Tachometer not working…

BillyMoore · Dec 28, 2022

91 GT, I just changed the dash cluster…car is new to me and the cluster was not original, but it did work. I bought another cluster, 140 mph speedometer which I believe is correct for the car. The tach drops to 0 when the key goes on but jumps to 4000 RPM when the engine starts. It moves up a little when revving engine but it isn’t working properly at all. All other gauges seem to work normally….except speedo bounces around 40mph. Any ideas in getting this squared away? All help or tips are appreciated. Thanks!

Mustang5L5 · Dec 29, 2022

If the other clusters tach worked, I would swap them out.

You can test the tach using a $10 signal generator off amazon if you really want to go that far. But if one tach worked, and this one doesn’t that points to a tach issue.

Was the previous tach a 6k unit( 4cyl) and now you have the 7k v8 tach?

BillyMoore · Dec 29, 2022

Actually the cluster I removed was a 200 mph Saleen cluster that was installed by a previous owner. My car has had a few performance mods made but I'm basically taking it back to original. The new cluster i installed is a 140 mph speedo and as far as I can tell it is from a GT, so it should have come out of a V8 car...

You mentioned swaping the tach...how involved is removing the tach from the cluster?

Trogdor · Dec 29, 2022

I would sell the Saleen cluster and use some of that money to buy a used tach.

Mustang5L5 · Dec 29, 2022

BillyMoore said:
..

You mentioned swaping the tach...how involved is removing the tach from the cluster?

It’s pretty easy. The cluster itself is modular so the tach portion pulls right out.

Check out this vid. At the end of the video I’m pulling the cluster apart to remove the tach. The beginning part talks about calibrating the tach but you can use this to just test to see if the tach actually works. The tach works off three pins. 12v+, ground and a signal wire. That wire is the Neg side of the coil.

But if the tach from the Saleen cluster worked, it points to a bad tach in this cluster or maybe an issue with the ribbon on the backside of the cluster. Flip the cluster over and find the three pins for the tach and where they connect to the ribbon. One of them is labeled S for signal. Trace that back to where the body harness plugs connect to the ribbon board and see if the connection end is in good shape. Often times those get bent up or break and don’t make a good connection.

Unfortunately just saying the tach is bad doesn’t tell us if it’s the actual tach, or a connection issue on the cluster wiring.

This vid is more for calibrating but it shows how you can test function and how to disassemble the cluster

View: https://youtu.be/UkHoSIdTpbc

General karthief · Dec 29, 2022

Trogdor said:
I would sell the Saleen cluster and use some of that money to buy a used tach.

@95steedamustang

95steedamustang · Dec 29, 2022

General karthief said:
@95steedamustang

Yep, I would be interested in the Saleen cluster if for sale.

General karthief · Dec 29, 2022

Well y'all need to get on the PM train, @BillyMoore if you need a replacement tach PM me, I may have one.
or more.

Mindseye007 · Jan 1, 2023

Mustang5L5 said:
It’s pretty easy. The cluster itself is modular so the tach portion pulls right out.

Check out this vid. At the end of the video I’m pulling the cluster apart to remove the tach. The beginning part talks about calibrating the tach but you can use this to just test to see if the tach actually works. The tach works off three pins. 12v+, ground and a signal wire. That wire is the Neg side of the coil.

But if the tach from the Saleen cluster worked, it points to a bad tach in this cluster or maybe an issue with the ribbon on the backside of the cluster. Flip the cluster over and find the three pins for the tach and where they connect to the ribbon. One of them is labeled S for signal. Trace that back to where the body harness plugs connect to the ribbon board and see if the connection end is in good shape. Often times those get bent up or break and don’t make a good connection.

Unfortunately just saying the tach is bad doesn’t tell us if it’s the actual tach, or a connection issue on the cluster wiring.

This vid is more for calibrating but it shows how you can test function and how to disassemble the cluster

View: https://youtu.be/UkHoSIdTpbc

Your videos are amazing.

chrlsful · Jan 1, 2023

whats the big silver box ('s name) at the top or back of the vid?
(supplies the "signal" I guess. It all went by pretty fast ona 1st look)

I love pic.
Instructional vids? as much as a visit to my friend's shop.

Thnx for puttin it up~
- -Chad
Amherst
MA

Mustang5L5 · Jan 1, 2023

chrlsful said:
whats the big silver box ('s name) at the top or back of the vid?
(supplies the "signal" I guess. It all went by pretty fast ona 1st look)

I love pic.
Instructional vids? as much as a visit to my friend's shop.

Thnx for puttin it up~
- -Chad
Amherst
MA

Silver box is just my 12v power supply for bench testing.

The item in the link below is what I’m using to generate the signal for the tach

Frequency Generator, DROK DC 3.3V-30V 5-30mA 1Hz-150kHz Adjustable Output PWM Pulse Duty Cycle Square Wave Function Signal Generator Module https://a.co/d/dmEiPm7

chrlsful · Jan 1, 2023

that's the BIG silver box at back?
I thought the Freq. Gen. was the lill blk plastic bx w/the digital read out.
Boy. Better re-view more than just once.

OK, thnx yet again. Thought it was sompin bringin in the juice, wasnt sure
what a name 4 it would B ("ac to dc converter"? I need 1 to get my CB goin in the house).

Mustang5L5 · Jan 1, 2023

This little box circled in red is the frequency generator I’m using to signal the tach.

Silver box is just a 30A 12v power supply I stole from a 3D printer I scrapped.

Tach and frequency generator need to use the same 12v power supply

chrlsful · Jan 1, 2023

Thnx 4 da post-back
OK "30 amp / 12 volt 'power supply' " is it then.
I think it could make my Citizen's Band radio go.
Thnx.

And the tach prt number is E8ZF - 178316 - BA 3513-1 (may B not that last '35...' sequence)

BillyMoore · Jan 8, 2023

Update… thanks for all the advice and tips, I took the cluster apart and got myself a soldering iron and a roll of solder…I re-soldered all the connections, reassembled the cluster and it works like a charm.

Tachometer not working…

BillyMoore

Member

Mustang5L5

That is…until I whipped out my Bissell

BillyMoore

Member

Trogdor

Mustang5L5

That is…until I whipped out my Bissell

General karthief

wonder how much it would cost to ship you a pair

95steedamustang

I tend to be on the ocd side…

General karthief

wonder how much it would cost to ship you a pair

Mindseye007

chrlsful

Active Member

Mustang5L5

That is…until I whipped out my Bissell

chrlsful

Active Member

Mustang5L5

That is…until I whipped out my Bissell

chrlsful

Active Member

BillyMoore

Member

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