Tachometer Calibration/Photoelectric Meter - Ford Mustang Forum
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post #1 of 14 (permalink) Old 09-29-2019 Thread Starter
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My tach reads high due to poor needle placement during an odometer gear change. I think it’s off by about 500 rpm but I’m not 100% on that. I’ve thought about taking the needle off and re-positioning it, but I’d just be taking a guess as where to put it (like prom nite).
I’ve been googling recalibration services to see if I can find someplace to send it off to be recalibrated. Do y’all know of any such places that work on ours? I’ve emailed two places that say that fix gauges for “classics,” but I’m not sure if they will work on one form a ‘95 as they haven’t responded yet.
I thought though in the meantime it would be nice to know exactly how fast the idle speed is. I came across this photoelectric do-dad that counts rpms. I think you put a piece of reflective tape on whatever you’re measuring and aim at it like you would a timing light. Where would I put the tape? The harmonic balancer?
Here’s the gadget and here are a few places I’ve found that work on tachs. Do y’all think a ‘95 would be too “modern” for these guys?
https://www.summitracing.com/parts/w...yABEgK_ovD_BwE

http://www.tachman.com/

http://www.rsgaugeworks.com/thankyou.html






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post #2 of 14 (permalink) Old 09-29-2019
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Simple solution. Buy an electronic tach and connect it to your distributor. Tachs record your engine rpms not transmission rpms (which is what your odometer reads). If your odometer gear has been changed, your speedometer may be off also.

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post #3 of 14 (permalink) Old 09-29-2019 Thread Starter
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Originally Posted by Travis98146 View Post
Simple solution. Buy an electronic tach and connect it to your distributor. Tachs record your engine rpms not transmission rpms (which is what your odometer reads). If your odometer gear has been changed, your speedometer may be off also.
Not exactly the issue.
When I was changing the odometer gear I had gauge cluster upside down on the work bench. Well I pressed down too hard (unknowingly) and the needle got pressed too far against the face of the cluster. So it was dragging against the face and getting stuck. So I took the gauge cluster back off and I pulled the needle off and put it back on to where it would move freely. After the cluster was back in the car I fired it up and it was reading higher than it used to. It works other than that. The needle position is just off. I think I’m idling around 750 but it reads around 1,200.
I have/had a little shift light and according to it it was about 500 rpm high. It’s now on the fritz though. No aftermarket tach’s for me thanks. It wouldn’t fit well with my motif.
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post #4 of 14 (permalink) Old 09-30-2019
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My tach reads high due to poor needle placement during an odometer gear change. I think it’s off by about 500 rpm but I’m not 100% on that. I’ve thought about taking the needle off and re-positioning it, but I’d just be taking a guess as where to put it (like prom nite).
I’ve been googling recalibration services to see if I can find someplace to send it off to be recalibrated. Do y’all know of any such places that work on ours? I’ve emailed two places that say that fix gauges for “classics,” but I’m not sure if they will work on one form a ‘95 as they haven’t responded yet.
I thought though in the meantime it would be nice to know exactly how fast the idle speed is. I came across this photoelectric do-dad that counts rpms. I think you put a piece of reflective tape on whatever you’re measuring and aim at it like you would a timing light. Where would I put the tape? The harmonic balancer?
Here’s the gadget and here are a few places I’ve found that work on tachs. Do y’all think a ‘95 would be too “modern” for these guys?
https://www.summitracing.com/parts/w...yABEgK_ovD_BwE

Tachometer Repair Restoration for Antique Classic Cars Auto

RS Gaugeworks Thank You

Thanks
A mechanical tachometer is another means of checking shaft speeds. Not cheap, maybe rentable. I would measure the pulley diameters, see which accessory is most easily accessible, probably the alternator or A/C pulley, figure in the pulley ratios, measure speed at idle, then you know eng. idle speed.

Such tachs have various types of tips to accommodate most types of shaft ends.
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post #5 of 14 (permalink) Old 09-30-2019
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I guess I should have added that you can just go ahead and buy a new tach unit. Or take it to a speedometer/tachometer shop and pay them to repair the damage.
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post #6 of 14 (permalink) Old 09-30-2019 Thread Starter
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I guess I should have added that you can just go ahead and buy a new tach unit. Or take it to a speedometer/tachometer shop and pay them to repair the damage.
I knew you were referring to buying a new tach. But I’d rather not have one.
I’ve reached out to a couple shops so I’ll see what they say. If someone says they can do it and not charge an arm and a leg I’ll go that route. If it cost too much I’ll just keep what I have I guess.
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post #7 of 14 (permalink) Old 09-30-2019
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Are you willing to try repositioning the needle again yourself, and just need a secondary tach to verify accuracy? Or are you looking for something to drive around with while the cluster is out for a rebuild?

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post #8 of 14 (permalink) Old 09-30-2019 Thread Starter
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Are you willing to try repositioning the needle again yourself, and just need a secondary tach to verify accuracy? Or are you looking for something to drive around with while the cluster is out for a rebuild?
I have the original cluster hanging on the wall in the garage and it works except for the fuel gauge. I could put it back in and see where it it’s idling. The cluster that’s in there now is from a Cobra. I got it to replace the broken original. I wonder if I would be able to place the needle where it needs to be while the car is idling?
Like see where the old one idles. Plug in the cobra one without the “glass” around it and place the needle close to where it should be.
However, I dunno if the needle will act right if one puts it on when the motor is on. I guess maybe it would.
For kicks I searched from some 94/95 Cobra clusters and they’ve about doubled in price since I bought mine almost. Almost ten years ago I think I paid around $150, now they’re $300-$400+. Too mucho
If the price is right I’d like to have someone set the needle to where it reads what the motor is doing. I’m not worried about it sitting while the cluster is out. I’m afraid if I reset it myself I’ll be taking it off and on all weekend and hoping I got it close and not worse. Even if I had something to compare it to I’m not sure it’d work right. But in the mean time (or if it never gets fixed) it’d be nice to have a tool that would let me know how far off it really is. Mainly Incase I ever want to adjust the idle again to try to get it to hang less.

Last edited by 90lxwhite; 09-30-2019 at 03:42 PM.
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post #9 of 14 (permalink) Old 09-30-2019 Thread Starter
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I just spoke to one place and he said it’d be about $90 plus the shipping. But he didn’t sound like he really wanted to do it though. He said, lit sounds like the needle is just off,” take it off and reset it.” “So I told him that I don’t really know where the motor is idling so I don’t know where to set it.” Then he said I should go to autozone and have them use an OBD scanner to see where the idle is and I said that that won’t work because mine is OBDI.
I don’t think whole take the needle off and reposition it thing will work. That’s how I got to where I am now. After I changed the odometer gear and had the cluster back in the car the needle wouldn’t move because it was pressed too far down. So I took the needle off and I put it on where it would rise and fall easily by hand. I set it to zero and installed the cluster back into the car. When I cranked it up the needle jumped up and idled over 1k rpm.
This place is who I called, Dicks Speedo. I think the dicks part is right. The google reviews are mixed. There are just as many one star reviews as there are 5. The one stars are mostly for them being rude and acting like D!cks. https://www.dicksspeedotach.com/
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post #10 of 14 (permalink) Old 10-06-2019 Thread Starter
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Jackpot!

Here’s a dude who specializes in ‘94-‘04 clusters. I emailed for a quote. I bet it’s $120.
https://accutach.com/ford-clusters
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post #11 of 14 (permalink) Old 10-06-2019 Thread Starter
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Originally Posted by 90lxwhite View Post
Here’s a dude who specializes in ‘94-‘04 clusters. I emailed for a quote. I bet it’s $120.
https://accutach.com/ford-clusters
He said it’d be $50 for s recalibration. But he also sent me a link with instructions on how to recalibrate it yourself using a 12v source and a car battery charger. The instructions are a little vague for me. But I think it’s saying once you hook it up to the power and charger the needle should read 1,800. If it doesn’t I guess you set it to 1,800 while it’s powered up, and I guess tje needle will fall to zero once the power is disconnected and it’s recalibrated?
The rigging up of the equipment looks like a little more electrical than I wanna do. It doesn’t look bad really, but $50 to have someone else do it doesn’t sound too awful.
https://websites.godaddy.com/blob/19...9.pdf?2089e5c1
*Edit*
That’s pretty much the procedure. I emailed asking about it and the guy emailed me back.
Hook it up set it to 1,800 and unhook it.
I’ve never really studied the tach this well before. Well there are four hash marks between each number. What does that mean, that each mark equals 200 rpm?
I never really paid attention to how many hashes there were until now so I always assumed that the line above the 1 equaled 1,100. I’m guessing the hash marks are more for aesthetics than accuracy.
Which hash mark would y’all say would be 1,800?
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Last edited by 90lxwhite; 10-06-2019 at 11:09 PM.
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Yeah, each hash represents a 200 RPM increment. There's a picture on page 5 of that PDF showing what it should look like at 1800 RPM.

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post #13 of 14 (permalink) Old 10-07-2019 Thread Starter
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Originally Posted by Urambo Tauro View Post
Yeah, each hash represents a 200 RPM increment. There's a picture on page 5 of that PDF showing what it should look like at 1800 RPM.
Ha ah yeah I see it. A little under two.. I wonder how he knows that’s not 1,900.. 😉
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Here is a how-to
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