional" services. It should be noted perhaps that laying flat on the bench, the needle rests on 0 which would lead me to believe that's how it was done by the "professional".

[shelbydoug]

Unless you originally bent the pointer removing the cluster, it's more likely that it is the jewel movement that is screwed up.

I recently had my two tachs serviced and my '68 tach was working but not indicating over about 1,200rpm's.

My Tech found that the jewel movement was clogged with metallic dust and needed to be cleaned.

Before you go "re-alighning" your indicator needle, you need to have the jewel movement looked at for cleaning before you go and destroy the thing, BUT that is entirely up to you as the caretaker.

This is a situation where a little knowledge can be dangerous. I hope it works out well for you though?

Respectfully, please refer to my original post, this is the state the meter is in AFTER having paid out-the-wazoo for "professional" services. It should be noted perhaps that laying flat on the bench, the needle rests on 0 which would lead me to believe that's how it was done by the "professional".

Did you use my recommended Tech? 

You do realize that the position of the dial indicator is affected by gravity and will rest in different locations depending on how you have it orientated, right?   

[Royce Peterson]

I have tested them by using the coil wire from the car, just as it is wired in the factory schematic. I once put three tachometers in series, while still using the one in the car. Started the car and tested the three on the fender - they matched the RPM of the one in the car and also matched my MATCO Tach / Dwell Meter.

Undoubtedly there is some way to synthesize the current to the coil but why bother if you have the car?

[DGSOH]

I have tested them by using the coil wire from the car, just as it is wired in the factory schematic. I once put three tachometers in series, while still using the one in the car. Started the car and tested the three on the fender - they matched the RPM of the one in the car and also matched my MATCO Tach / Dwell Meter.

Undoubtedly there is some way to synthesize the current to the coil but why bother if you have the car?

The car's pretty much put up for the winter and though technically it's ready to run I'd probably gas myself in the process... been there, done that - not pretty.

It's all back together now, I'll just wait until spring and hope for the best. I do have to say though, for what on the surface seems like an easy task, i.e. pulling and reinstalling the cluster, it's far more of a pita when worrying about scratches, dings, etc.. Not so bad on a beater.

Tip: Cut up a plastic 1/2 gal. milk jug for the flat sides then slide those between the cluster and the dashpad on both removal and reinstall. It'll prevent scuffing and scratching of the pad on those that are tight fitting like mine.

[Royce Peterson]

LOL I am usually not working on beaters - typically cars with values of $100K and up is more like it. I usually take off the steering wheel and mask the column with plastic sheet before attempting an instrument cluster removal / installation.

[JD]

All, DGSOH's car is hardly a "beater",  multi-year restoration on a car he's owned for decades years.  He's had a few interruptions that were out of his control, resulting in many "chef's" having their hands on it.  But he's getting it right now.

Hope 2022 is your year DGS.

[DGSOH]

All, DGSOH's car is hardly a "beater",  multi-year restoration on a car he's owned for decades years.  He's had a few interruptions that were out of his control, resulting in many "chef's" having their hands on it.  But he's getting it right now.

Hope 2022 is your year DGS.

Thanks JD - hope you and yours are well. And I hope 2022 is a year everyone can be proud of... we could all use one.

I had a couple of non-Shelby '68(s) before this car - those were definitely beaters so you just slapped $ht in and out as fast as you could to get it running/driving again. That was my reference. The Shelby is anything but today though truth be told, before the resto it was careening its way towards beater-dom.

I would be remiss to not mention all the assistance especially you JD, others on this forum and in the community have given in dragging it back to glory. It's been a slog but glad I did it. Also glad I'm just doing niggly, nitpicky things at this point. She's an imperfect, needy beast she is but what a blast to drive on the right road on the right day.

And yes, ownership anniversary of 35 years next month. It feels like a lifetime, or 2, ago.